Acidotermophilic bacteria Alicyclobacillus acidoterrestris is one of the main contaminants in the fruit industry forming biofilms which are difficult to remove from the production line by conventional methods. An alternative approach aims for the use of essential oils to prevent Alicyclobacillus biofilm development. The effect of clove essential oil on A. acidoterrestris biofilms on glass and polyvinyl chloride surfaces under static and agitated culture conditions was investigated by atomic force microscopy and the plate count method. The medium-flow and the type of technical surface significantly influenced A. acidoterrestris biofilm. The PVC was colonized in a greater extent comparing to glass. Clove essential oil in 0.05% (v/v) caused 25.1–65.0% reduction of biofilms on the technical surfaces along with substantial changes in their morphology by a decrease in the biofilm: height, surface roughness, and surface area difference. The oil also induced alteration in individual bacterial cells length and visible increase of their roughness. Clove essential oil seems to release EPS from biofilm and thus induce detachment of bacteria from the surface. Due to anti-A. acidoterrestris biofilm activity, the clove oil may be used in the juice industry to hinder a development of A. acidoterrestris biofilms on production surfaces.

Better understanding the mechanisms of Leonurus cardiaca L. extract (LCE) activity is necessary to prepare recommendations for the use of LCE-based herbal products for preventive/supportive purposes in case of infective endocarditis (IE) and other staphylococcal invasive infections. The aim of the study was to analyze molecular mechanisms of LCE effect on Staphylococcus aureus and blood platelets in the context of their interactions playing a pivotal role in such disorders. Using atomic force microscopy, we demonstrated that adhesion forces of S. aureus were markedly reduced after exposure to LCE at subinhibitory concentrations. The effect resulted from the impact of LCE on S. aureus cell morphology and the composition of phospholipids and fatty acids in bacterial membranes (assessed by HPLC), which modulated their stabilization, hydrophobicity, and charge. Moreover, using FACS we showed also that LCE significantly reduced GP IIb/IIIa expression on blood platelets, thus the disruption of platelet-fibrinogen interactions seems to explain antiplatelet effect of LCE. The obtained results prove the usefulness of LCE in the prevention of S. aureus adhesion, platelet activation, and vegetations development, however, also pointed out the necessity of excluding the cationic antibiotics from the treatment of S. aureus-associated IE and other invasive diseases, when motherwort herb is used simultaneously as an addition to the daily diet.

Summary: The evaluation of bacterial adhesive properties at a single‐cell level is critical for under standing the role of phenotypic heterogeneity in bacterial attachment and community formation. Bacterial population exhibits a wide variety of adhesive properties at the single‐cell level, suggesting that bacterial adhesion is a rather complex process and some bacteria are prone to phenotypic heterogeneity. This heterogeneity was more pronounced for Escherichia coli , where two subpopulations were detected. Subpopulations exhibiting higher adhesion forces may be better adapted to colonize a new surface, especially during sudden changes in environmental conditions. Escherichia coli was characterized by a higher adhesion force, a stronger ability to form biofilm and larger heterogeneity index calculated in comparison with Bacillus subtilis . Higher adhesion forces are associated with a more efficient attachment of bacteria observed in an adhesion assay and might provide a basis for successful colonization, survival and multiplications in changing environment. The atomic force microscopy provides a platform for investigation of the adhesion heterogeneity of individual cells within a population, which may be expected to underpin further elucidation of the adaptive significance of phenotypic heterogeneity in a natural environment.

Bacterial populations that exhibit phenotypic subgroups of cells with different biophysical properties are better adapted to colonize diverse surfaces, thereby facilitating survival and dissemination in varied environments. In this study, we applied atomic force microscopy (AFM) to investigate lipopolysaccharide (LPS)-mediated heterogeneity in the adhesion and mechanics of individual Escherichia coli ATCC 25922 cells within a clonal population. Our results, based on both single-cell and population level analyses, revealed that partial LPS removal by ethylenediaminetetraacetic acid (EDTA) substantially altered the bacterial cell surface, rendering it smoother and featureless. EDTA-induced disorganization of the outer membrane not only diminished both adhesion forces and cell elasticity but also markedly reduced the structural diversity of the cell envelope, thereby decreasing cell-to-cell heterogeneity. Notably, the population no longer exhibited cells with a strongly adherent and stiff phenotype. Our findings indicate that the structural and chemical diversity of the outer membrane, primarily conferred by LPS, is a key determinant of phenotypic heterogeneity, with important implications for bacterial adhesion, environmental adaptation, and responses to antimicrobial stressors. Overall, this study emphasizes the essential role of LPS in modulating bacterial surface interactions and mechanical behavior, and demonstrates the utility of AFM-based force spectroscopy with colloidal probes as a quantitative platform for analyzing single-cell variability.