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Open accessJournal ArticleDOI: 10.1128/JB.00106-10

HU Protein Affects Transcription of Surface Polysaccharide Synthesis Genes in Porphyromonas gingivalis

01 Dec 2010-Journal of Bacteriology (American Society for Microbiology)-Vol. 192, Iss: 23, pp 6217-6229
Abstract: K-antigen capsule synthesis is an important virulence determinant of the oral anaerobe Porphyromonas gingivalis. We previously reported that the locus required for synthesis of this surface polysaccharide in strain W83 (TIGR identification PG0106 to PG0120) is transcribed as a large (∼16.7-kb) polycistronic message. Through sequence analysis, we have now identified a 77-bp inverted repeat located upstream (206 bp) of the start codon of PG0106 that is capable of forming a large hairpin structure. Further sequence analysis just upstream and downstream of the capsule synthesis genes revealed the presence of two genes oriented in the same direction as the operon that are predicted to encode DNA binding proteins: PG0104, which is highly similar (57%) to DNA topoisomerase III, and PG0121, which has high similarity (72%) to DNA binding protein HU (β-subunit). In this report, we show that these two genes, as well as the 77-bp inverted repeat region, are cotranscribed with the capsule synthesis genes, resulting in a large transcript that is ∼19.4 kb (based on annotation). We also show that a PG0121 recombinant protein is a nonspecific DNA binding protein with strong affinity to the hairpin structure, in vitro, and that transcript levels of the capsule synthesis genes are downregulated in a PG0121 deletion mutant. Furthermore, we show that this decrease in transcript levels corresponds to a decrease in the amount of polysaccharide produced. Interestingly, expression analysis of another polysaccharide synthesis locus (PG1136 to PG1143) encoding genes involved in synthesis of a surface-associated phosphorylated branched mannan (APS) indicated that this locus is also downregulated in the PG0121 mutant. Altogether our data indicate that HU protein modulates expression of surface polysaccharides in P. gingivalis strain W83. more

Topics: Operon (57%), HU Protein (56%), Sequence analysis (55%) more

Open accessJournal ArticleDOI: 10.1128/IAI.05016-11
Abstract: Periodontal disease is a chronic oral inflammatory disease that is triggered by bacteria such as Porphyromonas gingivalis. P. gingivalis strains exhibit great heterogeneity, with some strains being encapsulated while others are nonencapsulated. Although the encapsulated strains have been shown to be more virulent in a mouse abscess model, so far the role of the capsule in P. gingivalis interactions with host cells is not well understood and its role in virulence has not been defined. Here, we investigated the contribution of the capsule to triggering a host response following microbial infection, as well as its protective role following bacterial internalization by host phagocytic cells with subsequent killing, using the encapsulated P. gingivalis strain W50 and its isogenic nonencapsulated mutant, PgC. Our study shows significant time-dependent upregulation of the expression of various groups of genes in macrophages challenged with both the encapsulated and nonencapsulated P. gingivalis strains. However, cells infected with the nonencapsulated strain showed significantly higher upregulation of 9 and 29 genes at 1 h and 8 h postinfection, respectively, than cells infected with the encapsulated strain. Among the genes highly upregulated by the nonencapsulated PgC strain were ones coding for cytokines and chemokines. Maturation markers were induced at a 2-fold higher rate in dendritic cells challenged with the nonencapsulated strain for 4 h than in dendritic cells challenged with the encapsulated strain. The rates of phagocytosis of the nonencapsulated P. gingivalis strain by both macrophages and dendritic cells were 4.5-fold and 7-fold higher, respectively, than the rates of phagocytosis of the encapsulated strain. On the contrary, the survival of the nonencapsulated P. gingivalis strain was drastically reduced compared to the survival of the encapsulated strain. Finally, the encapsulated strain exhibited greater virulence in a mouse abscess model. Our results indicate that the P. gingivalis capsule plays an important role in aiding evasion of host immune system activation, promoting survival of the bacterium within host cells, and increasing virulence. As such, it is a major virulence determinant of P. gingivalis. © 2011, American Society for Microbiology. more

Topics: Porphyromonas gingivalis (58%), Bacterial capsule (53%), Virulence (53%)

98 Citations

Open access
01 Jan 1996-
Abstract: In Escherichia coli about one half of the negative supercoiling of DNA is constrained by proteins, in contrast to the situation in eukaryotic cells where most of the DNA is constrained by histones. The level of supercoiling in the unrestrained portion is controlled by a balance between the supercoiling activity of gyrase and the relaxing activity of DNA topoisomerase I. In the present work we show, by disrupting one or both genes encoding the heterodimeric protein HU, that an interplay exists in bacteria between HU and topoisomerase I activity: a decrease in the intracellular concentration of HU was accompanied by an increase in relaxing activity as measured in cell extracts. Conversely, a topA10 mutant of topoisomerase I, which has low levels of relaxing activity, was unable to accept an HU deficiency introduced by transduction. Thus it appears that the ability to increase relaxing activity, or to decrease an excess of supercoiling, is important for cells to survive in the absence of HU. These data can be explained in terms of HU constraining supercoiling in vivo as it does in vitro: the absence of HU would generate more unconstrained supercoiling, which in turn would require an increase in relaxing activity to maintain physiological levels. more

Topics: Escherichia coli (50%)

76 Citations

Open access
01 Jan 2007-
Topics: Histone (58%), Bacteria (53%)

37 Citations

Open accessJournal ArticleDOI: 10.1177/0022034519845001
Abstract: The oral cavity contains a rich consortium of exopolysaccharide-producing microbes. These extracellular polysaccharides comprise a major component of the oral biofilm. Together with extracellular proteins, DNA, and lipids, they form the biofilm matrix, which contributes to bacterial colonization, biofilm formation and maintenance, and pathogenesis. While a number of oral microbes have been studied in detail with regard to biofilm formation and pathogenesis, the exopolysaccharides have been well characterized for only select organisms, namely Streptococcus mutans and Aggregatibacter actinomycetemcomitans. Studies on the exopolysaccharides of other oral organisms, however, are in their infancy. In this review, we present the current research on exopolysaccharides of oral microbes regarding their biosynthesis, regulation, contributions to biofilm formation and stability of the matrix, and immune evasion. In addition, insight into the role of exopolysaccharides in biofilms is highlighted through the evaluation of emerging techniques such as pH probing of biofilm colonies, solid-state nuclear magnetic resonance for macromolecular interactions within biofilms, and super-resolution microscopy analysis of biofilm development. Finally, exopolysaccharide as a potential nutrient source for species within a biofilm is discussed. more

Topics: Biofilm matrix (73%), Biofilm (62%), Streptococcus mutans (53%)

25 Citations

Open accessJournal ArticleDOI: 10.3389/FCIMB.2017.00378
Abstract: Porphyromonas gingivalis is an important cause of serious periodontal diseases, and is emerging as a pathogen in several systemic conditions including some forms of cancer. Initial colonization by P. gingivalis involves interaction with gingival epithelial cells, and the organism can also access host tissues and spread haematogenously. To better understand the mechanisms underlying these properties, we utilized a highly saturated transposon insertion library of P. gingivalis, and assessed the fitness of mutants during epithelial cell colonization and survival in a murine abscess model by high-throughput sequencing (Tn-Seq). Transposon insertions in many genes previously suspected as contributing to virulence showed significant fitness defects in both screening assays. In addition, a number of genes not previously associated with P. gingivalis virulence were identified as important for fitness. We further examined fitness defects of four such genes by generating defined mutations. Genes encoding a carbamoyl phosphate synthetase, a replication-associated recombination protein, a nitrosative stress responsive HcpR transcription regulator, and RNase Z, a zinc phosphodiesterase, showed a fitness phenotype in epithelial cell colonization and in a competitive abscess infection. This study verifies the importance of several well-characterized putative virulence factors of P. gingivalis and identifies novel fitness determinants of the organism. more

Topics: Porphyromonas gingivalis (57%), Virulence (55%), Phenotype (50%)

25 Citations


Open accessJournal ArticleDOI: 10.1093/NAR/GKG595
Michael Zuker1Institutions (1)
Abstract: The abbreviated name,‘mfold web server’,describes a number of closely related software applications available on the World Wide Web (WWW) for the prediction of the secondary structure of single stranded nucleic acids. The objective of this web server is to provide easy access to RNA and DNA folding and hybridization software to the scientific community at large. By making use of universally available web GUIs (Graphical User Interfaces),the server circumvents the problem of portability of this software. Detailed output,in the form of structure plots with or without reliability information,single strand frequency plots and ‘energy dot plots’, are available for the folding of single sequences. A variety of ‘bulk’ servers give less information,but in a shorter time and for up to hundreds of sequences at once. The portal for the mfold web server is mfold. This URL will be referred to as ‘MFOLDROOT’. more

Topics: Web server (61%), Server (53%), Software portability (51%)

11,636 Citations

Journal ArticleDOI: 10.1016/S0168-9525(00)02024-2
Peter Rice1, Ian Longden1, Alan Bleasby1Institutions (1)
01 Jun 2000-Trends in Genetics
Abstract: The European Molecular Biology Open Software Suite (EMBOSS) is a mature package of software tools developed for the molecular biology community. It includes a comprehensive set of applications for molecular sequence analysis and other tasks and integrates popular third-party software packages under a consistent interface. EMBOSS includes extensive C programming libraries and is a platform to develop and release software in the true open source spirit. more

8,698 Citations

Open accessBook
01 Jun 1965-
Topics: Carbohydrate chemistry (65%)

3,726 Citations

Journal ArticleDOI: 10.1038/NRM831
James C. Wang1Institutions (1)
Abstract: DNA topoisomerases are the magicians of the DNA world — by allowing DNA strands or double helices to pass through each other, they can solve all of the topological problems of DNA in replication, transcription and other cellular transactions. Extensive biochemical and structural studies over the past three decades have provided molecular models of how the various subfamilies of DNA topoisomerase manipulate DNA. In this review, the cellular roles of these enzymes are examined from a molecular point of view. more

Topics: DNA supercoil (67%), DNA replication (63%), Topoisomerase (57%) more

2,050 Citations

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