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The nucleoid-associated protein HU? affects global gene expression in Porphyromonas gingivalis.

ABSTRACT: HU is a non-sequence-specific DNA-binding protein and one of the most abundant nucleoid-associated proteins in the bacterial cell. Like Escherichia coli, the genome of Porphyromonas gingivalis is predicted to encode both the HU? (PG1258) and the HU? (PG0121) subunit. We have previously reported that PG0121 encodes a non-specific DNA-binding protein and that PG0121 is co-transcribed with the K-antigen capsule synthesis operon. We also reported that deletion of PG0121 resulted in downregulation of capsule operon expression and produced a P. gingivalis strain that is phenotypically deficient in surface polysaccharide production. Here, we show through complementation experiments in an E. coli MG1655 hupAB double mutant strain that PG0121 encodes a functional HU homologue. Microarray and quantitative RT-PCR analysis were used to further investigate global transcriptional regulation by HU? using comparative expression profiling of the PG0121 (HU?) mutant strain to the parent strain, W83. Our analysis determined that expression of genes encoding proteins involved in a variety of biological functions, including iron acquisition, cell division and translation, as well as a number of predicted nucleoid associated proteins were altered in the PG0121 mutant. Phenotypic and quantitative real-time-PCR (qRT-PCR) analyses determined that under iron-limiting growth conditions, cell division and viability were defective in the PG0121 mutant. Collectively, our studies show that PG0121 does indeed encode a functional HU homologue, and HU? has global regulatory functions in P. gingivalis; it affects not only production of capsular polysaccharides but also expression of genes involved in basic functions, such as cell wall synthesis, cell division and iron uptake.

SUBMITTER: Priyadarshini R

PROVIDER: S-EPMC3709559 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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The nucleoid-associated protein HUβ affects global gene expression in Porphyromonas gingivalis.

Priyadarshini Richa R Cugini Carla C Arndt Annette A Chen Tsute T Tjokro Natalia O NO Goodman Steven D SD Davey Mary E ME

Microbiology (Reading, England) 20121122 Pt 2

HU is a non-sequence-specific DNA-binding protein and one of the most abundant nucleoid-associated proteins in the bacterial cell. Like Escherichia coli, the genome of Porphyromonas gingivalis is predicted to encode both the HUα (PG1258) and the HUβ (PG0121) subunit. We have previously reported that PG0121 encodes a non-specific DNA-binding protein and that PG0121 is co-transcribed with the K-antigen capsule synthesis operon. We also reported that deletion of PG0121 resulted in downregulation of ...[more]

PMID: 23175503

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Project description:Polyphosphate (polyP) is a ubiquitous and abundant compound found in bacteria, fungi, algae, plant, and animals. Among roles of intracellular polyP in bacteria are resistance and survival in the stationary phase of the growth against stress and stringent condition. Therefore, intracellular polyP is considered as a virulence factor of bacteria. In contrast, exogenous polyP has an antimicrobial activity against a variety of microorganisms. To date, much has been numerous studies of antibacterial effect of polyP against gram positive bacteria and fungi while relatively little reports have been published concerning gram negative bacteria. Here we describe bactericidal effect of polyP against gram negative periodontopathic bacterium, Porphyromonas gingivalis, and the transcriptional change by polyP in this bacterium. The bacterial growth was inhibited by polyP (chain length of P3~P75) at concentration of 0.02~0.03%, but not by Pi and PPi at the concentrations. polyP75 was chosen for further experiments, which suppressed the further growth of P. gingivalis as low as 0.03%. polyP75 completely killed the bacterial cells at the concentration of 0.035%. Microarray analysis was employed to identify genes that showed a greater than 1.5-fold difference in the expression by polyP75 at the concentration of 0.03%. It was found that 155 genes were up-regulated and 173 were down-regulated. Down-regulated genes include groups of energy metabolism-related genes, cell envelope-related genes, and genes in relation to biosynthesis of cofactors, prosthetic groups and carriers. Among the down-regulated genes were several involved in DNA replication, cell division protein, and biosynthesis of purines, pyrimidines, nucleosides and nucleotides. In contrast, a large number of ribosomal proteins, transciptional regulators and transposases were up-regulated. Oxidative stress-related genes and iron storage proteins also appeared to be increased in the expression. Real-time PCR confirmed up- and down-regulation of some selected genes. The overall results suggest that polyP has a bactericidal activity against P. gingivalis, interfering with translation, energy metabolism, DNA replication, cell division, and biosynthesis of purines, pyrimidines, nucleoside and nucleotides. polyP may be used as an agent for prevention and treatment of periodontal infections. Polyp-treated vs. untreated intensity ratio data linked below as a supplementary file. Keywords: agent response Twenty μg of each total RNA sample was used in separate hybridization experiments on identical arrays. The whole genome of 1,909 genes of P. gingivalis W83 (GenBank accession no. NC_002950) was submitted to NimbleGen System Inc. (Madison, WI) for microarray design and manufacture using maskless, digital micromirror technology. Five replicates of the genome were included per chip. An average of 19 different 60-base oligonucleotides (60-mer probes) represented each gene in the genome. Sixty-mer probes were selected such that each probe had at least three mismatches compared to all other 60-mers in the target genome. A quality control check (hybridization) was performed for each array, which contained on-chip control oligonucleotides. The arrays were analyzed using an Axon GenePix 4000B microarray scanner with associated software (Molecular Devices Corp., Sunnyvale, CA). Gene expression levels were calculated with NimbleScan Version 2.3 (NimbleGen). Relative signal intensities for each gene were generated using the Robust Multi-Array Average algorithm. The data were processed based on quantile normalization method using the R package. This normalization method aims to make the distribution of intensities for each array in a set of arrays the same. The background-adjusted, normalized, and log transformed intensity values were then analyzed using GeneSpring GX 7.3.1 (Silicon Genetics, Palo Alto, CA).

Dataset Information

The nucleoid-associated protein HU? affects global gene expression in Porphyromonas gingivalis.

Publications

The nucleoid-associated protein HUβ affects global gene expression in Porphyromonas gingivalis.

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