[Attempts of ultrastructural and biochemical characterisation of cell wall deficient "Brucella" (L forms) (author's...

In previous studies the in vivo conversion of Brucella suis to L-form state was put in evidence. The L forms isolated from mouse spleen had original structural aspects in common: the absence of the cell wall layer and the extracellular multilayer "membranous" structures. The biological characterization of these L forms and the preliminary identification of specific chemical markers of the bacterial envelope is reported in the present study, performed with the stable L forms well-growing in the liquid media. The electron microscopy confirmed the absence of cell wall and the presence of numerous dense multilayer membranous structures in the L forms cultivated for a long time on appropriate media. This aspect was changed in the L forms adapted to growth on the ordinary medium for brucella: numerous small dense bodies limited by unit membrane were observed. The chemical analysis of stable L forms showed the absence of diaminopimelic acid, confirming the lack of peptidoglycan. The result of chemical determination in L forms of the Na-2-keto-3-deoxyoctonate was negative. However, biological assays suggested that outer membrane components such as LPS and receptors for the bacteriophage Weybridge remained in the L forms, albeit in reduced amount as compared to parental brucella.