REDUCTION OF BENZYL VIOLOGEN DISTINGUISHES GENERA OF THE CLASS MOLLICUTES

We tested the ability of 62 growing strains belonging to the class Mol licutes to reduce the redox indicator and free-radical generator 1,1'- dibenzyl-4,4'-bipyridinium dichloride (benzylviologen [BV]) to a blue- violet-purple color, BV was reduced by 12 Acholeplasma species but not by Acholeplasma multiforme PN525(T) (T = type strain), BV was also re duced by five of nine Mesoplasma species and by four of six Entomoplas ma species, BV was not reduced by 19 Mycoplasma species, six Spiroplas ma species, five unnamed Spiroplasma strains belonging to different se rogroups, three Ureaplasma species, and one unnamed Ureaplasma strain, The BV-reducing ability was localized in the membrane of Acholeplasma laidlawii B-PG9 and was dependent on NADH, Reduction of BV could be e xpressed in mixed cultures, and this activity may be useful for recogn izing the contaminating presence of an Acholeplasma species, The reduc tive BV response may have phylogenetic value, We believe that the test described in this paper readily distinguishes all Acholeplasma specie s and some Mesoplasma and Entomoplasma species from all Mycoplasma, Sp iroplasma, and Ureaplasma species tested.