Evidence for the bacterial origin of Acholeplasma laidlawii A

L-forms from a Corynebacterium were induced in hyperosmolar media and gradually adapted to normal osmolarity over a period of two years. During this adaptation several morphologic L-form variants derived from the L-form cultures and were serologically identified as Acholeplasma laidlawii A. The possibility that the bacterial and L-form cultures were contaminated with acholeplasmas was carefully investigated; this was determined not to be the case. Membrane protein gel electrophoresis patterns of these L-form variants were identical to the ATCC A. laidlawii strain PG-8. Acholeplasma phage MVL-1 displayed no affinity for these L-form variants. Phage MVL-2 showed low affinity, but after virus enhancement in the specific host, high plaquing efficiency ensued. DNA hybridization experiments showed a high level of nucleotide sequence homology (greater than 90%) between the L-form-derived variants and PG-8. The homology between the diphtheroid L-forms and the PG-8 strain was 16.4% with te50 values of 86%; this indicates strong base pairing homology. These findings suggest that the L-form variants are acholeplasmas and that they are biologically and genetically related to the Corynebacterium L-forms.