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Zhang F.,Fujian Agriculture and forestry University | Zhong H.,Fujian Agriculture and forestry University | Han X.,Fujian Agriculture and forestry University | Guo Z.,Fujian Agriculture and forestry University | And 5 more authors.
Fungal Biology | Year: 2015

Aspergillus flavus, a common contaminant of crops and stored grains, can produce aflatoxins that are harmful to humans and other animals. Water activity (aw) is one of the key factors influencing both fungal growth and mycotoxin production. In this study, we used the isobaric tagging for relative and absolute quantitation (iTRAQ) technique to investigate the effect of aw on the proteomic profile of A. flavus. A total of 3566 proteins were identified, of which 837 were differentially expressed in response to variations in aw. Among these 837 proteins, 403 were over-expressed at 0.99 aw, whereas 434 proteins were over-expressed at 0.93 aw. According to Gene Ontology (GO) analysis, the secretion of extracellular hydrolases increased as aw was raised, suggesting that extracellular hydrolases may play a critical role in induction of aflatoxin biosynthesis. On the basis of Clusters of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) categorizations, we identified an exportin protein, KapK, that may down-regulate aflatoxin biosynthesis by changing the location of NirA. Finally, we considered the role of two osmotic stress-related proteins (Sln1 and Glo1) in the Hog1 pathway and investigated the expression patterns of proteins related to aflatoxin biosynthesis. The data uncovered in this study are critical for understanding the effect of water stress on toxin production and for the development of strategies to control toxin contamination of agricultural products. © 2014 The British Mycological Society. Source

Zhang F.,Fujian Agriculture and forestry University | Guo Z.,Fujian Agriculture and forestry University | Zhong H.,Fujian Agriculture and forestry University | Wang S.,Fujian Agriculture and forestry University | And 2 more authors.
Toxins | Year: 2014

Aspergillus flavus is one of the most important producers of carcinogenic aflatoxins in crops, and the effect of water activity (aw) on growth and aflatoxin production of A. flavus has been previously studied. Here we found the strains under 0.93 aw exhibited decreased conidiation and aflatoxin biosynthesis compared to that under 0.99 aw. When RNA-Seq was used to delineate gene expression profile under different water activities, 23,320 non-redundant unigenes, with an average length of 1297 bp, were yielded. By database comparisons, 19,838 unigenes were matched well (e-value < 10-5) with known gene sequences, and another 6767 novel unigenes were obtained by comparison to the current genome annotation of A. flavus. Based on the RPKM equation, 5362 differentially expressed unigenes (with |log2Ratio| ≥ 1) were identified between 0.99 aw and 0.93 awtreatments, including 3156 up-regulated and 2206 down-regulated unigenes, suggesting that A. flavus underwent an extensive transcriptome response during water activity variation. Furthermore, we found that the expression of 16 aflatoxin producing-related genes decreased obviously when water activity decreased, and the expression of 11 development-related genes increased after 0.99 aw treatment. Our data corroborate a model where water activity affects aflatoxin biosynthesis through increasing the expression of aflatoxin producing-related genes and regulating development-related genes. © 2014 by the authors; licensee MDPI, Basel, Switzerland. Source

Yang J.,Beihang University | Yang Y.,Beihang University | Wu W.-M.,Stanford University | Zhao J.,Shenzhen Key Laboratory of Bioenergy | Jiang L.,Beihang University
Environmental Science and Technology | Year: 2014

Polyethylene (PE) has been considered nonbiodegradable for decades. Although the biodegradation of PE by bacterial cultures has been occasionally described, valid evidence of PE biodegradation has remained limited in the literature. We found that waxworms, or Indian mealmoths (the larvae of Plodia interpunctella), were capable of chewing and eating PE films. Two bacterial strains capable of degrading PE were isolated from this worm's gut, Enterobacter asburiae YT1 and Bacillus sp. YP1. Over a 28-day incubation period of the two strains on PE films, viable biofilms formed, and the PE films' hydrophobicity decreased. Obvious damage, including pits and cavities (0.3-0.4 μm in depth), was observed on the surfaces of the PE films using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The formation of carbonyl groups was verified using X-ray photoelectron spectroscopy (XPS) and microattenuated total reflectance/Fourier transform infrared (micro-ATR/FTIR) imaging microscope. Suspension cultures of YT1 and YP1 (108 cells/mL) were able to degrade approximately 6.1 ± 0.3% and 10.7 ± 0.2% of the PE films (100 mg), respectively, over a 60-day incubation period. The molecular weights of the residual PE films were lower, and the release of 12 water-soluble daughter products was also detected. The results demonstrated the presence of PE-degrading bacteria in the guts of waxworms and provided promising evidence for the biodegradation of PE in the environment. © 2014 American Chemical Society. Source

Wang L.,China Kweichow Moutai Distillery Co. | Wang Y.-Y.,BGI Shenzhen | Wang Y.-Y.,Shenzhen Key Laboratory of Environmental Microbial Genomics and Application | Wang D.-Q.,China Kweichow Moutai Distillery Co. | And 11 more authors.
Journal of the Institute of Brewing | Year: 2015

Microbes are the major producers of alcohol and aromatic compounds in alcohol beverages. It is believed that, in addition to production techniques and grains, different micro-ingredient compositions yield variations in aromas and tastes. The bacterial communities of the three key phases from Moutai liquor production were profiled with the Illumina sequencing platform. A total of 54 bacterial families were detected and the microbial structure showed clear differences among samples. In the starter-making phase, Leuconostocaceae and Enterococcaceae dominated the shaping stage, and Bacillaceae dominated the mature starter and ripening stages. In the latter two phases, Bacillaceae and Lactobacillales dominated in the early stage of stack fermentation and the anaerobic stage of pit fermentation, respectively. Most of the important microbes (approximately 26 families) might have originated from the starter and greatly affected the bacterial structure of the samples during the early stages of stack fermentation. Production techniques and environmental factors, such as temperature and oxygen, also shaped the unique bacterial composition during different phases. © 2015 The Institute of Brewing & Distilling. Source

Yang Y.,Beihang University | Yang J.,Beihang University | Wu W.-M.,Stanford University | Zhao J.,Shenzhen Key Laboratory of Bioenergy | And 4 more authors.
Environmental Science and Technology | Year: 2015

The role of gut bacteria of mealworms (the larvae of Tenebrio molitor Linnaeus) in polystyrene (PS) degradation was investigated. Gentamicin was the most effective inhibitor of gut bacteria among six antibiotics tested. Gut bacterial activities were essentially suppressed by feeding gentamicin food (30 mg/g) for 10 days. Gentamicin-feeding mealworms lost the ability to depolymerize PS and mineralize PS into CO2, as determined by characterizing worm fecula and feeding with 13C-labeled PS. A PS-degrading bacterial strain was isolated from the guts of the mealworms, Exiguobacterium sp. strain YT2, which could form biofilm on PS film over a 28 day incubation period and made obvious pits and cavities (0.2-0.3 mm in width) on PS film surfaces associated with decreases in hydrophobicity and the formation of C-O polar groups. A suspension culture of strain YT2 (108 cells/mL) was able to degrade 7.4 ± 0.4% of the PS pieces (2500 mg/L) over a 60 day incubation period. The molecular weight of the residual PS pieces was lower, and the release of water-soluble daughter products was detected. The results indicated the essential role of gut bacteria in PS biodegradation and mineralization, confirmed the presence of PS-degrading gut bacteria, and demonstrated the biodegradation of PS by mealworms. © 2015 American Chemical Society. Source

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