Bacillus methanolicus sp. nov., a new species of thermotolerant, methanol-utilizing, endospore-forming bacteria

Prokaryotic Life Associated with Coal-Fire Gas Vents Revealed by Metagenomics

The natural combustion of underground coal seams leads to the formation of gas, which contains molecular hydrogen and carbon monoxide. In places where hot coal gases are released to the surface, specific thermal ecosystems are formed. Here, 16S rRNA gene profiling and shotgun metagenome sequencing were employed to characterize the taxonomic diversity and genetic potential of prokaryotic communities of the near-surface ground layer near hot gas vents in an open quarry heated by a subsurface coal fire. The communities were dominated by only a few groups of spore-forming Firmicutes, namely the aerobic heterotroph Candidatus Carbobacillus altaicus, the aerobic chemolitoautotrophs Kyrpidia tusciae and Hydrogenibacillus schlegelii, and the anaerobic chemolithoautotroph Brockia lithotrophica. Genome analysis predicted that these species can obtain energy from the oxidation of hydrogen and/or carbon monoxide in coal gases. We assembled the first complete closed genome of a member of uncultured class-level division DTU015 in the phylum Firmicutes. This bacterium, 'Candidatus Fermentithermobacillus carboniphilus' Bu02, was predicted to be rod-shaped and capable of flagellar motility and sporulation. Genome analysis showed the absence of aerobic and anaerobic respiration and suggested chemoheterotrophic lifestyle with the ability to ferment peptides, amino acids, N-acetylglucosamine, and tricarboxylic acid cycle intermediates. Bu02 bacterium probably plays the role of a scavenger, performing the fermentation of organics formed by autotrophic Firmicutes supported by coal gases. A comparative genome analysis of the DTU015 division revealed that most of its members have a similar lifestyle.

Interrogating the Role of the Two Distinct Fructose-Bisphosphate Aldolases of Bacillus methanolicus by Site-Directed Mutagenesis of Key Amino Acids and Gene Repression by CRISPR Interference

The Gram-positive Bacillus methanolicus shows plasmid-dependent methylotrophy. This facultative ribulose monophosphate (RuMP) cycle methylotroph possesses two fructose bisphosphate aldolases (FBA) with distinct kinetic properties. The chromosomally encoded FBA^C is the major glycolytic aldolase. The gene for the major gluconeogenic aldolase FBA^P is found on the natural plasmid pBM19 and is induced during methylotrophic growth. The crystal structures of both enzymes were solved at 2.2 Å and 2.0 Å, respectively, and they suggested amino acid residue 51 to be crucial for binding fructose-1,6-bisphosphate (FBP) as substrate and amino acid residue 140 for active site zinc atom coordination. As FBA^C and FBA^P differed at these positions, site-directed mutagenesis (SDM) was performed to exchange one or both amino acid residues of the respective proteins. The aldol cleavage reaction was negatively affected by the amino acid exchanges that led to a complete loss of glycolytic activity of FBA^P. However, both FBA^C and FBA^P maintained gluconeogenic aldol condensation activity, and the amino acid exchanges improved the catalytic efficiency of the major glycolytic aldolase FBA^C in gluconeogenic direction at least 3-fold. These results confirmed the importance of the structural differences between FBA^C and FBA^P concerning their distinct enzymatic properties. In order to investigate the physiological roles of both aldolases, the expression of their genes was repressed individually by CRISPR interference (CRISPRi). The fba ^C RNA levels were reduced by CRISPRi, but concomitantly the fba ^P RNA levels were increased. Vice versa, a similar compensatory increase of the fba ^C RNA levels was observed when fba ^P was repressed by CRISPRi. In addition, targeting fba ^P decreased tkt ^P RNA levels since both genes are cotranscribed in a bicistronic operon. However, reduced tkt ^P RNA levels were not compensated for by increased RNA levels of the chromosomal transketolase gene tkt ^C.

Enhanced Glutamate Synthesis and Export by the Thermotolerant Emerging Industrial Workhorse Bacillus methanolicus in Response to High Osmolarity

The thermotolerant methylotroph Bacillus methanolicus MGA3 was originally isolated from freshwater marsh soil. Due to its ability to use methanol as sole carbon and energy source, B. methanolicus is increasingly explored as a cell factory for the production of amino acids, fine chemicals, and proteins of biotechnological interest. During high cell density fermentation in industrial settings with the membrane-permeable methanol as the feed, the excretion of low molecular weight products synthesized from it will increase the osmotic pressure of the medium. This in turn will impair cell growth and productivity of the overall biotechnological production process. With this in mind, we have analyzed the core of the physiological adjustment process of B. methanolicus MGA3 to sustained high osmolarity surroundings. Through growth assays, we found that B. methanolicus MGA3 possesses only a restricted ability to cope with sustained osmotic stress. This finding is consistent with the ecophysiological conditions in the habitat from which it was originally isolated. None of the externally provided compatible solutes and proline-containing peptides affording osmostress protection for Bacillus subtilis were able to stimulate growth of B. methanolicus MGA3 at high salinity. B. methanolicus MGA3 synthesized the moderately effective compatible solute L-glutamate in a pattern such that the cellular pool increased concomitantly with increases in the external osmolarity. Counterintuitively, a large portion of the newly synthesized L-glutamate was excreted. The expression of the genes (gltAB and gltA2) for two L-glutamate synthases were upregulated in response to high salinity along with that of the gltC regulatory gene. Such a regulatory pattern of the system(s) for L-glutamate synthesis in Bacilli is new. Our findings might thus be generally relevant to understand the production of the osmostress protectant L-glutamate by those Bacilli that exclusively rely on this compatible solute for their physiological adjustment to high osmolarity surroundings.

Beyond alcohol oxidase: the methylotrophic yeast Komagataella phaffii utilizes methanol also with its native alcohol dehydrogenase Adh2

Methylotrophic yeasts are considered to use alcohol oxidases to assimilate methanol, different to bacteria which employ alcohol dehydrogenases with better energy conservation. The yeast Komagataella phaffii carries two genes coding for alcohol oxidase, AOX1 and AOX2. The deletion of the AOX1 leads to the Mut^S phenotype and the deletion of AOX1 and AOX2 to the Mut^– phenotype. The Mut^– phenotype is commonly regarded as unable to utilize methanol. In contrast to the literature, we found that the Mut^– strain can consume methanol. This ability was based on the promiscuous activity of alcohol dehydrogenase Adh2, an enzyme ubiquitously found in yeast and normally responsible for ethanol consumption and production. Using ¹³C labeled methanol as substrate we could show that to the largest part methanol is dissimilated to CO₂ and a small part is incorporated into metabolites, the biomass, and the secreted recombinant protein. Overexpression of the ADH2 gene in K. phaffii Mut^– increased both the specific methanol uptake rate and recombinant protein production, even though the strain was still unable to grow. These findings imply that thermodynamic and kinetic constraints of the dehydrogenase reaction facilitated the evolution towards alcohol oxidase-based methanol metabolism in yeast.

Establishment of a functional system for recombinant production of secreted proteins at 50 °C in the thermophilic Bacillus methanolicus

BACKGROUND

The suitability of bacteria as microbial cell factories is dependent on several factors such as price of feedstock, product range, production yield and ease of downstream processing. The facultative methylotroph Bacillus methanolicus is gaining interest as a thermophilic cell factory for production of value-added products from methanol. The aim of this study was to expand the capabilities of B. methanolicus as a microbial cell factory by establishing a system for secretion of recombinant proteins.

RESULTS

Native and heterologous signal peptides were tested for secretion of α-amylases and proteases, and we have established the use of the thermostable superfolder green fluorescent protein (sfGFP) as a valuable reporter protein in B. methanolicus. We demonstrated functional production and secretion of recombinant proteases, α-amylases and sfGFP in B. methanolicus MGA3 at 50 °C and showed that the choice of signal peptide for optimal secretion efficiency varies between proteins. In addition, we showed that heterologous production and secretion of α-amylase from Geobacillus stearothermophilus enables B. methanolicus to grow in minimal medium with starch as the sole carbon source. An in silico signal peptide library consisting of 169 predicted peptides from B. methanolicus was generated and will be useful for future studies, but was not experimentally investigated any further here.

CONCLUSION

A functional system for recombinant production of secreted proteins at 50 °C has been established in the thermophilic B. methanolicus. In addition, an in silico signal peptide library has been generated, that together with the tools and knowledge presented in this work will be useful for further development of B. methanolicus as a host for recombinant protein production and secretion at 50 °C.

Production of Value-Added Chemicals by Bacillus methanolicus Strains Cultivated on Mannitol and Extracts of Seaweed Saccharina latissima at 50°C

The facultative methylotroph Bacillus methanolicus MGA3 has previously been genetically engineered to overproduce the amino acids L-lysine and L-glutamate and their derivatives cadaverine and γ-aminobutyric acid (GABA) from methanol at 50°C. We here explored the potential of utilizing the sugar alcohol mannitol and seaweed extract (SWE) containing mannitol, as alternative feedstocks for production of chemicals by fermentation using B. methanolicus. Extracts of the brown algae Saccharina latissima harvested in the Trondheim Fjord in Norway were prepared and found to contain 12–13 g/l of mannitol, with conductivities corresponding to a salt content of ∼2% NaCl. Initially, 12 B. methanolicus wild type strains were tested for tolerance to various SWE concentrations, and some strains including MGA3 could grow on 50% SWE medium. Non-methylotrophic and methylotrophic growth of B. methanolicus rely on differences in regulation of metabolic pathways, and we compared production titers of GABA and cadaverine under such growth conditions. Shake flask experiments showed that recombinant MGA3 strains could produce similar and higher titers of cadaverine during growth on 50% SWE and mannitol, compared to on methanol. GABA production levels under these conditions were however low compared to growth on methanol. We present the first fed-batch mannitol fermentation of B. methanolicus and production of 6.3 g/l cadaverine. Finally, we constructed a recombinant MGA3 strain synthesizing the C30 terpenoids 4,4′-diaponeurosporene and 4,4′-diapolycopene, experimentally confirming that B. methanolicus has a functional methylerythritol phosphate (MEP) pathway. Together, our results contribute to extending the range of both the feedstocks for growth and products that can be synthesized by B. methanolicus.

Transaldolase in Bacillus methanolicus: biochemical characterization and biological role in ribulose monophosphate cycle

BACKGROUND

The Gram-positive facultative methylotrophic bacterium Bacillus methanolicus uses the sedoheptulose-1,7-bisphosphatase (SBPase) variant of the ribulose monophosphate (RuMP) cycle for growth on the C₁ carbon source methanol. Previous genome sequencing of the physiologically different B. methanolicus wild-type strains MGA3 and PB1 has unraveled all putative RuMP cycle genes and later, several of the RuMP cycle enzymes of MGA3 have been biochemically characterized. In this study, the focus was on the characterization of the transaldolase (Ta) and its possible role in the RuMP cycle in B. methanolicus.

RESULTS

The Ta genes of B. methanolicus MGA3 and PB1 were recombinantly expressed in Escherichia coli, and the gene products were purified and characterized. The PB1 Ta protein was found to be active as a homodimer with a molecular weight of 54 kDa and displayed K_M of 0.74 mM and V_max of 16.3 U/mg using Fructose-6 phosphate as the substrate. In contrast, the MGA3 Ta gene, which encodes a truncated Ta protein lacking 80 amino acids at the N-terminus, showed no Ta activity. Seven different mutant genes expressing various full-length MGA3 Ta proteins were constructed and all gene products displayed Ta activities. Moreover, MGA3 cells displayed Ta activities similar as PB1 cells in crude extracts.

CONCLUSIONS

While it is well established that B. methanolicus can use the SBPase variant of the RuMP cycle this study indicates that B. methanolicus possesses Ta activity and may also operate the Ta variant of the RuMP.

Methanol production by reversed methylotrophy constructed in Escherichia coli

We constructed a reversed methylotrophic pathway that produces methanol, a promising feedstock for production of useful compounds, from fructose 6-phosphate (F6P), which can be supplied by catabolism of biomass-derived sugars including glucose, by a synthetic biology approach. Using Escherichia coli as an expression host, we heterologously expressed genes encoding methanol utilization enzymes from methylotrophic bacteria, i.e. the NAD⁺-dependent methanol dehydrogenase (MDH) from Bacillus methanolicus S1 and an artificial fusion enzyme of 3-hexulose-6-phosphate synthase and 6-phospho-3-hexuloisomerase from Mycobacterium gastri MB19 (HPS-PHI). We confirmed that these enzymes can catalyze reverse reactions of methanol oxidation and formaldehyde fixation. The engineered E. coli strain co-expressing MDH and HPS-PHI genes produced methanol in resting cell reactions not only from F6P but also from glucose. We successfully conferred reversed methylotrophy to E. coli and our results provide a proof-of-concept for biological methanol production from biomass-derived sugar compounds.

Characterization of D-Arabitol as Newly Discovered Carbon Source of Bacillus methanolicus

Bacillus methanolicus is a Gram-positive, thermophilic, methanol-utilizing bacterium. As a facultative methylotroph, B. methanolicus is also known to utilize D-mannitol, D-glucose and, as recently discovered, sugar alcohol D-arabitol. While metabolic pathways for utilization of methanol, mannitol and glucose are known, catabolism of arabitol has not yet been characterized in B. methanolicus. In this work we present the elucidation of this hitherto uncharted pathway. In order to confirm our predictions regarding genes coding for arabitol utilization, we performed differential gene expression analysis of B. methanolicus MGA3 cells grown on arabitol as compared to mannitol via transcriptome sequencing (RNA-seq). We identified a gene cluster comprising eight genes that was up-regulated during growth with arabitol as a sole carbon source. The RNA-seq results were subsequently confirmed via qRT-PCR experiments. The transcriptional organization of the gene cluster identified via RNA-seq was analyzed and it was shown that the arabitol utilization genes are co-transcribed in an operon that spans from BMMGA3_RS07325 to BMMGA3_RS07365. Since gene deletion studies are currently not possible in B. methanolicus, two complementation experiments were performed in an arabitol negative Corynebacterium glutamicum strain using the four genes discovered via RNA-seq analysis as coding for a putative PTS for arabitol uptake (BMMGA3_RS07330, BMMGA3_RS07335, and BMMGA3_RS07340 renamed to atlABC) and a putative arabitol phosphate dehydrogenase (BMMGA3_RS07345 renamed to atlD). C. glutamicum is a natural D-arabitol utilizer that requires arabitol dehydrogenase MtlD for arabitol catabolism. The C. glutamicum mtlD deletion mutant was chosen for complementation experiments. Heterologous expression of atlABCD as well as the arabitol phosphate dehydrogenase gene atlD from B. methanolicus alone restored growth of the C. glutamicum ΔmtlD mutant with arabitol. Furthermore, D-arabitol phosphate dehydrogenase activities could be detected in crude extracts of B. methanolicus and these were higher in arabitol-grown cells than in methanol- or mannitol-grown cells. Thus, B. methanolicus possesses an arabitol inducible operon encoding, amongst others, a putative PTS system and an arabitol phosphate dehydrogenase for uptake and activation of arabitol as growth substrate.

High temperature-induced proteomic and metabolomic profiles of a thermophilic Bacillus manusensis isolated from the deep-sea hydrothermal field of Manus Basin

Thermophiles are organisms that grow optimally at 50 °C-80 °C and studies on the survival mechanisms of thermophiles have drawn great attention. Bacillus manusensis S50-6 is the type strain of a new thermophilic species isolated from hydrothermal vent in Manus Basin. In this study, we examined the growth and global responses of S50-6 to high temperature on molecular level using multi-omics method (genomics, proteomics, and metabolomics). S50-6 grew optimally at 50 °C (Favorable, F) and poorly at 65 °C (Non-Favorable, NF); it formed spores at F but not at NF condition. At NF condition, S50-6 formed long filaments containing undivided cells. A total of 1621 proteins were identified at F and NF conditions, and 613 proteins were differentially expressed between F and NF. At NF condition, proteins of glycolysis, rRNA mature and modification, and DNA/protein repair were up-regulated, whereas proteins of sporulation and amino acid/nucleotide metabolism were down-regulated. Consistently, many metabolites associated with amino acid and nucleotide metabolic processes were down-regulated at NF condition. Our results revealed molecular strategies of deep-sea B. manusensis to survive at unfavorable high temperature and provided new insights into the thermotolerant mechanisms of thermophiles. SIGNIFICANCE: In this study, we systematically characterized the genomic, proteomic and metabolomic profiles of a thermophilic deep-sea Bacillus manusensis under different temperatures. Based on these analysis, we propose a model delineating the global responses of B. manusensis to unfavorable high temperature. Under unfavorable high temperature, glycolysis is a more important energy supply pathway; protein synthesis is subjected to more stringent regulation by increased tRNA modification; protein and DNA repair associated proteins are enhanced in production to promote heat survival. In contrast, energy-costing pathways, such as sporulation, are repressed, and basic metabolic pathways, such as amino acid and nucleotide metabolisms, are slowed down. Our results provide new insights into the thermotolerant mechanisms of thermophilic Bacillus.

Pradoshia eiseniae gen. nov., sp. nov., a spore-forming member of the family Bacillaceae capable of assimilating 3-nitropropionic acid, isolated from the anterior gut of the earthworm Eisenia fetida

A Gram-stain-positive, spore-forming bacterium, EAG3^T, capable of growing on 3-nitropropionic acid as the sole source of carbon, nitrogen and energy, was isolated from the anterior gut of an earthworm (Eisenia fetida) reared at the Centre of Floriculture and Agribusiness Management of the University of North Bengal at Siliguri (26.7072° N, 88.3558° E), West Bengal, India. The DNA G+C content of strain EAG3^T was 42.5 mol%. Strain EAG3^T contained MK-7 and MK-8 as predominant menaquinones. The predominant polar lipids were phosphatidylglycerol, diphosphatidylglycerol and phosphatidylethanolamine. The major cellular fatty acids were 13-methyltetradecanoic acid, (9Z)-9-hexadecen-1-ol, 12-methyltetradecanoic acid and 14-methylpentadecanoic acid. The draft genome of strain EAG3^T, distributed in 57 contigs, was found to be 3.8 Mb. A total of 3811 potential coding sequences or genes were predicted, including 3672 protein-coding and 108 RNA-coding ones together with 31 pseudogenes. One hundred and thirty-five genes encoded hypothetical proteins with no meaningful homologies with known proteins. The EAG3^T genome encompassed two nitronate monooxygenase and one methylmalonate-semialdehyde dehydrogenase (CoA acylating) homologues. 16S rRNA gene sequence-based phylogeny revealed that the closest relative of strain EAG3^T was Bacillus methanolicus NCIMB 13113^T (95.7 % similarity). Phylogenetic, physiological and biochemical characteristics differentiated strain EAG3^T from B. methanolicus, as well as from the other close taxonomic relatives Planococcus rifietoensis M8^T, Bhargavaea cecembensis DSE10^T, Planomicrobium flavidum ISL-41^Tand Fermentibacilluspolygoni IEB3^T, with which strain EAG3^T had 93.3-94.2 % 16S rRNA gene sequence similarities. The new isolate, therefore, was considered as representing a novel genus of family Bacillaceae, for which the name Pradoshia eiseniae gen. nov., sp. nov. is proposed, with EAG3^T (=LMG 30312^T=JCM 32460^T) as the type strain.

Current advance in bioconversion of methanol to chemicals

Methanol has become an attractive substrate for biotechnological applications due to its abundance and low-price. Chemicals production from methanol could alleviate the environmental concerns, costs, and foreign dependency associated with the use of petroleum feedstock. Recently, a growing fraction of research has focused on metabolites production using methanol as sole carbon and energy source or as co-substrate with carbohydrates by native or synthetic methylotrophs. In this review, we summarized the recent significant progress in native and synthetic methylotrophs and their application for methanol bioconversion into various products. Moreover, strategies for improvement of methanol metabolism and new perspectives on the generation of desired products from methanol were also discussed, which will benefit for the development of a methanol-based economy.

Development of Bacillus methanolicus methanol dehydrogenase with improved formaldehyde reduction activity

Methanol dehydrogenase (MDH), an NAD⁺-dependent oxidoreductase, reversibly converts formaldehyde to methanol. This activity is a key step for both toxic formaldehyde elimination and methanol production in bacterial methylotrophy. We mutated decameric Bacillus methanolicus MDH by directed evolution and screened mutants for increased formaldehyde reduction activity in Escherichia coli. The mutant with the highest formaldehyde reduction activity had three amino acid substitutions: F213V, F289L, and F356S. To identify the individual contributions of these residues to the increased reduction activity, the activities of mutant variants were evaluated. F213V/F289L and F213V/F289L/F356S showed 25.3- and 52.8-fold higher catalytic efficiency (k_cat/K_m) than wild type MDH, respectively. In addition, they converted 5.9- and 6.4-fold more formaldehyde to methanol in vitro than the wild type enzyme. Computational modelling revealed that the three substituted residues were located at MDH oligomerization interfaces, and may influence oligomerization stability: F213V aids in dimer formation, and F289L and F356S in decamer formation. The substitutions may stabilise oligomerization, thereby increasing the formaldehyde reduction activity of MDH.

Lignite coal burning seam in the remote Altai Mountains harbors a hydrogen-driven thermophilic microbial community

Thermal ecosystems associated with underground coal combustion sites are rare and less studied than geothermal features. Here we analysed microbial communities of near-surface ground layer and bituminous substance in an open quarry heated by subsurface coal fire by metagenomic DNA sequencing. Taxonomic classification revealed dominance of only a few groups of Firmicutes. Near-complete genomes of three most abundant species, ‘Candidatus Carbobacillus altaicus’ AL32, Brockia lithotrophica AL31, and Hydrogenibacillus schlegelii AL33, were assembled. According to the genomic data, Ca. Carbobacillus altaicus AL32 is an aerobic heterotroph, while B. lithotrophica AL31 is a chemolithotrophic anaerobe assimilating CO₂ via the Calvin cycle. H. schlegelii AL33 is an aerobe capable of both growth on organic compounds and carrying out CO₂ fixation via the Calvin cycle. Phylogenetic analysis of the large subunit of RuBisCO of B. lithotrophica AL31 and H. schlegelii AL33 showed that it belongs to the type 1-E. All three Firmicutes species can gain energy from aerobic or anaerobic oxidation of molecular hydrogen, produced as a result of underground coal combustion along with other coal gases. We propose that thermophilic Firmicutes, whose spores can spread from their original geothermal habitats over long distances, are the first colonizers of this recently formed thermal ecosystem.

Description of Bacillus kexueae sp. nov. and Bacillus manusensis sp. nov., isolated from hydrothermal sediments

Two Gram-staining-positive, strictly aerobic bacilli, designated as strains Ma50-5^T and Ma50-6^T, were isolated from the hydrothermal sediments of Manus Basin in the western Pacific Ocean. Based on 16S rRNA gene sequence, strains Ma50-5^T and Ma50-6^T were most closely related to Bacillus alveayuensis (97.0 and 97.2 % identity, respectively). The 16S rRNA gene sequence identity between strains Ma50-5^T and Ma50-6^T was 97.4 %. The identities between strains Ma50-5^T and Ma50-6^T and other closely related organisms were below 97.0 %. The G+C contents of the genomic DNA of strains Ma50-5^T and Ma50-6^T were 43.4 and 47.6 mol%, respectively. The major fatty acids (>10 %) of both strains were iso-C15 : 0 and iso-C17 : 0. The predominant isoprenoid quinone detected in both strains was menaquinone-7. Phylogenetic, physiological, biochemical and morphological analyses suggested that strains Ma50-5^T and Ma50-6^T represent two novel species of the genus Bacillus, for which the names Bacillus kexueae sp. nov. (type strain Ma50-5^T=KCTC 33881^T=CCTCC AB 2017020^T) and Bacillus manusensis sp. nov. (type strain Ma50-6^T=KCTC 33882^T=CCTCC AB 2017019^T), respectively, are proposed.

Bacillus marinisedimentorum sp. nov., isolated from marine sediment

A novel Gram-stain-positive, motile and facultatively anaerobic strain, designated NC2-31^T, was isolated from sediment from the coast of Weihai, PR China. Optimal growth occurred at 37 °C, pH 7.5 and with 2.0-3.0 % (w/v) NaCl. MK-7 was the major respiratory quinone. Meso-diaminopimelic acid was a diagnostic diamino acid in the peptidoglycan. The major polar lipids of NC2-31^T were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). The genomic DNA G+C content of the strain was 46.3 mol%. The predominant cellular fatty acids (>10.0 %) of NC2-31^T were iso-C15 : 0 (18.9 %), anteiso-C15 : 0 (15.8 %), summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH) (15.3 %) and iso-C16 : 0 (10.3 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that NC2-31^T should be classified as representing a member of the genus Bacillus. Based on data from the current polyphasic study, NC2-31^T represents a novel species within the genus Bacillus, for which the name Bacillusmarinisedimentorum sp. nov. is proposed with type strain NC2-31^T (=KCTC 33721^T=MCCC 1K01239^T).

Ancylobacter pratisalsi sp. nov. with plant growth promotion abilities from the rhizosphere of Plantago winteri Wirtg

A Gram-negative bacterium, designated E130^T, was isolated from rhizospheric soil of Plantago winteri Wirtg. from a natural salt meadow as part of an investigation on rhizospheric bacteria from salt-resistant plant species and evaluation of their plant growth-promoting abilities. Cells were rods, non-motile, aerobic, and oxidase and catalase positive, grew in a temperature range of between 4 and 37 °C, and in the presence of 0.5-5 % NaCl (w/v). Based on 16S rRNA gene sequence analysis, strain E130^T is affiliated within the genus Ancylobacter, sharing the highest similarity with Ancylobacter rudongensis DSM 17131^T (97.6 %), Ancylobacter defluvii CCUG 63806^T (97.5 %) and Ancylobacter dichloromethanicus DSM 21507^T (97.4 %). The DNA G+C content of strain E130^T was 65.1 mol%. Its respiratory quinones were Q-9 and Q-10 and its major polar lipids comprised phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and unidentified phospholipid. Major fatty acids of the strains E130^T were C12 : 0, C16 : 0, C18 : 1ω7c and C19 : 0cycloω8c. The DNA-DNA relatedness of E130^T to A. rudongensis DSM 17131^T, A. defluvii CCUG 63806^T and A. dichloromethanicus DSM 21507^T was 29.2, 21.2 and 32.2 % respectively. On the basis of our polyphasic taxonomic study the new isolate represents a novel species, for which the name Ancylobacter pratisalsi sp. nov. is proposed. The type strain is E130^T (LMG 29367^T=DSM 102029^T).

Genome-Based Genetic Tool Development for Bacillus methanolicus: Theta- and Rolling Circle-Replicating Plasmids for Inducible Gene Expression and Application to Methanol-Based Cadaverine Production

Bacillus methanolicus is a thermophilic methylotroph able to overproduce amino acids from methanol, a substrate not used for human or animal nutrition. Based on our previous RNA-seq analysis a mannitol inducible promoter and a putative mannitol activator gene mtlR were identified. The mannitol inducible promoter was applied for controlled gene expression using fluorescent reporter proteins and a flow cytometry analysis, and improved by changing the -35 promoter region and by co-expression of the mtlR regulator gene. For independent complementary gene expression control, the heterologous xylose-inducible system from B. megaterium was employed and a two-plasmid gene expression system was developed. Four different replicons for expression vectors were compared with respect to their copy number and stability. As an application example, methanol-based production of cadaverine was shown to be improved from 6.5 to 10.2 g/L when a heterologous lysine decarboxylase gene cadA was expressed from a theta-replicating rather than a rolling-circle replicating vector. The current work on inducible promoter systems and compatible theta- or rolling circle-replicating vectors is an important extension of the poorly developed B. methanolicus genetic toolbox, valuable for genetic engineering and further exploration of this bacterium.

Control of Wilt and Rot Pathogens of Tomato by Antagonistic Pink Pigmented Facultative Methylotrophic Delftia lacustris and Bacillus spp

The studies on the biocontrol potential of pink pigmented facultative methylotrophic (PPFM) bacteria other than the genus Methylobacterium are scarce. In the present study, we report three facultative methylotrophic isolates; PPO-1, PPT-1, and PPB-1, respectively, identified as Delftia lacustris, Bacillus subtilis, and Bacillus cereus by 16S rRNA gene sequence analysis. Hemolytic activity was tested to investigate the potential pathogenicity of isolates to plants and humans, the results indicates that the isolates PPO-1, PPT-1, and PPB-1 are not pathogenic strains. Under in vitro conditions, D. lacustris PPO-1, B. subtilis PPT-1, and B. cereus PPB-1 showed direct antagonistic effect by inhibiting the mycelial growth of fungal pathogens; Fusarium oxysporum f. sp. lycopersici (2.15, 2.05, and 1.95 cm), Sclerotium rolfsii (2.14, 2.04, and 1.94 cm), Pythium ultimum (2.12, 2.02, and 1.92 cm), and Rhizoctonia solani (2.18, 2.08, and 1.98 cm) and also produced volatile inhibitory compounds. Under plant growth chamber condition methylotrophic bacterial isolates; D. lacustris PPO-1, B. subtilis PPT-1, and B. cereus PPB-1 significantly reduced the disease incidence of tomato. Under greenhouse condition, D. lacustris PPO-1, B. subtilis PPT-1, and B. cereus PPB-1 inoculated tomato plants, when challenged with F. oxysporum f. sp. lycopersici, S. rolfsii, P. ultimum, and R. solani, increased the pathogenesis related proteins (β-1,3-glucanase and chitinase) and defense enzymes (phenylalanine ammonia lyase, peroxidase, polyphenol oxidase, and catalase) on day 5 after inoculation. In the current study, we first report the facultative methylotrophy in pink pigmented D. lacustris, B. subtilis, and B. cereus and their antagonistic potential against fungal pathogens. Direct antagonistic and ISR effects of these isolates against fungal pathogens of tomato evidenced their possible use as a biocontrol agent.

Aureibacillus halotolerans gen. nov., sp. nov., isolated from marine sediment

A Gram-staining-positive, strictly aerobic, spore-forming and rod-shaped motile bacterium with peritrichous flagellae, designated strain S1203T, was isolated from the sediment of the northern Okinawa Trough. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S1203T formed a lineage within the family Bacillaceae that was distinct from the most closely related genera Bacillus, Bhargavaea, Planomicrobium and Virgibacillus with gene sequence similarities ranging from 86.2 to 93.76 %. Optimal growth occurred in the presence of 4-8 % (w/v) NaCl, at pH 7.0-8.0 and 25-32 °C. The cell-wall peptidoglycan was based on meso-diaminopimelic acid and unsaturated menaquinone with seven isoprene units (MK-7) as the predominant respiratory quinone. The major fatty acids (>10 % of total fatty acids) were anteiso-C15 : 0, iso-C15 : 0 and C16 : 0.The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, an unidentified glycolipid and an unidentified phospholipid. The DNA G+C content of strain S1203T was 47.7 mol%. On the basis of polyphasic analysis, strainS1203T was considered to represent a novel species in a new genus of the family Bacillaceae, for which the name Aureibacillus halotolerans gen. nov., sp. nov. is proposed; the type strain of Aureibacillus halotolerans is S1203T ( = DSM 28697T = JCM 30067T = MCCC 1K00259T).

Transcriptome analysis of thermophilic methylotrophic Bacillus methanolicus MGA3 using RNA-sequencing provides detailed insights into its previously uncharted transcriptional landscape

Background

Bacillus methanolicus MGA3 is a thermophilic, facultative ribulose monophosphate (RuMP) cycle methylotroph. Together with its ability to produce high yields of amino acids, the relevance of this microorganism as a promising candidate for biotechnological applications is evident. The B. methanolicus MGA3 genome consists of a 3,337,035 nucleotides (nt) circular chromosome, the 19,174 nt plasmid pBM19 and the 68,999 nt plasmid pBM69. 3,218 protein-coding regions were annotated on the chromosome, 22 on pBM19 and 82 on pBM69. In the present study, the RNA-seq approach was used to comprehensively investigate the transcriptome of B. methanolicus MGA3 in order to improve the genome annotation, identify novel transcripts, analyze conserved sequence motifs involved in gene expression and reveal operon structures. For this aim, two different cDNA library preparation methods were applied: one which allows characterization of the whole transcriptome and another which includes enrichment of primary transcript 5′-ends.

Results

Analysis of the primary transcriptome data enabled the detection of 2,167 putative transcription start sites (TSSs) which were categorized into 1,642 TSSs located in the upstream region (5′-UTR) of known protein-coding genes and 525 TSSs of novel antisense, intragenic, or intergenic transcripts. Firstly, 14 wrongly annotated translation start sites (TLSs) were corrected based on primary transcriptome data. Further investigation of the identified 5′-UTRs resulted in the detailed characterization of their length distribution and the detection of 75 hitherto unknown cis-regulatory RNA elements. Moreover, the exact TSSs positions were utilized to define conserved sequence motifs for translation start sites, ribosome binding sites and promoters in B. methanolicus MGA3. Based on the whole transcriptome data set, novel transcripts, operon structures and mRNA abundances were determined. The analysis of the operon structures revealed that almost half of the genes are transcribed monocistronically (940), whereas 1,164 genes are organized in 381 operons. Several of the genes related to methylotrophy had highly abundant transcripts.

Conclusion

The extensive insights into the transcriptional landscape of B. methanolicus MGA3, gained in this study, represent a valuable foundation for further comparative quantitative transcriptome analyses and possibly also for the development of molecular biology tools which at present are very limited for this organism.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1239-4) contains supplementary material, which is available to authorized users.

Methylotrophy in the thermophilic Bacillus methanolicus, basic insights and application for commodity production from methanol

Using methanol as an alternative non-food feedstock for biotechnological production offers several advantages in line with a methanol-based bioeconomy. The Gram-positive, facultative methylotrophic and thermophilic bacterium Bacillus methanolicus is one of the few described microbial candidates with a potential for the conversion of methanol to value-added products. Its capabilities of producing and secreting the commercially important amino acids L-glutamate and L-lysine to high concentrations at 50 °C have been demonstrated and make B. methanolicus a promising target to develop cell factories for industrial-scale production processes. B. methanolicus uses the ribulose monophosphate cycle for methanol assimilation and represents the first example of plasmid-dependent methylotrophy. Recent genome sequencing of two physiologically different wild-type B. methanolicus strains, MGA3 and PB1, accompanied with transcriptome and proteome analyses has generated fundamental new insight into the metabolism of the species. In addition, multiple key enzymes representing methylotrophic and biosynthetic pathways have been biochemically characterized. All this, together with establishment of improved tools for gene expression, has opened opportunities for systems-level metabolic engineering of B. methanolicus. Here, we summarize the current status of its metabolism and biochemistry, available genetic tools, and its potential use in respect to overproduction of amino acids.

Evolution in the Bacillaceae

The family Bacillaceae constitutes a phenotypically diverse and globally ubiquitous assemblage of bacteria. Investigation into how evolution has shaped, and continues to shape, this family has relied on several widely ranging approaches from classical taxonomy, ecological field studies, and evolution in soil microcosms to genomic-scale phylogenetics, laboratory, and directed evolution experiments. One unifying characteristic of the Bacillaceae , the endospore, poses unique challenges to answering questions regarding both the calculation of evolutionary rates and claims of extreme longevity in ancient environmental samples.

Complete genome sequence of Bacillus methanolicus MGA3, a thermotolerant amino acid producing methylotroph

Bacillus methanolicus MGA3 was isolated from freshwater marsh soil and characterised as a thermotolerant and methylotrophic L-glutamate producer. The complete genome consists of a circular chromosome and the two plasmids pBM19 and pBM69. It includes genomic information about C1 metabolism and amino acid biosynthetic pathways.

Proteomic analysis of the thermophilic methylotroph Bacillus methanolicus MGA3

Bacillus methanolicus MGA3 is a facultative methylotroph of industrial relevance that is able to grow on methanol as its sole source of carbon and energy. The Gram-positive bacterium possesses a soluble NAD(+) -dependent methanol dehydrogenase and assimilates formaldehyde via the ribulose monophosphate (RuMP) cycle. We used label-free quantitative proteomics to generate reference proteome data for this bacterium and compared the proteome of B. methanolicus MGA3 on two different carbon sources (methanol and mannitol) as well as two different growth temperatures (50°C and 37°C). From a total of approximately 1200 different detected proteins, approximately 1000 of these were used for quantification. While the levels of 213 proteins were significantly different at the two growth temperatures tested, the levels of 109 proteins changed significantly when cells were grown on different carbon sources. The carbon source strongly affected the synthesis of enzymes related to carbon metabolism, and in particular, both dissimilatory and assimilatory RuMP cycle enzyme levels were elevated during growth on methanol compared to mannitol. Our data also indicate that B. methanolicus has a functional tricarboxylic acid cycle, the proteins of which are differentially regulated on mannitol and methanol. Other proteins presumed to be involved in growth on methanol were constitutively expressed under the different growth conditions. All MS data have been deposited in the ProteomeXchange with the identifiers PXD000637 and PXD000638 (http://proteomecentral.proteomexchange.org/dataset/PXD000637, http://proteomecentral.proteomexchange.org/dataset/PXD000638).

Characterization of two transketolases encoded on the chromosome and the plasmid pBM19 of the facultative ribulose monophosphate cycle methylotroph Bacillus methanolicus

Background

Transketolase (TKT) is a key enzyme of the pentose phosphate pathway (PPP), the Calvin cycle and the ribulose monophosphate (RuMP) cycle. Bacillus methanolicus is a facultative RuMP pathway methylotroph. B. methanolicus MGA3 harbors two genes putatively coding for TKTs; one located on the chromosome (tkt^C) and one located on the natural occurring plasmid pBM19 (tkt^P).

Results

Both enzymes were produced in recombinant Escherichia coli, purified and shown to share similar biochemical parameters in vitro. They were found to be active as homotetramers and require thiamine pyrophosphate for catalytic activity. The inactive apoform of the TKTs, yielded by dialysis against buffer containing 10 mM EDTA, could be reconstituted most efficiently with Mn²⁺ and Mg²⁺. Both TKTs were thermo stable at physiological temperature (up to 65°C) with the highest activity at neutral pH. Ni²⁺, ATP and ADP significantly inhibited activity of both TKTs. Unlike the recently characterized RuMP pathway enzymes fructose 1,6-bisphosphate aldolase (FBA) and fructose 1,6-bisphosphatase/sedoheptulose 1,7-bisphosphatase (FBPase/SBPase) from B. methanolicus MGA3, both TKTs exhibited similar kinetic parameters although they only share 76% identical amino acids. The kinetic parameters were determined for the reaction with the substrates xylulose 5-phosphate (TKT^C: k_cat/K_M: 264 s^-1 mM^-1; TKT^P: k_cat/K_M: 231 s^-1 mM) and ribulose 5-phosphate (TKT^C: k_cat/K_M: 109 s^-1 mM; TKT^P: k_cat/K_M: 84 s^-1 mM) as well as for the reaction with the substrates glyceraldehyde 3-phosphate (TKT^C: k_cat/K_M: 108 s^-1 mM; TKT^P: k_cat/K_M: 71 s^-1 mM) and fructose 6-phosphate (TKT^C k_cat/K_M: 115 s^-1 mM; TKT^P: k_cat/K_M: 448 s^-1 mM).

Conclusions

Based on the kinetic parameters no major TKT of B. methanolicus could be determined. Increased expression of tkt^P, but not of tkt^C during growth with methanol [J Bacteriol 188:3063–3072, 2006] argues for TKT^P being the major TKT relevant in the RuMP pathway. Neither TKT exhibited activity as dihydroxyacetone synthase, as found in methylotrophic yeast, or as the evolutionary related 1-deoxyxylulose-5-phosphate synthase. The biological significance of the two TKTs for B. methanolicus methylotrophy is discussed.

Characterization of fructose 1,6-bisphosphatase and sedoheptulose 1,7-bisphosphatase from the facultative ribulose monophosphate cycle methylotroph Bacillus methanolicus

The genome of the facultative ribulose monophosphate (RuMP) cycle methylotroph Bacillus methanolicus encodes two bisphosphatases (GlpX), one on the chromosome (GlpX(C)) and one on plasmid pBM19 (GlpX(P)), which is required for methylotrophy. Both enzymes were purified from recombinant Escherichia coli and were shown to be active as fructose 1,6-bisphosphatases (FBPases). The FBPase-negative Corynebacterium glutamicum Δfbp mutant could be phenotypically complemented with glpX(C) and glpX(P) from B. methanolicus. GlpX(P) and GlpX(C) share similar functional properties, as they were found here to be active as homotetramers in vitro, activated by Mn(2+) ions and inhibited by Li(+), but differed in terms of the kinetic parameters. GlpX(C) showed a much higher catalytic efficiency and a lower Km for fructose 1,6-bisphosphate (86.3 s(-1) mM(-1) and 14 ± 0.5 μM, respectively) than GlpX(P) (8.8 s(-1) mM(-1) and 440 ± 7.6 μM, respectively), indicating that GlpX(C) is the major FBPase of B. methanolicus. Both enzymes were tested for activity as sedoheptulose 1,7-bisphosphatase (SBPase), since a SBPase variant of the ribulose monophosphate cycle has been proposed for B. methanolicus. The substrate for the SBPase reaction, sedoheptulose 1,7-bisphosphate, could be synthesized in vitro by using both fructose 1,6-bisphosphate aldolase proteins from B. methanolicus. Evidence for activity as an SBPase could be obtained for GlpX(P) but not for GlpX(C). Based on these in vitro data, GlpX(P) is a promiscuous SBPase/FBPase and might function in the RuMP cycle of B. methanolicus.

Bacillus thaonhiensis sp. nov., a new species, was isolated from the forest soil of Kyonggi University by using a modified culture method

Using a new culture method for unculturable soil bacteria, we discovered a novel species, NHI-38(T), from the forest soil of Kyonggi University campus, South Korea. It was a Gram-positive, rod-shaped, and endospore-forming bacterial strain. It grew over a wide pH range (6.5-9.5), with an optimum range of pH 7-9, and in a wide range of temperatures (15-60 °C), with an optimum range of 35-45 °C. Growth was possible at 0-2 % NaCl concentration, and the optimal range was between 0.5 and 1.5 % NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that this new species clustered within the genus Bacillus; it was closely related to "Bacillus abyssalis" SCSIO 15042(T) (98.86 %), B. methanolicus NCIMB 13113(T) (95.97 %), B. vietnamensis 15-1(T) (95.8 %), B. seohaeanensis BH724(T) (95.5 %), B. timonensis MM10403188(T) (95.33 %), and B. subtilis subsp. subtilis NCIB 3610(T) (94.87 %). The main fatty acid components of this bacterium were iso-C15:0 (35.92 %), summed feature 3 (C16:1ω7c/C16:1ω6c; 16.92 %), and anteiso-C15:0 (14.19 %). The predominant quinone in this bacterial strain was MK-7. The polar lipid profile primarily comprised phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. The genomic DNA G+C composition of the isolate was 40.7 mol%. The DNA-DNA hybridization results indicated that this strain was distinct from other Bacillus species, the degree of similarity being 50 % with "B. abyssalis", 56 % with B. methanolicus, 47 % with B. vietnamensis, 43 % with B. seohaeanensis, 46 % with B. timonensis, and 32 % with B. subtilis. Based on our results, we regard strain NHI-38(T) as a novel member of the Bacillus genus, and we propose the name Bacillus thaonhiensis (=KACC 17216(T) = KEMB 9005-019(T) = JCM 18863(T)).

Bacillus songklensis sp. nov., isolated from soil

A Gram-stain-positive, spore-forming, rod-shaped, motile, strictly aerobic bacterial strain, designated CAU 1033(T), was isolated from soil and its taxonomic position was investigated using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CAU 1033(T) formed a distinct lineage within the genus Bacillus and was most closely related to Bacillus drentensis KCTC 13025(T) (similarity 95.9 %). CAU 1033(T) contained MK-7 as the only isoprenoid quinone and iso-C15 : 0 and anteiso-C15 : 0 as the major fatty acids. The cell wall peptidoglycan of strain CAU 1033(T) contained meso-diaminopimelic acid and the major whole-cell sugars were arabinose, sucrose and ribose. The polar lipids were composed of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids, four unidentified aminophospholipids, an unidentified aminolipid, two unidentified glycolipids and another unidentified polar lipid. The DNA G+C content was 41.4 mol%. On the basis of phenotypic data and phylogenetic inference, strain CAU 1033(T) was classified as a representative of a novel species in the genus Bacillus for which the name Bacillus songklensis sp. nov. is proposed. The type strain is CAU 1033(T) ( = KCTC 13881(T) = CCUG 61889(T)).

Methylotrophic Bacillus methanolicus encodes two chromosomal and one plasmid born NAD+ dependent methanol dehydrogenase paralogs with different catalytic and biochemical properties

Bacillus methanolicus can utilize methanol as the sole carbon source for growth and it encodes an NAD⁺-dependent methanol dehydrogenase (Mdh), catalyzing the oxidation of methanol to formaldehyde. Recently, the genomes of the B. methanolicus strains MGA3 (ATCC53907) and PB1 (NCIMB13113) were sequenced and found to harbor three different putative Mdh encoding genes, each belonging to the type III Fe-NAD⁺-dependent alcohol dehydrogenases. In each strain, two of these genes are encoded on the chromosome and one on a plasmid; only one chromosomal act gene encoding the previously described activator protein ACT was found. The six Mdhs and the ACT proteins were produced recombinantly in Escherichia coli, purified, and characterized. All Mdhs required NAD⁺ as cosubstrate, were catalytically stimulated by ACT, exhibited a broad and different substrate specificity range and displayed both dehydrogenase and reductase activities. All Mdhs catalyzed the oxidation of methanol; however the catalytic activity for methanol was considerably lower than for most other alcohols tested, suggesting that these enzymes represent a novel class of alcohol dehydrogenases. The kinetic constants for the Mdhs were comparable when acting as pure enzymes, but together with ACT the differences were more pronounced. Quantitative PCR experiments revealed major differences with respect to transcriptional regulation of the paralogous genes. Taken together our data indicate that the repertoire of methanol oxidizing enzymes in thermotolerant bacilli is larger than expected with complex mechanisms involved in their regulation.

Overexpression of the formaldehyde dehydrogenase gene from Brevibacillus brevis to enhance formaldehyde tolerance and detoxification of tobacco

The faldh gene coding for a putative Brevibacillus brevis formaldehyde dehydrogenase (FALDH) was isolated and then transformed into tobacco. A total of three lines of transgenic plants were generated, with each showing 2- to 3-fold higher specific formaldehyde dehydrogenase activities than wild-type tobacco, a result that demonstrates the functional activity of the enzyme in formaldehyde (HCHO) oxidation. Overexpression of faldh in tobacco confers a high tolerance to exogenous HCHO and an increased ability to take up HCHO. A (13)C-nuclear magnetic resonance technique revealed that the transgenic plants were able to oxidize more aqueous HCHO to formate than the wild-type (WT) plants. When treated with gaseous HCHO, the transgenic tobacco exhibited an enhanced ability to transform more HCHO into formate, citrate acid, and malate but less glycine than the WT plants. These results indicate that the increased capacity of the transgenic tobacco to take up, tolerate, and metabolize higher concentrations of HCHO was due to the overexpression of B. brevis FALDH, revealing the essential function of this enzyme in HCHO detoxification. Our results provide a potential genetic engineering strategy for improving the phytoremediation of HCHO pollution.

Bacillus taxonomy in the genomic era finds phenotypes to be essential though often misleading

Bacillus is a diverse bacterial genus characterized by cells growing aerobically and forming dormant endospores. Although Bacillus species were some of the first bacteria ever characterized, their relationships to one another remain enigmatic. The recent deluge of environmental sequencing projects has further complicated our view of Bacillus taxonomy and diversity. In this review we discuss the current state of Bacillus taxonomy and focus on two examples that highlight the ecological diversity found within identical 16S rDNA-based clusters: the identification of ecologically distinct clusters of B. simplex in Evolution Canyons and the demarcation of species in the industrially and medically important B. cereus group. These examples highlight the difficulties of purely 16S rDNA-based taxonomy, emphasizing the need to interpret the massive amounts of molecular data from environmental sequencing projects in a bacterial ecology framework. Such interpretations are likely to reveal ecological diversity within Bacillus that extends beyond that previously imaginable, providing a true picture of Bacillus ecology and evolution.

Bacillus methylotrophicus sp. nov., a methanol-utilizing, plant-growth-promoting bacterium isolated from rice rhizosphere soil

A Gram-positive bacterium, designated strain CBMB205(T), was isolated from the rhizosphere soil of traditionally cultivated, field-grown rice. Cells were strictly aerobic, motile, rod-shaped and formed endospores. The best growth was achieved at 30°C and pH 7.0 in ammonium mineral salts (AMS) medium containing 600 mM methanol. A comparative 16S rRNA gene sequence-based phylogenetic analysis placed strain CBMB205(T) in a clade with the species Bacillus amyloliquefaciens, Bacillus vallismortis, Bacillus subtilis, Bacillus atrophaeus, Bacillus mojavensis and Bacillus licheniformis and revealed pairwise similarities ranging from 98.2 to 99.2 %. DNA-DNA hybridization experiments revealed a low level (<36 %) of DNA-DNA relatedness between strain CBMB205(T) and its closest relatives. The major components of the fatty acid profile were C₁₅:₀ anteiso, C₁₅:₀ iso, C₁₆:₀ iso and C₁₇:₀ anteiso. The diagnostic diamino acid of the cell wall was meso-diaminopimelic acid. The G+C content of the genomic DNA was 45.0 mol%. The lipids present in strain CBMB205(T) were diphosphatidylglycerol, phosphatidylglycerol, a minor amount of phosphatidylcholine and two unknown phospholipids. The predominant respiratory quinone was MK-7. Studies of DNA-DNA relatedness, morphological, physiological and chemotaxonomic analyses and phylogenetic data based on 16S rRNA gene sequencing enabled strain CBMB205(T) to be described as representing a novel species of the genus Bacillus, for which the name Bacillus methylotrophicus sp. nov. is proposed. The type strain is CBMB205(T) (=KACC 13105(T)=NCCB 100236(T)).

Bhargavaea cecembensis gen. nov., sp. nov., isolated from the Chagos-Laccadive ridge system in the Indian Ocean

A novel Gram-positive, rod-shaped, non-motile, non-spore-forming bacterium, strain DSE10(T), was isolated from a deep-sea sediment sample collected at a depth of 5904 m from the Chagos-Laccadive ridge system in the Indian Ocean. Cells of strain DSE10(T) were positive for catalase, oxidase, urease and lipase activities and contained iso-C(14 : 0), iso-C(15 : 0), iso-C(16 : 0) and anteiso-C(15 : 0) as the major fatty acids. The major respiratory quinones were MK-6 and MK-8 and the major lipids were phosphatidylglycerol and diphosphatidylglycerol. The cell-wall peptidoglycan contained diaminopimelic acid as the diagnostic diamino acid. A blast sequence similarity search based on 16S rRNA gene sequences indicated that the genera Planococcus, Planomicrobium, Bacillus and Geobacillus were the nearest phylogenetic neighbours to the novel isolate with gene sequence similarities ranging from 94.9 to 95.2 %. Phylogenetic analyses using neighbour-joining, minimum-evolution and maximum-parsimony methods indicated that strain DSE10(T) formed a deeply rooted lineage distinct from the clades represented by the genera Planococcus, Planomicrobium, Bacillus and Geobacillus. Further, strain DSE10(T) could be distinguished from the above-mentioned genera based on the presence of signature nucleotides G, A, C, T, C, A, G, C and T at positions 182, 444, 480, 492, 563, 931, 1253, 1300 and 1391, respectively, in the 16S rRNA gene sequence. Based on the phenotypic and phylogenetic characteristics determined in this study, strain DSE10(T) was assigned as the type species of a new genus, Bhargavaea gen. nov., as Bhargavaea cecembensis sp. nov. The type strain of Bhargavaea cecembensis gen. nov., sp. nov. is DSE10(T) (=LMG 24411(T)=JCM 14375(T)). The genomic DNA G+C content of strain DSE10(T) is 59.5+/-2.5 mol%.

Novel methylotrophic bacteria isolated from the River Thames (London, UK)

Enrichment and elective culture for methylotrophs from sediment of the River Thames in central London yielded a diversity of pure cultures representing several genera of Gram-negative and Gram-positive bacteria, which were mainly of organisms not generally regarded as typically methylotrophic. Substrates leading to successful isolations included methanol, monomethylamine, dimethylamine, trimethylamine, methanesulfonate and dimethylsulfone. Several isolates were studied in detail and shown by their biochemical and morphological properties and 16S rRNA gene sequencing to be Sphingomonas melonis strain ET35, Mycobacterium fluoranthenivorans strain DSQ3, Rhodococcus erythropolis strain DSQ4, Brevibacterium casei strain MSQ5, Klebsiella oxytoca strains MMA/F and MMA/1, Pseudomonas mendocina strain TSQ4, and Flavobacterium sp. strains MSA/1 and MMA/2. The results show that facultative methylotrophy is present across a wide range of Bacteria, suggesting that turnover of diverse C(1)-compounds is of much greater microbiological and environmental significance than is generally thought. The origins of the genes encoding the enzymes of methylotrophy in diverse heterotrophs need further study, and could further our understanding of the phylogeny and antiquity of methylotrophic systems.

Bacillus methanolicus: a candidate for industrial production of amino acids from methanol at 50 degrees C

Amino acids are among the major products in biotechnology in both volume and value, and the global market is growing. Microbial fermentation is the dominant method used for industrial production, and today the most important microorganisms used are Corynebacteria utilizing sugars. For low-prize bulk amino acids, the possibility of using alternative substrates such as methanol has gained considerable interest. In this mini review, we highlight the unique genetics and favorable physiological traits of thermotolerant methylotroph Bacillus methanolicus, which makes it an interesting candidate for overproduction of amino acids from methanol. B. methanolicus genes involved in methanol consumption are plasmid-encoded and this bacterium has a high methanol conversion rate. Wild-type strains can secrete 58 g/l of L: -glutamate in fed-batch cultures at 50 degrees C and classical mutants secreting 37 g/l of L: -lysine have been selected. The relative high growth temperature is an advantage with respect to both reactor cooling requirements and low contamination risks. Key genes in L: -lysine and L: -glutamate production have been cloned, high-cell density methanol fermentation technology established, and recently a gene delivery method was developed for this organism. We discuss how this new knowledge and technology may lead to the construction of improved L: -lysine and L: -glutamate producing strains by metabolic engineering.

Upregulated transcription of plasmid and chromosomal ribulose monophosphate pathway genes is critical for methanol assimilation rate and methanol tolerance in the methylotrophic bacterium Bacillus methanolicus

The natural plasmid pBM19 carries the key mdh gene needed for the oxidation of methanol into formaldehyde by Bacillus methanolicus. Five more genes, glpX, fba, tkt, pfk, and rpe, with deduced roles in the cell primary metabolism, are also located on this plasmid. By using real-time PCR, we show that they are transcriptionally upregulated (6- to 40-fold) in cells utilizing methanol; a similar induction was shown for two chromosomal genes, hps and phi. These seven genes are involved in the fructose bisphosphate aldolase/sedoheptulose bisphosphatase variant of the ribulose monophosphate (RuMP) pathway for formaldehyde assimilation. Curing of pBM19 causes higher methanol tolerance and reduced formaldehyde tolerance, and the methanol tolerance is reversed to wild-type levels by reintroducing mdh. Thus, the RuMP pathway is needed to detoxify the formaldehyde produced by the methanol dehydrogenase-mediated conversion of methanol, and the in vivo transcription levels of mdh and the RuMP pathway genes reflect the methanol tolerance level of the cells. The transcriptional inducer of hps and phi genes is formaldehyde, and not methanol, and introduction of multiple copies of these two genes into B. methanolicus made the cells more tolerant of growth on high methanol concentrations. The recombinant strain also had a significantly higher specific growth rate on methanol than the wild type. While pBM19 is critical for growth on methanol and important for formaldehyde detoxification, the maintenance of this plasmid represents a burden for B. methanolicus when growing on mannitol. Our data contribute to a new and fundamental understanding of the regulation of B. methanolicus methylotrophy.

Isolation and molecular detection of methylotrophic bacteria occurring in the human mouth

Diverse methylotrophic bacteria were isolated from the tongue, and supra- and subgingival plaque in the mouths of volunteers and patients with periodontitis. One-carbon compounds such as dimethylsulfide in the mouth are likely to be used as growth substrates for these organisms. Methylotrophic strains of Bacillus, Brevibacterium casei, Hyphomicrobium sulfonivorans, Methylobacterium, Micrococcus luteus and Variovorax paradoxus were characterized physiologically and by their 16S rRNA gene sequences. The type strain of B. casei was shown to be methylotrophic. Enzymes of methylotrophic metabolism were characterized in some strains, and activities consistent with growth using known pathways of C1-compound metabolism demonstrated. Genomic DNA from 18 tongue and dental plaque samples from nine volunteers was amplified by the polymerase chain reaction using primers for the 16S rRNA gene of Methylobacterium and the mxaF gene of methanol dehydrogenase. MxaF was detected in all nine volunteers, and Methylobacterium was detected in seven. Methylotrophic activity is thus a feature of the oral bacterial community.

Bacillus alveayuensis sp. nov., a thermophilic bacterium isolated from deep-sea sediments of the Ayu Trough

Two thermophilic, spore-forming strains, TM1Tand TM5, were isolated from deep-sea sediment (4000 m below sea level) of the Ayu Trough in the western Pacific Ocean. Cells of the two strains were Gram-positive, motile and rod-shaped. Their spores were ellipsoidal, subterminal to terminal and occurred in swollen sporangia. The two strains grew at temperatures up to 65 °C and in the pH range 6·5–9·0. The NaCl concentration for optimal growth was 3·0 % (w/v) and growth was inhibited by 5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains TM1Tand TM5 belonged to the genusBacillus, and that strain TM1Twas most closely related toBacillus aeoliusDSM 15084T(96·7 %),Bacillus smithiiDSM 4216T(96·1 %),Bacillus methanolicusNCIMB 13113T(95·8 %) andBacillus pallidusDSM 3670T(95·7 %). Between the 16S rRNA gene sequences of strains TM1Tand TM5 there were only three nucleotide differences, implying that the two strains were of the same species. The cellular fatty acid profiles of the two strains were also very similar, with iso-C15 : 0, iso-C16 : 0, C16 : 0, iso-C17 : 0and anteiso-C17 : 0as the major components. The G+C content of strain TM1Twas 38·7 %. On the basis of phenotypic and molecular data, strains TM1Tand TM5 represent a novel species of the genusBacillus, for which the nameBacillus alveayuensissp. nov. is proposed. The type strain is TM1T(=KCTC 10634T=JCM 12523T).

Growth of Bacillus methanolicus in seawater-based media

Bacillus methanolicus has been proposed as a biocatalyst for the low cost production of commodity chemicals. The organism can use methanol as sole carbon and energy source, and it grows aerobically at elevated temperatures. Methanol can be made available from off-shore conversion of natural gas to methanol, through gas-to-liquid technology. Growth of the organism in seawater-based medium would further reduce the costs of chemical production performed near an off-shore natural gas source. The growth of strain PB1 (ATCC 51375) in shake flask experiments with trypticase soy broth medium showed minimal salt-inhibition at the concentration of NaCl in seawater. The ability of B. methanolicus PB1 to grow in Pacific Ocean water using methanol as a carbon and energy source was also tested. Following a simple adaptation procedure, PB1 was able to grow on methanol in semi-defined medium with 100% seawater with good growth yields and similar growth rates compared with those achieved on media prepared in deionized water.

Reclassification of Brevibacillus brevis strains NCIMB 13288 and DSM 6472 (=NRRL NRS-887) as Aneurinibacillus danicus sp. nov. and Brevibacillus limnophilus sp. nov

Comparison of the hypervariable region (269-279 bases in length) at the 5' end of the 16S rDNA sequences of 29 bacterial strains that were identified previously as Brevibacillus brevis showed that 13 strains clustered with Aneurinibacillus species, eight strains clustered with Bacillus species and eight strains clustered with Brevibacillus species. Based on DNA-DNA hybridization results, 27 strains, not including [Brevibacillus brevis] NCIMB 13288 and [Brevibacillus brevis] DSM 6472, were reidentified as Aneurinibacillus migulanus, Aneurinibacillus thermoaerophilus, Bacillus methanolicus, Bacillus oleronius, Brevibacillus agri, Brevibacillus brevis and Brevibacillus parabrevis. [Brevibacillus brevis] NCIMB 13288, which was located in the Aneurinibacillus cluster, showed low DNA-DNA relatedness (<14 %) and low 16S rDNA sequence similarity (96.8-97.9 %) to other Aneurinibacillus species. [Brevibacillus brevis] DSM 6472, which was located in the Brevibacillus cluster, also showed low DNA-DNA relatedness (<12 %) and low 16S rDNA sequence similarity (95.4-98.8 %) to other Brevibacillus species. These genotypic and phylogenetic data, plus phenotypic and chemotaxonomic characteristics, suggest that [Brevibacillus brevis] NCIMB 13288 (=IAM 15048) and [Brevibacillus brevis] DSM 6472 (=NRRL NRS-887) represent novel species of the genera Aneurinibacillus and Brevibacillus, respectively, for which the names Aneurinibacillus danicus sp. nov. and Brevibacillus limnophilus sp. nov. are proposed.

Plasmid-dependent methylotrophy in thermotolerant Bacillus methanolicus

Bacillus methanolicus can efficiently utilize methanol as a sole carbon source and has an optimum growth temperature of 50 degrees C. With the exception of mannitol, no sugars have been reported to support rapid growth of this organism, which is classified as a restrictive methylotroph. Here we describe the DNA sequence and characterization of a 19,167-bp circular plasmid, designated pBM19, isolated from B. methanolicus MGA3. Sequence analysis of pBM19 demonstrated the presence of the methanol dehydrogenase gene, mdh, which is crucial for methanol consumption in this bacterium. In addition, five genes (pfk, encoding phosphofructokinase; rpe, encoding ribulose-5-phosphate 3-epimerase; tkt, encoding transketolase; glpX, encoding fructose-1,6-bisphosphatase; and fba, encoding fructose-1,6-bisphosphate aldolase) with deduced roles in methanol assimilation via the ribulose monophosphate pathway are encoded by pBM19. A shuttle vector, pTB1.9, harboring the pBM19 minimal replicon (repB and ori) was constructed and used to transform MGA3. Analysis of the resulting recombinant strain demonstrated that it was cured of pBM19 and was not able to grow on methanol. A pTB1.9 derivative harboring the complete mdh gene could not restore growth on methanol when it was introduced into the pBM19-cured strain, suggesting that additional pBM19 genes are required for consumption of this carbon source. Screening of 13 thermotolerant B. methanolicus wild-type strains showed that they all harbor plasmids similar to pBM19, and this is the first report describing plasmid-linked methylotrophy in any microorganism. Our findings should have an effect on future genetic manipulations of this organism, and they contribute to a new understanding of the biology of methylotrophs.

Stable isotope probing of rRNA and DNA reveals a dynamic methylotroph community and trophic interactions with fungi and protozoa in oxic rice field soil

Stable isotope probing (SIP) is a novel technique to characterize structure and in situ function of active microbial populations, which is based on the incorporation of 13C-labelled substrates into nucleic acids. Here, we have traced methylotrophic members of a rice field soil microbial community, which became active upon continuous addition of 13C-methanol (< 22 mM) as studied in microcosms. By combining rRNA- and DNA-based SIP, as well as domain-specific real-time PCR detection of templates in fractions of centrifugation gradients, we were able to detect 13C-labelled bacterial rRNA after 6 days of incubation. Fingerprinting and comparative sequence analysis of 'heavy' bacterial rRNA showed that mostly members of the Methylobacteriaceae and a novel clade within the Methylophilaceae formed part of the indigenous methylotrophic community. Over time, however, the Methylophilaceae were enriched. Unexpectedly, nucleic acids of eukaryotic origin were detected, mostly in intermediately 13C-labelled gradient fractions. These eukaryotes were identified as fungi mostly related to Fusarium and Aspergillus spp., and also Cercozoa, known as predatory soil flagellates. The detection of fungi and protozoa in 13C-enriched nucleic acid fractions suggests a possible involvement in either direct assimilation of label by the fungi, or a food web, i.e. that primary 13C-methanol consuming methylotrophs were decomposed by fungi and grazed by protozoa.

Role of the Bacillus methanolicus citrate synthase II gene, citY, in regulating the secretion of glutamate in L-lysine-secreting mutants

The thermotolerant, restrictive methylotroph Bacillus methanolicus MGA3 (ATCC 53907) can secrete 55 g of glutamate per liter (maximum yield, 0.36 g/g) at 50 degrees C with methanol as a carbon source and a source of ammonia in fed-batch bioreactors. A homoserine dehydrogenase mutant, 13A52-8A66, secreting up to 35 g of L-lysine per liter in fed-batch fermentations had minimal 2-oxoglutarate dehydrogenase activity [7.3 nmol min(-1) (mg of protein)(-1)], threefold-increased pyruvate carboxylase activity [535 nmol min(-1) (mg of protein)(-1)], and elevated citrate synthase (CS) activity [292 nmol min(-1) (mg of protein)(-1)] and simultaneously secreted glutamate (20 to 30 g per liter) and L-lysine. The flow of carbon from oxaloacetate is split between transamination to aspartate and formation of citrate. To investigate the regulation of this branch point, the B. methanolicus gene citY encoding a CSII protein with activity at 50 degrees C was cloned from 13A52-8A66 into a CS-deficient Escherichia coli K2-1-4 strain. A citY-deficient B. methanolicus mutant, NCS-L-7, was also isolated from the parent strain of 13A52-8A66 by N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis, followed by selection with monofluoroacetate disks on glutamate plates. Characterization of these strains confirmed that citY in strain 13A52-8A66 was not altered and that B. methanolicus possessed several forms of CS. Analysis of citY cloned from NCS-L-7 showed that the reduced CS activity resulted from a frameshift mutation. The level of glutamate secreted by NCS-L-7 was reduced sevenfold and the ratio of L-lysine to glutamate secreted was increased 4.5-fold compared to the wild type in fed-batch cultures with glutamate feeding. This indicates that glutamate secretion in L-lysine-overproducing mutants can be altered in favor of increased L-lysine secretion by regulating in vivo CS activity.

Dissimilation of [(13)C]methanol by continuous cultures of Bacillus methanolicus MGA3 at 50 degrees C studied by (13)C NMR and isotope-ratio mass spectrometry

Using a continuous culture of Bacillus methanolicus MGA3 limited by 100 mM methanol in the feed and growing at a dilution rate D=0.25 h(-1), transients in dissolved methanol were studied to determine the effects of methanol toxicity and the pathway of methanol dissimilation to CO(2). Steady-state cultures were disturbed by pulses of methanol resulting in a rapid change in concentration of 6.4-12.8 mM. B. methanolicus MGA3 responded to a sudden increase in available methanol by a transient decline in the biomass concentration in the reactor. In most cases the culture returned to steady state between 4 and 12 h after pulse addition. However, at a methanol pulse of 12.8 mM, complete biomass washout occurred and the culture did not return to steady state. Integrating the response curves of the dry biomass concentration over a 12 h time period showed that a methanol pulse can cause an average transient decline in the biomass yield of up to 22%. (13)C NMR experiments using labelled methanol indicated that the transient partial or complete biomass washout was probably caused by toxic accumulation of formaldehyde in the culture. These experiments also showed accumulation of formate, indicating that B. methanolicus possesses formaldehyde dehydrogenase and formate dehydrogenase activity resulting in a methanol dissimilation pathway via formate to CO(2). Studies using isotope-ratio mass spectrometry provided further evidence of a methanol dissimilation pathway via formate. B. methanolicus MGA3, growing continuously under methanol limitation, consumed added formate at a rate of approximately 0.85 mmol l(-1) h(-1). Furthermore, significant accumulation of (13)CO(2) in the reactor exhaust gas was measured in response to a pulse addition of [(13)C]formic acid to the bioreactor. This indicates that B. methanolicus dissimilates methanol carbon to CO(2) in order to detoxify formaldehyde by both a linear pathway to formate and a cyclic mechanism as part of the RuMP pathway.

Molecular, biochemical, and functional characterization of a Nudix hydrolase protein that stimulates the activity of a nicotinoprotein alcohol dehydrogenase

The cytoplasmic coenzyme NAD(+)-dependent alcohol (methanol) dehydrogenase (MDH) employed by Bacillus methanolicus during growth on C(1)-C(4) primary alcohols is a decameric protein with 1 Zn(2+)-ion and 1-2 Mg(2+)-ions plus a tightly bound NAD(H) cofactor per subunit (a nicotinoprotein). Mg(2+)-ions are essential for binding of NAD(H) cofactor in MDH protein expressed in Escherichia coli. The low coenzyme NAD(+)-dependent activity of MDH with C(1)-C(4) primary alcohols is strongly stimulated by a second B. methanolicus protein (ACT), provided that MDH contains NAD(H) cofactor and Mg(2+)-ions are present in the assay mixture. Characterization of the act gene revealed the presence of the highly conserved amino acid sequence motif typical of Nudix hydrolase proteins in the deduced ACT amino acid sequence. The act gene was successfully expressed in E. coli allowing purification and characterization of active ACT protein. MDH activation by ACT involved hydrolytic removal of the nicotinamide mononucleotide NMN(H) moiety of the NAD(H) cofactor of MDH, changing its Ping-Pong type of reaction mechanism into a ternary complex reaction mechanism. Increased cellular NADH/NAD(+) ratios may reduce the ACT-mediated activation of MDH, thus preventing accumulation of toxic aldehydes. This represents a novel mechanism for alcohol dehydrogenase activity regulation.