Studies of two strains of Actinopolyspora halophila, an extremely halophilic actinomycete

Abstract

Actinopolyspora halophila is an extremely halophilic actinomycete requiring a minimum salt concentration of 12% (w/v) for growth in liquid media at 37°C. During antibiotic sensitivity testing of the organism, an erythromycin-resistant phenotypic variant designated A. halophila ER, was isolated. This strain was approximately 60-fold more resistant to erythromycin than the wild-type strain, and, moreover, was capable of growth in 6% sodium chloride. Optimal growth of both strains in liquid media was observed in 20% salt. After resuspension in water for up to 20 days, the organism exhibited good growth in fresh salt-containing media. Cultures resuspended in salt-containing media, however, were subject to extensive cellular autolysis. In addition to resistance to β-lactam antibiotics which was mediated by cellular and exocellular β-lactamases, the organism was insensitive to all other tested antibiotics except amakacin, chloramphenicol, kanamycin, gentamycin, naladixic acid, streptomycin, and tetracycline. No plasmids were detected in either strain. A. halophila possessed high cellular levels of catalase, β-lactamase, and β-glucosidase. A variety of exocellular enzymes including protease, β-lactamase, xylanase, and carboxymethyl cellulase, were secreted maximally into growth media containing 15% NaCl.