Investigation of the Mechanisms of Transition of Gram-Negative Bacterial Cells into Induced Anabiosis Using Computational Methods of Classical Molecular Dynamics

TL;DR

This paper investigates how Gram-negative bacteria become dormant using computational methods and 4HR, revealing how it affects their cell membranes.

Contribution

The study reveals novel dose-dependent mechanisms of 4HR-induced dormancy in Gram-negative bacteria through molecular dynamics and experimental validation.

Findings

4HR micelles penetrate and redistribute within bacterial membranes, causing structural changes.

High concentrations of 4HR lead to membrane saturation and cell death via mummification.

TEM images show a third black band in membranes treated with 4HR, indicating structural disruption.

Abstract

Studying the mechanisms by which Gram-negative heterotrophic bacteria transition from active metabolism to dormancy is an important task, as it is directly related to the problem of bacterial antibiotic resistance and the spread of nosocomial infections. Using electron microscopy, microbiology, and molecular modeling, we investigated the dose-dependent mechanisms of action of 4-hexylresorcinol (4HR), a chemical analog of the anabiosis autoinducer, on the cell membranes of Gram-negative bacteria (using Escherichia coli as an example), leading to the formation of stressed, dormant, and mummified cells. It was shown that 4HR penetrates membranes equally easily both as single molecules and as micelles, distributing itself across the membrane so that the hydrocarbon radicals are aligned parallel to the lipid tails. When micelles penetrate the membrane, uneven distribution of 4HR within and between leaflets occurs, as well as lipid redistribution within the membrane, leading to the appearance of a third peak on the phospholipid electron density profile and a third black band in the membrane region in TEM images of such cells. At 4HR concentrations in solution of 200 µM, its micelles cover the cell membranes in a thick layer, penetrate into the membrane, and completely saturate it. Even higher concentrations create agglomerates or actually micellar arrays within the cell membranes, leading to cell death through mummification.

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