Isolation and characterization of a mildly thermophilic nonsulfur purple bacterium containing bacteriochlorophyllb

Abstract

A mildly thermophilic bacterium isolated from a New Mexican hot spring microbial mat is described. The organism is a budding bacterium and contained bacteriochlorophyll b as sole chlorophyll pigment. The organism grew up to 47°C and grew optimally around 42°C. The new organism required only biotin and a reduced sulfur source (for biosynthetic purposes) as growth factors, and utilized a relatively restricted group of organic compounds as sole carbon sources. The hotspring anoxygenic phototroph also fixed N2 up to 47°C and showed ammonia ‘switch-off’ of nitrogenase activity, typical of mesophilic phototrophic bacteria. The new organism, which we refer to as Rhodopseudomonas strain GI, is the first bacteriochlorophyll b-containing nonsulfur purple bacterium shown capable of growth above 45°C.