T-mycoplasmas: Growth patterns and physical characteristics of some human strains

Five T-mycoplasmas isolated from patients with nonspecific urethritis and five laboratory strains of T-mycoplasma were examined for differentiating biological properties. The strains differed by the presence or absence of a lag phase and the number of T-mycoplasmas constituting a colony-forming unit (cfu). Most T-mycoplasmas had no lag phase and a cfu consisting of single organisms. All had biphasic ultraviolet inactivation curves typical of suspensions containing both mononucleate and binucleate cells. Binucleate cells probably were in the process of division. They resisted sonication for 3 min. Sonication disrupted multicellular cfu in to single cells within 2 min. Stationary-phase organisms died more rapidly than exponential-phase cells. T-mycoplasmas replicated at 2 C; they grew more slowly in T-broth at 40 C and died in 2.5 min at 56 C. Inactivation curves at 45 C and 50 C differed but insufficiently to permit identification of individual strains. At pressures less than 5 psi, single-cell suspensions passed through filter membranes with 0.65-mum and 0.45-mum pores but were retained by membranes with 0.22-mum pores.