Information about the functions of extracellular autoregulators, which adapt microorganisms to the stresses “scheduled” in the development cycle of microbial cultures (stresses of new medium, starvation, or space exhaustion (high cell density)) is summarized in the review. In a number of bacteria and yeasts, derivatives of alkylhydroxybenzenes (AHB), particularly of the class of alkyl resorcinols, act as autoregulators with adaptogenic functions. The chemical structure of AHB determines their amphiphility; capacity for physical and chemical interaction with membrane lipids, proteins, and DNA; properties as natural modifiers of biological membranes and enzymes; and the expression of antioxidant activity. Increase of AHB concentration up to the critical level (10⁻⁵-10⁻⁴ M) results in cessation of cell division and in transition of the microbial culture to the stationary phase; further increase to 10⁻⁴-10⁻³ M induces a transition of some of the cells of a post-stationary culture to the anabiotic state with the formation of cystlike resting cells (CRC), even in non-spore-forming bacteria. AHB participate in the regulation of the phenotypic variability of bacteria. The dynamics of extra-and intracellular concentrations of AHB in growing microbial cultures and the polymodality of their effect determine the adaptogenic functions of AHB as autoinhibitors of culture growth, autoinducers of anabiosis, and autoinhibitors of germination of resting forms. Manifestation of any given function depends on the concentration of AHB, the physiological state of the recipient cells, and on environmental factors. The species nonspecificity of AHB effects points to their significant role in the regulation of the development and functioning of microbial communities.

Differences in generation of dormant forms (DF) were revealed between two strains of non-sporeforming gram-negative bacteria Azospirillum brasilense, Sp7 (non-endophytic) and Sp245 (endophytic...

The colony-forming ability of long (3–9 months) incubated cystlike resting cells (CRC) of the nonspore-forming gram-positive bacteria Micrococcus luteus and Arthrobacter globiformiswas studied in...

Ability to produce dormant forms (DF) was demonstrated for non-spore-forming bacteria Staphylococcus aureus (a nonpathogenic strain) and Corynebacterium pseudodiphtheriticum (an organism of the normal oropharyngeal flora). The salient features of the sthaphylococcal and corynebacterial DF were (1) prolonged (4 months) preservation of viability; (2) resistance to damaging factors (heat treatment); and (3) specific morphology and ultrastructure. The optimal conditions for DF formation were (1) transfer of stationary-phase cultures into saline solution with CaCl₂ (10–300 mM) (for S. aureus); (2) growth in SR1 synthetic medium with fivefold nitrogen limitation (for C. pseudodiphtheriticum); and (3) incubation with (1–5) × 10⁻⁴ M of C₁₂-AHB, an alkylhydroxybenzene akin to microbial anabiosis autoinducers. Increase of C₁₂-AHB concentration to 7 × 10⁻⁴–2 × 10⁻³ M resulted in “mummification” of cells with irreversible loss of viability without autolytic processes. Germination of dormant forms was followed by increasing of phenotypic variability, as seen from (1) diversity of colony types and (2) emergence of antibiotic-resistant clones on selective media. The share of kanamycin-resistant S. aureus variants was most numerous (0.002–0.01%) in 4-month DF suspensions in SALINE with CaCl₂. In the C. pseudodiphtheriticum DF produced under the effect of C₁₂-AHB, the share of kanamycin-resistant variants was also found to increase. These data point to an association between the emergence of antibiotic-resistant variants of bacteria and their persistence in dormant state mediated by starvation stress and regulated by AHB.

Cystlike resting cells (CRC) of non-spore-forming gram-negative bacteria of the genus Pseudomonas, P. aurantiaca and P. fluorescens, were obtained and characterized for the first time; their...