Morphostructural damage to bacterial cells exposed to chlorine-containing derivatives of 5-,6-,7-aminoindoles assessed by scanning electron microscope

The cell wall and membranes of Gram-positive and Gram-negative bacteria provide a physical, osmotic, and metabolic barrier between the internal contents of the bacterial cell and the external environment. Observation of changes in the integrity of the bacterial structure using a scanning electron microscope (SEM) can help elucidate the detailed mechanisms of cell death. The aim of the study was to analyze the morphological changes in microbial cells exposed to new compounds with antimicrobial activity — chlorine-containing derivatives of 5-,6-,7-aminoindoles using SEM. Methods. The present study was carried out using strains of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli obtained from patients with nonspecific diseases of the respiratory, urinary tract, and intestines with different sensitivities to traditionally used antimicrobial drugs. Results. As a result, the studied chloromethyl-containing compounds of the indole series showed own biological activity, namely antimicrobial. Control cells were morphologically correct and typical. Statistical analysis of cell surface morphometry in control and experimental samples did not reveal significant changes in size after exposure to compounds with laboratory codes T1, T4, T7 and T12. At the same time, compared with control untreated cells of P. aeruginosa, S. aureus and E. coli, treatment with chlorine-substituted derivatives of 5-,6-,7-aminoindoles caused obvious morphological changes, which indicates a deteriorated state of the cell wall. Filamentous cells were observed in P. aeruginosa exposure to T7 and T12. The appearance of long filaments may be associated with the stress experienced by the cell after exposure to the compounds under study. It is believed that the formation of such filaments in bacteria under stress conditions results from defects in cell division, especially in the separation of daughter cells. There are data according to which, when DNA synthesis is suppressed, a bacterium changes its morphology, becomes longer, without reaching cell division. Treatment with T1, T7 and T12 resulted in degradation of the P. aeruginosa cell wall, while treatment with T4 caused the formation of pores on the cell surface. In this study, microscopy showed marked morphological changes in the cell walls of S. aureus, which led to deformation of the cell wall under the influence of T1, T4, T7 and T12. Treatment of E. coli T1, T4, T7 and T12 cells at a concentration of 500 μg/ml caused cell lysis, although normal cells were also found. The appearance of cellular debris around whole E. coli cells indicates membrane damage, which probably leads to a change in osmotic pressure. Conclusion. The results using SEM confirmed the data on the antimicrobial activity of chlorine-substituted derivatives of 5-,6-,7-aminoindoles.