Summary auto-generated
Researchers isolated a novel thermophilic bacterium designated MV1075T from deep-sea hydrothermal chimney samples at the Mid-Atlantic Ridge. The organism is a rod-shaped, Gram-negative, motile bacterium with a characteristic sheath-like outer membrane (toga) typical of Thermotogales. Growth occurs at 25–65°C with optimal conditions at 55°C, pH 7, and 30 g/L sea salt. The isolate is an obligate chemo-organotroph that utilizes both carbohydrates and complex proteinaceous substrates, including glucose, cellobiose, sucrose, starch, and cellulose. Notably, elemental sulfur is not required for growth but enhances metabolism when present, increasing acetate and amino acid production. During cultivation on glucose medium, the bacterium produces acetate, lactate, isovalerate, isobutyrate, H₂, CO₂, and H₂S. The DNA G+C content is 29 mol%. Phylogenetic analysis of the 16S rRNA gene sequences places this strain within the order Thermotogales, Bacteria domain. Based on morphological, physiological, and molecular characteristics distinct from existing genera, this isolate is designated as a new genus and species: Marinitoga camini gen. nov., sp. nov.
Key findings
- MV1075T is a thermophilic, anaerobic, rod-shaped bacterium isolated from deep-sea hydrothermal vents with optimal growth at 55°C, pH 7, and 30 g/L sea salt
- The organism is an obligate chemo-organotroph capable of fermenting diverse carbohydrates and proteinaceous substrates, producing organic acids, H₂, CO₂, and H₂S
- Phylogenetic analysis of 16S rRNA sequences establishes MV1075T as a novel genus within the order Thermotogales, designated Marinitoga camini
- Elemental sulfur and cystine enhance growth and metabolic activity but are not essential; sulfur inhibition by H₂ is relieved in presence of sulfur with H₂S production
- The bacterium possesses the characteristic toga (sheath-like outer membrane) structure of Thermotogales with 29 mol% G+C content in genomic DNA
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Abstract
A thermophilic, anaerobic, chemo-organotrophic sulfur-reducing bacterium, designated MV1075(T), was isolated from a deep-sea hydrothermal chimney sample collected on the Mid-Atlantic Ridge. Cells were rod-shaped with a sheath-like outer structure, motile with polar flagella and stained Gram-negative. They appeared singly, in pairs or in short chains. The temperature range for growth was 25--65 degrees C, with an optimum at 55 degrees C. Growth was observed from pH 5 to pH 9, and the optimum pH was around 7. The salinity range for growth was 15--70 g sea salt l(-1) (corresponding to 10--45 g NaCl l(-1)), with an optimum at 30 g l(-1) (20 g NaCl l(-1)). The isolate was able to grow on a broad spectrum of carbohydrates or complex proteinaceous substrates. Sulfur was not necessary for growth. Growth was inhibited by H(2), but, in presence of sulfur, this inhibition was removed and H(2)S was produced. The G+C content of the genomic DNA was 29 mol%. Phylogenetic analyses of the 16S rRNA gene located the strain within the order Thermotogales, in the domain Bacteria. On the basis of 16S rDNA sequence comparisons, in combination with morphological and physiological characteristics, it is proposed that the isolate should be described as a novel species of a new genus, Marinitoga gen. nov., of which Marinitoga camini sp. nov. is the type species. The type strain is MV1075(T) (=CNCM I-2413(T)=DSM 13578(T)).