 | ||
ThermoanaerobacterRANK: GenusTAXONOMY: Bacteria -> Terrabacteria group -> Firmicutes -> Clostridia -> Thermoanaerobacterales -> Thermoanaerobacteraceae -> Thermoanaerobacter OVERVIEW: All species are obligately anaerobic thermophiles and have a Gram-positive cell wall, i.e., although the Gram-stain reaction varies among the individual species and even within strains from the same species, they have a Gram-positive cell-wall structure. Most species exhibit a sluggish motility and a peritrichous arrangement of 2–6 flagella (retarded peritrichous flagellation). Cells are rod shaped and occur in various arrangements that vary by species. Many of the Thermoanaerobacter species form pleomorphic cells during the late exponential and stationary growth phases assembling through nonsymmetric cell division chains of alternating rod-shaped and coccoid cells. Other types of pleomorphic rods are formed, presumably through weakening of the cell wall by lysozyme-like enzymes that are the remnants of the sporulation process (Figure 1). Growth temperature optima range from 55–75 °C, with growth ranges of 35–78 °C and a temperature span over 35 °C. The pH for growth ranges from pH25C 4.0–9.9, with a pH optimum of 5.8–8.5. Several species also exhibit a wide pH optimum of about 3 units without a sharp peak. All species are able to grow organoheterotrophically using various fermentation pathways including the homoacetogenic or Wood–Ljungdahl pathway, or using inorganic electron acceptors (e.g., Thermoanaerobacter sulfuriphilus using S0 as an electron acceptor and lactate as an electron donor and carbon source). Some Thermoanaerobacter strains are also able to grow chemolithoheterotrophically by coupling H2 oxidation to growth (Fardeau et al., 1994). Furthermore, others are facultative chemolithoautotrophs, growing with H2 + CO2 (such as Thermoanaerobacter kivui) or Fe(III) + H2 + CO2 (such as Thermoanaerobacter siderophilus). Generally, typical fermentation products from hexoses are ethanol, acetate, lactate, H2, and CO2. DNA G+C content (mol%): 30–39. Type species: Thermoanaerobacter ethanolicus |