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Phylogenetic diversity of gram-positive bacteria cultured from marine sediments.

ABSTRACT: Major advances in our understanding of marine bacterial diversity have been gained through studies of bacterioplankton, the vast majority of which appear to be gram negative. Less effort has been devoted to studies of bacteria inhabiting marine sediments, yet there is evidence to suggest that gram-positive bacteria comprise a relatively large proportion of these communities. To further expand our understanding of the aerobic gram-positive bacteria present in tropical marine sediments, a culture-dependent approach was applied to sediments collected in the Republic of Palau from the intertidal zone to depths of 500 m. This investigation resulted in the isolation of 1,624 diverse gram-positive bacteria spanning 22 families, including many that appear to represent new taxa. Phylogenetic analysis of 189 representative isolates, based on 16S rRNA gene sequence data, indicated that 124 (65.6%) belonged to the class Actinobacteria while the remaining 65 (34.4%) were members of the class Bacilli. Using a sequence identity value of >/=98%, the 189 isolates grouped into 78 operational taxonomic units, of which 29 (37.2%) are likely to represent new taxa. The high degree of phylogenetic novelty observed during this study highlights the fact that a great deal remains to be learned about the diversity of gram-positive bacteria in marine sediments.

SUBMITTER: Gontang EA

PROVIDER: S-EPMC1907118 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature

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Phylogenetic diversity of gram-positive bacteria cultured from marine sediments.

Gontang Erin A EA Fenical William W Jensen Paul R PR

Applied and environmental microbiology 20070330 10

Major advances in our understanding of marine bacterial diversity have been gained through studies of bacterioplankton, the vast majority of which appear to be gram negative. Less effort has been devoted to studies of bacteria inhabiting marine sediments, yet there is evidence to suggest that gram-positive bacteria comprise a relatively large proportion of these communities. To further expand our understanding of the aerobic gram-positive bacteria present in tropical marine sediments, a culture- ...[more]

PMID: 17400789

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Project description:The rapid evolution of antibiotic resistance is shrinking our stockpile of commercially available antibiotics. Therefore, new antimicrobials with novel mechanisms of action (MoAs) are desperately needed. The free fatty acid, (Z)-13-methyltetra-4-decenoic acid ((Z)-4C-14:1), isolated from a marine sediment bacterium Olleya marilimosa, displays strong inhibition of Gram-positive pathogens with minimal cytotoxic effects to mammalian cells. Here, we applied a combination of experimental approaches to identify the mechanism by which (Z)-4C-14:1 kills the Gram-positive bacterium Bacillus subtilis. Using quick and cost-effective bacterial cytological profiling (BCP), we established the cytological signatures of 17 antibiotics representing 6 general classes of antibiotic MoAs. We used BCP to demonstrate that while (Z)-4C-14:1-treated B. subtilis cells display unique morphological features compared to other antibiotic classes, (Z)-4C-14:1 mode of action shares substantial overlap with the fast-acting antibiotic colistin specifically in Gram-positive cells and daptomycin, both of which target bacterial permeability by destroying the cell membrane and causing extensive cell surface alterations. To further determine if the cell membrane of B. subtilis was the target of (Z)-4C-14:1, we used cell membrane- and peptidoglycan-specific diagnostic stains to investigate bacterial permeability. Our results indicate that (Z)-4C-14:1 destabilizes the cell membrane by pore formation in Gram-positive bacteria and emphasize the importance of mining the marine environment for naturally occurring antibiotics.IMPORTANCEWith the lack of new antibiotics in the drug discovery pipeline, coupled with accelerated evolution of antibiotic resistance, new sources of antibiotics that target pathogens of clinical importance are paramount. Here, we use bacterial cytological profiling to identify the mechanism of action of the monounsaturated fatty acid (Z)-13-methyltetra-4-decenoic acid isolated from the marine bacterium Olleya marilimosa with antibacterial effects against Gram-positive bacteria. The fatty acid antibiotic was found to rapidly destabilize the cell membrane by pore formation and membrane aggregation in Bacillus subtilis, suggesting that this fatty acid may be a promising adjuvant used in combination to enhance antibiotic sensitivity.

Dataset Information

Phylogenetic diversity of gram-positive bacteria cultured from marine sediments.

Publications

Phylogenetic diversity of gram-positive bacteria cultured from marine sediments.

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