Four novel bacterial strains were isolated from cryogenic tubes used to collect air samples at altitudes of 24, 28 and 41 km. The four strains, 24K T , 28K T , 41KF2a T and 41KF2b T , were identified as members of the genus Bacillus. Phylogenetic analysis based on 16S rRNA gene sequences indicated that three of the strains, 24K T , 28K T and 41KF2a T , are very similar to one another (>98 % sequence similarity) and show a similarity of 98-99 % with Bacillus licheniformis and 98 % with Bacillus sonorensis. DNA-DNA hybridization studies showed that strains 24K T , 28K T and 41KF2a T exhibit <70 % similarity with each other and with B. licheniformis and B. sonorensis. Differences in phenotypic and chemotaxonomic characteristics between the novel strains and B. licheniformis and B. sonorensis further confirmed that these three isolates are representatives of three separate novel species. Strain 41KF2b T showed 100 % 16S rRNA gene sequence similarity to Bacillus pumilus, but differed from its nearest phylogenetic neighbour in a number of phenotypic and chemotaxonomic characteristics and showed only 55 % DNA-DNA relatedness. Therefore, the four isolates represent four novel species for which the names Bacillus aerius sp. nov. (type strain, 24K T =MTCC 7303 T =JCM 13348 T), Bacillus aerophilus sp. nov. (type strain, 28K T =MTCC 7304 T =JCM 13347 T), Bacillus stratosphericus sp. nov. (type strain, 41KF2a T =MTCC 7305 T =JCM 13349 T) and Bacillus altitudinis sp. nov. (type strain, 41KF2b T =MTCC 7306 T =JCM 13350 T) are proposed.
Despite decades of study, electron flow and energy conservation in methanogenic Archaea are still not thoroughly understood. For methanogens without cytochromes, flavin-based electron bifurcation has been proposed as an essential energy-conserving mechanism that couples exergonic and endergonic reactions of methanogenesis. However, an alternative hypothesis posits that the energy-converting hydrogenase Eha provides a chemiosmosis-driven electron input to the endergonic reaction. In vivo evidence for both hypotheses is incomplete. By genetically eliminating all nonessential pathways of H 2 metabolism in the model methanogen Methanococcus maripaludis and using formate as an additional electron donor, we isolate electron flow for methanogenesis from flux through Eha. We find that Eha does not function stoichiometrically for methanogenesis, implying that electron bifurcation must operate in vivo. We show that Eha is nevertheless essential, and a substoichiometric requirement for H 2 suggests that its role is anaplerotic. Indeed, H 2 via Eha stimulates methanogenesis from formate when intermediates are not otherwise replenished. These results fit the model for electron bifurcation, which renders the methanogenic pathway cyclic, and as such requires the replenishment of intermediates. Defining a role for Eha and verifying electron bifurcation provide a complete model of methanogenesis where all necessary electron inputs are accounted for. M ethanogenesis is an anaerobic respiration carried out by a phylogenetically related group of Archaea within the phylum Euryarchaeota. Methanogens are divided into two metabolic types, those without and those with cytochromes (1). Methanogens without cytochromes use H 2 as an electron donor and are termed hydrogenotrophic. Some species can substitute H 2 with formate, and a few can use secondary alcohols. CO 2 is the electron acceptor and is reduced to methane. Methanogens with cytochromes reduce certain methyl compounds or the methyl carbon of acetate to methane and are called methylotrophic. Many can also use H 2 and CO 2 , as can hydrogenotrophic methanogens.Although the pathways of methanogenesis have long been known, an understanding of energy conservation has been slower to emerge. Methanogens with and without cytochromes both export Na + when a methyl group is transferred from the carrier tetrahydromethanopterin (H 4 MPT) to coenzyme M (CoM) (Fig. 1). The Na + gradient across the membrane is used directly for ATP synthesis or is converted by an antiporter to a proton gradient. However, for methanogenesis from CO 2 , the initial reduction of CO 2 to a formyl group attached to methanofuran (MFR) is endergonic. How energy is provided to drive this reaction is not well understood. Methanogens with and without cytochromes have membrane-associated energy-converting hydrogenases that couple the reduction of low-potential ferredoxins (Fd) to a chemiosmotic membrane gradient (2). If such a Fd donates electrons for CO 2 reduction, an energy-converting hydrogenase is the conduit of ener...
Strain Sd/3T (=MTCC 4374T=DSM 15820T), an arsenic-resistant bacterium, was isolated from a sand sample obtained from an arsenic-contaminated aquifer in Chakdah district in West Bengal, India (23° 3′ N 88° 35′ E). The bacterium was Gram-positive, rod-shaped, non-motile, endospore-forming and yellowish-orange pigmented. It possessed all the characteristics that conform to the genus Bacillus, such as it had A4 β murein type (l-orn-d-Asp) peptidoglycan variant, MK-7 as the major menaquinone and iso-C15 : 0 and anteiso-C15 : 0 as the major fatty acids. Based on its chemotaxonomic and phylogenetic characteristics, strain Sd/3T was identified as a species of the genus Bacillus. It exhibited maximum similarity (95 %) at the 16S rRNA gene level with Bacillus cohnii; however, DNA–DNA similarity with B. cohnii was 60·7 %. Strain Sd/3T also exhibited a number of phenotypic differences from B. cohnii (DSM 6307T). These data suggest that Sd/3T represents a novel species of the genus Bacillus. The name Bacillus indicus sp. nov. is proposed.
BackgroundBacteriocins are antimicrobial peptides that are produced by bacteria as a defense mechanism in complex environments. Identification and characterization of novel bacteriocins in novel strains of bacteria is one of the important fields in bacteriology.Methodology/FindingsThe strain GI-9 was identified as Brevibacillus sp. by 16 S rRNA gene sequence analysis. The bacteriocin produced by strain GI-9, namely, laterosporulin was purified from supernatant of the culture grown under optimal conditions using hydrophobic interaction chromatography and reverse-phase HPLC. The bacteriocin was active against a wide range of Gram-positive and Gram-negative bacteria. MALDI-TOF experiments determined the precise molecular mass of the peptide to be of 5.6 kDa and N-terminal sequencing of the thermo-stable peptide revealed low similarity with existing antimicrobial peptides. The putative open reading frame (ORF) encoding laterosporulin and its surrounding genomic region was fished out from the draft genome sequence of GI-9. Sequence analysis of the putative bacteriocin gene did not show significant similarity to any reported bacteriocin producing genes in database.ConclusionsWe have identified a bacteriocin producing strain GI-9, belonging to the genus Brevibacillus sp. Biochemical and genomic characterization of laterosporulin suggests it as a novel bacteriocin with broad spectrum antibacterial activity.
Strain HHS 22T was isolated from a glacial water sample from the snout of the Hamta glacier located in the Himalayan mountain ranges of India. Phenotypic, chemotaxonomic and phylogenetic analyses established the affiliation of the isolate to the genus Pedobacter. The genus Pedobacter was created to accommodate species characterized by Gram-negative rods that are heparinaseproducing, obligately aerobic, with or without gliding motility, negative for urease, lipase, gelatinase, arginine dihydrolase, indole production and nitrate reduction, and contain iso-C 15 : 0 , iso-C 15 : 0 2-OH, iso-C 15 : 0 3-OH, C 16 : 0 , C 16 : 1 v5c, C 16 : 1 v7c, C 16 : 0 3-OH, iso-C 17 : 0 3-OH and iso-C 17 : 1 v9c fatty acids (Steyn et al., 1998). Five species of Pedobacter have been described thus far, and they have been isolated from soil (Pedobacter heparinus, Pedobacter africanus and Pedobacter saltans), fish (Pedobacter piscium) and a glacier in the Tyrolean Alps (Austria) (Pedobacter cryoconitis) (Steyn et al., 1998;Margesin et al., 2003). In the present report, we have characterized a bacterium isolated from a glacial water sample collected from the snout of a glacier. Phenotypic, chemotaxonomic and phylogenetic analyses establish the affiliation of the isolate to the genus Pedobacter. The data also suggest that the isolate is different from the recognized species of Pedobacter. Therefore, it is proposed to assign the isolate to a novel species, for which the name Pedobacter himalayensis sp. nov. is proposed. . Based on their morphology these colonies could be grouped into 26 different morphotypes. Representative strains from each morphotype were initially characterized based on their 16S rRNA gene sequence. Analysis using the BLAST program indicated that all the strains were closely related to recognized species (>98 % sequence similarity). Strain HHS 1 is closely related to Pseudomonas meridiana (GenBank/EMBL/DDBJ accession no. AJ537602), HHS 5 and HHS 23 to Pseudomonas antarctica (AJ537601), HHS 12, HHS 13, HHS 24 and HHS 29 to Pseudomonas veronii (AY267192), HHS 3 and HHS 15 to Pseudomonas migulae (AY047218), HHS 2, HHS 9 and HHS 16 to Pseudomonas fluorescens (AY538263), HHS 8 to Pseudomonas lini (AY035996), HHS 17, HHS 18, HHS 19 and HHS 20 to Pseudomonas jessinii (AY391278), HHS 4 to Serratia marcescens (AF076038), HHS 6, HHS 7 and HHS 32 to Janthinobacterium lividum (AY247410), HHS 10 to Bacillus subtilis (AY672765), HHS 27 and HHS 28 to Hafnia alvei (AY572428), HHS 31 to Exiguobacterium acetylicum (AY297792) and HHS 22T to Pedobacter cryoconitis (AJ585231). Because these isolates were isolated from glacial water they are likely to be psychrophilic and may thus represent either a psychrophilic variant of the previously reported strain or a novel species. Strain HHS 22 T was selected for detailed analysis to establish its identity based on a polyphasic taxonomic approach; a major consideration for choosing this strain was that only five species have been described so far for Pedobacter. Strain HHS 22T was maintained on ...
Background:PhoP is global regulator of Mycobacterium tuberculosis physiology. However, the role of phosphorylation of PhoP remains unknown. Results: PhoP activates complex lipid biosynthesis only upon phosphorylation. Conclusion: PhoP regulates lipid biosynthesis by a phosphorylation-dependent mechanism to contribute to morphology of the bacilli. Significance: This study sheds light on the unexplored role of phosphorylation of PhoP in regulating biosynthesis of lipids unique to M. tuberculosis.
BackgroundIncreasing multidrug-resistance in bacteria resulted in a greater need to find alternative antimicrobial substances that can be used for clinical applications or preservation of food and dairy products. Research on antimicrobial peptides including lipopeptides exhibiting both narrow and broad spectrum inhibition activities is increasing in the recent past. Therefore, the present study was aimed at isolation and characterization of antimicrobial lipopeptide producing bacterial strains from fecal contaminated soil sample.ResultsThe phenotypic and 16S rRNA gene sequence analysis of all isolates identified them as different species of Gram-negative genera Citrobacter and Enterobacter. They exhibited common phenotypic traits like citrate utilization, oxidase negative and facultative anaerobic growth. The HPLC analysis of solvent extracts obtained from cell free fermented broth revealed the presence of multiple antimicrobial lipopeptides. The comprehensive mass spectral analysis (MALDI-TOF MS and GC-MS) of HPLC purified fractions of different isolates revealed that the lipopeptides varied in their molecular weight between (m/z) 607.21 to 1536.16 Da. Isomers of mass ion m/z 984/985 Da was produced by all strains. The 1495 Da lipopeptides produced by strains S-3 and S-11 were fengycin analogues and most active against all strains. While amino acid analysis of lipopeptides suggested most of them had similar composition as in iturins, fengycins, kurstakins and surfactins, differences in their β-hydroxy fatty acid content proposed them to be isoforms of these lipopeptides.ConclusionAlthough antimicrobial producing strains can be used as biocontrol agents in food preservation, strains with ability to produce multiple antimicrobial lipopeptides have potential applications in biotechnology sectors such as pharmaceutical and cosmetic industry. This is the first report on antibacterial lipopeptides production by strains of Citrobacter and Enterobacter.
A bacterial strain producing two antimicrobial peptides was isolated from a rhizosphere soil sample and identified as Bacillus subtilis based on both phenotypic and 16S rRNA gene sequence phylogenetic analysis. It grew optimally up to 14% NaCl and produced antimicrobial peptide within 24 h of growth. The peptides were purified using a combination of chemical extraction and chromatographic techniques. The MALDI-TOF analysis of HPLC purified fractions revealed that the strain SK.DU.4 secreted a bacteriocin-like peptide with molecular mass of 5323.9 Da and a surface-active lipopeptide (m/z 1056 Da). The peptide mass fingerprinting of low-molecular-weight bacteriocin exhibited significant similarity with stretches of secreted lipoprotein of Methylomicrobium album BG8 and displayed 70% sequence coverage. MALDI MS/MS analysis elucidated the lipopeptide as a cyclic lipopeptide with a β-hydroxy fatty acid linked to Ser of a peptide with seven α-amino acids (Asp-Tyr-Asn-Gln-Pro-Asn-Ser) and assigned it to iturin-like group of antimicrobial biosurfactants. However, it differed in amino acid composition with other members of the iturin family. Both peptides were active against Gram-positive bacteria, suggesting that they had an additive effect.
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