Ultrastructural Organization and Enzymes of the Antioxidant Defense System in the Dormant Cells of Gram-Negative Bacteria Stenotrophomonas sp. Strain FM3 and Morganella morganii subsp. sibonii Strain FF1

Anabiotic dormant forms (DF) of gram-negative bacterial epibionts of the smooth clawed frog Xenopus laevis—Stenotrophomonas sp. strain FM3 and Morganella morganii subsp. sibonii strain FF1, were obtained and characterized. The ultrastructural features of the dormant cells of strains FM3 and FF1 (large periplasmic space, dense heterogeneous cytoplasm, and ordered reorganization of the compacted nucleoid) were typical of the cystlike cells (CLC) of the previously studied other taxa of gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, P. fluorescens, Azospirillum brasilense , etc.). Preservation of potentially active enzymes of the antioxidant defense systems was not previously reported for anabiotic dormant forms. They are probably responsible for DF survival at early stages of their germination, providing for resistance to new medium stress and other stressors in the absence of de novo enzyme synthesis. Our results are of interest for both basic microbiology and biomedicine, since strains FM3 and FF1 are phylogenetically related to bacterial agents of nosocomial clinical infections and emergence of their dormant forms may explain resistance of nosocomial infections to sanitary treatment.