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Metagenomics 16S in ground beef

ABSTRACT: Comparison of the microbial community structures in ground beef inoculated with O26:H11 21765 or O157:H7 EDL933 strains

PROVIDER: PRJEB13580 | ENA |

REPOSITORIES: ENA

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			Action	DRS
	ERR1361630_1.fastq.gz	Fastqsanger.gz
	ERR1361630_2.fastq.gz	Fastqsanger.gz
	ERR1361628_1.fastq.gz	Fastqsanger.gz
	ERR1361628_2.fastq.gz	Fastqsanger.gz
	ERR1361629_1.fastq.gz	Fastqsanger.gz

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Project description:Shiga toxin-producing Escherichia coli (STEC) are food-borne pathogens that can cause severe symptoms in humans. Raw milk products are often incriminated as vectors for human STEC infection. However, raw milk naturally contains molecules, such as the milk fat globule membrane and associated proteins, that could inhibit pathogen adhesion by acting as mimetic ligands. This study aimed to: evaluate the capability of STEC cells to adhere to bovine milk fat globule membrane proteins (MFGMPs); highlight STEC surface proteins associated with adhesion; and evaluate the variation between different STEC serotypes. We evaluated the physicochemical interactions between STEC and milk fat globules (MFGs) by analyzing hydrophobic properties and measuring the z-potential. We used a plate adhesion assay to assess adhesion between MFGMPs and 15 Escherichia coli strains belonging to three key serotypes (O157:H7, O26:H11, and O103:H2). A relative quantitative proteomic approach was conducted by mass spectrometry to identify STEC surface proteins that may be involved in STEC-MFG adhesion. The majority of E. coli strains showed a hydrophilic profile. The z-potential values of the strains and MFGs were between -3.7 and -2.9 mV and between -12.2 more or less 0.14 mV, respectively. Our results suggest that non-specific interactions are not strongly involved in STEC-MFG association and that molecular bonds could form between STEC and MFGs. Plate adhesion assays showed a weak adhesion of O157:H7 E. coli strains to MFGMPs. In contrast, O26:H11 and O103:H2 serotypes attached more to MFGMPs. Relative quantitative proteomic analysis showed that the O26:H11 str. 21765 differentially expressed five outer membrane-associated proteins or lipoproteins compared with the O157:H7 str. EDL933. This analysis also found strain-specific differentially expressed proteins, including four O26:H11 str. 21765-specific proteins/lipoproteins and eight O103:H2 str. PMK5-specific proteins. For the first time, we demonstrated STEC adhesion to MFGMPs and discovered a serotype effect. Several outer membrane proteins-OmpC and homologous proteins, intimin, Type 1 Fimbriae, and AIDA-I-that may be involved in STEC-MFG adhesion were highlighted. More research on STEC's ability to adhere to MFGMs in diverse biological environments, such as raw milk cheeses and the human GI tract, is needed to confirm the anti-adhesion properties of the STEC-MFG complex.

Project description:RpoS is a conserved stress regulator that plays a critical role in survival under stress conditions in Escherichia coli and other γ-proteobacteria. RpoS is also involved in virulence of many pathogens including Salmonella and Vibrio species. Though well characterized in non-pathogenic E. coli K12 strains, the effect of RpoS on transcriptome expression has not been examined in pathogenic isolates. E. coli O157:H7 is a serious human enteropathogen, possessing a genome 20% larger than that of E. coli K12, and many of the additional genes are required for virulence. The genomic difference may result in substantial changes in RpoS-regulated gene expression. To test this, we compared the transcriptional profile of wild type and rpoS mutants of the E. coli O157:H7 EDL933 type strain. The rpoS mutation had a pronounced effect on gene expression in stationary phase, and more than 1,000 genes were differentially expressed (two-fold, p<0.05). By contrast, we found 11 genes expressed differently in exponential phase. Western blot analysis revealed that, as expected, RpoS level was low in exponential phase and substantially increased in stationary phase. The defect in rpoS resulted in impaired expression of genes responsible for stress response (e.g., gadA, katE and osmY), arginine degradation (astCADBE), putrescine degradation (puuABCD), fatty acid oxidation (fadBA and fadE), and virulence (ler, espI and cesF). For EDL933-specific genes on O-islands, we found 50 genes expressed higher in wild type EDL933 and 49 genes expressed higher in the rpoS mutants. The protein levels of Tir and EspA, two LEE-encoded virulence factors, were elevated in the rpoS mutants under LEE induction conditions. Our results show that RpoS has a profound effect on global gene expression in the pathogenic strain O157:H7 EDL933, and the identified RpoS regulon, including many EDL933-specific genes, differs substantially from that of laboratory K12 strains. In this study, we characterized the RpoS regulon of E. coli O157:H7 strain EDL933 using microarray analysis.

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Metagenomics 16S in ground beef

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