Riberbitsch9204

implified food sample preparation and chip operation for end users. Due to the miniaturized size of lab-on-a-chip platform, the detection was achieved by using up to 1000-time less reagents than standard reference methods, making it a competitive approach for rapid screening and surveillance study in food industries. In addition, multiple clinically important Campylobacter species (C. jejuni, C. coli, C. lari) could be tested by our device. This device has potential for wide application in food safety management and clinical diagnostics especially in the resource-limited regions. Copyright © 2020 American Society for Microbiology.This study was aimed at assessing whether the repeated exposure of twelve strains of Salmonella spp., Escherichia coli and Listeria monocytogenes to the alternative non-thermal decontamination techniques ultraviolet light (UV-C) and non-thermal atmospheric plasma (NTAP) may cause the emergence of variants showing an increased resistance to clinically relevant antibiotics (ampicillin, cefotaxime, ciprofloxacin, gentamicin, streptomycin, tetracycline, erythromycin, vancomycin and colistin). UV-C and NTAP treatments were applied on the surface of inoculated BHI agar plates. Survivors were recovered and, after 24 hours growth in BHI broth, subjected again to the decontamination treatment and this was repeated for 10 consecutive cycles. A total of 174 strain/decontamination technique/antibiotic combinations were tested and 12 variant strains with an increased resistance to one of the antibiotics studied were identified, with increases in minimum inhibitory concentrations in MH broth ranging from 2 to 256 fold. They evidences that two novel, not yet widely used, non-thermal microbial decontamination techniques, ultraviolet light and non-thermal atmospheric plasma, can select variants with increased resistance towards various clinically relevant antibiotics, such as ciprofloxacin, streptomycin, tetracycline and erythromycin. Whole genome analysis of the resistant variants obtained for Salmonella spp. allowed identifying the genetic changes responsible for the observed phenotypes, which suggested that some antimicrobial classes are more susceptible to the cross-resistance phenomena observed. This information is relevant, since these novel decontamination techniques are being proposed as possible alternative green techniques for the decontamination of environments and equipment in food and clinical settings. MK-8719 Copyright © 2020 American Society for Microbiology.The cyclodipeptide pulcherriminic acid produced by Bacillus licheniformis is derived from cyclo(L-Leu-L-Leu) and possesses excellent antibacterial activities. In this study, we achieved high-level production of pulcherriminic acid via multistep metabolic engineering of B. licheniformis DWc9n*. Firstly, we increased leucine (Leu) supply by overexpressing the ilvBHC-leuABCD operon and ilvD involved in Leu biosynthesis to obtain strain W1, and the engineered strain W2 was further attained by deletion of gene bkdAB encoding branched-chain α-keto acid dehydrogenase in W1. As a result, intracellular Leu content and pulcherriminic acid yield of W2 strain reached 147.4 mg/g DCW (dry cell weight) and 189.9 mg/L, which were 227.6% and 48.9% higher than those of DWc9n*, respectively. Secondly, the strain W3 was constructed through overexpressing leucyl-tRNA synthase gene leuS in W2, and it produced 367.7 mg/L pulcherriminic acid. Thirdly, the original promoter of pulcherriminic acid synthetase cluster yvmC-cypX in W3 waW4/pHY-yvmA could be able to achieve 556.1 mg/L pulcherriminic acid production, which is the highest yield so far to the best of our knowledge. Copyright © 2020 American Society for Microbiology.Biocatalysis has emerged as an important tool in synthetic organic chemistry enabling the chemical industry to execute reactions with high regio- or enantioselectivity and under usually mild reaction conditions while avoiding toxic waste. Target substrates and products of reactions catalyzed by carboxylic ester hydrolases are often poorly water-soluble and require organic solvents, enzymes are evolved by nature to be active in cells, i.e. in aqueous rather than organic solvents. Therefore, biocatalysts withstanding organic solvents are urgently needed. Current strategies to identify such enzymes rely on laborious tests carried out by incubation in different organic solvents and determination of residual activities. Here, we describe a simple assay useful to screen large libraries of carboxylic ester hydrolases for resistance and activity in water miscible organic solvents. We have screened a set of 26 enzymes, most of them identified in this study, with four different water miscible organic solvents. The trigluble bulky substrates were identified. Our results thus contribute to fostering the identification and biotechnological application of CEs. Copyright © 2020 Bollinger et al.Shiga toxin-producing Escherichia coli (STEC) strains are important zoonotic foodborne pathogens, causing diarrhea, hemorrhagic colitis, and life-threatening hemolytic uremic syndrome (HUS) in humans. However, antibiotic treatment of STEC infection is associated with an increased risk of HUS. Therefore, there is an urgent need for early and effective therapeutic strategies. Here, we isolated lytic T7-like STEC phage PHB19 and identified a novel O91-specific polysaccharide depolymerase (Dep6) in the C-terminus of the PHB19 tailspike protein. Dep6 exhibited strong hydrolase activity across wide pH (pH 4-8) and temperature (20-60°C) ranges, and degraded polysaccharides on the surface of STEC strain HB10. In addition, both Dep6 and PHB19 degraded biofilms formed by STEC strain HB10. In a mouse STEC infection model, delayed Dep6 treatment (3 h post-infection) resulted in only 33% survival compared with 83% survival when treated simultaneously. In comparison, pre-treatment with Dep6 led to 100% survival compared wim STEC strain HB10, which was subsequently killed by serum complement in vitro In a mouse model, PHB19 and Dep6 protected against STEC infection and caused a significant reduction in the levels of pro-inflammatory cytokines. This study reports the use of an O91-specific polysaccharide depolymerase for the treatment of STEC infection in mice. Copyright © 2020 American Society for Microbiology.