Characterization and genomic analysis of chromate resistant and reducing Bacillus cereus strain SJ1

<p>Abstract</p> <p>Background</p> <p>Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr(VI) and Cr(III). Chromate [Cr(VI)] is carcinogenic, mutational, and teratogenic due to its strong oxidizing nature. Biotransformation of Cr(VI) to less-toxic Cr(III) by chromate-resistant and reducing bacteria has offered an ecological and economical option for chromate detoxification and bioremediation. However, knowledge of the genetic determinants for chromate resistance and reduction has been limited so far. Our main aim was to investigate chromate resistance and reduction by <it>Bacillus cereus </it>SJ1, and to further study the underlying mechanisms at the molecular level using the obtained genome sequence.</p> <p>Results</p> <p><it>Bacillus cereus </it>SJ1 isolated from chromium-contaminated wastewater of a metal electroplating factory displayed high Cr(VI) resistance with a minimal inhibitory concentration (MIC) of 30 mM when induced with Cr(VI). A complete bacterial reduction of 1 mM Cr(VI) was achieved within 57 h. By genome sequence analysis, a putative chromate transport operon, <it>chrIA</it>1, and two additional <it>chrA </it>genes encoding putative chromate transporters that likely confer chromate resistance were identified. Furthermore, we also found an azoreductase gene <it>azoR </it>and four nitroreductase genes <it>nitR </it>possibly involved in chromate reduction. Using reverse transcription PCR (RT-PCR) technology, it was shown that expression of adjacent genes <it>chrA</it>1 and <it>chrI </it>was induced in response to Cr(VI) but expression of the other two chromate transporter genes <it>chrA</it>2 and <it>chrA</it>3 was constitutive. In contrast, chromate reduction was constitutive in both phenotypic and gene expression analyses. The presence of a resolvase gene upstream of <it>chrIA</it>1, an arsenic resistance operon and a gene encoding Tn7-like transposition proteins ABBCCCD downstream of <it>chrIA</it>1 in <it>B. cereus </it>SJ1 implied the possibility of recent horizontal gene transfer.</p> <p>Conclusion</p> <p>Our results indicate that expression of the chromate transporter gene <it>chrA</it>1 was inducible by Cr(VI) and most likely regulated by the putative transcriptional regulator ChrI. The bacterial Cr(VI)-resistant level was also inducible. The presence of an adjacent arsenic resistance gene cluster nearby the <it>chrIA</it>1 suggested that strong selective pressure by chromium and arsenic could cause bacterial horizontal gene transfer. Such events may favor the survival and increase the resistance level of <it>B. cereus </it>SJ1.</p

Structural Basis of Enzymatic Activity for the Ferulic Acid Decarboxylase (FADase) from Enterobacter sp. Px6-4

Microbial ferulic acid decarboxylase (FADase) catalyzes the transformation of ferulic acid to 4-hydroxy-3-methoxystyrene (4-vinylguaiacol) via non-oxidative decarboxylation. Here we report the crystal structures of the Enterobacter sp. Px6-4 FADase and the enzyme in complex with substrate analogues. Our analyses revealed that FADase possessed a half-opened bottom β-barrel with the catalytic pocket located between the middle of the core β-barrel and the helical bottom. Its structure shared a high degree of similarity with members of the phenolic acid decarboxylase (PAD) superfamily. Structural analysis revealed that FADase catalyzed reactions by an “open-closed” mechanism involving a pocket of 8×8×15 Å dimension on the surface of the enzyme. The active pocket could directly contact the solvent and allow the substrate to enter when induced by substrate analogues. Site-directed mutagenesis showed that the E134A mutation decreased the enzyme activity by more than 60%, and Y21A and Y27A mutations abolished the enzyme activity completely. The combined structural and mutagenesis results suggest that during decarboxylation of ferulic acid by FADase, Trp25 and Tyr27 are required for the entering and proper orientation of the substrate while Glu134 and Asn23 participate in proton transfer

Impact of volatile phenols and their precursors on wine quality and control measures of Brettanomyces/Dekkera yeasts

Volatile phenols are aromatic compounds and one of the key molecules responsible for olfactory defects in wine. The yeast genus Brettanomyces is the only major microorganism that has the ability to covert hydroxycinnamic acids into important levels of these compounds, especially 4-ethylphenol and 4-ethylguaiacol, in red wine. When 4-ethylphenols reach concentrations greater than the sensory threshold, all wine’s organoleptic characteristics might be influenced or damaged. The aim of this literature review is to provide a better understanding of the physicochemical, biochemical, and metabolic factors that are related to the levels of p-coumaric acid and volatile phenols in wine. Then, this work summarizes the different methods used for controlling the presence of Brettanomyces in wine and the production of ethylphenols

Antioxidative protection of dietary bilberry, chokeberry and Lactobacillus plantarum HEAL19 in mice subjected to intestinal oxidative stress by ischemia-reperfusion

<p>Abstract</p> <p>Background</p> <p>Ischemia-reperfusion (I/R) in the intestines is an inflammatory condition which activates leukocytes and reactive oxygen species (ROS) and leads to lipid peroxidation and DNA damage. Bilberry and chokeberry fruits are rich sources of polyphenols which may act as antioxidants and prevent lipid peroxidation. Lactic acid bacteria (LAB) may improve microbial status in the intestines and increase the metabolic activity towards polyphenolic degradation. The aim of the study was to clarify antioxidative effects of bilberry and chokeberry fruits alone and with addition of a LAB-strain, <it>Lactobacillus plantarum </it>HEAL19, in an I/R-model in mice.</p> <p>Methods</p> <p>Male BALB/cJ mice were fed the experimental diets for 10 days. Diets consisted of standard chow supplemented with either bilberry (<it>Vaccinium myrtillus</it>) or chokeberry (<it>Aronia × prunifolia</it>) powder alone or in combination with the LAB-strain <it>Lactobacillus plantarum </it>HEAL19. I/R-injury was induced by holding superior mesenteric artery clamped for 30 minutes followed by reperfusion for 240 minutes. Thereafter, colonic and caecal tissues and contents were collected. Malondialdehyde (MDA) was used as indicator of lipid peroxidation and was measured by a calorimetric assay, lactobacilli were cultured on Rogosa agar plates and <it>Enterobacteriaceae </it>on VRBG agar plates, anthocyanins and phenolic acids were analysed by HPLC-DAD-ESI-MSn.</p> <p>Results</p> <p>MDA was significantly decreased in the colon of groups fed bilberry alone (p = 0.030) and in combination with <it>L. plantarum </it>HEAL19 (p = 0.021) compared to the IR-control but not in chokeberry-fed groups. Supplementation with bilberry or chokeberry alone reduced the total number of lactobacilli on the mucosa. Higher concentrations of anthocyanins were found in the colon than in the caecum content of mice. A more varied composition of different anthocyanins was also observed in the colon content compared to the caecum of bilberry-fed mice. Phenolic acids formed by microbial degradation of the dietary polyphenols in the gut could be detected. More phenolic metabolites were found in the intestines of bilberry-fed mice than in the chokeberry-fed ones.</p> <p>Conclusions</p> <p>Bilberry alone and in combination with <it>L. plantarum </it>HEAL19 exerts a better protection against lipid peroxidation than chokeberry. These dietary supplements may be used to prevent or suppress oxidative stress.</p

Enzyme-Linked Aptamer Assays (Elaas), Based On A Competition Format For A Rapid And Sensitive Detection Of Ochratoxin A In Wine

ISI Document Delivery No.: 715BU Times Cited: 29 Cited Reference Count: 32 Cited References: Alarcon SH, 2006, TALANTA, V69, P1031, DOI 10.1016/j.talanta.2005.12.024 Amezqueta S, 2009, FOOD CONTROL, V20, P326, DOI 10.1016/j.foodcont.2008.05.017 [Anonymous], 2005, OFFICIAL J EUROPEA L, VL25, P3 Baldrich E, 2005, ANAL CHEM, V77, P4774, DOI 10.1021/ac0502450 Brody E. N., 2000, REV MOL BIOTECHNOL, V74, P5, DOI DOI 10.1016/S1389-0352(99)00004-5 Bruno JG, 2009, J FLUORESC, V19, P427, DOI 10.1007/s10895-008-0429-8 Burdaspal P, 2007, FOOD ADDIT CONTAM, V24, P976, DOI 10.1080/02652030701311155 Cruz-Aguado JA, 2008, J AGR FOOD CHEM, V56, P10456, DOI 10.1021/jf801957h Cruz-Aguado JA, 2008, ANAL CHEM, V80, P8853, DOI 10.1021/ac8017058 De Saeger S, 2002, INT J FOOD MICROBIOL, V75, P135, DOI 10.1016/S0168-1605(01)00749-8 ELLINGTON AD, 1990, NATURE, V346, P818, DOI 10.1038/346818a0 Hamula CLA, 2006, TRAC-TREND ANAL CHEM, V25, P681, DOI 10.1016/j.trac.2006.05.007 Jayasena SD, 1999, CLIN CHEM, V45, P1628 JENISON RD, 1994, SCIENCE, V263, P1425, DOI 10.1126/science.7510417 Joshi R, 2009, MOL CELL PROBE, V23, P20, DOI 10.1016/j.mcp.2008.10.006 Mairal T, 2008, ANAL BIOANAL CHEM, V390, P989, DOI 10.1007/s00216-007-1346-4 Mann D, 2005, BIOCHEM BIOPH RES CO, V338, P1928, DOI 10.1016/j.bbrc.2005.10.172 Ngundi MM, 2005, ANAL CHEM, V77, P148, DOI 10.1021/ac048957y Papamichael KI, 2007, SENSOR ACTUAT B-CHEM, V121, P178, DOI 10.1016/j.snb.2006.09.024 Prieto-Simon B, 2008, BIOSENS BIOELECTRON, V23, P995, DOI 10.1016/j.bios.2007.10.002 Radi AE, 2009, ELECTROCHIM ACTA, V54, P2180, DOI 10.1016/j.electacta.2008.10.013 Radoi A, 2009, ANAL LETT, V42, P1187, DOI 10.1080/00032710902890447 Ricci F, 2007, ANAL CHIM ACTA, V605, P111, DOI 10.1016/j.aca.2007.10.046 Rusanova TY, 2009, ANAL CHIM ACTA, V653, P97, DOI 10.1016/j.aca.2009.08.036 Stoltenburg R, 2007, BIOMOL ENG, V24, P381, DOI 10.1016/j.bioeng.2007.06.001 Tombelli S, 2007, BIOMOL ENG, V24, P191, DOI 10.1016/j.bioeng.2007.03.003 TUERK C, 1990, SCIENCE, V249, P505, DOI 10.1126/science.2200121 Turner NW, 2009, ANAL CHIM ACTA, V632, P168, DOI 10.1016/j.aca.2008.11.010 van der Gaag B, 2003, FOOD CONTROL, V14, P251, DOI 10.1016/S0956-7135(03)00008-2 Wilson C, 1998, CHEM BIOL, V5, P609, DOI 10.1016/S1074-5521(98)90289-7 Wochner A, 2007, BIOTECHNIQUES, V43, P344, DOI 10.2144/000112532 Zezza F, 2009, ANAL BIOANAL CHEM, V395, P1317, DOI 10.1007/s00216-009-2994-3 Barthelmebs, Lise Jonca, Justyna Hayat, Akhtar Prieto-Simon, Beatriz Marty, Jean-Louis Higher Education Commission of Pakistan Akhtar HAYAT benefits from a grant of Higher Education Commission of Pakistan. The authors are very grateful to Richard Cooke and Michele Laudie from the LGDP of Perpignan University for aptamer sequencing and to Soft Flow Biotechnology for kindly providing the monoclonal antibody. 30 ELSEVIER SCI LTD OXFORD FOOD CONTROLOchratoxin A (OTA) is one of the most important mycotoxins because of its high toxicity to both humans and animals and its occurrence in a number of basic foods and agro-products. The need to develop high-performing methods for OTA analysis able to improve the traditional ones is evident. In this work, through in vitro SELEX (Systematic Evolution of Ligands by EXponential enrichment) two aptamers, designated H8 and H12 were produced that bind with nanomolar affinity with Ochratoxin A (OTA). Two strategies were investigated by using an indirect and a direct competitive Enzyme-Linked Aptamer Assay (ELAA) and were compared to the classical competitive Enzyme-Linked Immunosorbent Assay (ELISA) for the determination of OTA in spiked red wine samples. The limit of detection attained (1 ng/mL), the midpoint value obtained (5 ng/mL) and the analysis time needed (125 min) for the real sample analysis validate the direct competitive ELAA as useful screening tool for routine use in the control of OTA level in wine. (C) 2010 Elsevier Ltd. All rights reserved

Kinetics and intensity of the expression of genes involved in the stress response tightly induced by phenolic acids in lactobacillus plantarum

International audienceIn Lactobacillus plantarum, PadR, the negative transcriptional regulator of padA encoding the phenolic acid decarboxylase, is divergently oriented from padA. Moreover, it forms an operonic structure with usp1, a gene whose products display homology with proteins belonging to the UspA family of universal stress proteins. PadR is inactivated by the addition of p-coumaric, ferulic or caffeic acid to the culture medium. In order to better characterize the stress response of this bacterium to phenolic acids, we report here the kinetics and quantitative expression by qRT-PCR of the 3 genes from the padA locus. The expression of the 3 genes is very low in the non-induced condition, while the addition of 1.2 mMp-coumaric acid induces an increase in the expression of padA, padR and usp1 by factors of 8,000, 37 and 13, respectively. These maximum relative transcript levels are obtained after 5 min of induction at the end of the exponential growth phase, while phenolic acid decarboxylase activity, not detectable before induction, is increased by a factor of 8,000 in 10 min. The apparent half-life of padA mRNA is about 1.4 min. The padA-padR system displays dynamic characteristics that are valuable to the development of tools for gene expression in this bacterium. Copyright (c) 2008 S. Karger AG, Basel

Gene of non-target microorganisms : a new tool to monitor the exposure of soil microbial communities to b-triketone herbicides ?

International audienc