Remodelling compartment in root cementum.

BACKGROUND: Bone remodelling represents the most remarkable bone response to mechanical stress and mineral homeostasis. It is the consequence of complex highly orchestrated and tightly regulated cellular processes taking place in a specialised entity - the bone remodelling compartment (BRC). MATERIALS AND METHODS: Cementum is an understudied tissue that requires more research to understand its biology, pathology, and potential for regeneration. Although analogue to bone in structure and composition distinct structural and functional differences were ascribed to each of these mineralised tissues. The precise role of cementocytes in cementum turnover is unclear but they may work the same way as osteocytes in bone remodelling, regulating the full process. RESULTS: Although cementum is not liable to regular physiological remodelling as bone is, pathological cases triggered by orthodontic forces or large periapical periodontitis, those lesions can acutely induce cementum remodelling. Nevertheless, the cellular mechanisms behind this particular remodelling process are yet to be identified, as its eventual involvement of specialised anatomic structures as the BRC. CONCLUSIONS: Hypothesizing that similar cellular mechanisms underlie bone and cementum remodelling, the present work shows, for the first time, the histological evidence of a specialized remodelling compartment in dental hard tissues.

The history of Helicobacter pylori: from phylogeography to paleomicrobiology.

The study of the gastric pathogen Helicobacter pylori brought us interesting data on the history of mankind. Based on multi-locus sequence typing, it was possible to trace the migration of Homo sapiens all around the world, and to infer the time when he went Out of Africa. Beside these phylogeographic aspects, paleomicrobiology gave us important information on life in the Neolithic period, following the discovery of Ötzi, the Iceman, who was living in the Tyrolean Alps 5200 years ago, and from whom a Helicobacter pylori genome was sequenced. This review presents the data accumulated in these different fields.

Dormant phages of Helicobacter pylori reveal distinct populations in Europe.

Prophages of Helicobacter pylori, a bacterium known to co-evolve in the stomach of its human host, were recently identified. However, their role in the diversity of H. pylori strains is unknown. We demonstrate here and for the first time that the diversity of the prophage genes offers the ability to distinguish between European populations, and that H. pylori prophages and their host bacteria share a complex evolutionary history. By comparing the phylogenetic trees of two prophage genes (integrase and holin) and the multilocus sequence typing (MLST)-based data obtained for seven housekeeping genes, we observed that the majority of the strains belong to the same phylogeographic group in both trees. Furthermore, we found that the Bayesian analysis of the population structure of the prophage genes identified two H. pylori European populations, hpNEurope and hpSWEurope, while the MLST sequences identified one European population, hpEurope. The population structure analysis of H. pylori prophages was even more discriminative than the traditional MLST-based method for the European population. Prophages are new players to be considered not only to show the diversity of H. pylori strains but also to more sharply define human populations.

Proteome variability among Helicobacter pylori isolates clustered according to genomic methylation.

AIMS: To understand whether the variability found in the proteome of Helicobacter pylori relates to the genomic methylation, virulence and associated gastric disease. METHODS AND RESULTS: We applied the Minimum-Common-Restriction-Modification (MCRM) algorithm to genomic methylation data of 30 Portuguese H. pylori strains, obtained by genome sensitivity to Type II restriction enzymes' digestion. All the generated dendrograms presented three clusters with no association with gastric disease. Comparative analysis of two-dimensional gel electrophoresis (2DE) maps obtained for total protein extracts of 10 of these strains, representative of the three main clusters, revealed that among 70 matched protein spots (in a universe of 300), 16 were differently abundant (P < 0·05) among clusters. Of these, 13 proteins appear to be related to the cagA genotype or gastric disease. The abundance of three protein species, DnaK, GlnA and HylB, appeared to be dictated by the methylation status of their gene promoter. CONCLUSIONS: Variations in the proteome profile of strains with common geographic origin appear to be related to differences in cagA genotype or gastric disease, rather than to clusters organized according to strain genomic methylation. SIGNIFICANCE AND IMPACT OF THE STUDY: The simultaneous study of the genomic methylation and proteome is important to correlate epigenetic modifications with gene expression and pathogen virulence.

Transmission pathway of Helicobacter pylori: does food play a role in rural and urban areas?

Helicobacter pylori is a Gram-negative microaerophilic bacterium that has colonized the human gastric mucosa. This infection is very common and affects more than half of the human population. The prevalence is however unbalanced between rural developing areas (more than 80%) and urban developed areas (less than 40%). H. pylori is responsible for several pathologies, such as gastritis, peptic ulcer and gastric cancer but its transmission pathway is still not clear. The risk factors for H. pylori infection include poor social and economic development; poor hygienic practices; absence of hygienic drinking water; and unsanitary prepared food. There is evidence supporting a gastro-oral, oral-oral and faecal-oral transmission, but no predominant mechanism of transmission has been yet identified. Transmission may occur in a vertical mode (e.g. from parents to child) or in a horizontal mode (across individuals or from environmental contamination). In either case, the involvement of water and food cannot be excluded as vehicles or sources of infection. Indirect evidence of presence of H. pylori in water and food, namely the detection of its DNA and survival studies after artificial contamination of food and water has been described. This paper reviews data both favourable and against the role of water and food in the transmission of H. pylori, exploring their role as a potential transmission vehicle for person-to-person and food-chain transmission. The likelihood of the transmission pathway in developing rural and developed urban areas appears to be different. In developed areas, person-to-person transmission within families appears to be dominant, while in the rural developing areas the transmission pathway appears to be more complex. In this later case, the transmission by contaminated food, water, or via intensive contact between infants and non-parental caretakers may have a greater influence than within-family transmission.

Viral and bacterial contamination in recreational waters: a case study in the Lisbon bay area.

AIMS: To assess the presence of viral pathogens in bathing water samples and to evaluate the interdependency of bacterial indicator counts and viral detection. METHODS AND RESULTS: Bathing water samples of 16 beaches collected along a Portuguese Coastal area were screened for the hepatitis A virus (HAV) and norovirus genogroup I (NVGI) using RT-PCR technique. Bacteriological water quality was also assessed, according to European regulations. HAV and NVGI were detected in 95% and 27% of the water samples, respectively, whereas bacteriological quality was good in all but one sample, according to current water quality regulations. CONCLUSIONS: All water samples would be considered of excellent quality according to the most recent European regulations. No relationship between viral detection and regulatory-based bacterial indicators was found. SIGNIFICANCE AND IMPACT OF THE STUDY: The current results reinforce the importance of increased surveillance for pathogenic viruses in bathing waters.

A new algorithm for cluster analysis of genomic methylation: the Helicobacter pylori case.

MOTIVATION: The genomic methylation analysis is useful to type bacteria that have a high number of expressed type II methyltransferases. Methyltransferases are usually committed to Restriction and Modification (R-M) systems, in which the restriction endonuclease imposes high pressure on the expression of the cognate methyltransferase that hinder R-M system loss. Conventional cluster methods do not reflect this tendency. An algorithm was developed for dendrogram construction reflecting the propensity for conservation of R-M Type II systems. RESULTS: The new algorithm was applied to 52 Helicobacter pylori strains from different geographical regions and compared with conventional clustering methods. The algorithm works by first grouping strains that share a common minimum set of R-M systems and gradually adds strains according to the number of the R-M systems acquired. Dendrograms revealed a cluster of African strains, which suggest that R-M systems are present in H.pylori genome since its human host migrates from Africa. AVAILABILITY: The software files are available at http://www.ff.ul.pt/paginas/jvitor/Bioinformatics/MCRM_algorithm.zip.