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  • 1
    Language: English
    In: Sci Rep, 2017, Vol.7(1), pp.8370-8370
    Description: Although clinical antibiotic-resistant bacteria have attracted tremendous attention in the microbiology community, the resistant bacteria that persist in natural environments have been overlooked for a longtime. We previously proposed a new species Paramesorhizobium desertii, isolated from the soil of the Taklimakan Desert in China that is highly resistant to most β-lactam antibiotics. To identify potential β-lactamase(s) in this bacteria, we first confirmed the carbapenemase activity in the freeze–thawed supernatant of a P. desertii A-3-E culture using the modified Hodge assay. We then identified a novel chromosome-encoded carbapenemase (PAD-1) in strain A-3-E, using a shotgun proteomic analysis of the supernatant and genomic information. The bioinformatics analysis indicated that PAD-1 is a class A carbapenemase. Subsequent enzyme kinetic assays with purified PAD-1 confirmed its carbapenemase activity, which is similar to that of clinically significant class A carbapenemases, including BKC-1 and KPC-2. Because the location in which A-3-E was isolated is not affected by human activity, PAD-1 is unlikely to be associated with the selection pressures exerted by modern antibiotics. This study confirmed the diversity of antibiotic-resistant determinants in the environmental resistome.
    Keywords: Article;
    ISSN: 2045-2322
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  • 2
    In: MicrobiologyOpen, October 2017, Vol.6(5), pp.n/a-n/a
    Description: Two‐component systems in are associated with its virulence, drug resistance, motility, biofilm formation, and other characteristics. In this study, we used Rec, a genetic engineering method, to investigate the function of A1S_2811 in strain 17978. A1S_2811, a hypothetical hybrid sensor histidine kinase/response regulator, has four histidine‐containing phosphotransfer domains, a CheA‐like regulatory domain, and a CheY‐like receiver domain at its C terminus. Compared with the 17978 strain, both surface motility and biofilm formation at the gas–liquid interface decreased significantly in the A1S_2811 knock‐out strain. The number of pilus‐like structures and the amount of extrapolymeric substances on the cell surface also decreased in the A1S_2811 null strain. Transcription of , which encodes an ‐acylhomoserine lactone synthase in , decreased significantly in the A1S_2811 null strain, and supplementation with synthetic ‐(3‐oxodecanoyl) homoserine‐‐lactone rescued the surface motility and biofilm formation phenotype in the null mutant. We speculate that A1S_2811 regulates surface motility and biofilm formation, not by regulating type pili‐associated genes expression, but by regulating the chaperone/usher pili‐associated operon and the AbaI‐dependent quorum‐sensing pathway‐associated A1S_0112‐0119 operon instead. A1S_2811 regulates surface motility and biofilm formation not by regulating the expression of genes associated with type IV pili, but regulating the csuA/BABCDE operon associated with CU pili and A1S_0112‐0119 operon associated with AbaI‐dependent quorum‐sensing pathway instead.
    Keywords: Acinetobacter baumannii ; Biofilm Formation ; Motility ; Pili ; Quorum Sensing ; Two‐Component Systems
    ISSN: 2045-8827
    E-ISSN: 2045-8827
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