Search

Antarctic fishes, living in an extreme environment and normally exposed to pathogens, are a promising source of antimicrobial peptides (AMPs). These are emerging as next-generation drugs due to their activity against multidrug resistant (MDR) bacteria. To infect hosts, beyond intrinsic/acquired resistance, MDR species also use virulence factors such as protease secretion. Hence, AMPs targeting virulence factors could represent a novel strategy to counteract the antimicrobial resistance (AMR). In this paper, we focused on a mutant peptide, named KHS-Cnd, that was obtained from the scaffold of the chionodracine (Cnd), a natural peptide identified in the icefish Chionodraco hamatus. We studied different effects caused by the peptide interaction with the cell membrane of two model bacteria, E. coli and B. cereus. First, we investigated its membranolytic activity revealing that the peptide action is more evident on E. coli, with a 69 % uptake of the used dye at 3 μM, whereas for B. cereus we found only a 65 % uptake at 6 μM. Successively, we determined the impact of this lysis on total protein concentration in the medium and an increase was estimated for both bacteria (84 % after 1 h for E. coli and 90 % for B. cereus, respectively). Moreover, we evaluated the changes in the proteolytic activity of the supernatant, that is an important aspect of bacterial resistance, showing that there was a significant reduction for both bacteria, although at higher level in the case of E. coli. The membranolytic activity was evidenced also morphologically with TEM analysis and a different alteration was evidenced for the two bacteria. Moreover, NMR metabolomics analysis showed that peptide induces changes in E. coli and B. cereus extracellular metabolites especially at the higher tested concentrations: this metabolic variation could be used as a fingerprinting of the peptide action on bacteria physiology due to its interaction with cell wall. Finally, we determined the KHS-Cnd cytotoxicity on human primary cell lines to verify its selectivity toward bacterial cell membranes and we found low toxicity until a concentration of 5 μM. Considering that the peptide exerts both membranolytic and anti-virulence activity on E. coli at 1.5 μM, we confirmed the interesting potential of this AMP as a new drug to counteract AMR., Competing Interests: Declaration of Competing Interest The authors have nothing to declare., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The physiological changes induced by indoleacetic acid (IAA) treatment were investigated in the totally sequenced Escherichia coli K-12 MG1655. DNA macroarrays were used to measure the mRNA levels for all the 4290 E. coli protein-coding genes; 50 genes (1.1 %) exhibited significantly different expression profiles. In particular, genes involved in the tricarboxylic acid cycle, the glyoxylate shunt and amino acid biosynthesis (leucine, isoleucine, valine and proline) were up-regulated, whereas the fermentative adhE gene was down-regulated. To confirm the indications obtained from the macroarray analysis the activity of 34 enzymes involved in central metabolism was measured; this showed an activation of the tricarboxylic acid cycle and the glyoxylate shunt. The malic enzyme, involved in the production of pyruvate, and pyruvate dehydrogenase, required for the channelling of pyruvate into acetyl-CoA, were also induced in IAA-treated cells. Moreover, it was shown that the enhanced production of acetyl-CoA and the decrease of NADH/NAD+ ratio are connected with the molecular process of the IAA response. The results demonstrate that IAA treatment is a stimulus capable of inducing changes in gene expression, enzyme activity and metabolite level involved in central metabolic pathways in E. coli.

Indole-3-acetic acid (IAA) is a ubiquitous molecule playing regulatory roles in many living organisms. To elucidate the physiological changes induced by IAA treatment, we used Escherichia coli K-12 as a model system. By microarray analysis we found that 16 genes showed an altered expression level in IAA-treated cells. One-third of these genes encode cell envelope components, or proteins involved in bacterial adaptation to unfavourable environmental conditions. We thus investigated the effect of IAA treatment on some of the structural components of the envelope that may be involved in cellular response to stresses. This showed that IAA-treated cells had increased the production of trehalose, lipopolysaccharide (LPS), exopolysaccharide (EPS) and biofilm. We demonstrated further that IAA triggers an increased tolerance to several stress conditions (heat and cold shock, UV-irradiation, osmotic and acid shock and oxidative stress) and different toxic compounds (antibiotics, detergents and dyes) and this correlates with higher levels of the heat shock protein DnaK. We suggest that IAA triggers an increased level of alert and protection against external adverse conditions by coordinately enhancing different cellular defence systems. [ABSTRACT FROM AUTHOR]