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AI-2-dependent gene regulation in Staphylococcus epidermidis

ABSTRACT: Autoinducer 2 (AI-2), a widespread by-product of the LuxS-catalyzed S-ribosylhomocysteine cleavage reaction in the activated methyl cycle, has been suggested to serve as an intra- and interspecies signaling molecule, but in many bacteria AI-2 control of gene expression is not completely understood. Particularly, we have a lack of knowledge about AI-2 signaling in the important human pathogens Staphylococcus aureus and S. epidermidis. Here, to determine the role of LuxS and AI-2 in S. epidermidis, we analyzed genome-wide changes in gene expression in an S. epidermidis luxS mutant and after addition of AI-2 synthesized by over-expressed S. epidermidis Pfs and LuxS enzymes. Genes under AI-2 control included mostly genes involved in sugar, nucleotide, amino acid, and nitrogen metabolism, but also virulence-associated genes coding for lipase and bacterial apoptosis proteins. In addition, we demonstrate by liquid chromatography/mass-spectrometry of culture filtrates that the pro-inflammatory phenol-soluble modulin (PSM) peptides, key virulence factors of S. epidermidis, are under luxS/AI-2 control. Our results provide a detailed molecular basis for the role of LuxS in S. epidermidis virulence and suggest a signaling function for AI-2 in this bacterium. Keywords: wild type without glucose control vs luxS mutant vs luxS mutant with auto-inducer II

ORGANISM(S): Staphylococcus epidermidis RP62A Rickettsia rickettsii Coxiella burnetii RSA 493 Granulibacter bethesdensis Staphylococcus epidermidis ATCC 12228 Coxiella burnetii Chlamydia muridarum Chlamydia trachomatis D/UW-3/CX Staphylococcus epidermidis Staphylococcus haemolyticus JCSC1435 Borreliella burgdorferi B31 Chlamydia pneumoniae AR39 Staphylococcus aureus subsp. aureus MW2 Chlamydia caviae GPIC

PROVIDER: GSE9427 | GEO | 2008/10/10

SECONDARY ACCESSION(S): PRJNA103171

REPOSITORIES: GEO

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Project description:LuxS is an enzyme involved in the activated methyl cycle and the by-product autoinducer 2 (AI-2) was a quorum sensing signal in some species. In our previous study, the functional LuxS in AI-2 production was verified in the porcine respiratory pathogen Actinobacillus pleuropneumoniae. Enhanced biofilm formation and reduced virulence were observed in the luxS mutant. To comprehensively understand the luxS function, in this study, the transcriptional profiles were compared between the A. pleuropneumoniae luxS mutant and its parental strain in four different growth phases using microarray. Many genes associated with infection were differentially expressed. The biofilm formation genes pgaABC in the luxS mutant were up-regulated in early exponential phase, while 8 genes associated with adhesion were down-regulated in late exponential phase. A group of genes involved in iron acquisition and metabolism were regulated in four growth phases. Further investigations on these virulence traits demonstrated that the luxS mutant showed enhanced biofilm formation and reduced adhesion ability and these effects were not due to lack of AI-2. But AI-2 could increase biofilm formation and adhesion of A. pleuropneumoniae independent of LuxS. Growth under iron restricted condition could be controlled by LuxS through AI-2 production. These results revealed pleiotropic roles of LuxS and AI-2 on A. pleuropneumoniae virulence traits. A. pleuropneumoniae strains were cultured in TSB medium supplemented with 10 M-NM-<g/ml of nicotinamide adenine dinucleotide (NAD) and 10% (v/v)filtered cattle serum at 37M-BM-0C. The samples were collected from early exponential phase, middle exponential phase, late exponential phase and stationary phase respectively and the total RNA were extracted using RNA-Solv Reagent (Omega) according to the manufacturerM-bM-^@M-^Ys instructions. For each time point, four biological replicates were combined into two samples. The intensities were normalized and transformed into log2 value.The fold changes >=1.5 or <=-1.5 were selected as differentially expressed genes.

Project description:LuxS is an enzyme involved in the activated methyl cycle. The by-product of this cycle, autoinducer 2 (AI-2), could be an important quorum sensing signal. LuxS was conserved and regulated many behaviors in different bacteria, but in most species, whether the regulations are related to AI-2 mediated quorum sensing is still unknown. In our previous study, Actinobacillus pleuropneumoniae, the etiologic agent of porcine contagious pleuropneumonia, was found to possess the functional LuxS affecting biofilm formation and virulence. In this study, microarray was used to compare the transcriptional profiles of the A. pleuropneumoniae wildtype strain 4074, luxS mutant and its AI-2 supplemented strain in four different growth phases. The results demonstrated that both LuxS and AI-2 played important roles in metabolism of this bacterium. AI-2 did not recover the gene expression changes caused by luxS deletion but caused more extensive metabolic alterations in the luxS mutant in a concentration dependent manner. Regulations of the genes involved in iron metabolism, carbonhydrate transport and host cell adhesion were validated by real-time RT-PCR and phenotypic investigations under different conditions. The results demonstrated that sugar uptake was repressed by LuxS independent of AI-2. However, iron metabolism, an important process of infection for A. pleuropneumoniae, could be controlled by LuxS through AI-2. Adhesion to host cells was also affected by LuxS and AI-2, but exogenous AI-2 displayed more obvious effects. Our results indicated that both LuxS and AI-2 are essential in the metabolism of A. pleuropneumoniae. The function of LuxS/AI-2 displayed pleiotropic roles in different conditions. AI-2 may not serve as a quorum sensing autoinducer but a metabolite or an environmental cue to affect the metabolism and virulence traits of this important pathogen. A. pleuropneumoniae strains were cultured in TSB medium supplemented with 10 M-NM-<g/ml of nicotinamide adenine dinucleotide (NAD) and 10% (v/v) filtered cattle serum at 37M-BM-0C. For samples from the mutant supplemented with AI-2, 100M-NM-<M and 25M-NM-<M AI-2 precursor (DPD) were added into the medium before early exponential phase as well as one hour before late exponential phase to cover the whole growth phase respectively. The samples were collected from early, middle, late exponential phase and stationary phase respectively and the total RNA were extracted using RNA-Solv Reagent (Omega) according to the manufacturerM-bM-^@M-^Ys instructions. For each time point, four biological replicates were combined into two samples. The intensities were normalized and transformed into log2 value. The values for each time point were averaged and the genes with log2 ratio >=1 or <=-1 were selected as differentially expressed genes.

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).

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AI-2-dependent gene regulation in Staphylococcus epidermidis

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