A coding polymorphism in matrix metalloproteinase 9 reduces risk of scarring sequelae of ocular Chlamydia trachomatis infection.

BACKGROUND: Trachoma, an infectious disease of the conjunctiva caused by Chlamydia trachomatis, is an important global cause of blindness. A dysregulated extracellular matrix (ECM) proteolysis during the processes of tissue repair following infection and inflammation are thought to play a key role in the development of fibrotic sequelae of infection, which ultimately leads to blindness. Expression and activity of matrix metalloproteinase 9 (MMP-9), a major effector of ECM turnover, is up-regulated in the inflamed conjunctiva of trachoma subjects. Genetic variation within the MMP9 gene affects in vitro MMP9 expression levels, enzymatic activity and susceptibility to various inflammatory and fibrotic conditions. METHODS: We genotyped 651 case-control pairs from trachoma endemic villages in The Gambia for coding single nucleotide polymorphisms (SNPs) in the MMP9 gene using the high-throughput Sequenom system. Single marker and haplotype conditional logistic regression (CLR) analysis for disease association was performed. RESULTS: The Q279R mutation located in exon 6 of MMP9 was found to be associated with lower risk for severe disease sequelae of ocular Chlamydia trachomatis infection. This mutation, which leads to a nonsynonymous amino-acid change within the active site of the enzyme may reduce MMP-9-induced degradation of the structural components of the ECM during inflammatory episodes in trachoma and its associated fibrosis. CONCLUSION: This work supports the hypothesis that MMP-9 has a role in the pathogenesis of blinding trachoma

Evolutionary Genomics of a Temperate Bacteriophage in an Obligate Intracellular Bacteria (Wolbachia)

Genome evolution of bacteria is usually influenced by ecology, such that bacteria with a free-living stage have large genomes and high rates of horizontal gene transfer, while obligate intracellular bacteria have small genomes with typically low amounts of gene exchange. However, recent studies indicate that obligate intracellular species that host-switch frequently harbor agents of horizontal transfer such as mobile elements. For example, the temperate double-stranded DNA bacteriophage WO in Wolbachia persistently transfers between bacterial coinfections in the same host. Here we show that despite the phage's rampant mobility between coinfections, the prophage's genome displays features of constraint related to its intracellular niche. First, there is always at least one intact prophage WO and usually several degenerate, independently-acquired WO prophages in each Wolbachia genome. Second, while the prophage genomes are modular in composition with genes of similar function grouping together, the modules are generally not interchangeable with other unrelated phages and thus do not evolve by the Modular Theory. Third, there is an unusual core genome that strictly consists of head and baseplate genes; other gene modules are frequently deleted. Fourth, the prophage recombinases are diverse and there is no conserved integration sequence. Finally, the molecular evolutionary forces acting on prophage WO are point mutation, intragenic recombination, deletion, and purifying selection. Taken together, these analyses indicate that while lateral transfer of phage WO is pervasive between Wolbachia with occasional new gene uptake, constraints of the intracellular niche obstruct extensive mixture between WO and the global phage population. Although the Modular Theory has long been considered the paradigm of temperate bacteriophage evolution in free-living bacteria, it appears irrelevant in phages of obligate intracellular bacteria

Molecular Characterization of Podoviral Bacteriophages Virulent for Clostridium perfringens and Their Comparison with Members of the Picovirinae

Clostridium perfringens is a Gram-positive, spore-forming anaerobic bacterium responsible for human food-borne disease as well as non-food-borne human, animal and poultry diseases. Because bacteriophages or their gene products could be applied to control bacterial diseases in a species-specific manner, they are potential important alternatives to antibiotics. Consequently, poultry intestinal material, soil, sewage and poultry processing drainage water were screened for virulent bacteriophages that lysed C. perfringens. Two bacteriophages, designated ΦCPV4 and ΦZP2, were isolated in the Moscow Region of the Russian Federation while another closely related virus, named ΦCP7R, was isolated in the southeastern USA. The viruses were identified as members of the order Caudovirales in the family Podoviridae with short, non-contractile tails of the C1 morphotype. The genomes of the three bacteriophages were 17.972, 18.078 and 18.397 kbp respectively; encoding twenty-six to twenty-eight ORF's with inverted terminal repeats and an average GC content of 34.6%. Structural proteins identified by mass spectrometry in the purified ΦCP7R virion included a pre-neck/appendage with putative lyase activity, major head, tail, connector/upper collar, lower collar and a structural protein with putative lysozyme-peptidase activity. All three podoviral bacteriophage genomes encoded a predicted N-acetylmuramoyl-L-alanine amidase and a putative stage V sporulation protein. Each putative amidase contained a predicted bacterial SH3 domain at the C-terminal end of the protein, presumably involved with binding the C. perfringens cell wall. The predicted DNA polymerase type B protein sequences were closely related to other members of the Podoviridae including Bacillus phage Φ29. Whole-genome comparisons supported this relationship, but also indicated that the Russian and USA viruses may be unique members of the sub-family Picovirinae