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Wang K, Lu H, Zou M, Wang G, Zhao J, Huang X, Ren F, Hu H, Huang J, Min X. DegS protease regulates antioxidant capacity and adaptability to oxidative stress environment in Vibrio cholerae. Front Cell Infect Microbiol 2023; 13:1290508. [PMID: 38053530 PMCID: PMC10694293 DOI: 10.3389/fcimb.2023.1290508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 11/06/2023] [Indexed: 12/07/2023] Open
Abstract
Adaptation to oxidative stress is critical for survival of Vibrio cholerae in aquatic ecosystems and hosts. DegS activates the σE envelope stress response. We have previously revealed that DegS may be involved in regulating the oxidative stress response. In this study, we demonstrated that deletion of the degS gene attenuates the antioxidant capacity of V. cholerae. In addition, our results further revealed that the regulation of antioxidant capacity by DegS in V. cholerae could involve the cAMP-CRP complex, which regulates rpoS. XthA is an exonuclease that repairs oxidatively damaged cells and affects the bacterial antioxidant capacity. qRT-PCR showed that DegS, σE, cAMP, CRP, and RpoS positively regulate xthA gene transcription. XthA overexpression partially compensates for antioxidant deficiency in the degS mutant. These results suggest that DegS affects the antioxidant capacity of V.cholerae by regulating xthA expression via the cAMP-CRP-RpoS pathway. In a mouse intestinal colonization experiment, our data showed that V.cholerae degS, rpoE, and rpoS gene deletions were associated with significantly reduced resistance to oxidative stress and the ability to colonize the mouse intestine. In conclusion, these findings provide new insights into the regulation of antioxidant activity by V.cholerae DegS.
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Affiliation(s)
- Kaiying Wang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Huifang Lu
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Mei Zou
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Guangli Wang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Jiajun Zhao
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Xiaoyu Huang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Fangyu Ren
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Huaqin Hu
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Jian Huang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
| | - Xun Min
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China
- School of Laboratory Medicine, Zunyi Medical University, Zunyi, Guizhou, China
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Zhang J, Zheng M, Tang Z, Zhong S, Bu T, Li Q. The Regulatory Functions of the Multiple Alternative Sigma Factors RpoE, RpoHI, and RpoHII Depend on the Growth Phase in Rhodobacter sphaeroides. Microorganisms 2023; 11:2678. [PMID: 38004690 PMCID: PMC10673084 DOI: 10.3390/microorganisms11112678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 10/26/2023] [Accepted: 10/27/2023] [Indexed: 11/26/2023] Open
Abstract
Bacterial growth, under laboratory conditions or in a natural environment, goes through different growth phases. Some gene expressions are regulated with respect to the growth phase, which allows bacteria to adapt to changing conditions. Among them, many gene transcriptions are controlled by RpoHI or RpoHII in Rhodobacter sphaeroides. In a previous study, it was proven that the alternative sigma factors, RpoE, RpoHI, and RpoHII, are the major regulators of oxidative stress. Moreover, the growth of bacteria reached a stationary phase, and following the outgrowth, rpoE, rpoHI, and rpoHII mRNAs increased with respect to the growth phase. In this study, we demonstrated the regulatory function of alternative sigma factors in the rsp_0557 gene. The gene rsp_0557 is expressed with respect to the growth phase and belongs to the RpoHI/RpoHII regulons. Reporter assays showed that the antisigma factor ChrR turns on or over the RpoE activity to regulate rsp_0557 expression across the growth phase. In the exponential phase, RpoHII and sRNA Pos19 regulate the expression of rsp_0557 to an appropriate level under RpoE control. In the stationary phase, RpoHI and Pos19 stabilize the transcription of rsp_0557 at a high level. During outgrowth, RpoHI negatively regulates the transcription of rsp_0557. Taken together, our data indicate that these regulators are recruited by cells to adapt to or survive under different conditions throughout the growth phase. However, they still did not display all of the regulators involved in growth phase-dependent regulation. More research is still needed to learn more about the interaction between the regulators and the process of adapting to changed growth conditions and environments.
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Affiliation(s)
| | | | | | | | | | - Qingfeng Li
- College of Life Sciences, Sichuan Agricultural University, Ya’an 625014, China; (J.Z.); (M.Z.); (Z.T.); (S.Z.); (T.B.)
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Wang J, Yang Z, Wang G, Shang S, Tang X, Xiao H. Diversity of epiphytic bacterial communities on male and female Sargassum thunbergii. AMB Express 2022; 12:97. [PMID: 35841460 PMCID: PMC9288574 DOI: 10.1186/s13568-022-01439-1] [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: 03/04/2022] [Accepted: 07/11/2022] [Indexed: 11/22/2022] Open
Abstract
The epiphytic bacteria are the most abundant microorganisms on marine macroalga. However, there are few studies on the distribution of these epiphytic bacteria on male and female Sargassum thunbergii. In this study, the composition and diversity of epiphytic bacterial communities on male and female S. thunbergii were investigated by using the traditional culture-based method and 16S rDNA high-throughput sequencing. The results showed that the dominant bacterial phyla and genera were the same on both male and female S. thunbergii. However, there were significant differences in the relative abundance of epiphytic bacteria at the genus level. Furthermore, male and female S. thunbergii had their own indicative species and specific bacteria. In addition, the predicted functions of the epiphytic bacteria mainly differed in transport and metabolism, environmental adaptation and spore development. This study enriches the baseline knowledge of epiphytic bacteria related to dioecious algae and paves the way for further studies of the relationships between epiphytic microbial communities and the sex of algae.
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Affiliation(s)
- Jing Wang
- College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Zhibo Yang
- College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Gaoge Wang
- College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Shuai Shang
- College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China.,College of Biological and Environmental Engineering, Binzhou University, Binzhou, 256600, China
| | - Xuexi Tang
- College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China.,Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266000, China
| | - Hui Xiao
- College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China. .,Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266000, China.
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Lakey BD, Myers KS, Alberge F, Mettert EL, Kiley PJ, Noguera DR, Donohue TJ. The essential Rhodobacter sphaeroides CenKR two-component system regulates cell division and envelope biosynthesis. PLoS Genet 2022; 18:e1010270. [PMID: 35767559 PMCID: PMC9275681 DOI: 10.1371/journal.pgen.1010270] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 07/12/2022] [Accepted: 05/20/2022] [Indexed: 12/13/2022] Open
Abstract
Bacterial two-component systems (TCSs) often function through the detection of an extracytoplasmic stimulus and the transduction of a signal by a transmembrane sensory histidine kinase. This kinase then initiates a series of reversible phosphorylation modifications to regulate the activity of a cognate, cytoplasmic response regulator as a transcription factor. Several TCSs have been implicated in the regulation of cell cycle dynamics, cell envelope integrity, or cell wall development in Escherichia coli and other well-studied Gram-negative model organisms. However, many α-proteobacteria lack homologs to these regulators, so an understanding of how α-proteobacteria orchestrate extracytoplasmic events is lacking. In this work we identify an essential TCS, CenKR (Cell envelope Kinase and Regulator), in the α-proteobacterium Rhodobacter sphaeroides and show that modulation of its activity results in major morphological changes. Using genetic and biochemical approaches, we dissect the requirements for the phosphotransfer event between CenK and CenR, use this information to manipulate the activity of this TCS in vivo, and identify genes that are directly and indirectly controlled by CenKR in Rb. sphaeroides. Combining ChIP-seq and RNA-seq, we show that the CenKR TCS plays a direct role in maintenance of the cell envelope, regulates the expression of subunits of the Tol-Pal outer membrane division complex, and indirectly modulates the expression of peptidoglycan biosynthetic genes. CenKR represents the first TCS reported to directly control the expression of Tol-Pal machinery genes in Gram-negative bacteria, and we predict that homologs of this TCS serve a similar function in other closely related organisms. We propose that Rb. sphaeroides genes of unknown function that are directly regulated by CenKR play unknown roles in cell envelope biosynthesis, assembly, and/or remodeling in this and other α-proteobacteria. The bacterial cell envelope is home to an array of important functions including energy conservation, motility, influx/efflux of nutrients and toxins, modulation of cell morphology and division, cell-cell interaction, and biofilm formation. Consequently, it is a major target of antibiotics and antimicrobial agents that inhibit these essential processes. Key to the recognition of environmental stressors or stimuli are bacterial TCSs, however systems that monitor or directly regulate cell envelope assembly and homeostasis are not widely conserved amongst bacteria. Here, we use Rhodobacter sphaeroides as a model to investigate the function of the CenKR TCS in this and other α-proteobacteria. We show that this essential TCS plays a key role in maintenance of the cell envelope through the regulation of outer membrane integrity and division, cell wall remodeling and homeostasis, and an alternate sigma factor that controls global cellular stress response. We provide evidence that this TCS and its function is widely conserved in α-proteobacteria and identify genes of unknown function as candidates for the study of cell envelope assembly in this and related bacteria.
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Affiliation(s)
- Bryan D. Lakey
- Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Kevin S. Myers
- Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - François Alberge
- Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Erin L. Mettert
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Patricia J. Kiley
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Daniel R. Noguera
- Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Timothy J. Donohue
- Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail:
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Adnan F, Jalil A, Ahmed T, Rahman A, Dawood N, Haider G, Siddiqui MF, Rostock L, Guenther S, Schaufler K. TRAP transporter TakP: a key player in the resistance against selenite-induced oxidative stress in Rhodobacter sphaeroides. Microbiol Res 2021; 252:126828. [PMID: 34543948 DOI: 10.1016/j.micres.2021.126828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 03/28/2021] [Accepted: 07/20/2021] [Indexed: 11/24/2022]
Abstract
Almost one-third of all proteins require metal ions as an essential component in key biological processes and approximately half of all enzymes are associated with one or more metal ions. The naturally occurring selenium is very toxic at higher levels, but few bacteria can reduce it into the less toxic insoluble elemental selenium. Selenium is required for the synthesis of selenocysteine, an essential residue involved in the active sites of various enzymes. The purple non-sulphur bacteria, Rhodobacter sphaeroidesis demonstrated for its selenite reduction capacity. The exact mechanism of selenite toxicity is unknown but it reacts with glutathione to form selenodiglutathione, producing the highly toxic compounds namely, H2O2and O2-. A R. sphaeroidesstrain with mutated takP gene, a member of the TRAP (tripartite ATP-independent periplasmic) family of transporter, was reported to be showing more resistance towards selenite in the growth medium but the reason for the resistance is unknown. TRAP transporters are the best-studied family of substrate-binding protein and in our previous study it was confirmed that the gene takP in R. sphaeroides is down-regulated by a small non-coding RNA SorY, providing more resistance to the bacterium against the oxidative stress. By comparative growth analysis and sensitivity assays in the presence of 2 mM selenite, it was observed that the SorY knockout strain is more sensitive to selenite while overexpression of the sRNA conferred more resistance to the bacterium like the takP mutant strain. TakP is involved in the import of malate into the cell, which under oxidative stress needs to be down-regulated to limit malate flux into the cell. Limited malate flux leads to metabolic rearrangements in the cell to avoid excessive generation of prooxidant NADH and facilitate constant generation of antioxidant NADPH. In the presence and absence of selenite, a drastic increase in the NADPH and decrease in the NADH levels are reported respectively. Accumulation of metallic selenium in the cytoplasm was detected via atomic absorption spectrophotometer and our analysis clearly demonstrated the presence of more selenium in the electron micrographs of the SorY knockout strain compared to the takP mutant grown under dark semi-aerobic growth conditions in the presence of selenite. Hence based on our analysis, it is confirmed that lack of TakP transporter led to reduced selenite influx into the cytoplasm, relieving cells with limited generation of ROS, eventually exhibiting more resistance against selenite-induced oxidative stress.
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Affiliation(s)
- Fazal Adnan
- Atta ur Rahman School of Applied Biosciences (ASAB), National University of Sciences & Technology (NUST), Islamabad, Pakistan.
| | - Amna Jalil
- Atta ur Rahman School of Applied Biosciences (ASAB), National University of Sciences & Technology (NUST), Islamabad, Pakistan.
| | - Tahir Ahmed
- Atta ur Rahman School of Applied Biosciences (ASAB), National University of Sciences & Technology (NUST), Islamabad, Pakistan.
| | - Afra Rahman
- Atta ur Rahman School of Applied Biosciences (ASAB), National University of Sciences & Technology (NUST), Islamabad, Pakistan.
| | - Nawal Dawood
- Atta ur Rahman School of Applied Biosciences (ASAB), National University of Sciences & Technology (NUST), Islamabad, Pakistan.
| | - Ghulam Haider
- Atta ur Rahman School of Applied Biosciences (ASAB), National University of Sciences & Technology (NUST), Islamabad, Pakistan.
| | | | - Leon Rostock
- Institute of Pharmacy, Pharmaceutical Biology, University of Greifswald, Germany.
| | - Sebastian Guenther
- Institute of Pharmacy, Pharmaceutical Biology, University of Greifswald, Germany.
| | - Katharina Schaufler
- Institute of Pharmacy, Pharmaceutical Microbiology, University of Greifswald, Germany; Institute of infection medicine, Kiel University, Germany.
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Prognostic factors in adult brainstem glioma: a tertiary care center analysis and review of the literature. J Neurol 2021; 269:1574-1590. [PMID: 34342680 PMCID: PMC8857120 DOI: 10.1007/s00415-021-10725-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 07/22/2021] [Accepted: 07/24/2021] [Indexed: 11/24/2022]
Abstract
Introduction Adult brainstem gliomas (BSGs) are rare central nervous system tumours characterized by a highly heterogeneous clinical course. Median survival times range from 11 to 84 months. Beyond surgery, no treatment standard has been established. We investigated clinical and radiological data to assess prognostic features providing support for treatment decisions. Methods 34 BSG patients treated between 2000 and 2019 and aged ≥ 18 years at the time of diagnosis were retrospectively identified from the databases of the two largest Austrian Neuro-Oncology centres. Clinical data including baseline characteristics, clinical disease course, applied therapies, the outcome as well as neuroradiological and neuropathological findings were gathered and analysed. The tumour apparent diffusion coefficient (ADC), volumetry of contrast-enhancing and non-contrast-enhancing lesions were determined on magnetic resonance imaging scans performed at diagnosis. Results The median age at diagnosis was 38.5 years (range 18–71 years). Tumour progression occurred in 26/34 (76.5%) patients after a median follow up time of 19 months (range 0.9–236.2). Median overall survival (OS) and progression-free survival (PFS) was 24.1 months (range 0.9–236.2; 95% CI 18.1–30.1) and 14.5 months (range 0.7–178.5; 95% CI 5.1–23.9), respectively. Low-performance status, high body mass index (BMI) at diagnosis and WHO grading were associated with shorter PFS and OS at univariate analysis (p < 0.05, log rank test, respectively). ADC values below the median were significantly associated with shorter OS (14.9 vs 44.2 months, p = 0.018). Conclusion ECOG, BMI, WHO grade and ADC values were associated with the survival prognosis of BSG patients and should be included in the prognostic assessment.
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Eisenhardt KMH, Remes B, Grützner J, Spanka DT, Jäger A, Klug G. A Complex Network of Sigma Factors and sRNA StsR Regulates Stress Responses in R. sphaeroides. Int J Mol Sci 2021; 22:ijms22147557. [PMID: 34299177 PMCID: PMC8307010 DOI: 10.3390/ijms22147557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 07/01/2021] [Accepted: 07/09/2021] [Indexed: 11/16/2022] Open
Abstract
Adaptation of bacteria to a changing environment is often accompanied by remodeling of the transcriptome. In the facultative phototroph Rhodobacter sphaeroides the alternative sigma factors RpoE, RpoHI and RpoHII play an important role in a variety of stress responses, including heat, oxidative stress and nutrient limitation. Photooxidative stress caused by the simultaneous presence of chlorophylls, light and oxygen is a special challenge for phototrophic organisms. Like alternative sigma factors, several non-coding sRNAs have important roles in the defense against photooxidative stress. RNAseq-based transcriptome data pointed to an influence of the stationary phase-induced StsR sRNA on levels of mRNAs and sRNAs with a role in the photooxidative stress response. Furthermore, StsR also affects expression of photosynthesis genes and of genes for regulators of photosynthesis genes. In vivo and in vitro interaction studies revealed that StsR, that is under control of the RpoHI and RpoHII sigma factors, targets rpoE mRNA and affects its abundance by altering its stability. RpoE regulates expression of the rpoHII gene and, consequently, expression of stsR. These data provide new insights into a complex regulatory network of protein regulators and sRNAs involved in defense against photooxidative stress and the regulation of photosynthesis genes.
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Adaptation to Photooxidative Stress: Common and Special Strategies of the Alphaproteobacteria Rhodobacter sphaeroides and Rhodobacter capsulatus. Microorganisms 2020; 8:microorganisms8020283. [PMID: 32093084 PMCID: PMC7074977 DOI: 10.3390/microorganisms8020283] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 02/10/2020] [Accepted: 02/13/2020] [Indexed: 12/20/2022] Open
Abstract
Photosynthetic bacteria have to deal with the risk of photooxidative stress that occurs in presence of light and oxygen due to the photosensitizing activity of (bacterio-) chlorophylls. Facultative phototrophs of the genus Rhodobacter adapt the formation of photosynthetic complexes to oxygen and light conditions, but cannot completely avoid this stress if environmental conditions suddenly change. R. capsulatus has a stronger pigmentation and faster switches to phototrophic growth than R. sphaeroides. However, its photooxidative stress response has not been investigated. Here, we compare both species by transcriptomics and proteomics, revealing that proteins involved in oxidation-reduction processes, DNA, and protein damage repair play pivotal roles. These functions are likely universal to many phototrophs. Furthermore, the alternative sigma factors RpoE and RpoHII are induced in both species, even though the genetic localization of the rpoE gene, the RpoE protein itself, and probably its regulon, are different. Despite sharing the same habitats, our findings also suggest individual strategies. The crtIB-tspO operon, encoding proteins for biosynthesis of carotenoid precursors and a regulator of photosynthesis, and cbiX, encoding a putative ferrochelatase, are induced in R. capsulatus. This specific response might support adaptation by maintaining high carotenoid-to-bacteriochlorophyll ratios and preventing the accumulation of porphyrin-derived photosensitizers.
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Abstract
This year marks the 50th anniversary of the discovery of σ70 as a protein factor that was needed for bacterial RNA polymerase to accurately transcribe a promoter in vitro. It was 25 years later that the Group IV alternative σs were described as a distinct family of proteins related to σ70 . In the intervening time, there has been an ever-growing list of Group IV σs, numbers of genes they transcribe, insight into the diverse suite of processes they control, and appreciation for their impact on bacterial lifestyles. This work summarizes knowledge of the Rhodobacter sphaeroides σE -ChrR pair, a member of the ECF11 subfamily of Group IV alternative σs, in protecting cells from the reactive oxygen species, singlet oxygen. It describes lessons learned from analyzing ChrR, a zinc-dependent anti-σ factor, that are generally applicable to Group IV σs and relevant to the response to single oxygen. This MicroReview also illustrates insights into stress responses in this and other bacteria that have been acquired by analyzing or modeling the activity of the σE -ChrR across the bacterial phylogeny.
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Affiliation(s)
- Timothy J. Donohue
- Bacteriology Department, Great Lakes Bioenergy Research CenterWisconsin Energy Institute, University of Wisconsin‐MadisonMadisonWI53726USA
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10
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Otero-Asman JR, Wettstadt S, Bernal P, Llamas MA. Diversity of extracytoplasmic function sigma (σ ECF ) factor-dependent signaling in Pseudomonas. Mol Microbiol 2019; 112:356-373. [PMID: 31206859 DOI: 10.1111/mmi.14331] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2019] [Indexed: 12/23/2022]
Abstract
Pseudomonas bacteria are widespread and are found in soil and water, as well as pathogens of both plants and animals. The ability of Pseudomonas to colonize many different environments is facilitated by the multiple signaling systems these bacteria contain that allow Pseudomonas to adapt to changing circumstances by generating specific responses. Among others, signaling through extracytoplasmic function σ (σECF ) factors is extensively present in Pseudomonas. σECF factors trigger expression of functions required under particular conditions in response to specific signals. This manuscript reviews the phylogeny and biological roles of σECF factors in Pseudomonas, and highlights the diversity of σECF -signaling pathways of this genus in terms of function and activation. We show that Pseudomonas σECF factors belong to 16 different phylogenetic groups. Most of them are included within the iron starvation group and are mainly involved in iron acquisition. The second most abundant group is formed by RpoE-like σECF factors, which regulate the responses to cell envelope stress. Other groups controlling solvent tolerance, biofilm formation and the response to oxidative stress, among other functions, are present in lower frequency. The role of σECF factors in the virulence of Pseudomonas pathogenic species is described.
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Affiliation(s)
- Joaquín R Otero-Asman
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Sarah Wettstadt
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Patricia Bernal
- Department of Biology, Faculty of Sciences, Universidad Autónoma de Madrid, Madrid, Spain
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
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11
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Zhao Z, Peng T, Oh JI, Glaeser J, Weber L, Li Q, Klug G. A response regulator of the OmpR family is part of the regulatory network controlling the oxidative stress response of Rhodobacter sphaeroides. ENVIRONMENTAL MICROBIOLOGY REPORTS 2019; 11:118-128. [PMID: 30451391 DOI: 10.1111/1758-2229.12718] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 11/12/2018] [Indexed: 06/09/2023]
Abstract
As a free-living bacterium Rhodobacter sphaeroides needs to respond to many environmental stresses. Oxidative stress, membrane stress or heat stress induce the ompR-1 gene encoding a protein of the OmpR family. Overexpression of OmpR-1 results in increased resistance to organic peroxides and diamide. Our data demonstrate that OmpR-1 positively affects expression of several sRNAs with an established role in R. sphaeroides stress defences and negatively affects the promoter of the rpoHI gene. The RpoHI sigma factor has a main role in the activation of many stress responses. Thus OmpR-1 has a balancing effect on the activation of the RpoHI regulon. We present a model with OmpR-1 as part of a regulatory network controlling stress defences in R. sphaeroides.
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Affiliation(s)
- Zhiping Zhao
- Institut für Mikrobiologie und Molekularbiologie, Interdiziplinäres Forschungszentrum, Justus-Liebig-Universität Giessen, Giessen, Germany
- Department of Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong, China
| | | | - Jeong-Il Oh
- Department of Microbiology, Pusan National University, Busan, South Korea
| | - Jens Glaeser
- Institut für Mikrobiologie und Molekularbiologie, Interdiziplinäres Forschungszentrum, Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Lennart Weber
- Institut für Mikrobiologie und Molekularbiologie, Interdiziplinäres Forschungszentrum, Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Qingfeng Li
- Institut für Mikrobiologie und Molekularbiologie, Interdiziplinäres Forschungszentrum, Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Gabriele Klug
- Institut für Mikrobiologie und Molekularbiologie, Interdiziplinäres Forschungszentrum, Justus-Liebig-Universität Giessen, Giessen, Germany
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12
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Peng T, Kan J, Lun J, Hu Z. Identification of novel sRNAs involved in oxidative stress response in the fish pathogen Vibrio alginolyticus by transcriptome analysis. JOURNAL OF FISH DISEASES 2019; 42:277-291. [PMID: 30488970 DOI: 10.1111/jfd.12926] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 10/23/2018] [Accepted: 10/25/2018] [Indexed: 06/09/2023]
Abstract
Vibrio alginolyticus as an important pathogen in aquaculture can encounter the oxidative stress produced by the immune system during infection. Previous studies showed that sRNAs have important functions in response to oxidative stress in bacteria; however, less of sRNAs related to oxidative stress response were identified in V. alginolyticus. In this study, a total of 749 novel sRNAs were identified by RNA sequencing; among them, 128 sRNAs were up- or downregulated in response to oxidative stress. In addition, 1,870 genes exhibited variation on mRNA levels in oxidative stress response. By analysing the target genes of the sRNAs, we concluded that these sRNAs could regulate expressions of genes responsible for iron transport, catalase, GSH-dependent defence system, electron transferred and stress response. Moreover, the functions of the sRNAs are also seemed related to the pathogenicity in V. alginolyticus. Based on the results, we constructed the oxidative stress model in V. alginolyticus. This study provides us the first outlook of sRNAs function in oxidative stress response in V. alginolyticus. Furthermore, this study can help us to prevent and control this important opportunistic pathogen in aquaculture.
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Affiliation(s)
- Tao Peng
- Department of Biology, Shantou University, Shantou, China
| | - Jie Kan
- Department of Biology, Shantou University, Shantou, China
| | - Jingsheng Lun
- Department of Biology, Shantou University, Shantou, China
| | - Zhong Hu
- Department of Biology, Shantou University, Shantou, China
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Amar A, Pezzoni M, Pizarro RA, Costa CS. New envelope stress factors involved in σ E activation and conditional lethality of rpoE mutations in Salmonella enterica. MICROBIOLOGY-SGM 2018; 164:1293-1307. [PMID: 30084765 DOI: 10.1099/mic.0.000701] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Salmonella enterica serovar Typhimurium (S. typhimurium) can cause food- and water-borne illness with diverse clinical manifestations. One key factor for S. typhimurium pathogenesis is the alternative sigma factor σE, which is encoded by the rpoE gene and controls the transcription of genes required for outer-membrane integrity in response to alterations in the bacterial envelope. The canonical pathway for σE activation involves proteolysis of the antisigma factor RseA, which is triggered by unfolded outer-membrane porins (OMPs) and lipopolysaccharides (LPS) that have accumulated in the periplasm. This study reports new stress factors that are able to activate σE expression. We demonstrate that UVA radiation induces σE activity in a pathway that is dependent on the stringent response regulator ppGpp. Survival assays revealed that rpoE has a role in the defence against lethal UVA doses that is mediated by functions that are dependent on and independent of the alternative sigma factor RpoS. We also report that the envelope stress generated by phage infection requires a functional rpoE gene for optimal bacterial tolerance and that it is able to induce σE activity in an RseA-dependent fashion. σE activity is also induced by hypo-osmotic shock in the absence of osmoregulated periplasmic glucans (OPGs). It is known that the rpoE gene is not essential in S. typhimurium. However, we report here two cases of the conditional lethality of rpoE mutations in this micro-organism. We demonstrate that rpoE mutations are not tolerated in the absence of OPGs (at low to moderate osmolarity) or LPS O-antigen. The latter case resembles that of the prototypic Escherichia coli strain K12, which neither synthesizes a complete LPS nor tolerates null rpoE mutations.
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Affiliation(s)
- Agustina Amar
- Dpto. de Radiobiología, Comisión Nacional de Energía Atómica, General San Martín, Argentina
| | - Magdalena Pezzoni
- Dpto. de Radiobiología, Comisión Nacional de Energía Atómica, General San Martín, Argentina
| | - Ramón A Pizarro
- Dpto. de Radiobiología, Comisión Nacional de Energía Atómica, General San Martín, Argentina
| | - Cristina S Costa
- Dpto. de Radiobiología, Comisión Nacional de Energía Atómica, General San Martín, Argentina
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Bol’shakov MA, Ashikhmin AA, Makhneva ZK, Moskalenko AA. Effect of Light with Different Spectral Composition on Cell Growth and Pigment Composition of the Membranes of Purple Sulfur Bacteria Allochromatium minutissimum and Allochromatium vinosum. Microbiology (Reading) 2018. [DOI: 10.1134/s0026261718020042] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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The PhyR homolog RSP_1274 of Rhodobacter sphaeroides is involved in defense of membrane stress and has a moderate effect on RpoE (RSP_1092) activity. BMC Microbiol 2018; 18:18. [PMID: 29486719 PMCID: PMC5830050 DOI: 10.1186/s12866-018-1161-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 02/20/2018] [Indexed: 11/10/2022] Open
Abstract
Background A major role of the PhyR-NepR-σ(EcfG) cascade in the general stress response was demonstrated for some bacterial species and considered as conserved in Alphaproteobacteria. The σ(EcfG) factor activates its target genes in response to diverse stresses and NepR represents its anti-sigma factor. PhyR comprises a response regulator domain and a sigma factor domain and acts as anti-sigma factor antagonist. The facultative phototrophic alphaproteobacterium Rhodobacter sphaeroides harbours a PhyR homolog in the same genomic context as found in other members of this class. Results Our study reveals increased expression of the phyR gene in response to superoxide, singlet oxygen, and diamide and also an effect of PhyR on rpoE expression. RpoE has a central role in mounting the response to singlet oxygen in R. sphaeroides. Despite these findings a mutant lacking PhyR was not significantly impeded in resistance to oxidative stress, heat stress or osmotic stress. However a role of PhyR in membrane stress is demonstrated. Conclusion These results support the view that the effect of the PhyR-NepR-σ(EcfG) cascade on diverse stress responses varies among members of the Alphaproteobacteria. In the facultative phototroph Rhodobacter sphaeroides PhyR plays no major role in the general stress or the oxidative stress response but rather has a more specialized role in defense of membrane stress. Electronic supplementary material The online version of this article (10.1186/s12866-018-1161-4) contains supplementary material, which is available to authorized users.
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Weber L, Thoelken C, Volk M, Remes B, Lechner M, Klug G. The Conserved Dcw Gene Cluster of R. sphaeroides Is Preceded by an Uncommonly Extended 5' Leader Featuring the sRNA UpsM. PLoS One 2016; 11:e0165694. [PMID: 27802301 PMCID: PMC5089854 DOI: 10.1371/journal.pone.0165694] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 10/17/2016] [Indexed: 11/18/2022] Open
Abstract
Cell division and cell wall synthesis mechanisms are similarly conserved among bacteria. Consequently some bacterial species have comparable sets of genes organized in the dcw (division andcellwall) gene cluster. Dcw genes, their regulation and their relative order within the cluster are outstandingly conserved among rod shaped and gram negative bacteria to ensure an efficient coordination of growth and division. A well studied representative is the dcw gene cluster of E. coli. The first promoter of the gene cluster (mraZ1p) gives rise to polycistronic transcripts containing a 38 nt long 5’ UTR followed by the first gene mraZ. Despite reported conservation we present evidence for a much longer 5’ UTR in the gram negative and rod shaped bacterium Rhodobacter sphaeroides and in the family of Rhodobacteraceae. This extended 268 nt long 5’ UTR comprises a Rho independent terminator, which in case of termination gives rise to a non-coding RNA (UpsM). This sRNA is conditionally cleaved by RNase E under stress conditions in an Hfq- and very likely target mRNA-dependent manner, implying its function in trans. These results raise the question for the regulatory function of this extended 5’ UTR. It might represent the rarely described case of a trans acting sRNA derived from a riboswitch with exclusive presence in the family of Rhodobacteraceae.
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Affiliation(s)
- Lennart Weber
- Institute of Microbiology and Molecular Biology, IFZ, Justus-Liebig-University Giessen, Giessen, Germany
| | - Clemens Thoelken
- Institute of Pharmaceutical Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Marcel Volk
- Institute of Microbiology and Molecular Biology, IFZ, Justus-Liebig-University Giessen, Giessen, Germany
| | - Bernhard Remes
- Institute of Microbiology and Molecular Biology, IFZ, Justus-Liebig-University Giessen, Giessen, Germany
| | - Marcus Lechner
- Institute of Pharmaceutical Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Gabriele Klug
- Institute of Microbiology and Molecular Biology, IFZ, Justus-Liebig-University Giessen, Giessen, Germany
- * E-mail:
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Müller KMH, Berghoff BA, Eisenhardt BD, Remes B, Klug G. Characteristics of Pos19 - A Small Coding RNA in the Oxidative Stress Response of Rhodobacter sphaeroides. PLoS One 2016; 11:e0163425. [PMID: 27669425 PMCID: PMC5036791 DOI: 10.1371/journal.pone.0163425] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 09/08/2016] [Indexed: 02/07/2023] Open
Abstract
The phototrophic bacterium Rhodobacter sphaeroides induces several small RNAs (sRNAs) when singlet oxygen (1O2) levels are elevated, a situation also referred to as photo-oxidative stress. An RNA-seq study identified the RSs0019 sRNA, which is renamed Pos19 (photo-oxidative stress induced sRNA 19). Pos19 is part of the RpoE regulon and consequently induced upon 1O2 and peroxide stress. The 219 nt long Pos19 transcript contains a small open reading frame (sORF) of 150 nt, which is translated in vivo. Over-expression of Pos19 results in reduced mRNA levels for several genes, of which numerous are involved in sulfur metabolism. The negative effect on the potential targets is maintained even when translation of the sORF is abolished, arguing that regulation is entailed by the sRNA itself. Reporter studies further revealed that regulation of the most affected mRNA, namely RSP_0557, by Pos19 is Hfq-dependent. Direct binding of Pos19 to Hfq was shown by co-immunoprecipitation. Physiological experiments indicated Pos19 to be involved in the balance of glutathione biosynthesis. Moreover, a lack of Pos19 leads to elevated reactive oxygen species levels. Taken together our data identify the sRNA Pos19 as a coding sRNA with a distinct expression pattern and potential role under oxidative stress in the phototrophic bacterium R. sphaeroides.
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Affiliation(s)
- Katrin M. H. Müller
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität, Heinrich-Buff-Ring 26, 35392, Giessen, Germany
| | - Bork A. Berghoff
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität, Heinrich-Buff-Ring 26, 35392, Giessen, Germany
| | - Benjamin D. Eisenhardt
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität, Heinrich-Buff-Ring 26, 35392, Giessen, Germany
| | - Bernhard Remes
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität, Heinrich-Buff-Ring 26, 35392, Giessen, Germany
| | - Gabriele Klug
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität, Heinrich-Buff-Ring 26, 35392, Giessen, Germany
- * E-mail:
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Peng T, Berghoff BA, Oh JI, Weber L, Schirmer J, Schwarz J, Glaeser J, Klug G. Regulation of a polyamine transporter by the conserved 3' UTR-derived sRNA SorX confers resistance to singlet oxygen and organic hydroperoxides in Rhodobacter sphaeroides. RNA Biol 2016; 13:988-999. [PMID: 27420112 DOI: 10.1080/15476286.2016.1212152] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Singlet oxygen is generated by bacteriochlorophylls when light and oxygen are simultaneously present in Rhodobacter sphaeroides. Singlet oxygen triggers a specific response that is partly regulated by the alternative sigma factor RpoHI/HII. The sRNA RSs2461 has previously been identified as an RpoHI/HII-dependent sRNA and is derived from the 3' UTR of the mRNA for an OmpR-type transcriptional regulator. Similar to the RpoHI/HII-dependent CcsR and SorY sRNAs, RSs2461 affects the resistance of R. sphaeroides against singlet oxygen and was therefore renamed here SorX. Furthermore, SorX has a strong impact on resistance against organic hydroperoxides that usually occur as secondary damages downstream of singlet oxygen. The 75-nt SorX 3' fragment, which is generated by RNase E cleavage and highly conserved among related species, represents the functional entity. A target search identified potA mRNA, which encodes a subunit of a polyamine transporter, as a direct SorX target and stress resistance via SorX could be linked to potA. The PotABCD transporter is an uptake system for spermidine in E. coli. While spermidine is generally described as beneficial during oxidative stress, we observed significantly increased sensitivity of R. sphaeroides to organic hydroperoxides in the presence of spermidine. We therefore propose that the diminished import of spermidine, due to down-regulation of potA by SorX, counteracts oxidative stress. Together with results from other studies this underlines the importance of regulated transport to bacterial stress defense.
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Affiliation(s)
- Tao Peng
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Bork A Berghoff
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Jeong-Il Oh
- b Department of Microbiology , Pusan National University , Busan , Korea
| | - Lennart Weber
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Jasmin Schirmer
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Johannes Schwarz
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Jens Glaeser
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Gabriele Klug
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
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Makhneva ZK, Ashikhmin AA, Bolshakov MA, Moskalenko AA. 3-Acetyl-chlorophyll formation in light-harvesting complexes of purple bacteria by chemical oxidation. BIOCHEMISTRY (MOSCOW) 2016; 81:176-86. [DOI: 10.1134/s0006297916020115] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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20
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Adnan F, Weber L, Klug G. The sRNA SorY confers resistance during photooxidative stress by affecting a metabolite transporter in Rhodobacter sphaeroides. RNA Biol 2016; 12:569-77. [PMID: 25833751 PMCID: PMC4615379 DOI: 10.1080/15476286.2015.1031948] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Exposure to oxygen and light generates photooxidative stress by the bacteriochlorophyll a mediated formation of singlet oxygen (1O2) in the facultative photosynthetic bacterium Rhodobacter sphaeroides. We have identified SorY as an sRNA, which is induced under several stress conditions and confers increased resistance against 1O2. SorY by direct interaction affects the takP mRNA, encoding a TRAP-T transporter. We present a model in which SorY reduces the metabolite flux into the tricarboxylic acid cycle (TCA cycle) by reducing malate import through TakP. It was previously shown that oxidative stress in bacteria leads to switch from glycolysis to the pentose phosphate pathway and to reduced activity of the TCA cycle. As a consequence the production of the prooxidant NADH is reduced and production of the protective NADPH is enhanced. In R. sphaeroides enzymes for glycolysis, pentose phosphate pathway, Entner–Doudoroff pathway and gluconeogenesis are induced in response to 1O2 by the alternative sigma factor RpoHII. The same is true for the sRNA SorY. By limiting malate import SorY thus contributes to the balance of the metabolic fluxes under photooxidative stress conditions. This assigns a so far unknown function to an sRNA in oxidative stress response.
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Affiliation(s)
- Fazal Adnan
- a Institute of Microbiology and Molecular Biology ; IFZ ; Giessen University ; Giessen , Germany
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Laloi C, Havaux M. Key players of singlet oxygen-induced cell death in plants. FRONTIERS IN PLANT SCIENCE 2015; 6:39. [PMID: 25699067 PMCID: PMC4316694 DOI: 10.3389/fpls.2015.00039] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 01/15/2015] [Indexed: 05/03/2023]
Abstract
The production of reactive oxygen species (ROS) is an unavoidable consequence of oxygenic photosynthesis. Singlet oxygen ((1)O2) is a highly reactive species to which has been attributed a major destructive role during the execution of ROS-induced cell death in photosynthetic tissues exposed to excess light. The study of the specific biological activity of (1)O2 in plants has been hindered by its high reactivity and short lifetime, the concurrent production of other ROS under photooxidative stress, and limited in vivo detection methods. However, during the last 15 years, the isolation and characterization of two (1)O2-overproducing mutants in Arabidopsis thaliana, flu and ch1, has allowed the identification of genetically controlled (1)O2 cell death pathways and a (1)O2 acclimation pathway that are triggered at sub-cytotoxic concentrations of (1)O2. The study of flu has revealed the control of cell death by the plastid proteins EXECUTER (EX)1 and EX2. In ch1, oxidized derivatives of β-carotene, such as β-cyclocitral and dihydroactinidiolide, have been identified as important upstream messengers in the (1)O2 signaling pathway that leads to stress acclimation. In both the flu and ch1 mutants, phytohormones act as important promoters or inhibitors of cell death. In particular, jasmonate has emerged as a key player in the decision between acclimation and cell death in response to (1)O2. Although the flu and ch1 mutants show many similarities, especially regarding their gene expression profiles, key differences, such as EXECUTER-independent cell death in ch1, have also been observed and will need further investigation to be fully understood.
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Affiliation(s)
- Christophe Laloi
- Laboratoire de Génétique et Biophysique des Plantes, Institut de Biologie Environnementale et Biotechnologie, Commissariat à l’Énergie Atomique et aux Énergies AlternativesMarseille, France
- CNRS, UMR 7265 Biologie Végétale et Microbiologie EnvironnementalesMarseille, France
- Aix Marseille UniversitéMarseille, France
- *Correspondence: Christophe Laloi, Laboratoire de Génétique et Biophysique des Plantes, Institut de Biologie Environnementale et Biotechnologie, Commissariat à l’Énergie Atomique et aux nergies Alternatives, F -13009 Marseille, France e-mail: ; Michel Havaux, Laboratoire d’Ecophysiologie Moléculaire des Plantes, Institut de Biologie Environnementale et Biotechnologie, Commissariat à l’Énergie Atomique et aux Énergies Alternatives, F-13108 Saint-Paul-lez-Durance, France e-mail:
| | - Michel Havaux
- CNRS, UMR 7265 Biologie Végétale et Microbiologie EnvironnementalesMarseille, France
- Aix Marseille UniversitéMarseille, France
- Laboratoire d’Ecophysiologie Moléculaire des Plantes, Institut de Biologie Environnementale et Biotechnologie, Commissariat à l’Énergie Atomique et aux Énergies AlternativesSaint-Paul-lez-Durance, France
- *Correspondence: Christophe Laloi, Laboratoire de Génétique et Biophysique des Plantes, Institut de Biologie Environnementale et Biotechnologie, Commissariat à l’Énergie Atomique et aux nergies Alternatives, F -13009 Marseille, France e-mail: ; Michel Havaux, Laboratoire d’Ecophysiologie Moléculaire des Plantes, Institut de Biologie Environnementale et Biotechnologie, Commissariat à l’Énergie Atomique et aux Énergies Alternatives, F-13108 Saint-Paul-lez-Durance, France e-mail:
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Abstract
Fatty acids play important functional and protective roles in living systems. This paper reports on the synthesis of a previously unidentified 19 carbon furan-containing fatty acid, 10,13-epoxy-11-methyl-octadecadienoate (9-(3-methyl-5-pentylfuran-2-yl)nonanoic acid) (19Fu-FA), in phospholipids from Rhodobacter sphaeroides. We show that 19Fu-FA accumulation is increased in cells containing mutations that increase the transcriptional response of this bacterium to singlet oxygen ((1)O2), a reactive oxygen species generated by energy transfer from one or more light-excited donors to molecular oxygen. We identify a previously undescribed class of S-adenosylmethionine-dependent methylases that convert a phospholipid 18 carbon cis unsaturated fatty acyl chain to a 19 carbon methylated trans unsaturated fatty acyl chain (19M-UFA). We also identify genes required for the O2-dependent conversion of this 19M-UFA to 19Fu-FA. Finally, we show that the presence of (1)O2 leads to turnover of 19Fu-Fa in vivo. We propose that furan-containing fatty acids like 19Fu-FA can act as a membrane-bound scavenger of (1)O2, which is naturally produced by integral membrane enzymes of the R. sphaeroides photosynthetic apparatus.
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