Spirochaeta bajacaliforniensis sp. n. from a microbial mat community at Laguna Figueroa,Baja California Norte,Mexico

A new anaerobic spirochete was isolated from anaerobic muds beneath the laminated sediment in the evaporite flat at Laguna Figueroa, Baja California Norte, Mexico. The organism is a member of the stratified microbial community involved in the deposition of the laminated sediments in the lagoon. The size of the spirochete is 0.3 by 30 m, with a wave amplitude of 0.5 m and a wavelength of 1.25 m. The periplasmic flagella have a 1-2-1 arrangement. The outer membrane of the modified Gramnegative cell wall (the sheath) is irregularly crenulated and has a sillon. The growth medium contained yeast extract, trypticase, cellobiose, sodium thioglycolate and at least 20% natural seawater. Chemically defined artificial seawater media did not support growth. Optimal growth occurred with a seawater concentration of 80% at 36° C and a pH of 7.5. Glucose was fermented to acetate, ethanol, carbon dioxide and hydrogen. The guanine+cytosine content of the DNA was 50 mol %. the spirochete body reacts positively to antibodies raised against eukaryotic brain tubulin protein. On the basis of its free-living anaerobic habitat, its unique morphological and physiological characteristics and G+C ratio, it is proposed that this isolate be considered a new species and named Spirochaeta bajacaliforniensis.