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The antibiotics potentiator bicarbonate causes upregulation of tryptophanase and iron acquisition proteins in Escherichia coli

ABSTRACT: We have reported that bicarbonate (NaHCO3) potentiates the activity of aminoglycosides in Escherichia coli, but the action mechanism was not identified. To eventually understand how NaHCO3 can potentiate antibiotics, we thought that a rational first step was to examine the effect of NaHCO3 separately and to inspect initial gene expression changes triggered by it. In this work we started by confirming that NaHCO3 can reduce the number of viable E. coli bacteria. We then investigated, via RNAseq, gene expression changes induced by NaHCO3. There were upregulated and downregulated genes, among the top upregulated genes (~10-fold increase in expression) was tnaA, the gene encoding tryptophanase (TnaA), the enzyme that degrades tryptophan to indole. Considering that higher expression of tnaA likely led to increases in indole, we tested the effect of indole and found both growth inhibition and synergy with NaHCO3. We suggest that indole may participate in growth inhibition of E. coli. The RNAseq analysis also revealed upregulation (≥4-fold) of genes encoding proteins for the acquisition of iron and downregulation (≥16-fold) of genes encoding iron-sulfur-holding proteins, hence NaHCO3 apparently triggered also an iron deficit response. We suggest that iron deficiency may also be involved in growth inhibition by NaHCO3.

ORGANISM(S): Escherichia coli

PROVIDER: GSE110493 | GEO | 2018/11/01

REPOSITORIES: GEO

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Project description:We have shown the quorum-sensing signals acylhomoserine lactones (AHLs), autoinducer-2 (AI-2), and indole influence the biofilm formation of Escherichia coli. Here, we investigate how the environment, i.e., temperature, affects indole and AI-2 signaling in E. coli. We show in biofilms that indole addition leads to more extensive differential gene expression at 30ï°C (186 genes) than at 37ï°C (59 genes), that indole reduces biofilm formation (without affecting growth) more significantly at 25ï°C and 30ï°C than at 37ï°C, and that the effect is associated with the quorum-sensing protein SdiA. The addition of indole at 30ï°C compared to 37ï°C most significantly repressed genes involved in uridine monophosphate (UMP) biosynthesis (carAB, pyrLBI, pyrC, pyrD, pyrF, and upp) and uracil transport (uraA). These uracil-related genes are also repressed at 30ï°C by SdiA, which confirms SdiA is involved in indole signaling. Also, compared to 37ï°C, indole more significantly decreased flagella-related qseB, flhD, and fliA promoter activity, enhanced antibiotic resistance, and inhibited cell division at 30ï°C. In contrast to indole and SdiA, the addition of (S)-4,5-dihydroxy-2,3-pentanedione (the AI-2 precursor) leads to more extensive differential gene expression at 37ï°C (63 genes) than at 30ï°C (11 genes), and, rather than repressing UMP synthesis genes, AI-2 induces them at 37ï°C (but not at 30ï°C). Also, the addition of AI-2 induces the transcription of virulence genes in enterohemorrhagic E. coli O157:H7 at 37oC but not at 30oC. Hence, cell signals cause diverse responses at different temperatures, and indole- and AI-2-based signaling are intertwined. Experiment Overall Design: We performed seven sets of microarray experiments in LB medium (Table 2): (i) biofilm cells of the BW25113 wild-type strain grown for 7 h at 30Â°C vs. 37Â°C to determine the effect of temperature on E. coli biofilm formation (initial absorbance of 0.05), (ii) biofilm cells of the tnaA mutant grown for 7 h with 1 mM indole vs. no indole at 30Â°C to determine the effect of temperature on indole signaling in E. coli (initial absorbance of 0.05), (iii) biofilm cells of the tnaA mutant grown for 7 h with 1 mM indole vs. no indole at 37Â°C to determine the effect of temperature on indole signaling in E. coli, (iv) suspension cells of the wild-type strain vs. the sdiA mutant at an absorbance of 4.0 at 600 nm at 30Â°C (since production of indole takes place primarily in the stationary phase) to discern the genes that SdiA controls (initial absorbance of 0.05), (v) biofilm cells of the sdiA mutant grown for 7 h with 1 mM indole vs. no indole at 30Â°C to determine gene expression in response to indole in the absence of SdiA, (vi) suspension cells of the luxS mutant with 100 micro M AI-2 vs. no AI-2 at 30Â°C for 3 h to determine the effect of temperature on AI-2 signaling in E. coli (initial absorbance of 0.5), and (vii) suspension cells of the luxS mutant with 100 micro M AI-2 vs. no AI-2 at 37Â°C for 3 h to determine the effect of temperature on AI-2 signaling in E. coli. Ten g of glass wool (Corning Glass Works, Corning, N.Y.) was used to form large amounts of biofilms (Ren et al., 2004a) in 250 mL LB in 1 L Erlenmeyer shake flasks. RNA was isolated from the suspension and biofilm cells as described previously (Ren et al., 2004b).

Project description:Transcriptional profiles of Escherichia coli MG1655 in mixed culture with Pseudomonas aeruginosa PAO1 showed a number of E. coli genes to be upregulated including purA-F and other genes associated with purine synthesis. In contrast, genes associated with pyrimidine synthesis were unaffected. Competition experiments in both planktonic and biofilm cultures, using three purine synthesis mutants, purD, purH, and purT showed little difference in E. coli survival from the parent strain. As purines are components of the cell signals, cAMP and c-di-GMP, we conducted competition experiments with E. coli mutants lacking adenylate cyclase (cyaA), cAMP phosphodiesterase (cpdA), and the catabolite receptor protein (crp), as well as ydeH, an uncharacterized gene that has been associated with c-di-GMP synthesis. Survival of the cyaA and crp mutants during co-culture were significantly less than the parent strain. Supplementation of the media with 1mM cAMP could restore survival of the cyaA mutant but not the crp mutant. In contrast, survival of the cpdA mutant was similar to the parent strain. Survival of the ydeH mutant was moderately less than the parent, suggesting that cAMP has more impact on E. coli mixed culture growth than c-di-GMP. Addition of 1 mM indole restored the survival of both the cyaA and crp mutations. Mutants in genes for tryptophan synthesis (trpE) and indole production (tnaA) showed a loss of competition and recovery through indole supplementation, comparable to the cyaA and crp mutants. Overall, these results suggest indole and cAMP as major contributing factors to E. coli growth in mixed culture. Two replicates of LB grown E. coli ZK126 and P. aeruginosa PAO1 were grown in pure culture at 37C to an OD of 0.3 (log phase) and then mixed 1:1 and incubated for an additional 45 min. RNA was extracted, purified, reverse transcribed to cDNA and then analyzed on E. coli and P. aeruginosa chips from Affymetrix. Expression profiles were compared to pure culture E. coli and P. aeruginosa grown on LB.

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

Project description:Transcriptional profiles of Escherichia coli MG1655 in mixed culture with Pseudomonas aeruginosa PAO1 showed a number of E. coli genes to be upregulated including purA-F and other genes associated with purine synthesis. In contrast, genes associated with pyrimidine synthesis were unaffected. Competition experiments in both planktonic and biofilm cultures, using three purine synthesis mutants, purD, purH, and purT showed little difference in E. coli survival from the parent strain. As purines are components of the cell signals, cAMP and c-di-GMP, we conducted competition experiments with E. coli mutants lacking adenylate cyclase (cyaA), cAMP phosphodiesterase (cpdA), and the catabolite receptor protein (crp), as well as ydeH, an uncharacterized gene that has been associated with c-di-GMP synthesis. Survival of the cyaA and crp mutants during co-culture were significantly less than the parent strain. Supplementation of the media with 1mM cAMP could restore survival of the cyaA mutant but not the crp mutant. In contrast, survival of the cpdA mutant was similar to the parent strain. Survival of the ydeH mutant was moderately less than the parent, suggesting that cAMP has more impact on E. coli mixed culture growth than c-di-GMP. Addition of 1 mM indole restored the survival of both the cyaA and crp mutations. Mutants in genes for tryptophan synthesis (trpE) and indole production (tnaA) showed a loss of competition and recovery through indole supplementation, comparable to the cyaA and crp mutants. Overall, these results suggest indole and cAMP as major contributing factors to E. coli growth in mixed culture. E. coli MG1655 and P. aeruginosa PAO1 were grown in a minimal defined medium containing N-acetyl glucosamine, overnight at 37C to an OD of 1.5, and then inoculated in fresh media at an OD of 0.001 and grown in pure or mixed culture for 4-5 hours to a final OD of 0.5. RNA was extracted, purified, reverse transcribed to cDNA and then analyzed on E. coli and P. aeruginosa chips from Affymetrix. Expression profiles of mixed culture-grown organisms were compared to pure culture E. coli and P. aeruginosa grown on the same defined medium.

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The antibiotics potentiator bicarbonate causes upregulation of tryptophanase and iron acquisition proteins in Escherichia coli

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