Adaptation of mycoplasmas to adverse growth conditions: Morphology, ultrastructure, and genome expression of Mycoplasma gallisepticum S6 cells

Abstract

A considerable amount of experimental and theoretical data recently obtained in various laboratories of the world, including successful genome projects for 17 mycoplasma species, has greatly expanded our knowledge of the biology of minimal cell, which is associated with mycoplasmas, representing the class Mollicutes. However, the molecular bases of mycoplasma adaptation to biogenic and abiogenic stresses are still vague [1]. The goal of this work was to clarify the specific features of morphology, ultrastructure, and genomic expression of Mycoplasma gallisepticum S6 cells under various growth conditions. We are the first to demonstrate that the adaptation of M. gallisepticum S6 to stresses is associated with a specific remodeling of genome expression, which determines the reprogramming of mycoplasma cell biology in a manner allowing for survival under new conditions. Acholeplasma laidlawii , an omnipresent mycoplasma capable of infecting human, animal, and plant species and the main contaminant of cell cultures, and M. gallisepticum , a mycoplasma highly pathogenic for poultry and capable of infecting plants, the main contaminant of viral vaccines produced using chick embryos [2], are unique from the standpoint of their adaptive abilities. The absence of the cell wall, a miniature genome, and a limited metabolic potential are in no way important barriers for these mycoplasmas to survive under adverse conditions, overcome various host defense systems, and persist in the tissues of higher eukaryotes [1, 3‐5].