Project description:E. coli K-12 BW25113 mutant strain yncC expression in biofilm cells relative to E. coli wild-type strain expression in biofilm cells. All samples were cultured in LB with glasswool at 37C for 15 hours and E. coli K-12 MG1655 mutant yncC colony cells vs wild type colony cells in LB plates 15h 37C. Quorum-sensing signal autoinducer 2 (AI-2) stimulates Escherichia coli biofilm formation through the motility regulator MqsR that induces expression of the putative transcription factor encoded by yncC. Here we show YncC increases biofilm formation by decreasing mucoidy (corroborated by decreased exopolysaccharide production and increased sensitivity to bacteriophage P1 infection). Differential gene expression and gel shift assays demonstrated that YncC is a repressor of the predicted periplasmic protein-encoding gene ybiM which was corroborated by the isogenic yncC ybiM double mutation which repressed the yncC phenotypes (biofilm formation, mucoidy, and bacteriophage resistance). Through nickel-enrichment microarrays and additional gel shift assays, we found that the putative transcription factor B3023 (directly upstream of mqsR) binds the yncC promoter. Overexpressing MqsR, AI-2 import regulators LsrR/LsrK, and AI-2 exporter TqsA induced yncC transcription whereas the AI-2 synthase LuxS and B3023 repressed yncC. MqsR has a toxic effect on E. coli bacterial growth which is partially reduced by the b3023 mutation. Therefore, AI-2 quorum-sensing control of biofilm formation is mediated through regulator MqsR that induces expression of the transcription factor YncC which serves to inhibit the expression of periplasmic YbiM; this inhibition of YbiM prevents it from overexpressing exopolysaccharide (causing mucoidy) and prevents YbiM from inhibiting biofilm formation. Experiment Overall Design: Strains: E. coli K-12 BW25113 wild-type, mutant yncC Experiment Overall Design: and E. coli K-12 MG1655 wild-type, mutant yncC Experiment Overall Design: Medium: LB Experiment Overall Design: Biofilm grown on glasswool or colony cells growth in LB plates Experiment Overall Design: Time: 15 hours Experiment Overall Design: Temperature: 37C Experiment Overall Design: Cell type: biofilm or colony Experiment Overall Design: For the biofilm arrays in BW25113 background: Experiment Overall Design: Overnight cultures (16 h, 2.5 mL) of wild type E. coli BW25113 and BW25113 yncC in LB and LB with kanamycin (50 Î¼g/mL), respectively, were used to inoculate 250 mL LB with 10 g of glass wool (Corning Glass Works, Corning, NY) for forming biofilm. After incubating at 37Â°C for 15 h with shaking (250 rpm), biofilm cells were prepared by rinsing and sonicating the glass wool in sterile 0.85% NaCl solution at 0Â°C as described before. The total RNA was isolated from biofilm cells as described previously. Experiment Overall Design: The E. coli Genechip antisense genome array (P/N 900381, Affymetrix, Santa Clara, CA) containing probes for more than 4200 open reading frames (ORFs) was used to analyze the complete E. coli transcriptome as described previously. Hybridizations were performed for 16 h and the total cell intensity was scaled automatically in the software to an average value of 630. The Gene Expression Technical Manual (Affymetrix) was followed for the procedures of DNA microarrays, and the GeneChip operating software (Affymetrix) was applied to analyze data of DNA microarrays. The data quality was assessed following the manufacturer's guidelines (GeneChip Expression Analysis: Data Analysis Fundamentals; Affymetrix) and also was based on the expected signals of E. coli BW25113 and the yncC mutant genotypes (e.g., signals of the deleted genes, araA and rhaA, were low for both BW25113 and BW25113 yncC, while the signal of yncC was low for the yncC mutant). A gene was identified as differentially-expressed when the P value based on the False Discovery Rate Method was less than 0.05 and the expression ratio was greater than threefold since the standard deviation for the expression ratio for all of genes was 2. Experiment Overall Design: for the colony arrays in MG1655 background: Experiment Overall Design: For the agar biofilm, fresh single colonies of wild-type E. coli MG1655 and MG1655 yncC were re-streaked on LB agar plates, incubated, and about 0.05 g of the colony cultures on LB plate were quickly transferred to 2-mL collection tubes. The total RNA was isolated from these colony cells as described previously. The E. coli GeneChip Genome 2.0 Array (Affymetrix, P/N 900551, Santa Clara, CA) containing 10,208 probe sets for open reading frames, rRNA, tRNA, and intergenic regions for four E. coli strains: MG1655, CFT073, O157:H7-Sakai, and O157:H7-EDL933, was used to analyze the complete E. coli transcriptome. A gene was identified as differentially-expressed when the P value based on the False Discovery Rate Method (Benjamini & Hochberg, 1995) was less than 0.05 and the expression ratio was greater than threefold since the standard deviation for the expression ratio for all of MG1655 genes (except the deleted yncC gene) was 2.

Project description:E. coli K-12 BW25113 mutant strain hha expression in biofilm cells relative to E. coli wild-type strain expression in biofilm cells. Samples were cultured in LB with glasswool at 37C for 4 hours and in LB glu with glasswool at 37C for 4, 15 and 24 hours. Hha is a temperature- and osmolarity-dependent modulator of gene expression that is induced 30-fold in Escherichia coli biofilms. Here we show through whole-transcriptome analysis that Hha decreases biofilm formation in both LB and LB glu media by (i) repressing fliC encoding the main structural flagellar protein flagellin, (ii) by repressing fimA encoding the major structural subunit of type I fimbriae, (iii) by repressing ihfA encoding a subunit of the transcriptional regulator IHF that induces the transcription of type I fimbriae genes, (iv) by regulating tnaA encoding tryptophanase that inhibits biofilms, and (v) by repressing ybaJ that forms an operon with hha. Corroborating the microarray data, hha deletion increased motility 3.2 ± 0.1-fold, decreased extracellular indole concentrations 12 ± 2-fold, and decreased type I fimbriae (as measured by yeast agglutination). Biofilm tests using single and double mutants of fimA and ihfA and transcriptional studies of the fimA, ihfA and ybaJ-hha promoters confirmed that Hha represses biofilm by inhibiting type I fimbriae production and that it negatively regulates its own transcription and that of ybaJ. Nickel-enhanced DNA microarrays to determine in vivo Hha binding sites confirmed that Hha binds the ybaJ-hha promoter, that it binds fimZ, a positive regulator of fimA, and that it binds to the rare codon tRNAs argU, ileXY, and proL. Sequence analysis of fimZ, fimB, fimE, and the type I fimbriae gene cluster fimAICDFGH revealed a high bias for the rare codons of arginine, isoleucine, proline, leucine, and threonine, and overexpressing Hha leads to cell death. Therefore, it appears Hha decreases biofilms by decreasing type I fimbriae production as a result of inhibiting synthesis of tRNAs for rare codons. Keywords: effect of hha deletion in biofilm formation 4 hr LB and 4,15 and 24 hr LB glu

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