Persistence of bacterial pathogens as a physiological phenomenon

The complex ecosystem of humans and microbes has been presented as an associative symbiosis based on a mutual support of symbionts with different consequences for them. Conditions for the persistence of bacteria have been defined: their resistance to environmental factors, antagonism in biocenosis, and stability to withstand host defense mechanisms. The key role of bacterial peptidoglycan has been defined for their survival in an infected organism, and the classification for persistent mechanisms of pathogens has been given. The group of bacterial secreted protease providing microbial resistance to defense factors of the organism has been described. Host colonizing resistance has been presented as a physiological regulatory system controlling bacterial penetration into an organism. Regulatory mechanisms for bacterial persistence have been discussed.     

Effect of normal microflora of female reproductive tract in colonization resistance

The role of female reproductive tract microflora in the maintenance of biotope colonization resistance was described. The role of lactobacilli possessing antagonistic properties in the reproductive tract defense was assessed. Classification of bacterial mechanisms of colonization resistance including block of the adhesion, antagonistic action of normal microflora associated with the production of antibacterial substances and suppression of allochthonous bacteria persistence characteristics was presented. Colonization resistance was considered as a physiological phenomenon of microecological homeostasis being a result of symbiotic relations of a host organism and autochthonous microflora.     

Persistence and adaptive mutagenesis in biofilms

The mechanisms of formation of persisting cells in planktonic and structured microbial populations are considered. The relations between persistence and adaptive mutagenesis are discussed. Persisting cells are suggested to be among the major objects of adaptive mutagenesis and act as an instrument of the microevolution processes in microbial biofilms.     

Rhizobial communities in symbiosis with legumes: genetic diversity,competition and interactions with host plants

The term ‘Rhizobium-legume symbiosis’ refers to numerous plant-bacterial interrelationships. Typically, from an evolutionary perspective, these symbioses can be considered as species-to-species interactions, however, such plant-bacterial symbiosis may also be viewed as a low-scale environmental interplay between individual plants and the local microbial population. Rhizobium-legume interactions are therefore highly important in terms of microbial diversity and environmental adaptation thereby shaping the evolution of plant-bacterial symbiotic systems. Herein, the mechanisms underlying and modulating the diversity of rhizobial populations are presented. The roles of several factors impacting successful persistence of strains in rhizobial populations are discussed, shedding light on the complexity of rhizobial-legume interactions.     

Symbiotic relations of humans and microorganisms

Symbiosis is considered to be the biological basis of the infectious process. Particular attention is paid to the change of paradigm in symbiology and the introduction of a new term, associative symbiosis. The main structural-functional elements of associative symbiosis are estimated, and three vectors of the infectious process are distinguished: (1) host-normal flora, (2) host-associants, and (3) associants-indigenous microflora (microsymbiocenosis). The functions of microsymbionts that determine the colonization resistance of the host and the formation of dysbioses and pathobiocenoses are discussed. The phenomenon of microbial self-nonself recognition is determined on the basis of the opposite (increase/decrease) effects on the growth and persistent (including biofilm formation) characteristics of the dominant-associant pair under the conditions of microsymbiocenosis in humans. Material is presented to characterize the role of intercellular interactions of the symbionts at the level of prokaryotes and pro-eukaryotes under the conditions of infectious pathology.     

Bioautographic Technique for a Rapid Survey of Microbial Populations for the Production of Antibiotics and Other Metabolites

A method is described for the detection of microorganisms capable of producing antibiotics or other metabolites. The microbial population under study was bioautographed against any desired indicator organism. This was easily accomplished by lifting the entire agar layer out of a petri dish on which the microbial population was grown and transferring it to an agar surface seeded with an indicator organism. The use of this technique in the search for metabolites other than antibiotics is pointed out. The advantages of the method, over previously reported methods, are discussed.     

Symbiotic relations of human and microorganisms

Symbiosis has been considered as a biological basis of infectious process. Particular attention was paid to the change of paradigm in symbiology and the appearance of a novel term--associative symbiosis. Principal structural-and-functional elements of associative symbiosis were estimated, and 3 vectors of infectious process such as i) host--normaflora, ii) host--associants, iii) associants--indigious microflora (microsymbiocenosis) were isolated. Functions of microsymbionts that determine colonization resistance of the host, and the formation of dysbioses and pathobiocenoses were reviewed. Phenomenon of microbial recognition for "self-nonself" has been revealed on the basis of opportunistic (increase/decrease) interactions on growth persistent (including biofilm formation) peculiarities of a pair "dominant-associant" under conditions of microsymbiocenosis in human. Material was presented to characterize the role of intercellular interactions of symbionts at the level of prokaryotes, pro-eukaryotes under conditions of infectious pathology.     

Weight dynamics in females of invasive and autochthonous populations of <Emphasis Type="Italic">Harmonia axyridis</Emphasis> (Pallas) (Coleoptera,Coccinellidae) during the induction of reproductive diapause

Under natural conditions, predatory insects often faced the shortage of food caused by an increase in the predator population density and/or a decrease in the prey population density. Experimental studies demonstrated that females of two laboratory strains that originated from autochthonous (the Russian Far East) and invasive (Krasnodar territory of Russia) populations of the aphidophagous ladybird beetle, Harmonia axyridis showed two responses to the absence or shortage of aphids. The first response, termination of oviposition, was observed in several days after transfer to the poor diet, it was independent of photoperiod, and it was stronger in females of the invasive line. The second response, induction of reproductive diapause, was observed in 20 days after transfer to the poor diet, it interacted with the long-day photoperiodic response, and it was stronger in females of the autochthonous line. The induction of reproductive diapause (in comparison with a simple termination of oviposition) is a more basic and less easily reversible physiological process. Thus, we conclude that under natural conditions, females of invasive populations terminate oviposition with the first signs of a shortage of aphids more quickly than females of autochthonous populations and also more quickly start oviposition again with an increase in prey population density. Possibly, these features can be considered as adaptations to new, less stable and less predictable environmental conditions. DOI: 10.1134/S0013873816080029     

Lactase polymorphism in adult British natives: estimating allele frequencies by enzyme assays in autopsy samples.

In an attempt to estimate allele frequencies of lactase persistence in adult British natives, sucrase was assayed simultaneously with lactase under conditions that gave optimal activities for both enzymes. A trimodal distribution in the ratios of enzyme activities was demonstrated. Circumstantial evidence and statistical analyses suggest that the trimodal distribution is due to the different levels of lactase activity in the three genotypes--homozygous persistent, heterozygous, and homozygous nonpersistent, and that it is possible to correct for "nongenetic" variation by using sucrase as an internal standard. The allele frequency for lactase persistence was estimated to be .747. The implications of our findings on the genetic mechanisms involved in lactase persistence are discussed.     

Proteomics in antibiotic resistance and tolerance research: Mapping the resistome and the tolerome of bacterial pathogens

Antibiotic resistance, the ability of a microbial pathogen to evade the effects of antibiotics thereby allowing them to grow under elevated drug concentrations, is an alarming health problem worldwide and has attracted the attention of scientists for decades. On the other hand, the clinical importance of persistence and tolerance as alternative mechanisms for pathogens to survive prolonged lethal antibiotic doses has recently become increasingly appreciated. Persisters and high-tolerance populations are thought to cause the relapse of infectious diseases, and provide opportunities for the pathogens to evolve resistance during the course of antibiotic therapy. Although proteomics and other omics methodology have long been employed to study resistance, its applications in studying persistence and tolerance are still limited. However, due to the growing interest in the topic and recent progress in method developments to study them, there have been some proteomic studies that yield fresh insights into the phenomenon of persistence and tolerance. Combined with the studies on resistance, these collectively guide us to novel molecular targets for the potential drugs for the control of these dangerous pathogens. In this review, we surveyed previous proteomic studies to investigate resistance, persistence, and tolerance mechanisms, and discussed emerging experimental strategies for studying these phenotypes with a combination of adaptive laboratory evolution and high-throughput proteomics.     

From persistence to symbiosis of microorganisms

Primary results of study of problem of microorganism persistence over the last 2 decades on 7 all-Russian conferences in Orenburg are examined in the article. Milestones of both fundamental research and practically significant studies are designated, the role of persistent potential of microorganisms in infectious pathology is evaluated. The emerging turn of studies from persistence to symbiosis is consonant with the idea of international project "Human microbiom" and allows to use the persistent potential of microorganisms as one of the instruments of resolving issues of infectology.     

Immunity and stress

Changes occurring in stress response in the immune system and their effect upon resistance against infectious diseases, were studied. The main mechanisms of the stress induction involve: enhancement of the corticotropin-releasing factor and/or adrenocorticotropic hormone synthesis under the effect of interleukin-1; induced by an infection synthesis of the adrenocorticotropic hormone by lymphocytes, enhancement of the corticotropin-releasing factor synthesis under the effect of a psycho-emotional tension. The main reasons of decline in the immune-competence in stress, are discussed. Significance of stress-response as one of the mechanisms of the organism physiological response to extreme circumstances, is considered.     

Hepatitis B virus: biology, immunopathogenesis, NK/NKT system in viral persistence

In this review, the problem of hepatitis B is considered as related to the recent data on the biology of the viral agent, on the pathogenesis of disturbances that it causes in an organism as well as on accompanying deviations in its immune system. Special attention is paid to mechanisms of hepatitis B virus (HBV) persistence and the role of regulatory lymphocytes of NK/NKT system in this process. Some problems in further studies are specified.     

Integrative processes in modern epidemiology

The integration of achievements in population ecology and the molecular genetics of pathogenic microorganisms into nowadays epidemiology of infectious diseases and the formation of its corresponding trends are discussed. The decisive role of highly complicated key problems of general epidemiology, such as the regularities of the autochthonous existence of pathogenic bacteria in the environment, the mechanisms of the pathogenicity regulation of infective agents and the formation of their epidemic variants, the mechanisms of the prolonged reservation of pathogenic bacteria at interepidemic (interepizootic) periods, the mechanisms of transformation of active (vegetative) and dormant forms in bacterial populations at different stages of epidemic and epizootic cycles, is demonstrated. The detection and analysis of such processes, and especially their latent mechanisms, become possible with the use of new concepts and methodological approaches, highly productive for the progress of epidemiology.     

Modern concept of the makeup of intestinal microflora in healthy adults]

Analysis of the literature data on the significance of normal intestinal microbial population in the vital activity of the organism, and also on the sequelae of unfavourable shifts in the intestinal microecology is presented. The results of personal studies on the composition of normal microbial population in healthy adults are discussed; criteria for the assessment of normal intestinal biocenosis are given. The importance of bifidum flora is emphasized, and the necessity of its correction in various pathological conditions is underlined.     

The problem of estimation of the organism adaptable opportunities under stressful influences

The human organism testing in conditions of modern scientific and technical progress constant stressful influences (industrial, social, psycho-emotional) was carried out for continuous adaptation to the environment: changing of the level of functioning of separate systems and a corresponding tension of regulatory mechanisms occurred. In the article, theoretical bases and methodology of studying the adaptable capacities of the organism are considered. The prenosological diagnostics was used for studying functional conditions on the verge of norm and pathology. The heart rate variability analysis was used based on mathematical model of functional conditions. Concrete technologies and results of evaluation of the adaptation capacities of the organism in space and aviation medicine are presented as well as in applied physiology.     

Behavioural flexibility in the mating system buffers population extinction: lessons from the lesser spotted woodpecker Picoides minor

1. In most stochastic models addressing the persistence of small populations, environmental noise is included by imposing a synchronized effect of the environment on all individuals. However, buffer mechanisms are likely to exist that may counteract this synchronization to some degree. 2. We have studied whether the flexibility in the mating system, which has been observed in some bird species, is a potential mechanism counteracting the synchronization of environmental fluctuations. Our study organism is the lesser spotted woodpecker Picoides minor (Linnaeus), a generally monogamous species. However, facultative polyandry, where one female mates with two males with separate nests, was observed in years with male-biased sex ratio. 3. We constructed an individual-based model from data and observations of a population in Taunus, Germany. We tested the impact of three behavioural scenarios on population persistence: (1) strict monogamy; (2) polyandry without costs; and (3) polyandry assuming costs in terms of lower survival and reproductive success for secondary males. We assumed that polyandry occurs only in years with male-biased sex ratio and only for females with favourable breeding conditions. 4. Even low rates of polyandry had a strong positive effect on population persistence. The increase of persistence with carrying capacity was slower in the monogamous scenario, indicating strong environmental noise. In the polyandrous scenarios, the increase of persistence was stronger, indicating a buffer mechanism. In the polyandrous scenarios, populations had a higher mean population size, a lower variation in number of individuals, and recovered faster after a population breakdown. Presuming a realistic polyandry rate and costs for polyandry, there was still a strong effect of polyandry on persistence. 5. The results show that polyandry and in general flexibility in mating systems is a buffer mechanism that can significantly reduce the impact of environmental and demographic noise in small populations. Consequently, we suggest that even behaviour that seems to be exceptional should be considered explicitly when predicting the persistence of populations.     

Cyanide detoxification by microbial consortia of natural-industrial complexes of gold heap leaching

Microorganisms that have adapted not only to high concentrations of pollutants but also to environmental conditions develop in autochthonous microbial communities of natural-industrial complexes of gold heap leaching. The biotechnological potential and diversity of autochthonous microbial communities involved in cyanide detoxification was evaluated by the example of a deposit situated in the Sakha (Yakutia) Republic. Under the zoning conditions of the ore heap, the biological component had a greater impact on cyanide destruction than chemical transformation. Metabolically active representatives of a microbial consortium are capable of surviving developed under these conditions. Phylotypes of the genus Serratia and family Alcaligenaceae that are capable of cyanide destruction and are potentially promising for the detoxification of wastes of gold heap leaching were revealed.