Auxotrophy in natural isolate: minimal requirements for growth of the Antarctic psychrotrophic bacterium Pseudomonas syringae Lz4W

Abstract

A chemically defined minimal medium has been developed for growing the Antarctic psychrotrophic bacterium Pseudomonas syringae Lz4W, a model system for studying cold adaptation. This natural isolate from Antarctica has an absolute requirement for two branched chain amino acids, isoleucine and valine, in addition to low osmolality of the growth medium. The bacterium contains threonine deaminase but lacks acetohydroxyacid synthase suggesting that a defect lies in the isoleucine and valine biosynthetic pathway causing auxotrophy. Succinate was found to be preferred carbon source over glucose as it could suppress the glucose metabolizing enzymes in the cells, like in other pseudomonads. The development of the minimal medium (MM Lz) for growing the Antarctic P. syringae Lz4W strain would be useful for investigation of the catabolite repression control mechanism at a very low temperature (below 5 degrees C), which is predominant in vast area of our global ecosystems.