HYDROLYSIS OF N'-BENZOYL-ARGININE-P-NITROANILIDE STEREOISOMERS AS A PHENOTYPIC TEST - A STUDY OF GRAM-POSITIVE HALOTOLERANT BACTERIA

We tested a variety of halotolerant Gram-positive coccoid bacteria and other halotolerant bacteria for hydrolytic activity towards the L- an d the D-isomer of N'-benzoyl-arginine-p-nitroanilide (BAPA). D-BAPA cl eaving activity was earlier shown to be associated with endospore-form ing bacteria and related organisms. Four groups were distinguished on the basis of their behavior towards the BAPA isomers: 1. D-BAPA cleavi ng bacteria: several Bacillus strains, two Planococcus species, and Ma rinococcus hispanicus. 2. Strain M96/12b, an endospore-forming bacteri um, that cleaves both isomers. 3. L-BAPA cleaving bacteria: Gram-negat ive halotolerant bacteria (Halomonas elongata, Vibrio costicola), the Gram-positive coccoid bacterium Micrococcus luteus, and Bacillus paste urii. 4. A number of Gram-positive cocci that cleave neither L-BAPA no r D-BAPA. Also a few ectoine-producing Bacillus species (B. halophilus , B. pantothenticus) fall in this category. We recommended to include the tests for L-BAPA and D-BAPA hydrolysis in phenotypic tests and num erical taxonomy studies of Gram-positive bacteria.