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Ran X, Zhu Z, Long H, Tian Q, You L, Wu X, Liu Q, Huang S, Li S, Niu X, Wang J. Manganese Stress Adaptation Mechanisms of Bacillus safensis Strain ST7 From Mine Soil. Front Microbiol 2021; 12:758889. [PMID: 34899642 PMCID: PMC8656422 DOI: 10.3389/fmicb.2021.758889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 10/21/2021] [Indexed: 11/23/2022] Open
Abstract
The mechanism of bacterial adaption to manganese-polluted environments was explored using 50 manganese-tolerant strains of bacteria isolated from soil of the largest manganese mine in China. Efficiency of manganese removal by the isolated strains was investigated using atomic absorption spectrophotometry. Bacillus safensis strain ST7 was the most effective manganese-oxidizing bacteria among the tested isolates, achieving up to 82% removal at a Mn(II) concentration of 2,200 mg/L. Bacteria-mediated manganese oxide precipitates and high motility were observed, and the growth of strain ST7 was inhibited while its biofilm formation was promoted by the presence of Mn(II). In addition, strain ST7 could grow in the presence of high concentrations of Al(III), Cr(VI), and Fe(III). Genome-wide analysis of the gene expression profile of strain ST7 using the RNA-seq method revealed that 2,580 genes were differently expressed under Mn(II) exposure, and there were more downregulated genes (n = 2,021) than upregulated genes (n = 559) induced by Mn stress. KAAS analysis indicated that these differently expressed genes were mainly enriched in material metabolisms, cellular processes, organism systems, and genetic and environmental information processing pathways. A total of twenty-six genes from the transcriptome of strain ST7 were involved in lignocellulosic degradation. Furthermore, after 15 genes were knocked out by homologous recombination technology, it was observed that the transporters, multicopper oxidase, and proteins involved in sporulation and flagellogenesis contributed to the removal of Mn(II) in strain ST7. In summary, B. safensis ST7 adapted to Mn exposure by changing its metabolism, upregulating cation transporters, inhibiting sporulation and flagellogenesis, and activating an alternative stress-related sigB pathway. This bacterial strain could potentially be used to restore soil polluted by multiple heavy metals and is a candidate to support the consolidated bioprocessing community.
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Affiliation(s)
- Xueqin Ran
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Zhongmei Zhu
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Hong Long
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Qun Tian
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Longjiang You
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Xingdiao Wu
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Qin Liu
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Shihui Huang
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Sheng Li
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Xi Niu
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
| | - Jiafu Wang
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Animal Science/Institute of Agro-Bioengineering, Guizhou University, Guiyang, China
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Li Z, Zhu L, Yu Z, Liu L, Chou SH, Wang J, He J. 6S-1 RNA Contributes to Sporulation and Parasporal Crystal Formation in Bacillus thuringiensis. Front Microbiol 2020; 11:604458. [PMID: 33324388 PMCID: PMC7726162 DOI: 10.3389/fmicb.2020.604458] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 11/04/2020] [Indexed: 11/13/2022] Open
Abstract
6S RNA is a kind of high-abundance non-coding RNA that globally regulates bacterial transcription by interacting with RNA polymerase holoenzyme. Through bioinformatics analysis, we found that there are two tandem 6S RNA-encoding genes in the genomes of Bacillus cereus group bacteria. Using Bacillus thuringiensis BMB171 as the starting strain, we have explored the physiological functions of 6S RNAs, and found that the genes ssrSA and ssrSB encoding 6S-1 and 6S-2 RNAs were located in the same operon and are co-transcribed as a precursor that might be processed by specific ribonucleases to form mature 6S-1 and 6S-2 RNAs. We also constructed two single-gene deletion mutant strains ΔssrSA and ΔssrSB and a double-gene deletion mutant strain ΔssrSAB by means of the markerless gene knockout method. Our data show that deletion of 6S-1 RNA inhibited the growth of B. thuringiensis in the stationary phase, leading to lysis of some bacterial cells. Furthermore, deletion of 6S-1 RNA also significantly reduced the spore number and parasporal crystal content. Our work reveals that B. thuringiensis 6S RNA played an important regulatory role in ensuring the sporulation and parasporal crystal formation.
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Affiliation(s)
- Zhou Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Li Zhu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Zhaoqing Yu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Lu Liu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Shan-Ho Chou
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Jieping Wang
- Agricultural BioResources Institute, Fujian Academy of Agricultural Sciences, Fuzhou, China
| | - Jin He
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
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Role of Glutamate Synthase in Biofilm Formation by Bacillus subtilis. J Bacteriol 2020; 202:JB.00120-20. [PMID: 32393519 DOI: 10.1128/jb.00120-20] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 05/04/2020] [Indexed: 11/20/2022] Open
Abstract
Bacillus subtilis forms robust biofilms in the presence of large amounts of carbon sources, such as glycerol. However, little is known about the importance of the metabolic systems, or the relationship between metabolic systems and regulatory systems, involved in biofilm formation. Glutamate synthase, encoded by gltAB, is an enzyme that converts 2-ketoglutarate (a tricarboxylic acid [TCA] cycle intermediate) and glutamine into glutamate, which is a general amino group donor in metabolism. Here, we show that a ΔgltA mutant exhibited early arrest of biofilm formation in complex medium containing glycerol. This phenotype was not due to glutamate auxotrophy. Consistent with its biofilm formation phenotype, the ΔgltA mutant exhibited an early decrease in expression of the epsA and tapA operons, which are responsible for production of biofilm matrix polymers. This resulted from decreased activity of their regulator, Spo0A, as evidenced by reduced expression of other Spo0A-regulated genes in the ΔgltA mutant. The ΔgltA mutation prevented biofilm formation only in the presence of large amounts of glycerol. Moreover, limited expression of citrate synthase (but not other TCA enzymes) restored biofilm-forming ability to the ΔgltA mutant. These results indicate that the ΔgltA mutant accumulates an inhibitory intermediate (citrate) in the TCA cycle in the presence of large amounts of glycerol. The ΔgltA mutant formed biofilms when excess iron was added to the medium. Taken together, the data suggest that accumulation of citrate ions by the ΔgltA mutant causes iron shortage due to chelation, which prevents activation of Spo0A and causes defective biofilm formation.IMPORTANCE Bacillus subtilis, a model organism for bacterial biofilm formation, forms robust biofilms in a medium-dependent manner. Although the regulatory network that controls biofilm formation has been well studied, the importance of the underlying metabolic systems remains to be elucidated. The present study demonstrates that a metabolic disorder in a well-conserved metabolic system causes accumulation of an inhibitory metabolic intermediate that prevents activation of the system that regulates biofilm formation. These findings increase our understanding of the coordination between cellular metabolic status and the regulatory networks governing biofilm formation.
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Zheng C, Yu Z, Du C, Gong Y, Yin W, Li X, Li Z, Römling U, Chou SH, He J. 2-Methylcitrate cycle: a well-regulated controller of Bacillus sporulation. Environ Microbiol 2019; 22:1125-1140. [PMID: 31858668 DOI: 10.1111/1462-2920.14901] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 11/26/2019] [Accepted: 12/16/2019] [Indexed: 12/23/2022]
Abstract
Bacillus thuringiensis is the most widely used eco-friendly biopesticide, containing two primary determinants of biocontrol, endospore and insecticidal crystal proteins (ICPs). The 2-methylcitrate cycle is a widespread carbon metabolic pathway playing a crucial role in channelling propionyl-CoA, but with poorly understood metabolic regulatory mechanisms. Here, we dissect the transcriptional regulation of the 2-methylcitrate cycle operon prpCDB and report its unprecedented role in controlling the sporulation process of B. thuringiensis. We found that the transcriptional activity of the prp operon encoding the three critical enzymes PrpC, PrpD, and PrpB in the 2-methylcitrate cycle was negatively regulated by the two global transcription factors CcpA and AbrB, while positively regulated by the LysR family regulator CcpC, which jointly account for the fact that the 2-methylcitrate cycle is specifically and highly active in the stationary phase of growth. We also found that the prpD mutant accumulated 2-methylcitrate, the intermediate metabolite of the 2-methylcitrate cycle, which delayed and inhibited sporulation at the early stage. Thus, our results not only revealed sophisticated transcriptional regulatory mechanisms for the metabolic 2-methylcitrate cycle but also identified 2-methylcitrate as a novel regulator of sporulation in B. thuringiensis.
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Affiliation(s)
- Cao Zheng
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, People's Republic of China.,Hubei Province Research Center of Engineering Technology for Utilization of Botanical Functional Ingredients, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, College of Life Science and Technology, Hubei Engineering University, Xiaogan, Hubei, 432000, People's Republic of China
| | - Zhaoqing Yu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, People's Republic of China
| | - Cuiying Du
- Hubei Province Research Center of Engineering Technology for Utilization of Botanical Functional Ingredients, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, College of Life Science and Technology, Hubei Engineering University, Xiaogan, Hubei, 432000, People's Republic of China
| | - Yujing Gong
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, People's Republic of China
| | - Wen Yin
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, People's Republic of China
| | - Xinfeng Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, People's Republic of China
| | - Zhou Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, People's Republic of China
| | - Ute Römling
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Shan-Ho Chou
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, People's Republic of China
| | - Jin He
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, People's Republic of China
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Xie J, Peng J, Yi Z, Zhao X, Li S, Zhang T, Quan M, Yang S, Lu J, Zhou P, Xia L, Ding X. Role of hsp20 in the Production of Spores and Insecticidal Crystal Proteins in Bacillus thuringiensis. Front Microbiol 2019; 10:2059. [PMID: 31551991 PMCID: PMC6737285 DOI: 10.3389/fmicb.2019.02059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 08/20/2019] [Indexed: 01/04/2023] Open
Abstract
The small heat shock protein plays an important role in response to stresses. We wanted to investigate how Hsp20 affects sporulation and production of insecticidal crystal proteins (ICPs) in Bacillus thuringiensis (Bt) at the stationary growth phase when cells are starved. The hsp20 gene was knocked out in Bt4.0718 (wide type), which is a B. thuringiensis strain screened in our laboratory, using endonuclease I-SceI mediated unmarked gene replacement method. Deletion of Hsp20 resulted in a decrease in both sporulation and ICPs production. Bt4-Δhsp20 cells and its ICP did not have a significant difference in shape and size but entered the decline phase 2 h earlier than the Bt4.0718. In order to find the mechanism that underlies these phenotypes, we completed a proteomic study of differentially expressed proteins (DEPs). In Bt4-Δhsp20 cells, 11 DEPs were upregulated and 184 DEPs downregulated. These affected DEPs are involved in multiple metabolic pathways: (1) six DEPs (two upregulated and four downregulated) are directly related to the sporulation and ICPs synthesis; (2) supply of amino acids including amino acid synthesis and protein recycling; (3) the energy supplementation (the tricarboxylic acid cycle and glycolysis); (4) purine metabolism and mRNA stability. These results suggest that hsp20 may be critical in maintaining the homeostasis of B. thuringiensis during the production of spores and ICPs, and could provide new sight into the sporulation and ICPs formation in B. thuringiensis.
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Affiliation(s)
- Junyan Xie
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Jinli Peng
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Zixian Yi
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Xiaoli Zhao
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Shuiming Li
- Shenzhen Key Laboratory of Microbial Genetic Engineering, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China
| | - Tong Zhang
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Meifang Quan
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Shuqing Yang
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Jiaoyang Lu
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Pengji Zhou
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Liqiu Xia
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
| | - Xuezhi Ding
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Provincial Key Laboratory of Microbial Molecular Biology, College of Life Science, Hunan Normal University, Changsha, China
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Harris KA, Odzer NB, Breaker RR. Disruption of the OLE ribonucleoprotein complex causes magnesium toxicity in Bacillus halodurans. Mol Microbiol 2019; 112:1552-1563. [PMID: 31461569 DOI: 10.1111/mmi.14379] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2019] [Indexed: 12/26/2022]
Abstract
OLE RNAs represent an unusual class of bacterial noncoding RNAs common in Gram-positive anaerobes. The OLE RNA of the alkaliphile Bacillus halodurans is highly expressed and naturally interacts with at least two RNA-binding proteins called OapA and OapB. The phenotypes of the corresponding knockouts include growth inhibition when exposed to ethanol or other short-chain alcohols or when incubated at modestly reduced temperatures (e.g. 20°C). Intriguingly, the OapA 'PM1' mutant, which carries two amino acid changes to a highly conserved region, yields a dominant-negative phenotype that causes more severe growth defects under these same stress conditions. Herein, we report that the PM1 strain also exhibits extreme sensitivity to elevated Mg2+ concentrations, beginning as low as 2 mM. Suppressor mutants predominantly map to genes for aconitate hydratase and isocitrate dehydrogenase, which are expected to alter cellular citrate concentrations. Citrate reduces the severity of the Mg2+ toxicity phenotype, but neither the genomic mutations nor the addition of citrate to the medium overcomes ethanol toxicity or temperature sensitivity. These findings reveal that OLE RNA and its protein partners are involved in biochemical responses under several stress conditions, wherein the unusual sensitivity to Mg2+ can be independently suppressed by specific genomic mutations.
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Affiliation(s)
- Kimberly A Harris
- Howard Hughes Medical Institute, Yale University, New Haven, CT, USA.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Nicole B Odzer
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Ronald R Breaker
- Howard Hughes Medical Institute, Yale University, New Haven, CT, USA.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
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Pirated Siderophores Promote Sporulation in Bacillus subtilis. Appl Environ Microbiol 2017; 83:AEM.03293-16. [PMID: 28283524 PMCID: PMC5411514 DOI: 10.1128/aem.03293-16] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 03/07/2017] [Indexed: 11/20/2022] Open
Abstract
In microbial communities, bacteria chemically and physically interact with one another. Some of these interactions are mediated by secreted specialized metabolites that act as either intraspecies or interspecies signals to alter gene expression and to change cell physiology. Bacillus subtilis is a well-characterized soil microbe that can differentiate into multiple cell types, including metabolically dormant endospores. We were interested in identifying microbial interactions that affected sporulation in B. subtilis. Using a fluorescent transcriptional reporter, we observed that coculturing B. subtilis with Escherichia coli promoted sporulation gene expression via a secreted metabolite. To identify the active compound, we screened the E. coli Keio Collection and identified the sporulation-accelerating cue as the siderophore enterobactin. B. subtilis has multiple iron acquisition systems that are used to take up the B. subtilis-produced siderophore bacillibactin, as well as to pirate exogenous siderophores such as enterobactin. While B. subtilis uses a single substrate binding protein (FeuA) to take up both bacillibactin and enterobactin, we discovered that it requires two distinct genes to sporulate in response to these siderophores (the esterase gene besA for bacillibactin and a putative esterase gene, ybbA, for enterobactin). In addition, we found that siderophores from a variety of other microbial species also promote sporulation in B. subtilis. Our results thus demonstrate that siderophores can act not only as bacterial iron acquisition systems but also as interspecies cues that alter cellular development and accelerate sporulation in B. subtilis. IMPORTANCE While much is known about the genetic regulation of Bacillus subtilis sporulation, little is understood about how other bacteria influence this process. This work describes an interaction between Escherichia coli and B. subtilis that accelerates sporulation in B. subtilis. The interaction is mediated by the E. coli siderophore enterobactin; we show that other species' siderophores also promote sporulation gene expression in B. subtilis. These results suggest that siderophores not only may supply bacteria with the mineral nutrient iron but also may play a role in bacterial interspecies signaling, providing a cue for sporulation. Siderophores are produced by many bacterial species and thus potentially play important roles in altering bacterial cell physiology in diverse environments.
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Abstract
Pathogenic bacteria must contend with immune systems that actively restrict the availability of nutrients and cofactors, and create a hostile growth environment. To deal with these hostile environments, pathogenic bacteria have evolved or acquired virulence determinants that aid in the acquisition of nutrients. This connection between pathogenesis and nutrition may explain why regulators of metabolism in nonpathogenic bacteria are used by pathogenic bacteria to regulate both metabolism and virulence. Such coordinated regulation is presumably advantageous because it conserves carbon and energy by aligning synthesis of virulence determinants with the nutritional environment. In Gram-positive bacterial pathogens, at least three metabolite-responsive global regulators, CcpA, CodY, and Rex, have been shown to coordinate the expression of metabolism and virulence genes. In this chapter, we discuss how environmental challenges alter metabolism, the regulators that respond to this altered metabolism, and how these regulators influence the host-pathogen interaction.
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Abstract
Virulence gene expression serves two main functions, growth in/on the host, and the acquisition of nutrients. Therefore, it is obvious that nutrient availability is important to control expression of virulence genes. In any cell, enzymes are the components that are best informed about the availability of their respective substrates and products. It is thus not surprising that bacteria have evolved a variety of strategies to employ this information in the control of gene expression. Enzymes that have a second (so-called moonlighting) function in the regulation of gene expression are collectively referred to as trigger enzymes. Trigger enzymes may have a second activity as a direct regulatory protein that can bind specific DNA or RNA targets under particular conditions or they may affect the activity of transcription factors by covalent modification or direct protein-protein interaction. In this chapter, we provide an overview on these mechanisms and discuss the relevance of trigger enzymes for virulence gene expression in bacterial pathogens.
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10
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Abstract
Iron-sulfur clusters act as important cofactors for a number of transcriptional regulators in bacteria, including many mammalian pathogens. The sensitivity of iron-sulfur clusters to iron availability, oxygen tension, and reactive oxygen and nitrogen species enables bacteria to use such regulators to adapt their gene expression profiles rapidly in response to changing environmental conditions. In this review, we discuss how the [4Fe-4S] or [2Fe-2S] cluster-containing regulators FNR, Wbl, aconitase, IscR, NsrR, SoxR, and AirSR contribute to bacterial pathogenesis through control of both metabolism and classical virulence factors. In addition, we briefly review mammalian iron homeostasis as well as oxidative/nitrosative stress to provide context for understanding the function of bacterial iron-sulfur cluster sensors in different niches within the host.
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Affiliation(s)
- Halie K Miller
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.
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11
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Inverse metabolic engineering of Bacillus subtilis for xylose utilization based on adaptive evolution and whole-genome sequencing. Appl Microbiol Biotechnol 2014; 99:885-96. [DOI: 10.1007/s00253-014-6131-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 08/23/2014] [Accepted: 09/29/2014] [Indexed: 10/24/2022]
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Two roles for aconitase in the regulation of tricarboxylic acid branch gene expression in Bacillus subtilis. J Bacteriol 2013; 195:1525-37. [PMID: 23354745 DOI: 10.1128/jb.01690-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously, it was shown that an aconitase (citB) null mutation results in a vast overaccumulation of citrate in the culture fluid of growing Bacillus subtilis cells, a phenotype that causes secondary effects, including the hyperexpression of the citB promoter. B. subtilis aconitase is a bifunctional protein; to determine if either or both activities of aconitase were responsible for this phenotype, two strains producing different mutant forms of aconitase were constructed, one designed to be enzymatically inactive (C450S [citB2]) and the other designed to be defective in RNA binding (R741E [citB7]). The citB2 mutant was a glutamate auxotroph and accumulated citrate, while the citB7 mutant was a glutamate prototroph. Unexpectedly, the citB7 strain also accumulated citrate. Both mutant strains exhibited overexpression of the citB promoter and accumulated high levels of aconitase protein. These strains and the citB null mutant also exhibited increased levels of citrate synthase protein and enzyme activity in cell extracts, and the major citrate synthase (citZ) transcript was present at higher-than-normal levels in the citB null mutant, due at least in part to a >3-fold increase in the stability of the citZ transcript compared to the wild type. Purified B. subtilis aconitase bound to the citZ 5' leader RNA in vitro, but the mutant proteins did not. Together, these data suggest that wild-type aconitase binds to and destabilizes the citZ transcript in order to maintain proper cell homeostasis by preventing the overaccumulation of citrate.
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Mittal M, Pechter KB, Picossi S, Kim HJ, Kerstein KO, Sonenshein AL. Dual role of CcpC protein in regulation of aconitase gene expression in Listeria monocytogenes and Bacillus subtilis. MICROBIOLOGY-SGM 2012; 159:68-76. [PMID: 23139400 DOI: 10.1099/mic.0.063388-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The role of the CcpC regulatory protein as a repressor of the genes encoding the tricarboxylic acid branch enzymes of the Krebs cycle (citrate synthase, citZ; aconitase, citB; and isocitrate dehydrogenase, citC) has been established for both Bacillus subtilis and Listeria monocytogenes. In addition, hyperexpression of citB-lacZ reporter constructs in an aconitase null mutant strain has been reported for B. subtilis. We show here that such hyperexpression of citB occurs in L. monocytogenes as well as in B. subtilis and that in both species the hyperexpression is unexpectedly dependent on CcpC. We propose a revision of the existing CcpC-citB regulatory scheme and suggest a mechanism of regulation in which CcpC represses citB expression at low citrate levels and activates citB expression when citrate levels are high.
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Affiliation(s)
- Meghna Mittal
- Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Kieran B Pechter
- Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Silvia Picossi
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Hyun-Jin Kim
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Kathryn O Kerstein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Abraham L Sonenshein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA.,Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
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Michta E, Schad K, Blin K, Ort-Winklbauer R, Röttig M, Kohlbacher O, Wohlleben W, Schinko E, Mast Y. The bifunctional role of aconitase in Streptomyces viridochromogenes Tü494. Environ Microbiol 2012; 14:3203-19. [PMID: 23116164 DOI: 10.1111/1462-2920.12006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 09/24/2012] [Indexed: 12/01/2022]
Abstract
In many organisms, aconitases have dual functions; they serve as enzymes in the tricarboxylic acid cycle and as regulators of iron metabolism. In this study we defined the role of the aconitase AcnA in Streptomyces viridochromogenes Tü494, the producer of the herbicide phosphinothricyl-alanyl-alanine, also known as phosphinothricin tripeptide or bialaphos. A mutant in which the aconitase gene acnA was disrupted showed severe defects in morphology and physiology, as it was unable to form any aerial mycelium, spores nor phosphinothricin tripeptide. AcnA belongs to the iron regulatory proteins (IRPs). In addition to its catalytic function, AcnA plays a regulatory role by binding to iron responsive elements (IREs) located on the untranslated region of certain mRNAs. A mutation preventing the formation of the [4Fe-4S] cluster of AcnA eliminated its catalytic activity, but did not inhibit RNA-binding ability. In silico analysis of the S. viridochromogenes genome revealed several IRE-like structures. One structure is located upstream of recA, which is involved in the bacterial SOS response, and another one was identified upstream of ftsZ, which is required for the onset of sporulation in streptomycetes. The functionality of different IRE structures was proven with gel shift assays and specific IRE consensus sequences were defined. Furthermore, RecA was shown to be upregulated on post-transcriptional level under oxidative stress conditions in the wild-type strain but not in the acnA mutant, suggesting a regulatory role of AcnA in oxidative stress response.
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Affiliation(s)
- Ewelina Michta
- Interfakultäres Institut für Mikrobiologie und Infektionsmedizin (IMIT), Mikrobiologie/Biotechnologie, Fakultät für Biologie, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
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15
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Kirchberg J, Büttner D, Thiemer B, Sawers RG. Aconitase B is required for optimal growth of Xanthomonas campestris pv. vesicatoria in pepper plants. PLoS One 2012; 7:e34941. [PMID: 22493725 PMCID: PMC3321045 DOI: 10.1371/journal.pone.0034941] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 03/11/2012] [Indexed: 11/23/2022] Open
Abstract
The aerobic plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria (Xcv) colonizes the intercellular spaces of pepper and tomato. One enzyme that might contribute to the successful proliferation of Xcv in the host is the iron-sulfur protein aconitase, which catalyzes the conversion of citrate to isocitrate in the tricarboxylic acid (TCA) cycle and might also sense reactive oxygen species (ROS) and changes in cellular iron levels. Xcv contains three putative aconitases, two of which, acnA and acnB, are encoded by a single chromosomal locus. The focus of this study is aconitase B (AcnB). acnB is co-transcribed with two genes, XCV1925 and XCV1926, encoding putative nucleic acid-binding proteins. In vitro growth of acnB mutants was like wild type, whereas in planta growth and symptom formation in pepper plants were impaired. While acnA, XCV1925 or XCV1926 mutants showed a wild-type phenotype with respect to bacterial growth and in planta symptom formation, proliferation of the acnB mutant in susceptible pepper plants was significantly impaired. Furthermore, the deletion of acnB led to reduced HR induction in resistant pepper plants and an increased susceptibility to the superoxide-generating compound menadione. As AcnB complemented the growth deficiency of an Escherichia coli aconitase mutant, it is likely to be an active aconitase. We therefore propose that optimal growth and survival of Xcv in pepper plants depends on AcnB, which might be required for the utilization of citrate as carbon source and could also help protect the bacterium against oxidative stress.
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Affiliation(s)
- Janine Kirchberg
- Department of Microbiology, Institute of Biology, Martin-Luther University Halle-Wittenberg, Halle (Saale), Germany
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16
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Baumgart M, Mustafi N, Krug A, Bott M. Deletion of the aconitase gene in Corynebacterium glutamicum causes strong selection pressure for secondary mutations inactivating citrate synthase. J Bacteriol 2011; 193:6864-73. [PMID: 21984793 PMCID: PMC3232852 DOI: 10.1128/jb.05465-11] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Accepted: 10/03/2011] [Indexed: 01/29/2023] Open
Abstract
The aconitase gene acn of Corynebacterium glutamicum is regulated by four transcriptional regulators, indicating that the synthesis of this enzyme is carefully controlled. To understand the causes for this elaborate regulation, the properties of the Δacn-1 deletion mutant were analyzed in detail. The mutant was glutamate auxotrophic in glucose minimal medium, showed a strong growth defect, and secreted large amounts of acetate. None of these phenotypes could be complemented by plasmid-encoded aconitase, suggesting the presence of a secondary mutation. In fact, a point mutation within the gltA gene encoding citrate synthase was identified that caused the instability of the protein and an almost complete lack of its enzymatic activity. Subsequently, 27 further, independent Δacn clones were isolated, and 15 of them were found to contain distinct mutations in gltA, causing the loss of citrate synthase activity. A similar result was observed for mutants lacking the isocitrate dehydrogenase gene icd. In this case, 8 of 24 Δicd clones contained additional mutations in gltA. Indirect evidence was obtained that elevated intracellular citrate concentrations could be the cause of this selection pressure. Accordingly, the careful control of aconitase synthesis might have evolved due to the necessity to avoid inhibitory cytoplasmic citrate levels on the one hand and to prevent the excessive synthesis of an oxygen-sensitive protein requiring both iron and sulfur on the other hand.
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Affiliation(s)
- Meike Baumgart
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Nurije Mustafi
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Andreas Krug
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Michael Bott
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
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Whole-genome sequencing and phenotypic analysis of Bacillus subtilis mutants following evolution under conditions of relaxed selection for sporulation. Appl Environ Microbiol 2011; 77:6867-77. [PMID: 21821766 DOI: 10.1128/aem.05272-11] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Little is known about how genetic variation at the nucleotide level contributes to competitive fitness within species. During a 6,000-generation study of Bacillus subtilis evolved under relaxed selection for sporulation, a new strain, designated WN716, emerged with significantly different colony and cell morphologies; loss of sporulation, competence, acetoin production, and motility; multiple auxotrophies; and increased competitive fitness (H. Maughan and W. L. Nicholson, Appl. Environ. Microbiol. 77:4105-4118, 2011). The genome of WN716 was analyzed by OpGen optical mapping, whole-genome 454 pyrosequencing, and the CLC Genomics Workbench. No large chromosomal rearrangements were found; however, 34 single-nucleotide polymorphisms (SNPs) and +1 frameshifts were identified in WN716 that resulted in amino acid changes in coding sequences of annotated genes, and 11 SNPs were located in intergenic regions. Several classes of genes were affected, including biosynthetic pathways, sporulation, competence, and DNA repair. In several cases, attempts were made to link observed phenotypes of WN716 with the discovered mutations, with various degrees of success. For example, a +1 frameshift was identified at codon 13 of sigW, the product of which (SigW) controls a regulon of genes involved in resistance to bacteriocins and membrane-damaging antibiotics. Consistent with this finding, WN716 exhibited sensitivity to fosfomycin and to a bacteriocin produced by B. subtilis subsp. spizizenii and exhibited downregulation of SigW-dependent genes on a transcriptional microarray, consistent with WN716 carrying a knockout of sigW. The results suggest that propagation of B. subtilis for less than 2,000 generations in a nutrient-rich environment where sporulation is suppressed led to rapid initiation of genomic erosion.
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Gao W, Dai S, Liu Q, Xu H, Bai Y, Qiao M. Effect of site-directed mutagenesis of citB on the expression and activity of Bacillus subtilis aconitase. Microbiology (Reading) 2010. [DOI: 10.1134/s002626171006007x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Facciotti MT, Pang WL, Lo FY, Whitehead K, Koide T, Masumura KI, Pan M, Kaur A, Larsen DJ, Reiss DJ, Hoang L, Kalisiak E, Northen T, Trauger SA, Siuzdak G, Baliga NS. Large scale physiological readjustment during growth enables rapid, comprehensive and inexpensive systems analysis. BMC SYSTEMS BIOLOGY 2010; 4:64. [PMID: 20470417 PMCID: PMC2880973 DOI: 10.1186/1752-0509-4-64] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 05/14/2010] [Indexed: 12/02/2022]
Abstract
Background Rapidly characterizing the operational interrelationships among all genes in a given organism is a critical bottleneck to significantly advancing our understanding of thousands of newly sequenced microbial and eukaryotic species. While evolving technologies for global profiling of transcripts, proteins, and metabolites are making it possible to comprehensively survey cellular physiology in newly sequenced organisms, these experimental techniques have not kept pace with sequencing efforts. Compounding these technological challenges is the fact that individual experiments typically only stimulate relatively small-scale cellular responses, thus requiring numerous expensive experiments to survey the operational relationships among nearly all genetic elements. Therefore, a relatively quick and inexpensive strategy for observing changes in large fractions of the genetic elements is highly desirable. Results We have discovered in the model organism Halobacterium salinarum NRC-1 that batch culturing in complex medium stimulates meaningful changes in the expression of approximately two thirds of all genes. While the majority of these changes occur during transition from rapid exponential growth to the stationary phase, several transient physiological states were detected beyond what has been previously observed. In sum, integrated analysis of transcript and metabolite changes has helped uncover growth phase-associated physiologies, operational interrelationships among two thirds of all genes, specialized functions for gene family members, waves of transcription factor activities, and growth phase associated cell morphology control. Conclusions Simple laboratory culturing in complex medium can be enormously informative regarding the activities of and interrelationships among a large fraction of all genes in an organism. This also yields important baseline physiological context for designing specific perturbation experiments at different phases of growth. The integration of such growth and perturbation studies with measurements of associated environmental factor changes is a practical and economical route for the elucidation of comprehensive systems-level models of biological systems.
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Affiliation(s)
- Marc T Facciotti
- Institute for Systems Biology, 1441 North 34th Street, Seattle, WA 98103, USA.
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Gao W, Dai S, Liu Q, Xu H, Qiao M. CitB mutation increases the alkaline protease productivity in Bacillus subtilis. J GEN APPL MICROBIOL 2010; 56:403-7. [DOI: 10.2323/jgam.56.403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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21
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Deletion of citrate synthase restores growth of Sinorhizobium meliloti 1021 aconitase mutants. J Bacteriol 2009; 191:7581-6. [PMID: 19820082 DOI: 10.1128/jb.00777-09] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti 1021 encodes only one predicted aconitase (AcnA) in its genome. AcnA has a significant degree of similarity with other bacterial aconitases that behave as dual proteins: enzymes and posttranscriptional regulators of gene expression. Similar to the case with these bacterial aconitases, AcnA activity was reversibly labile and was regained upon reconstitution with reduced iron. The aconitase promoter was active in root nodules. acnA mutants grew very poorly, had secondary mutations, and were quickly outgrown by pseudorevertants. The acnA gene was stably interrupted in a citrate synthase (gltA) null background, indicating that the intracellular accumulation of citrate may be deleterious for survival of strain 1021. No aconitase activity was detected in this mutant, suggesting that the acnA gene encodes the only functional aconitase of strain 1021. To uncover a function of AcnA beyond its catalytic role in the tricarboxylic acid cycle pathway, the gltA acnA double mutant was compared with the gltA single mutant for differences in motility, resistance to oxidative stress, nodulation, and growth on different substrates. However, no differences in any of these characteristics were found.
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22
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Schinko E, Schad K, Eys S, Keller U, Wohlleben W. Phosphinothricin-tripeptide biosynthesis: an original version of bacterial secondary metabolism? PHYTOCHEMISTRY 2009; 70:1787-1800. [PMID: 19878959 DOI: 10.1016/j.phytochem.2009.09.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 09/03/2009] [Accepted: 09/04/2009] [Indexed: 05/28/2023]
Abstract
Streptomyces viridochromogenes Tü494 produces the herbicide phosphinothricyl-alanyl-alanine (phosphinothricin-tripeptide=PTT; bialaphos). Its bioactive moiety phosphinothricin competitively inhibits bacterial and plant glutamine synthetases. The biosynthesis of PTT includes the synthesis of the unusual amino acid N-acetyl-demethyl-phosphinothricin and a three step condensation via non-ribosomal peptide synthetases. Two characteristics within the PTT biosynthesis make it suitable to study the evolution of secondary metabolism biosynthesis. First, PTT biosynthesis represents the only known system where all peptide synthetase modules are located on separate proteins. This 'single enzyme system' might be an archetype of the multimodular and multienzymatic non-ribosomal peptide synthetases in evolutionary terms. The second interesting feature of PTT biosynthesis is the pathway-specific aconitase Pmi that is involved in the supply of N-acetyl-demethyl-phosphinothricin. Pmi is highly similar to the tricarboxylic acid aconitase AcnA. They share 64% identity at the DNA level and both belong to the Iron-Regulatory-Protein/AcnA family. Despite their high sequence similarity, AcnA and Pmi catalyze different reactions and are not able to substitute for each other. Thus, the enzyme pair AcnA/Pmi presents an example of the evolution of a secondary metabolite-specific enzyme from a primary metabolism enzyme.
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Affiliation(s)
- Eva Schinko
- Mikrobiologie/Biotechnologie, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
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23
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Sadykov MR, Olson ME, Halouska S, Zhu Y, Fey PD, Powers R, Somerville GA. Tricarboxylic acid cycle-dependent regulation of Staphylococcus epidermidis polysaccharide intercellular adhesin synthesis. J Bacteriol 2008; 190:7621-32. [PMID: 18820013 PMCID: PMC2583607 DOI: 10.1128/jb.00806-08] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Accepted: 09/21/2008] [Indexed: 11/20/2022] Open
Abstract
Staphylococcus epidermidis is a major nosocomial pathogen primarily infecting immunocompromised individuals or those with implanted biomaterials (e.g., catheters). Biomaterial-associated infections often involve the formation of a biofilm on the surface of the medical device. In S. epidermidis, polysaccharide intercellular adhesin (PIA) is an important mediator of biofilm formation and pathogenesis. Synthesis of PIA is regulated by at least three DNA binding proteins (IcaR, SarA, and sigma(B)) and several environmental and nutritional conditions. Previously, we observed the environmental conditions that increased PIA synthesis decreased tricarboxylic acid (TCA) cycle activity. In this study, S. epidermidis TCA cycle mutants were constructed, and the function of central metabolism in PIA biosynthesis was examined. TCA cycle inactivation altered the metabolic status of S. epidermidis, resulting in a massive derepression of PIA biosynthetic genes and a redirection of carbon from growth into PIA biosynthesis. These data demonstrate that the bacterial metabolic status is a critical regulatory determinant of PIA synthesis. In addition, these data lead us to propose that the TCA cycle acts as a signal transduction pathway to translate external environmental cues into intracellular metabolic signals that modulate the activity of transcriptional regulators.
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Affiliation(s)
- Marat R Sadykov
- Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln, 155 VBS, Fair St. and East Campus Loop, Lincoln, NE 68583-0905, USA
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24
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Tännler S, Zamboni N, Kiraly C, Aymerich S, Sauer U. Screening of Bacillus subtilis transposon mutants with altered riboflavin production. Metab Eng 2008; 10:216-26. [DOI: 10.1016/j.ymben.2008.06.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2007] [Revised: 04/22/2008] [Accepted: 06/02/2008] [Indexed: 11/27/2022]
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25
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Goelzer A, Bekkal Brikci F, Martin-Verstraete I, Noirot P, Bessières P, Aymerich S, Fromion V. Reconstruction and analysis of the genetic and metabolic regulatory networks of the central metabolism of Bacillus subtilis. BMC SYSTEMS BIOLOGY 2008; 2:20. [PMID: 18302748 PMCID: PMC2311275 DOI: 10.1186/1752-0509-2-20] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Accepted: 02/26/2008] [Indexed: 12/15/2022]
Abstract
Background Few genome-scale models of organisms focus on the regulatory networks and none of them integrates all known levels of regulation. In particular, the regulations involving metabolite pools are often neglected. However, metabolite pools link the metabolic to the genetic network through genetic regulations, including those involving effectors of transcription factors or riboswitches. Consequently, they play pivotal roles in the global organization of the genetic and metabolic regulatory networks. Results We report the manually curated reconstruction of the genetic and metabolic regulatory networks of the central metabolism of Bacillus subtilis (transcriptional, translational and post-translational regulations and modulation of enzymatic activities). We provide a systematic graphic representation of regulations of each metabolic pathway based on the central role of metabolites in regulation. We show that the complex regulatory network of B. subtilis can be decomposed as sets of locally regulated modules, which are coordinated by global regulators. Conclusion This work reveals the strong involvement of metabolite pools in the general regulation of the metabolic network. Breaking the metabolic network down into modules based on the control of metabolite pools reveals the functional organization of the genetic and metabolic regulatory networks of B. subtilis.
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Affiliation(s)
- Anne Goelzer
- Unité Mathématique, Informatique et Génomes, Institut National Recherche Agronomique, UR1077, F-78350 Jouy-en-Josas, France.
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26
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Serio AW, Pechter KB, Sonenshein AL. Bacillus subtilis aconitase is required for efficient late-sporulation gene expression. J Bacteriol 2006; 188:6396-405. [PMID: 16923907 PMCID: PMC1595401 DOI: 10.1128/jb.00249-06] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus subtilis aconitase, encoded by the citB gene, is homologous to the bifunctional eukaryotic protein IRP-1 (iron regulatory protein 1). Like IRP-1, B. subtilis aconitase is both an enzyme and an RNA binding protein. In an attempt to separate the two activities of aconitase, the C-terminal region of the B. subtilis citB gene product was mutagenized. The resulting strain had high catalytic activity but was defective in sporulation. The defect was at a late stage of sporulation, specifically affecting expression of sigmaK-dependent genes, many of which are important for spore coat assembly and require transcriptional activation by GerE. Accumulation of gerE mRNA and GerE protein was delayed in the aconitase mutant strain. Pure B. subtilis aconitase bound to the 3' untranslated region of gerE mRNA in in vitro gel mobility shift assays, strongly suggesting that aconitase RNA binding activity may stabilize gerE mRNA in order to allow efficient GerE synthesis and proper timing of spore coat assembly.
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Affiliation(s)
- Alisa W Serio
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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27
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Serio AW, Sonenshein AL. Expression of yeast mitochondrial aconitase in Bacillus subtilis. J Bacteriol 2006; 188:6406-10. [PMID: 16923908 PMCID: PMC1595382 DOI: 10.1128/jb.00248-06] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expression of yeast mitochondrial aconitase (Aco1) in a Bacillus subtilis aconitase null mutant restored aconitase activity and glutamate prototrophy but only partially restored sporulation. Late sporulation gene expression in the Aco1-expressing strain was delayed.
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Affiliation(s)
- Alisa W Serio
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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28
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Kim HJ, Mittal M, Sonenshein AL. CcpC-dependent regulation of citB and lmo0847 in Listeria monocytogenes. J Bacteriol 2006; 188:179-90. [PMID: 16352834 PMCID: PMC1317608 DOI: 10.1128/jb.188.1.179-190.2006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Bacillus subtilis, the catabolite control protein C (CcpC) plays a critical role in regulating the genes encoding the enzymes of the tricarboxylic acid branch of the Krebs citric acid cycle. A gene encoding a potential CcpC homolog and two potential target genes were identified in the Listeria monocytogenes genome. In vitro gel mobility shift assays and DNase I footprinting experiments showed that L. monocytogenes CcpC (CcpC(Lm)) interacts with the promoter regions of citB(Lm) (the gene that is likely to encode aconitase) and lmo0847 (encoding a possible glutamine transporter) and that citrate is a specific inhibitor of this interaction. To study in vivo promoter activity, a new lacZ reporter system was developed. This system allows stable integration into the chromosome of a promoter region transcriptionally fused to a promoterless lacZ gene at a nonessential, ectopic locus. Analysis of strains carrying a citB(Lm)-lacZ or lmo0847-lacZ fusion revealed that CcpC(Lm) represses citB(Lm) and lmo0847 in media containing an excess of glucose and glutamine. In addition, regulation of citB(Lm) expression in rich medium was growth phase dependent; during exponential growth phase, expression was very low even in the absence of CcpC(Lm), but a higher level of citB(Lm) expression was induced in stationary phase, suggesting the involvement of another, as yet unidentified regulatory factor.
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Affiliation(s)
- Hyun-Jin Kim
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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Alsaker KV, Papoutsakis ET. Transcriptional program of early sporulation and stationary-phase events in Clostridium acetobutylicum. J Bacteriol 2005; 187:7103-18. [PMID: 16199581 PMCID: PMC1251621 DOI: 10.1128/jb.187.20.7103-7118.2005] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA microarray analysis of Clostridium acetobutylicum was used to examine the genomic-scale gene expression changes during the shift from exponential-phase growth and acidogenesis to stationary phase and solventogenesis. Self-organizing maps were used to identify novel expression patterns of functional gene classes, including aromatic and branched-chain amino acid synthesis, ribosomal proteins, cobalt and iron transporters, cobalamin biosynthesis, and lipid biosynthesis. The majority of pSOL1 megaplasmid genes (in addition to the solventogenic genes aad-ctfA-ctfB and adc) had increased expression at the onset of solventogenesis, suggesting that other megaplasmid genes may play a role in stationary-phase phenomena. Analysis of sporulation genes and comparison with published Bacillus subtilis results indicated conserved expression patterns of early sporulation genes, including spo0A, the sigF operon, and putative canonical genes of the sigma(H) and sigma(F) regulons. However, sigE expression could not be detected within 7.5 h of initial spo0A expression, consistent with the observed extended time between the appearance of clostridial forms and endospore formation. The results were compared with microarray comparisons of the wild-type strain and the nonsolventogenic, asporogenous M5 strain, which lacks the pSOL1 megaplasmid. While some results were similar, the expression of primary metabolism genes and heat shock proteins was higher in M5, suggesting a difference in metabolic regulation or a butyrate stress response in M5. The results of this microarray platform and analysis were further validated by comparing gene expression patterns to previously published Northern analyses, reporter assays, and two-dimensional protein electrophoresis data of metabolic genes (including all major solventogenesis genes), sporulation genes, heat shock proteins, and other solventogenesis-induced gene expression.
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Affiliation(s)
- Keith V Alsaker
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, USA
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Chatterjee I, Becker P, Grundmeier M, Bischoff M, Somerville GA, Peters G, Sinha B, Harraghy N, Proctor RA, Herrmann M. Staphylococcus aureus ClpC is required for stress resistance, aconitase activity, growth recovery, and death. J Bacteriol 2005; 187:4488-96. [PMID: 15968059 PMCID: PMC1151783 DOI: 10.1128/jb.187.13.4488-4496.2005] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ability of Staphylococcus aureus to adapt to various conditions of stress is the result of a complex regulatory response. Previously, it has been demonstrated that Clp homologues are important for a variety of stress conditions, and our laboratory has shown that a clpC homologue was highly expressed in the S. aureus strain DSM20231 during biofilm formation relative to expression in planktonic cells. Persistence and long-term survival are a hallmark of biofilm-associated staphylococcal infections, as cure frequently fails even in the presence of bactericidal antimicrobials. To determine the role of clpC in this context, we performed metabolic, gene expression, and long-term growth and survival analyses of DSM20231 as well as an isogenic clpC allelic-replacement mutant, a sigB mutant, and a clpC sigB double mutant. As expected, the clpC mutant showed increased sensitivity to oxidative and heat stresses. Unanticipated, however, was the reduced expression of the tricarboxylic acid (TCA) cycle gene citB (encoding aconitase), resulting in the loss of aconitase activity and preventing the catabolization of acetate during the stationary phase. clpC inactivation abolished post-stationary-phase recovery but also resulted in significantly enhanced stationary-phase survival compared to that of the wild-type strain. These data demonstrate the critical role of the ClpC ATPase in regulating the TCA cycle and implicate ClpC as being important for recovery from the stationary phase and also for entering the death phase. Understanding the stationary- and post-stationary-phase recovery in S. aureus may have important clinical implications, as little is known about the mechanisms of long-term persistence of chronic S. aureus infections associated with formation of biofilms.
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Affiliation(s)
- Indranil Chatterjee
- Institute of Medical Microbiology and Hygiene, Institutes of Infectious Disease Medicine, University of Saarland, Homburg/Saar, Germany
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31
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Chenoweth MR, Somerville GA, Krause DC, O'Reilly KL, Gherardini FC. Growth characteristics of Bartonella henselae in a novel liquid medium: primary isolation, growth-phase-dependent phage induction, and metabolic studies. Appl Environ Microbiol 2004; 70:656-63. [PMID: 14766538 PMCID: PMC348914 DOI: 10.1128/aem.70.2.656-663.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bartonella henselae is a zoonotic pathogen that usually causes a self-limiting infection in immunocompetent individuals but often causes potentially life-threatening infections, such as bacillary angiomatosis, in immunocompromised patients. Both diagnosis of infection and research into the molecular mechanisms of pathogenesis have been hindered by the absence of a suitable liquid growth medium. It has been difficult to isolate B. henselae directly from the blood of infected humans or animals or to grow the bacteria in liquid culture media under laboratory conditions. Therefore, we have developed a liquid growth medium that supports reproducible in vitro growth (3-h doubling time and a growth yield of approximately 5 x 10(8) CFU/ml) and permits the isolation of B. henselae from the blood of infected cats. During the development of this medium, we observed that B. henselae did not derive carbon and energy from the catabolism of glucose, which is consistent with genome nucleotide sequence data suggesting an incomplete glycolytic pathway. Of interest, B. henselae depleted amino acids from the culture medium and accumulated ammonia in the medium, an indicator of amino acid catabolism. Analysis of the culture medium throughout the growth cycle revealed that oxygen was consumed and carbon dioxide was generated, suggesting that amino acids were catabolized in a tricarboxylic acid (TCA) cycle-dependent mechanism. Additionally, phage particles were detected in the culture supernatants of stationary-phase B. henselae, but not in mid-logarithmic-phase culture supernatants. Enzymatic assays of whole-cell lysates revealed that B. henselae has a complete TCA cycle. Taken together, these data suggest B. henselae may catabolize amino acids but not glucose to derive carbon and energy from its host. Furthermore, the newly developed culture medium should improve isolation of B. henselae and basic research into the pathogenesis of the bacterium.
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Affiliation(s)
- M R Chenoweth
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA
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32
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Alsaker KV, Spitzer TR, Papoutsakis ET. Transcriptional analysis of spo0A overexpression in Clostridium acetobutylicum and its effect on the cell's response to butanol stress. J Bacteriol 2004; 186:1959-71. [PMID: 15028679 PMCID: PMC374416 DOI: 10.1128/jb.186.7.1959-1971.2004] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Spo0A is the regulator of stationary-phase events and is required for transcription of solvent formation genes in Clostridium acetobutylicum. In order to elucidate the role of spo0A in differentiation, we performed transcriptional analysis of 824(pMSPOA) (a spo0A-overexpressing C. acetobutylicum strain with enhanced sporulation) against a plasmid control strain. DNA microarray data were contrasted to data from a spo0A knockout strain (SKO1) that neither sporulates nor produces solvents. Transcripts of fatty acid metabolism genes, motility and chemotaxis genes, heat shock protein genes, and genes encoding the Fts family of cell division proteins were differentially expressed in the two strains, suggesting that these genes play roles in sporulation and the solvent stress response. 824(pMSPOA) alone showed significant downregulation of many glycolytic genes in stationary phase, which is consistent with metabolic flux analysis data. Surprisingly, spo0A overexpression resulted in only nominal transcriptional changes of regulatory genes (abrB and sigF) whose expression was significantly altered in SKO1. Overexpression of spo0A imparted increased tolerance and prolonged metabolism in response to butanol stress. While most of the differentially expressed genes appear to be part of a general stress response (similar to patterns in two plasmid control strains and a groESL-overexpressing strain), several genes were expressed at higher levels at early time points after butanol challenge only in 824(pMSPOA). Most of these genes were related to butyryl coenzyme A and butyrate formation and/or assimilation, but they also included the cell division gene ftsX, the gyrase subunit-encoding genes gyrB and gyrA, DNA synthesis and repair genes, and fatty acid synthesis genes, all of which might play a role in the immediate butanol stress response, and thus in enhanced butanol tolerance.
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Affiliation(s)
- Keith V Alsaker
- Department of Chemical Engineering, Northwestern University, Evanston, Illinois 60208, USA
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33
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Kim SI, Jourlin-Castelli C, Wellington SR, Sonenshein AL. Mechanism of repression by Bacillus subtilis CcpC, a LysR family regulator. J Mol Biol 2004; 334:609-24. [PMID: 14636591 DOI: 10.1016/j.jmb.2003.09.078] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bacillus subtilis CcpC is a LysR family transcriptional regulatory protein that negatively regulates genes encoding enzymes of the tricarboxylic acid branch of the Krebs cycle. In the present work, the promoter region of the aconitase (citB) gene was used to investigate the mechanism of repression by CcpC. The binding of CcpC to the citB promoter region was shown to depend on DNA elements located near positions -66 and -27. Binding to these elements induced a bend in the DNA at position -41. Introduction of mutations in the -27 region and the presence of citrate, the inducer, had similar effects. In either case, citB expression was derepressed in vivo, the affinity of CcpC binding was reduced in vitro, the angle of the bend was relaxed, and RNA polymerase gained greater access to the -35 region of the promoter.
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Affiliation(s)
- Sam-In Kim
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111-1800, USA
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34
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Kim HJ, Kim SI, Ratnayake-Lecamwasam M, Tachikawa K, Sonenshein AL, Strauch M. Complex regulation of the Bacillus subtilis aconitase gene. J Bacteriol 2003; 185:1672-80. [PMID: 12591885 PMCID: PMC148081 DOI: 10.1128/jb.185.5.1672-1680.2003] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The roles of the CcpC, CodY, and AbrB proteins in regulation of the Bacillus subtilis aconitase (citB) gene were found to be distinct and to vary with the conditions and phase of growth. CcpC, a citrate-inhibited repressor that is the primary factor regulating citB expression in minimal-glucose-glutamine medium, also contributed to repression of citB during exponential-phase growth in broth medium. A null mutation in codY had no effect on citB expression during growth in minimal medium even when combined with ccpC and abrB mutations. However, a codY mutation slightly relieved repression during exponential growth in broth medium and completely derepressed citB expression when combined with a ccpC mutation. An abrB mutation led to decreased expression of citB during stationary phase in both broth and minimal medium. All three proteins bound in vitro to specific and partially overlapping sites within the citB regulatory region. Interaction of CcpC and CodY with the citB promoter region was partially competitive.
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Affiliation(s)
- Hyun-Jin Kim
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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35
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Varghese S, Tang Y, Imlay JA. Contrasting sensitivities of Escherichia coli aconitases A and B to oxidation and iron depletion. J Bacteriol 2003; 185:221-30. [PMID: 12486059 PMCID: PMC141816 DOI: 10.1128/jb.185.1.221-230.2003] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Superoxide damages dehydratases that contain catalytic [4Fe-4S](2+) clusters. Aconitases are members of that enzyme family, and previous work showed that most aconitase activity is lost when Escherichia coli is exposed to superoxide stress. More recently it was determined that E. coli synthesizes at least two isozymes of aconitase, AcnA and AcnB. Synthesis of AcnA, the less-abundant enzyme, is positively controlled by SoxS, a protein that is activated in the presence of superoxide-generating chemicals. We have determined that this arrangement exists because AcnA is resistant to superoxide in vivo. Surprisingly, purified AcnA is extremely sensitive to superoxide and other chemical oxidants unless it is combined with an uncharacterized factor that is present in cell extracts. In contrast, AcnB is highly sensitive to a variety of chemical oxidants in vivo, in extracts, and in its purified form. Thus, the induction of AcnA during oxidative stress provides a mechanism to circumvent a block in the tricarboxylic acid cycle. AcnA appears to be as catalytically competent as AcnB, so the retention of the latter as the primary housekeeping enzyme must provide some other advantage. We observed that the [4Fe-4S] cluster of AcnB is in dynamic equilibrium with the surrounding iron pool, so that AcnB is rapidly demetallated when intracellular iron pools drop. AcnA and other dehydratases do not show this trait. Demetallated AcnB is known to bind its cognate mRNA. The absence of AcnB activity also causes the accumulation and excretion of citrate, an iron chelator for which E. coli synthesizes a transport system. Thus, AcnB may be retained as the primary aconitase because the lability of its exposed cluster allows E. coli to sense and respond to iron depletion.
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Affiliation(s)
- Shery Varghese
- Department of Microbiology, University of Illinois, Urbana, IL 61801, USA
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36
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Somerville GA, Chaussee MS, Morgan CI, Fitzgerald JR, Dorward DW, Reitzer LJ, Musser JM. Staphylococcus aureus aconitase inactivation unexpectedly inhibits post-exponential-phase growth and enhances stationary-phase survival. Infect Immun 2002; 70:6373-82. [PMID: 12379717 PMCID: PMC130419 DOI: 10.1128/iai.70.11.6373-6382.2002] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Staphylococcus aureus preferentially catabolizes glucose, generating pyruvate, which is subsequently oxidized to acetate under aerobic growth conditions. Catabolite repression of the tricarboxylic acid (TCA) cycle results in the accumulation of acetate. TCA cycle derepression coincides with exit from the exponential growth phase, the onset of acetate catabolism, and the maximal expression of secreted virulence factors. These data suggest that carbon and energy for post-exponential-phase growth and virulence factor production are derived from the catabolism of acetate mediated by the TCA cycle. To test this hypothesis, the aconitase gene was genetically inactivated in a human isolate of S. aureus, and the effects on physiology, morphology, virulence factor production, virulence for mice, and stationary-phase survival were examined. TCA cycle inactivation prevented the post-exponential growth phase catabolism of acetate, resulting in premature entry into the stationary phase. This phenotype was accompanied by a significant reduction in the production of several virulence factors and alteration in host-pathogen interaction. Unexpectedly, aconitase inactivation enhanced stationary-phase survival relative to the wild-type strain. Aconitase is an iron-sulfur cluster-containing enzyme that is highly susceptible to oxidative inactivation. We speculate that reversible loss of the iron-sulfur cluster in wild-type organisms is a survival strategy used to circumvent oxidative stress induced during host-pathogen interactions. Taken together, these data demonstrate the importance of the TCA cycle in the life cycle of this medically important pathogen.
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Affiliation(s)
- Greg A Somerville
- Laboratory of Human Bacterial Pathogenesis. Rocky Mountain Microscopy Branch. Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA
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37
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Soga T, Ueno Y, Naraoka H, Ohashi Y, Tomita M, Nishioka T. Simultaneous determination of anionic intermediates for Bacillus subtilis metabolic pathways by capillary electrophoresis electrospray ionization mass spectrometry. Anal Chem 2002; 74:2233-9. [PMID: 12038746 DOI: 10.1021/ac020064n] [Citation(s) in RCA: 337] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A method for simultaneous determination of anionic metabolites based on capillary electrophoresis (CE) coupled to electrospray ionization mass spectrometry is described. To prevent current drop by the system, electroosmotic flow (EOF) reversal by using a cationic polymer-coated capillary was indispensable. A mixture containing 32 standards including carboxylic acids, phosphorylated carboxylic acids, phosphorylated saccharides, nucleotides, and nicotinamide and flavin adenine coenzymes of glycolysis and the tricarboxylic acid cycle pathways were separated by CE and selectively detected by a quadrupole mass spectrometer with a sheath-flow electrospray ionization interface. Key to the analysis was EOF reversal using a cationic polymer-coated capillary and an electrolyte system consisting of 50 mM ammonium acetate, pH 9.0. The relative standard deviations of the method were better than 0.4% for migration times and between 0.9% and 5.4% for peak areas. The concentration detection limits for these metabolites were between 0.3 and 6.7 micromol/L with pressure injection of 50 mbar for 30 s (30 nL); i.e., mass detection limits ranged from 9 to 200 fmol, at a signal-to-noise ratio of 3. This method was applied to the comprehensive analysis of metabolic intermediates extracted from Bacillus subtilis, and 27 anionic metabolites could be directly detected and quantified.
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Affiliation(s)
- Tomoyoshi Soga
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan.
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38
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Gao H, Jiang X, Pogliano K, Aronson AI. The E1beta and E2 subunits of the Bacillus subtilis pyruvate dehydrogenase complex are involved in regulation of sporulation. J Bacteriol 2002; 184:2780-8. [PMID: 11976308 PMCID: PMC135025 DOI: 10.1128/jb.184.10.2780-2788.2002] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The pdhABCD operon of Bacillus subtilis encodes the pyruvate decarboxylase (E1alpha and E1beta), dihydrolipoamide acetyltransferase (E2), and dihydrolipoamide dehydrogenase (E3) subunits of the pyruvate dehydrogenase multienzyme complex (PDH). There are two promoters: one for the entire operon and an internal one in front of the pdhC gene. The latter may serve to ensure adequate quantities of the E2 and E3 subunits, which are needed in greater amounts than E1alpha and E1beta. Disruptions of the pdhB, pdhC, and pdhD genes were isolated, but attempts to construct a pdhA mutant were unsuccessful, suggesting that E1alpha is essential. The three mutants lacked PDH activity, were unable to grow on glucose and grew poorly in an enriched medium. The pdhB and pdhC mutants sporulated to only 5% of the wild-type level, whereas the pdhD mutant strain sporulated to 55% of the wild-type level. This difference indicated that the sporulation defect of the pdhB and pdhC mutant strains was due to a function(s) of these subunits independent of enzymatic activity. Growth, but not low sporulation, was enhanced by the addition of acetate, glutamate, succinate, and divalent cations. Results from the expression of various spo-lacZ fusions revealed that the pdhB mutant was defective in the late stages of engulfment or membrane fusion (stage II), whereas the pdhC mutant was blocked after the completion of engulfment (stage III). This analysis was confirmed by fluorescent membrane staining. The E1beta and E2 subunits which are present in the soluble fraction of sporulating cells appear to function independently of enzymatic activity as checkpoints for stage II-III of sporulation.
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Affiliation(s)
- Haichun Gao
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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39
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Baughn AD, Malamy MH. A mitochondrial-like aconitase in the bacterium Bacteroides fragilis: implications for the evolution of the mitochondrial Krebs cycle. Proc Natl Acad Sci U S A 2002; 99:4662-7. [PMID: 11880608 PMCID: PMC123704 DOI: 10.1073/pnas.052710199] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2001] [Accepted: 12/31/2001] [Indexed: 11/18/2022] Open
Abstract
Aconitase and isocitrate dehydrogenase (IDH) enzyme activities were detected in anaerobically prepared cell extracts of the obligate anaerobe Bacteroides fragilis. The aconitase gene was located upstream of the genes encoding the other two components of the oxidative branch of the Krebs cycle, IDH and citrate synthase. Mutational analysis indicates that these genes are cotranscribed. A nonpolar in-frame deletion of the acnA gene that encodes the aconitase prevented growth in glucose minimal medium unless heme or succinate was added to the medium. These results imply that B. fragilis has two pathways for alpha-ketoglutarate biosynthesis-one from isocitrate and the other from succinate. Homology searches indicated that the B. fragilis aconitase is most closely related to aconitases of two other Cytophaga-Flavobacterium-Bacteroides (CFB) group bacteria, Cytophaga hutchinsonii and Fibrobacter succinogenes. Phylogenetic analysis indicates that the CFB group aconitases are most closely related to mitochondrial aconitases. In addition, the IDH of C. hutchinsonii was found to be most closely related to the mitochondrial/cytosolic IDH-2 group of eukaryotic organisms. These data suggest a common origin for these Krebs cycle enzymes in mitochondria and CFB group bacteria.
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Affiliation(s)
- Anthony D Baughn
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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40
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Viollier PH, Nguyen KT, Minas W, Folcher M, Dale GE, Thompson CJ. Roles of aconitase in growth, metabolism, and morphological differentiation of Streptomyces coelicolor. J Bacteriol 2001; 183:3193-203. [PMID: 11325949 PMCID: PMC95221 DOI: 10.1128/jb.183.10.3193-3203.2001] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2000] [Accepted: 02/08/2001] [Indexed: 11/20/2022] Open
Abstract
The studies of aconitase presented here, along with those of citrate synthase (P. H. Viollier, W. Minas, G. E. Dale, M. Folcher, and C. J. Thompson, J. Bacteriol. 183:3184-3192, 2001), were undertaken to investigate the role of the tricarboxylic acid (TCA) cycle in Streptomyces coelicolor development. A single aconitase activity (AcoA) was detected in protein extracts of cultures during column purification. The deduced amino acid sequence of the cloned acoA gene constituted the N-terminal sequence of semipurified AcoA and was homologous to bacterial A-type aconitases and bifunctional eukaryotic aconitases (iron regulatory proteins). The fact that an acoA disruption mutant (BZ4) did not grow on minimal glucose media in the absence of glutamate confirmed that this gene encoded the primary vegetative aconitase catalyzing flux through the TCA cycle. On glucose-based complete medium, BZ4 had defects in growth, antibiotic biosynthesis, and aerial hypha formation, partially due to medium acidification and accumulation of citrate. The inhibitory effects of acids and citrate on BZ4 were partly suppressed by buffer or by introducing a citrate synthase mutation. However, the fact that growth of an acoA citA mutant remained impaired, even on a nonacidogenic carbon source, suggested alternative functions of AcoA. Immunoblots revealed that AcoA was present primarily during substrate mycelial growth on solid medium. Transcription of acoA was limited to the early growth phase in liquid cultures from a start site mapped in vitro and in vivo.
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Affiliation(s)
- P H Viollier
- Department of Molecular Microbiology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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41
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Ratnayake-Lecamwasam M, Serror P, Wong KW, Sonenshein AL. Bacillus subtilis CodY represses early-stationary-phase genes by sensing GTP levels. Genes Dev 2001; 15:1093-103. [PMID: 11331605 PMCID: PMC312684 DOI: 10.1101/gad.874201] [Citation(s) in RCA: 278] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
CodY, a highly conserved protein in the low G + C, gram-positive bacteria, regulates the expression of many Bacillus subtilis genes that are induced as cells make the transition from rapid exponential growth to stationary phase and sporulation. This transition has been associated with a transient drop in the intracellular pool of GTP. Many stationary-phase genes are also induced during exponential-growth phase by treatment of cells with decoyinine, a GMP synthetase inhibitor. The effect of decoyinine on an early-stationary-phase gene is shown here to be mediated through CodY and to reflect a reduction in guanine nucleotide accumulation. CodY proved to bind GTP in vitro. Moreover, CodY-mediated repression of target promoters was dependent on a high concentration of GTP, comparable to that found in rapidly growing exponential-phase cells. Because a codY-null mutant was able to sporulate under conditions of nutrient excess, CodY also appears to be a critical factor that normally prevents sporulation under such conditions. Thus, B. subtilis CodY is a novel GTP-binding protein that senses the intracellular GTP concentration as an indicator of nutritional conditions and regulates the transcription of early-stationary-phase and sporulation genes, allowing the cell to adapt to nutrient limitation.
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Affiliation(s)
- M Ratnayake-Lecamwasam
- Tufts University School of Medicine, Department of Molecular Biology and Microbiology, Boston, Massachusetts 02111, USA
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42
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Viollier PH, Minas W, Dale GE, Folcher M, Thompson CJ. Role of acid metabolism in Streptomyces coelicolor morphological differentiation and antibiotic biosynthesis. J Bacteriol 2001; 183:3184-92. [PMID: 11325948 PMCID: PMC95220 DOI: 10.1128/jb.183.10.3184-3192.2001] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2000] [Accepted: 02/08/2001] [Indexed: 11/20/2022] Open
Abstract
Studies of citrate synthase (CitA) were carried out to investigate its role in morphological development and biosynthesis of antibiotics in Streptomyces coelicolor. Purification of CitA, the major vegetative enzyme activity, allowed characterization of its kinetic properties. The apparent K(m) values of CitA for acetyl coenzyme A (acetyl-CoA) (32 microM) and oxaloacetate (17 microM) were similar to those of citrate synthases from other gram-positive bacteria and eukaryotes. CitA was not strongly inhibited by various allosteric feedback inhibitors (NAD(+), NADH, ATP, ADP, isocitrate, or alpha-ketoglutarate). The corresponding gene (citA) was cloned and sequenced, allowing construction of a citA mutant (BZ2). BZ2 was a glutamate auxotroph, indicating that citA encoded the major citrate synthase allowing flow of acetyl-CoA into the tricarboxylic acid (TCA) cycle. Interruption of aerobic TCA cycle-based metabolism resulted in acidification of the medium and defects in morphological differentiation and antibiotic biosynthesis. These developmental defects of the citA mutant were in part due to a glucose-dependent medium acidification that was also exhibited by some other bald mutants. Unlike other acidogenic bald strains, citA and bldJ mutants were able to produce aerial mycelia and pigments when the medium was buffered sufficiently to maintain neutrality. Extracellular complementation studies suggested that citA defines a new stage of the Streptomyces developmental cascade.
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Affiliation(s)
- P H Viollier
- Department of Molecular Microbiology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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43
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Abstract
Recent work has provided new insights into the mechanisms by which Bacillus subtilis responds to signals that reflect high population density and nutritional limitation, the mechanisms that regulate activation of the key transcription factor Spo0A, and the physical basis for critical aspects of the Spo0A phosphorelay.
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Affiliation(s)
- A L Sonenshein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
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44
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Yamamoto H, Murata M, Sekiguchi J. The CitST two-component system regulates the expression of the Mg-citrate transporter in Bacillus subtilis. Mol Microbiol 2000; 37:898-912. [PMID: 10972810 DOI: 10.1046/j.1365-2958.2000.02055.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
citS and citT genes encoding a new two-component system were identified in the 71 degrees region between the pel and citM loci on the Bacillus subtilis chromosome. citS- and citT-deficient strains were unable to grow on minimal plates including citrate as a sole carbon source. In addition, a strain deficient in citM, which encodes the secondary transporter of the Mg-citrate complex, exhibited the same phenotype on this medium. Northern blot analysis revealed that citM was polycistronically transcribed with the downstream yflN gene, and that CitS and CitT were necessary for transcription of the citM-yflN operon. Upon addition of 2 mM citrate to DSM, this operon was strongly induced after the middle of the exponential growth phase in the wild type, but not in the citST double null mutant. Moreover, the transcription of this operon was completely repressed in the presence of 1% glucose. We found a sequence exhibiting homology to a catabolite-responsive element (cre) in the citM promoter region. Glucose repression was lost in ccpA and citM-cre mutants. From the result of a citM-promoter deletion experiment, putative CitT target sequences were found to be located around two regions, from -62 to -74 and from -149 to -189, relative to the citM start point. Furthermore, DNase I footprinting assays revealed that these two CitT target regions extended maximally from -36 to -84 and from -168 to -194. From these findings, we concluded that the expression of citM is positively regulated by the CitST system and negatively regulated by CcpA.
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Affiliation(s)
- H Yamamoto
- Department of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, Nagano, Japan
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45
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Schwartz D, Kaspar S, Kienzlen G, Muschko K, Wohlleben W. Inactivation of the tricarboxylic acid cycle aconitase gene from Streptomyces viridochromogenes Tü494 impairs morphological and physiological differentiation. J Bacteriol 1999; 181:7131-5. [PMID: 10559181 PMCID: PMC94190 DOI: 10.1128/jb.181.22.7131-7135.1999] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The tricarboxylic acid (TCA) cycle aconitase gene acnA from Streptomyces viridochromogenes Tü494 was cloned and analyzed. AcnA catalyzes the isomerization of citrate to isocitrate in the TCA cycle, as indicated by the ability of acnA to complement the aconitase-deficient Escherichia coli mutant JRG3259. An acnA mutant was unable to develop aerial mycelium and to sporulate, resulting in a bald phenotype. Furthermore, the mutant did not produce the antibiotic phosphinothricin tripeptide, demonstrating that AcnA also affects physiological differentiation.
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Affiliation(s)
- D Schwartz
- Mikrobiologie/Biotechnologie, Eberhard-Karls-Universität Tübingen, D-72076 Tübingen, Germany.
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46
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Abstract
The aconitase protein of Bacillus subtilis was able to bind specifically to sequences resembling the iron response elements (IREs) found in eukaryotic mRNAs. The sequences bound include the rabbit ferritin IRE and IRE-like sequences in the B. subtilis operons that encode the major cytochrome oxidase and an iron uptake system. IRE binding activity was affected by the availability of iron both in vivo and in vitro. In eukaryotic cells, aconitase-like proteins regulate translation and stability of iron metabolism mRNAs in response to iron availability. A mutant strain of B. subtilis that produces an enzymatically inactive aconitase that was still able to bind RNA sporulated 40x more efficiently than did an aconitase null mutant, suggesting that a nonenzymatic activity of aconitase is important for sporulation. The results support the idea that bacterial aconitases, like their eukaryotic homologs, are bifunctional proteins, showing aconitase activity in the presence of iron and RNA binding activity when cells are iron-deprived.
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Affiliation(s)
- C Alén
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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47
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Abstract
Deletion of the citC gene, coding for isocitrate dehydrogenase, arrests sporulation of Bacillus subtilis at stage I after bipolar localization of the cell division protein FtsZ but before formation of the asymmetric septum. A spontaneous extragenic suppressor mutation that overcame the stage I block was found to map within the spoVG gene. The suppressing mutation and other spoVG loss-of-function mutations enabled citC mutant cells to form asymmetric septa and to activate the forespore-specific sigma factor sigmaF. However, little induction of mother cell-specific, sigmaE-dependent sporulation genes was observed in a citC spoVG double mutant, indicating that there is an additional defect(s) in compartmentalized gene expression in the citC mutant. These other defects could be partially overcome by reducing the synthesis of citrate, by buffering the medium, or by adding excess MnCl2. Overexpression of the spoVG gene in wild-type cells significantly delayed sigmaF activation. Increased expression and stability of SpoVG in citC mutant cells may contribute to the citC mutant phenotype. Inactivation of the spoVG gene caused a population of otherwise wild-type cells to produce a small number of minicells during growth and caused sporulating cells to complete asymmetric septation more rapidly than normal. Unlike the case for inactivation of the cell division inhibitor gene minD, many of these minicells contained DNA and appeared only when the primary sporulation signal transduction pathway, the Spo0A phosphorelay, was active. These results suggest that SpoVG interferes with or is a negative regulator of the pathway leading to asymmetric septation.
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Affiliation(s)
- K Matsuno
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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48
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Matsuno K, Blais T, Serio AW, Conway T, Henkin TM, Sonenshein AL. Metabolic imbalance and sporulation in an isocitrate dehydrogenase mutant of Bacillus subtilis. J Bacteriol 1999; 181:3382-91. [PMID: 10348849 PMCID: PMC93804 DOI: 10.1128/jb.181.11.3382-3391.1999] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A Bacillus subtilis mutant with a deletion in the citC gene, encoding isocitrate dehydrogenase, the third enzyme of the tricarboxylic acid branch of the Krebs cycle, exhibited reduced growth yield in broth medium and had greatly reduced ability to sporulate compared to the wild type due to a block at stage I, i.e., a failure to form the polar division septum. In early stationary phase, mutant cells accumulated intracellular and extracellular concentrations of citrate and isocitrate that were at least 15-fold higher than in wild-type cells. The growth and sporulation defects of the mutant could be partially bypassed by deletion of the major citrate synthase gene (citZ), by raising the pH of the medium, or by supplementation of the medium with certain divalent cations, suggesting that abnormal accumulation of citrate affects survival of stationary-phase cells and sporulation by lowering extracellular pH and chelating metal ions. While these genetic and environmental alterations were not sufficient to allow the majority of the mutant cell population to pass the stage I block (lack of asymmetric septum formation), introduction of the sof-1 mutant form of the Spo0A transcription factor, when coupled with a reduction in citrate synthesis, restored sporulation gene expression and spore formation nearly to wild-type levels. Thus, the primary factor inhibiting sporulation in a citC mutant is abnormally high accumulation of citrate, but relief of this metabolic defect is not by itself sufficient to restore competence for sporulation.
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Affiliation(s)
- K Matsuno
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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49
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Abstract
Krebs cycle enzyme activity in Bacillus subtilis was examined under aerobic and anaerobic conditions. Citrate synthase and aconitase activities in cells grown anaerobically in the presence of nitrate were reduced by as much as 10- and 30-fold, respectively, from levels observed under aerobic culture conditions. The maximum level of isocitrate dehydrogenase activity during anaerobic growth was only twofold lower than that in aerobic cultures. These reductions in activity under conditions of anaerobiosis were found to be primarily the result of reduced Krebs cycle gene transcription. This repression was not dependent on either the fnr or resDE gene products, which have been shown to regulate expression of other B. subtilis genes in response to anaerobic conditions. Additionally, catabolite control proteins CcpA and CcpB were not responsible for the repression. A dyad symmetry element located between positions -73 and -59 relative to the transcription start site of the aconitase gene (citB) promoter was previously shown to be a target of catabolite repression and the binding site for a putative negative regulator during aerobic growth. The deletion of the upstream arm of the dyad symmetry region abolished the citB repression observed during anaerobic growth. Furthermore, neither citZ or citB was repressed in an anaerobically grown citB mutant, an effect that was very likely the result of citrate accumulation. These results suggest that catabolite repression and anaerobic repression of citZ and citB are regulated by a common mechanism that does not involve CcpA, CcpB, Fnr, or ResDE.
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Affiliation(s)
- M M Nakano
- Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, Shreveport 71130, USA.
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