Adaptation to continuously changing habitat is one of the most important characteristics of microorganisms. A particularly effective form of adaptation is called phenotypic plasticity. This ability allows bacteria with a stable genotype to create different phenotypes in response to environmental changes. Such variability is not inheritable but is crucial for maintaining this specific bacterial population and, even more, for developing resistanc e to antibiotics. Studying the phenotypic plasticity, which underlies the resistance of microorganisms to traditional antibiotic therapy, is a key area of the current antimicrobial technologies. In this review, phenotypic plasticity is considered to be a strategy of bacterial survival and a mechanism for developing antibiotic resistance in dormant (resistant) cellular forms of bacteria. We suggest that studying the phenotypic variants of bacteria (L-forms; viable but nonculturable bacteria; persister cells) will result in the development of novel effective antimicrobial technologies.
Infections are a major cause of premature death. Fast and accurate laboratory diagnostics of infectious diseases is a key condition for the timely initiation and success of treatment. Potentially, it can reduce morbidity, as well as prevent the outbreak and spread of dangerous epidemics. The traditional methods of laboratory diagnostics of infectious diseases are quite time- and labour-consuming, require expensive equipment and trained personnel, which is crucial within limited resources. The fast biosensor-based methods that combine the diagnostic capabilities of biomedicine with modern technological advances in microelectronics, optoelectronics, and nanotechnology make an alternative.
The modern achievements in the development of label-free biosensors make them promising diagnostic tools that combine rapid detection of specific molecular markers, simplicity, ease-of-use, efficiency, accuracy, and cost-effectiveness with the tendency to the development of portable platforms. These qualities exceed the generally accepted standards of microbiological and immunological diagnostics and open up broad prospects for using these analytical systems in clinical practice directly at the site of medical care provision (point-of-care, POC concept).
A wide variety of modern biosensor designs are based on the use of diverse formats of analytical and technological strategies, identification of various regulatory and functional molecular markers associated with infectious pathogens. The solution to the existing problems in biosensing will open up great prospects for these rapidly developing diagnostic biotechnologies.
Introduction. With the advent of the paradigm of heterogeneity of the bacterial population, attention has been drawn to the phenotype of dormant cells, the active generation of which occurs when adverse environmental conditions of microorganisms appear. These cells are characterized by metabolic and reproductive dormancy, as well as antibiotic resistance. However, upon the occurrence of favorable living conditions, they are able to germinate again and cause an exacerbation of infectious diseases. In recent years, a threatening decrease in the effectiveness of antimicrobial therapy and an increase in the incidence of persistent, chronic and hospital infections have been associated with these phenotypes of pathogenic bacteria. Given the key role of fatty acid (FA) in the adaptation of bacteria, the aim of this study was to identify the specific features of changes in the fatty acid composition of gram-negative bacteria from the Enterobacteriaceae family during their long-term storage under extreme conditions and the formation of dormant (uncultured) subpopulations of cell forms.Materials and methods. Static cultures of following reference strains were used in the study: Yersinia pseudotuberculosis, Salmonella enterica Typhimurium, and Escherichia coli, stored under vaseline oil at 4-8°С for 5-10 years. Dormant cell forms were obtained by removing the oil layer and collecting the microbial mass. The ultrastructural features of the dormant cell forms were confirmed by transmission electron microscopy. The viability of dormant cells was assessed by a molecular genetic method. The lack of reproductive activity of dormant forms was checked by repeated inoculations on LB broth, Endo and Serov media and incubation at 4-6°C, 22-24°C, and 37°С. Methyl esters of total FAs were obtained according to the procedure approved by the European Committee for Standardization and recommended by the Sherlock MIS protocol. Analysis of fatty acid methyl esters was carried out by gas chromatography in combination with mass spectrometry. After preliminary homogenization of the bacterial masses, lipids were extracted, and FA spectra were obtained by electron impact at 70 eVResults. It was demonstrated that phenotypic uncultured generation of dormant cells is formed under extreme conditions (low temperature, nutrient deficiency, hypoxia) in populations of E. coli, Y. pseudotuberculosis and S. Typhimurium. A comparative analysis of changes in the fatty acid spectrum in the dormant phenotype revealed certain features compared to vegetative cells associated with a decrease in the unsaturation index and the dominance of long-chain saturated FAs (C14-C18).Conclusion. The biological significance of the observed transformations is apparently associated with the special role of these FA fractions in the reversible formation of dormant (uncultivated) cell phenotype and as an alternative source of carbohydrates in a metabolically inactive state, as well as their subsequent reversal to vegetative cells upon favorable living conditions.
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