Mechanisms of Interaction between DNA and Chemical Analogues of Microbial Anabiosis Autoinducers

The alkylhydroxybenzene (AHB) autoregulatory factors d₁ (fd₁) of microorganisms have been found to directly interact with highly polymeric DNA. This circumstance results in changes, related to alterations in the topology of this macromolecule, in DNA physicochemical properties. The physicochemical properties of DNA in the presence of chemical analogues of microbial AHBs (methylresorcinol; hexylresorcinol; and 2-(4-hydroxyphenyl)ethane-1-ol, also known as tyrosol) were investigated using adsorption spectrophotometry, fluorometry, heat denaturation, viscosimetry, and electrophoresis in agarose gel. A number of concordant effects pointing to DNA-AHB interactions were revealed that manifest themselves in the hypochromic properties of the resulting complexes, an increase in their melting temperature and viscosity, a decrease in their electrophoretic mobility, and a change in the fluorescent properties of AHBs upon complexation with DNA. Such alterations were particularly significant in the presence of hexylresorcinol, which possessed the maximum alkyl radical length among the fd₁ analogues tested. Using atomic force microscopy, we visualized the micellelike DNA structures forming in the presence of AHBs. The results obtained provided the basis for developing a hypothetical model of the interaction between the biopolymer macromolecule and low-molecular-weight AHBs that takes into account the differences in the hydrophobicity of individual AHB homologues functioning as ligands. In terms of our model, we discuss AHB involvement in the stabilization of DNA and alteration of its topology, i.e., in the process related to intragenomic rearrangements, which account for the intrapopulational variability of bacteria, including dissociation processes.     

IR spectroscopic research on the impact of chemical analogues of autoregulatory d<Subscript>1</Subscript> factors of microorganisms on structural changes in DNA

Using IR spectroscopy, we investigated the impact of chemical analogues of autoregulatory d₁ factors of microorganisms (methylresorcinol, hexylresorcinol, and tyrosol) on the conformational changes in DNA in films upon altering (decreasing) the relative humidity. We analyzed the appearance/disappearance of characteristic absorption bands of A and B DNA forms and determined D ₁₀₈₈/D ₁₂₂₄, the ratio between the band intensities of symmetrical and asymmetrical oscillations in their phosphate groups. The data obtained suggest the slowing down of the B → A structural transition in DNA in the presence of methylresorcinol and its speeding up in the presence of tyrosol. We discuss the mechanisms of this phenomenon in relation to the chemical composition of d 1 factors and their biological function.     

Regulation of the functional activity of lysozyme by alkylhydroxybenzenes

In our study, we investigated the capacity of alkylhydroxybenzenes (AHB), which are microbial anabiosis autoinducers, for alteration of the enzymatic activity of the hen egg-white lysozyme, as well as the efficiency of hydrolysis of specific (peptidoglycan) and nonspecific (chitin) substrates catalyzed by lysozyme. AHB homologues (C7-AHB and C12-AHB), which differ in their hydrophobicity and effects in their interaction with lysozyme, were used as modifying agents. C7-AHB stimulated enzymatic activity within the whole range of concentrations used (10^?7?10^?3 M). More hydrophobic C12-AHB exhibited this ability only at low concentrations and inhibited fermentative activity at high concentrations, acting as a mixed-type inhibitor. Both AHB homologues caused changes in the hydrophobicity of lysozyme molecules. An increase in the affinity level between the C7-AHB-modified enzyme and the nonspecific substrate (colloidal chitin or cell wall polymers of Saccharomyces sp.) was observed, which manifested itself in the enhancement of the hydrolysis rate by 200–500% (as compared to the native enzyme). A significant effect on the efficiency of the lysozyme-catalyzed modifications of the substrate (peptidoglycan, colloidal chitin) structure as a result of its complexation with AHB was demonstrated. A stabilizing effect of C7-AHB and C12-AHB was revealed, which ensured a high level of activity of the AHB-modified enzyme (as compared to the control) after heat treatment (functional stability), as well as at nonoptimal temperatures of catalysis (operational stability). The biological significance of lysozyme modification with AHB and the practical aspects of its application are discussed.