Summary auto-generated
This study describes the isolation and characterization of strain Fru22T, a strictly anaerobic, Gram-negative bacterium that grows optimally at 50°C in media containing up to 75 g/L NaCl. The organism was isolated from oily sedimentary residues and represents a new genus and species, Anaerophaga thermohalophila, based on phylogenetic analysis of 16S rDNA sequences. The strain ferments hexoses and pentoses to equal molar amounts of acetate, propionate, and succinate without producing CO2. When exposed to light during stationary phase, cells produce an orange-red carotenoid pigment similar to flexirubin. Notably, the organism produces an extracellular surface-active compound (tenside) that stabilizes oil-water emulsions, characterized as a lipopeptide containing fatty acids and sugar residues, heat-stable to 70°C and destroyed by protease treatment. The ability to thrive under combined heat and salinity stress while producing biosurfactants makes this organism potentially useful for microbially enhanced oil recovery applications in subsurface environments.
Key findings
- Anaerophaga thermohalophila is the first strictly anaerobic bacterium combining thermophily (optimum 50°C, maximum 55°C) and halophily (salt tolerance up to 12% w/v), an unusual combination not previously reported in the microbiological literature
- The strain produces a novel surface-active compound classified as a lipopeptide with low molecular mass (<12 kDa) containing fatty acids and sugar residues, stable up to 70°C and destroyed by protease but not lipase treatment
- 16S rDNA analysis confirms phylogenetic affiliation to the phylum Bacteroides with moderate relationship (91.6% similarity) to the genus Marinilabilia, justifying establishment of a new genus
- The organism produces an orange-red carotenoid pigment similar to flexirubin upon light exposure, making it only the second strictly anaerobic bacterium known to produce such pigments
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Abstract
The strictly anaerobic Gram-negative bacterium strain Fru22(T) grows at 50 degrees C in media containing up to 75 g NaCl l(-1). Hexoses and pentoses are fermented to equal molar amounts of acetate, propionate and succinate, and no CO(2) is formed. An orange-red pigment similar to flexirubin is produced during stationary phase upon exposure to light for several days. Cells also produce a surface-active extracellular compound which lowers the surface tension of the medium. This tenside is heat-tolerant up to 70 degrees C and is destroyed by treatment with proteinase K or trypsin, but not by lipase. Comparative 16S rDNA sequence analysis confirmed a phylogenetic affiliation of strain Fru22(T) to the phylum Bacteroides (Cytophaga/Flavobacterium/Bacteroides), moderately related to the genus Marinilabilia. Therefore, on the basis of phylogenetic, phenotypic and physiological evidence, a new genus, Anaerophaga, is proposed to harbour strain Fru22(T) (DSM 12881(T), OCM 798(T)) which is described as the type strain of a new species, Anaerophaga thermohalophila gen. nov., sp. nov.