An obligately anaerobic, coiled bacterium from Ace Lake, Antarctica

Abstract

Summary: A coiled or ‘C-shaped’, Gram-negative, non-motile bacterium was isolated from the anaerobic waters of Ace Lake, an Antarctic lake of salinity similar to seawater. The strain was obligately anaerobic and lacked oxidase, catalase and respiratory lipoquinones. It fermented glucose and peptones, and formed H2, CO2, and butyric, acetic and formic acids as major end-products. Pyruvate was metabolized to H2, CO2, and acetic and formic acids. The organism had an optimum temperature for growth of 15-16 °C, and no growth occurred at 22 °C. In synthetic medium, the generation time at 1·7 °C (in situ lake temperature) was 53 h. The optimum NaCl concentration for growth was 0·3 m, with poor growth at 0·1 m (5·8%, w/v). The mol% G + C of the DNA was 25·9 ± 0·4% (T m). The bacterium could not be accommodated within current bacterial species based on phenotypic criteria. Although coiled bacteria have been previously observed in Antarctic anaerobic environments, they had not been cultivated, and their metabolic capability and possible ecological role were unknown.