(526d) Alterations of Morphological and Mechanical Properties of Antibiotic-Resistant Bacteria upon Exposure to Cationic Conjugated Polyelectrolyte

Emergence of antibiotic-resistant bacteria due to misuse and overuse of antibiotics poses a considerable threat to animals and the human race. Therefore, we need to focus on the development of alternate antibiotics based on solid understanding of the cell-drug interactions. Recent studies have revealed that cationic conjugated molecules (oligoelectrolytes and polyelectrolytes) can be used for killing or inhibiting the growth of antibiotic-resistant bacteria. In our recent work, we have shown that cationic conjugated polyelectrolytes (CCPEs) and oligoelectrolytes (CCOEs) have different mechanisms of action against bacteria. CCPEs were found to be more efficient than CCOEs for treating antibiotic-resistant strain of Escherichia coli (E. coli). While many works focused on the design of conjugated molecules with antibacterial activity, the resulting alterations of mechanical and morphological properties of bacteria upon exposure to these cationic conjugated molecules have not been completely elucidated. In this work, we thus synthesized phenylene based cationic conjugated polyelectrolyte (CCPE) and studied the morphological and mechanical changes of the model bacteria, Gram-negative Escherichia coli (E. coli (both wild-type and ampicillin-resistant)), upon treatment with CCPE. Cells before and after treatment were studied using atomic force microscopy (BIO-AFM) and transmission electron microscopy (TEM). The results showed increase in surface roughness, and decrease in stiffness of cells upon treatment with conjugated molecule. Depending on the treatment conditions, the bacterial cells either formed large aggregates, or, vesicle/micelle-like structures near the cells, or blebs on the outer membrane of the bacteria. Also cells released certain species upon treatment as seen using gas chromatography-mass spectroscopy (GC-MS). Analyzing all these information by the side of growth inhibition data suggested alteration of outer membrane of bacteria and helped us to elucidate the bacterial growth inhibition mechanism.