Straight rods to slightly curved, rectangular or round ends (0.4-0.5 x 5-20 microns to 50 microns), curved forms, connected, T or Y, Gram-negative, non-motile, division by constriction , the presence of spherical protrusions 1-3 mm in diameter at the ends of the cells. Heterotrophic growth, anaerobic or microaerophilic complex on organic substrates, with S °, thiosulfate, L-cystine and low sulfate as electron acceptors. Use nitrate and FeCl3 in an atmosphere of H2/CO2. Optimum growth temperature 75 ° C (45-82 ° C) at an optimum pH of 4 (2.6 to 5.9).Division time from 15 to 18 h. DNA: 52 mol% G+ C. Habitat: acidic hot springs. A single species, Thermocladium modestius .
