48] The Halobacterium group: Microbiological methods

Abstract

This chapter describes microbiological methods for the isolation, cultivation, and maintenance of Halobacterium strains. It is found that phenotypic instabilities are correlated with complex alterations in Halobacterial plasmid DNA sequences. These observations suggest that rigorous criteria should be established to monitor constantly each wild-type halobacterial strain for genotypic and phenotypic purity. Maintenance or cultivation of halobacterial strains under inappropriate conditions may allow the inadvertent selection of spontaneously occurring pseudo-wildtype strains that are uniquely adapted to a particular laboratory environment. Halobacterium strains can be maintained on RM agar plates for 6 months to 1 year. The plates should be sealed tightly with parafilm to prevent desiccation. RM agar slants tightly sealed with parafilm and stored at 4° preserves Halobacterium strains for 1–2 yrs. Halobacterium strains can be isolated and cultured from natural environments by a variety of techniques. Liquid medium can be prepared by centrifuging the natural medium at 6000 g for 30 min followed by heat or membrane sterilization. Solid medium can be prepared using 1.5% w/v Noble Agar. More rapid growth in these natural media is obtained by supplementation with 0.5% (w/v) peptone.