Conditions affecting the viability of spheroplasts in urine.

Penicillin-induced spheroplasts from Escherichia coli and Proteus vulgaris, which at neutral pH had little resistance to osmotic lysis, retained viability in media of low osmolality at pH 5.0 to 5.5. In the presence of 1,000 IU of penicillin per ml (pH 5.0) in liquid media, E. coli remained in rod form without conspicuous growth. On hypotonic agar media at pH 5.2 with 1,000 IU of penicillin per ml, the bacteria grew out as L-type colonies. These findings are discussed in relation to penicillin therapy.