E S Babusenko

Bio: E S Babusenko is an academic researcher. The author has contributed to research in topics: Autolysis (biology) & Methylococcus capsulatus. The author has an hindex of 2, co-authored 2 publications receiving 25 citations.

Formation of resting cells in microbial suspensions undergoing autolysis

Abstract: Under experimentally selected conditions favoring spontaneous or induced autolysis of cell suspensions, the asporogenous bacteria Escherichia coli and Methylococcus capsulatus, the bacilli Bacillus cereus (under conditions of suppressed sporulation), and the yeast Saccharomyces cerevisiae were shown to be capable of forming cystlike resting cells. Their number was influenced by (1) cell density in the suspensions; (2) the presence of Ca2+ ions in nutrient-limited medium; (3) pH of medium; and (4) autolysis rate, dependent on the concentration of oleic acid (a chemical analogue of the autolysis-inducing d2 factor) introduced into the cell suspensions.

Membranotropic autoregulatory factors in methane oxidising bacteria

Abstract: It is possible that the methane oxidising bacteria M. capsulatus synthesise in the course of their development and secrete into the culture liquid extracellular metabolites — membranotropic autoregulatory factors d1 and d2 the synthesis of which had been observed earlier in other groups of microorganisms. It is shown that the physiological effect of the factor d2 is due to the influence of the fraction comprising free aliphatic acids and containing mainly palmitic and palmitoleic acids. One of the manifestations of the effect of the specific autoregulatory factor d1 as its concentration increases in the culture medium is the transition of the vegetative cells to a hypometabolic state. The active principle of the factor d1 is the lactone of 3-deoxypentonic acid. A practical use for the chemical analogues of the autoregulatory factors d1 and d2 is suggested. The bibliography includes 25 references.

Adaptogenic functions of extracellular autoregulators of microorganisms

Abstract: 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.

[Ultrastructure of resting cells of some non-spore-forming bacteria].

Abstract: Using electron microscopy (ultrathin sections and freeze-fractures), we investigated the ultrastructure of the resting cells formed in cultures of Micrococcus luteus, Arthrobacter globiformis, and Pseudomonas aurantiaca under conditions of prolonged incubation (up to 9 months). These resting cells included cystlike forms that were characterized by a complex cell structure and the following ultrastructural properties: (i) a thickened or multiprofiled cell wall (CW), typically made up of a layer of the preexisting CW and one to three de novo synthesized murein layers; (ii) a thick, structurally differentiated capsule; (iii) the presence of large intramembrane particles (d = 180–270 A), occurring both on the PF and EF faces of the membrane fractures of M. luteus and A. globiformis; (iv) a peculiar structure of the cytoplasm, which was either fine-grained or lumpy (coarse-grained) in different parts of the cell population; and (v) a condensed nucleoid. Intense formation of cystlike cells occurred in aged (2- to 9-month-old) bacterial cultures grown on diluted complex media or on nitrogen-, carbon-, and phosphorus-limited synthetic media, as well as in cell suspensions incubated in media with sodium silicate. The general morphological properties, ultrastructural organization, and physiological features of cystlike cells formed during the developmental cycle suggest that constitutive dormancy is characteristic of non-spore-forming bacteria.

Autoregulation of stress response in microorganisms

Abstract: Examples are considered of the involvement of low-molecular-weight autoregulators in the development of resistance of proliferating microbial cultures to unfavorable environmental impacts of various intensity, including impacts programmed to occur in the developmental cycle (“new medium stress,” starvation stress) and nonprogrammed impacts. It was shown that extracellular adaptation factors control the reversible adhesion of cells in submerged cultures and the processes of cell reactivation in the poststress period and are involved in the stabilization of cellular biopolymers (proteins and DNA) and subcellular structures (membranes); the adaptogens of the phenolic type also act as efficient scavengers of reactive oxygen species. The protective effect of the adaptogenic autoregulators is manifested in the increase of resistance of microbial cells to stressors of various nature and in the preservation of the cell proliferative ability.

Production of Dormant Stages and Stress Resistance of Polar Cyanobacteria

Abstract: Cyanobacteria represent the major component of the autotrophic community in many different types of habitats in both the Arctic and Antarctic. Their dominance is attributed mainly because of their high tolerance to the extreme polar environments. Low temperatures and desiccation are the main forms of physical environmental stressors. During freezing-melting and desiccation periods, the cells are exposed to radical dehydration effects which can be quite damaging. Polar cyanobacteria have evolved a diverse range of protective strategies in order to avoid, or tolerate, the various stresses. The most widespread adaptation to environmental stress is dormancy. Dormancy can be subdivided into diapause and quiescence. Diapause (the cyanobacterial akinete) is endogenously controlled: it is connected to external stressors but is not directly induced by them. Akinetes are more resistant to various insults and commonly considered as overwintering stages. However, the majority of cyanobacteria in the polar regions survive winters without the production of akinetes. This suggests that other alternative mechanisms contribute to survival during stressful conditions. Quiescence (the decrease of metabolic activity under exogenous control) is the transformation into a resistant state, with hardly visible morphological differentiation of the cell. It has been suggested that starvation and entrance into the stationary phase can induce changes in the ultrastructure (e.g., thickening of cell walls) and biochemistry (e.g.,sucrose and trehalose accumulation, changes in composition of fatty acids, secretion of extracellular polysaccharides) of the stressed cells. We accept that the stationary-phase and/or starvation-induced cells can represent alternative dormant stages of polar cyanobacteria which do not produce akinetes. This overview summarizes the present knowledge about production of dormant stages and stress resistance of polar cyanobacteria. It is clear that we still have paucity of information on this topic and that further research is necessary.