ABSTRACT
Antibiotic resistance is a serious global public health problem, and China is one of the countries with the serious problem of irrational antibiotic use and bacterial drug resistance.The world is headed for a post-antibiotic era.With the rapid development of microecology, microbiota has been linked with antibiotic resistance.From microecological point of view, it is possible for researchers in different fields to innovate new techniques for bacterial drug resistance, and to explore the evolution of pathogenic bacteria as well as the mechanism of their resistance to antibacterial agents.This paper reviews the research progress in bacterial resistance and microecology, and prospects the future research needs that should be prioritized to tackle antibiotic resistance.
ABSTRACT
The Escherichia coli fadR protein product, a paradigm/prototypical FadR regulator, positively regulates fabA and fabB, the two critical genes for unsaturated fatty acid (UFA) biosynthesis. However the scenario in the other Ɣ-proteobacteria, such as Shewanella with the marine origin, is unusual in that Rodionov and coworkers predicted that only fabA (not fabB) has a binding site for FadR protein. It raised the possibility of fad regulon contraction. Here we report that this is the case. Sequence alignment of the FadR homologs revealed that the N-terminal DNA-binding domain exhibited remarkable similarity, whereas the ligand-accepting motif at C-terminus is relatively-less conserved. The FadR homologue of S. oneidensis (referred to FadR_she) was over-expressed and purified to homogeneity. Integrative evidence obtained by FPLC (fast protein liquid chromatography) and chemical cross-linking analyses elucidated that FadR_she protein can dimerize in solution, whose identity was determined by MALDI-TOF-MS. In vitro data from electrophoretic mobility shift assays suggested that FadR_she is almost functionally-exchangeable/equivalent to E. coli FadR (FadR_ec) in the ability of binding the E. coli fabA (and fabB) promoters. In an agreement with that of E. coli fabA, S. oneidensis fabA promoter bound both FadR_she and FadR_ec, and was disassociated specifically with the FadR regulatory protein upon the addition of long-chain acyl-CoA thioesters. To monitor in vivo effect exerted by FadR on Shewanella fabA expression, the native promoter of S. oneidensis fabA was fused to a LacZ reporter gene to engineer a chromosome fabA-lacZ transcriptional fusion in E. coli. As anticipated, the removal of fadR gene gave about 2-fold decrement of Shewanella fabA expression by β-gal activity, which is almost identical to the inhibitory level by the addition of oleate. Therefore, we concluded that fabA is contracted to be the only one member of fad regulon in the context of fatty acid synthesis in the marine bacteria Shewanella genus.
Subject(s)
Amino Acid Sequence , Bacterial Proteins , Chemistry , Metabolism , Base Sequence , Binding Sites , DNA, Bacterial , Metabolism , Escherichia coli , Genetics , Metabolism , Fatty Acid Synthase, Type II , Genetics , Metabolism , Fatty Acids , Gene Expression Regulation, Bacterial , Molecular Sequence Data , Oleic Acid , Pharmacology , Protein Binding , Regulon , Genetics , Repressor Proteins , Chemistry , Metabolism , Shewanella , Genetics , MetabolismABSTRACT
NDM-1 (New Delhi metallo-beta-lactamase) gene encodes a metallo-beta-lactamase (MBL) with high carbapenemase activity, which makes the host bacterial strain easily dispatch the last-resort antibiotics known as carbapenems and cause global concern. Here we present the bioinformatics data showing an unexpected similarity between NDM-1 and beta-lactamase II from Erythrobacter litoralis, a marine microbial isolate. We have further expressed these two mature proteins in E. coli cells, both of which present as a monomer with a molecular mass of 25 kDa. Antimicrobial susceptibility assay reveals that they share similar substrate specificities and are sensitive to aztreonam and tigecycline. The conformational change accompanied with the zinc binding visualized by nuclear magnetic resonance, Zn(2+)-bound NDM-1, adopts at least some stable tertiary structure in contrast to the metal-free protein. Our work implies a close evolutionary relationship between antibiotic resistance genes in environmental reservoir and in the clinic, challenging the antimicrobial resistance monitoring.
Subject(s)
Amino Acid Sequence , Anti-Bacterial Agents , Pharmacology , Aztreonam , Pharmacology , Cephalosporinase , Chemistry , Genetics , Metabolism , Computational Biology , Methods , Drug Resistance, Bacterial , Genetics , Enzyme Stability , Evolution, Molecular , Minocycline , Pharmacology , Molecular Sequence Data , Phylogeny , Protein Structure, Tertiary , Sequence Homology, Nucleic Acid , Sphingomonadaceae , Genetics , Tigecycline , Zinc , Pharmacology , beta-Lactamases , Chemistry , Genetics , MetabolismABSTRACT
Throughout human history, pandemic bacterial diseases such as the plague and tuberculosis have posed an enormous threat to human beings. The discovery of antibiotics has provided us with powerful arsenal for the defense against bacterial infections. However, bacteria are acquiring more and more resistance genes to shield off antibiotics through mutation and horizontal gene transfer. Therefore, novel antibiotics must be produced and the arms race between bacterial pathogens and antibiotics is becoming increasingly intense. Recently, researchers have found that plasmids carrying a new metallo-beta-lactamase gene, blaNDM-1, and many other antibiotics resistance genes can easily spread through bacterial populations and confer recipient stains resistance to nearly all of the current antibiotics. It is a threat to the human health and a great challenge for our medical science, which we are facing. We need to find new ways to fight and win this arms racing.