Project description:Cinnamaldehyde is a natural antimicrobial and has been found to be effective against many foodborne pathogens including Escherichia coli O157:H7. Although its antimicrobial effects have been well investigated, limited information is available on its effects at the molecular level. Sublethal treatment at 200 mg/l cinnamaldehyde inhibited growth of E. coli O157:H7 at 37oC and for ≤ 2 h caused cell elongation, but from 2 to 4 h growth resumed and cells reverted to normal length. To understand this transient behaviour, genome-wide transcriptional analysis of E. coli O157:H7 was performed at 2 and 4 h exposure to cinnamaldehyde. Drastically different gene expression profiles were obtained at 2 and 4 h. At 2 h exposure, cinnamaldehyde induced overexpression of many oxidative stress-related genes, reduced DNA replication, and synthesis of protein, O-antigen and fimbriae. At 4 h, many cinnamaldehyde-induced repressive effects on E. coli O157:H7 gene expressions were reversed and oxidatve stress genes were nolonger differentially expressed.
Project description:Sulfonamides are traditional synthetic antimicrobial agents used in clinical and veterinary medical settings. Their long-term excessive overuse has resulted in widespread microbial resistance, limiting their application for medical interventions. Resistance to sulfonamides is primarily conferred by the alternative genes sul1, sul2, and sul3 encoding dihydropteroate synthase in bacteria. Studying the potential fitness cost of these sul genes is crucial for understanding the evolution and transmission of sulfonamide-resistant bacteria. In vitro studies have been conducted on the fitness cost of sul genes in bacteria. In this study, we provide critical insights into bacterial adaptation and transmission using an in vivo approach.
Project description:The rise of antimicrobial resistant pathogens calls for new antibacterial treatments, but potent new compounds are scarce. Development of new antibiotics is difficult, especially against Gram-negative bacteria, as here uptake is strongly hindered by the additional outer membrane. Most antimicrobial agents against Gram-negatives use the porin mediated pathway to cross the outer membrane, which limits the choice of an antibiotic, as it has to fit by size, charge and hydrophilicity. In E. coli, the major porins OmpF and OmpC are associated with antibiotic translocation and therefore also with unspecific antibiotic cross-resistance. In this regard, alternative uptake routes are of interest. We were interested in the uptake opportunities of the small, natural product antibiotic negamycin and thereby found new uptake pathways across the outer membrane of E. coli. Besides OmpF and OmpC, we investigated the role of the minor porins OmpN and ChiP in negamycin translocation. We detected an effect of OmpN and ChiP on negamycin susceptibility and confirmed passage by electrophysiological assays. The structure of OmpN was resolved in order to analyze the negamycin translocation mechanism by computational simulations. As abundancy of these minor porins was low in E. coli, their transcript levels were analyzed by RNA-Seq. Increased transcripts levels of ompN and chiP were observed upon negamycin treatment, hinting at a role in antibiotic uptake. These new, additional uptake pathways across the outer membrane of E. coli highlight the antibiotic potential of negamycin, especially as resistance development is low due to availability of multiple uptake routes at both the outer and inner membranes