Abstract
DNA methylation damage can be induced by endogenous and exogenous chemical agents, which has led every living organism to develop suitable response strategies. We investigated protein expression profiles of Escherichia coli upon exposure to the alkylating agent methyl-methane sulfonate (MMS) by differential proteomics. Quantitative proteomic data showed a massive downregulation of enzymes belonging to the glycolytic pathway and fatty acids degradation, strongly suggesting a decrease of energy production. A strong reduction in the expression of the N-acetylneuraminate lyases (NanA) involved in the sialic acid metabolism was also observed. Using a null NanA mutant and DANA, a substrate analog acting as competitive inhibitor, we demonstrated that down regulation of NanA affects biofilm formation and adhesion properties of E. coli MV1161. Exposure to alkylating agents also decreased biofilm formation and bacterial adhesion to Caco-2 eukaryotic cell line by the adherent invasive E. coli (AIEC) strain LF82. Our data showed that methylation stress impairs E. coli adhesion properties and suggest a possible role of NanA in biofilm formation and bacteria host interactions.
Highlights
All living organisms are exposed to alkylating conditions caused by both endogenous and exogenous species
Our results suggest a possible role of E. coli lyase NanA in biofilm formation and in interaction with eukaryotic cells
Bacterial cells were grown in four replicates and each culture was divided into two aliquots, one of them was treated with 0.04% methyl methanesulphonate (MMS) and the other one was kept untreated and used as control
Summary
All living organisms are exposed to alkylating conditions caused by both endogenous (metabolites, ROS, free radicals, etc.) and exogenous (pollutants, chemoterapics, drugs, etc) species. Biological macromolecules including DNA, RNA, proteins and lipids are sensitive to electrophilic species permeating cellular defenses and subjected to alkylation damages (Fu et al, 2012). Methylating agents, like methyl methanesulphonate (MMS), comprise a major class of DNA-damaging compounds that occur both endogenously and in the environment (Lobo et al, 2010). In bacteria, fluctuating levels of environmental alkylating agents activate an inducible response that enhances cellular resistance to the same agents. This adaptive response has been studied most extensively in Escherichia coli, in which induced alkylation resistance results from increased expression of four genes, ada, alkB, alkA, and aidB (Landini and Volkert, 2000; Rippa et al, 2010)
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