Intracellular Production of Brucella L Forms I. Recovery of L Forms from Tissue Culture Cells Infected with Brucella abortus.

Hatten, Betty A. (The University of Texas Southwestern Medical School, Dallas), and S. Edward Sulkin. Intracellular production of Brucella L forms. I. Recovery of L forms from tissue culture cells infected with Brucella abortus. J. Bacteriol. 91:285-296. 1966.-Infectivity of virulent Brucella abortus strain 3183 was less for hamster macrophages after a 2-hr adsorption period than for an attenuated strain (S19) and its tissue culture variant (30). Both strains S19 and 30 were very toxic for the cells, but 3183 was not toxic. Two types of L forms were recovered from a large percentage of hamster kidney cell cultures when disintegration of infected cells was accelerated by tissue culture medium of high pH. One type grew in finely granular microcolonies, was isolated from cells infected for short periods of time, and often reverted to the bacterial form. The other type occurred in small irregularly shaped forms which later developed into round bodies. Both stained specifically with fluorescein-conjugated B. abortus antiserum. Semisolid media containing 0.7% agar provided optimal subsurface L-form growth. L forms also grew well in Thioglycollate Medium but grew poorly in other liquid media. Surface L-form growth was supported by several agar media, but CO(2) was required for optimal growth. Monolayers infected with strain 3183 and examined immediately after adsorption contained occasional small, round bodies. Bizarre forms increased in number with time and, after 24 to 72 hr, large pink-staining inclusions were often present which persisted for several days. Also appearing at about the same time were smaller, dark-staining forms which were first seen in clusters but later dispersed and finally occurred in chainlike configurations. Direct fluorescent-antibody stains of infected cells established that the intracellular forms were related to the infecting strain of B. abortus.