Transformation of auxotrophic mutants of group H streptococci.

Stable auxotrophic mutants of a group H streptococcus (strain Challis) were isolated on a modified Mickelson defined medium after exposure to N-methyl- N-nitro-N-nitrosoguanidine. Such mutants were transformed to both prototrophy and streptomycin-resistance and hence may be used as nutritional markers in the study of streptococcal genetics.