The SAV1322 gene from Staphylococcus aureus: genomic and proteomic approaches to identification and characterization of gene function.

BACKGROUND: Bacterial two-component regulatory systems (TCRS) are associated with the expression of virulence factors and antibiotic susceptibility. In Staphylococcus aureus, 16 TCRS types have been identified. The histidine kinase/response regulator SAV1321/SAV1322 in the S. aureus shares considerable homology with the TCRS DesKR in Bacillus subtilis. However, a function for the SAV1322 locus has not yet been assigned. RESULTS: Deletion of the SAV1322 locus in S. aureus results in reduced growth when cultured under low (25 °C) and high (46 °C) temperature conditions. The sav1322 deletion mutant is more tolerant to oxidative stress in vitro and is less pathogenic in a murine infection model when compared with wild-type parent strain Mu50. Furthermore, the sav1322 mutant exhibits lower MICs for gentimicin, tetracyclines and glycopeptides, increased autolysis, and a thinner cell wall when compared with the wild-type strain. Microarray and proteomic analyses show that the expression of cell-wall-associated genes glmS and murZ are lower, and the expression of heat shock and stress-related genes (hrcA, ctsR, dnaK, dnaJ, grpE, clpB, and clpC) are higher in the sav1322 mutant when compared with the wild-type strain. In addition, the sav1322 mutant displays altered expression of proteins involved in carbohydrate/energy metabolism, cell wall metabolism, and stress or heat shock response, as well as other metabolic processes including lipid metabolism, amino acid biosynthesis, purine or pyrimidine metabolism, transcription, and protein biosynthesis. CONCLUSIONS: The S. aureus SAV1322 locus plays a pronounced role in temperature adaptation, antibiotic resistance, and virulence by regulating a wide range of genes and proteins involved in metabolism and stress tolerance.

Phylogeography and conservation genetics of the Amazonian freshwater stingray Paratrygon aiereba Müller & Henle, 1841 (Chondrichthyes: Potamotrygonidae)

The family Potamotrygonidae is monophyletic comprising three genera: Paratrygon Duméril, Potamotrygon Garman and Plesiotrygon Rosa, Castello & Thorson. The distribution of most species in this family is restricted to a single basin or fluvial system. Only Potamotrygon motoro, Potamotrygon orbignyi and Paratrygon aiereba are found in more than one river basin. In this study we investigate genetic structuring of Paratrygon aiereba, from five rivers of the Amazon region: Negro, Solimões-Amazon-Estuary system, Tapajós, Xingu and Araguaia. Sixty-three individuals were sequenced for ATPase 6, and a representative subsample of 27 individuals was sequenced for COI. The COI dataset analysis indicated that Paratrygon is sister to all other potamotrygonid genera and species. Population parameters inferred from the analysis of ATPase 6 sequences revealed that the populations of this species are structured within each river, with no or nearly non-existent gene flow occurring between rivers and a positive correlation between geographic and genetic distances. Paratrygon aiereba is comprised of three geographically restricted clades with K2P interclade distances of at least 2%. Intraspecific divergence within P. aiereba is similar to the interspecific divergence observed in Potamotrygon spp. sampled throughout the same geographic area. Using the premises of COI barcoding and the allopatric distribution of the three P. aiereba clades, the taxon P. aiereba most likely comprises three distinct biological species. Since freshwater stingrays of the family Potamotrygonidae are highly exploited for the aquarium trade, management and conservation strategies need to be implemented at the level of each river basin, rather than at the level of the Amazon basin.

A família Potamotrygonidae forma um clado monofilético com três gêneros: Paratrygon Duméril, Potamotrygon Garman e Plesiotrygon Rosa, Castello & Thorson. A maioria das espécies dessa família possui distribuição restrita a uma única bacia ou sistema fluvial, e somente as espécies Potamotrygon motoro, Potamotrygon orbignyi e Paratrygon aiereba estão presentes em mais de uma bacia hidrográfica. O presente estudo teve como objetivo investigar a estrutura genética de Paratrygon aiereba em alguns rios da região Amazônica: Negro, sistema Solimões-Amazonas, Tapajós, Xingu, e Araguaia. Para tal foram utilizados como marcador molecular os genes de ATPase subunidade 6, e COI. As análises com o fragmento de COI indicaram que o gênero Paratrygon é grupo irmão dos outros gêneros da família potamotrygonidae. Os resultados para o fragmento de ATPase mostraram que essas populações estão estruturadas dentro dos rios, com fluxo gênico restrito, ou mesmo sem fluxo gênico, apresentando uma correlação positiva entre distância genética e distância geográfica. Paratrygon aiereba é composta por três clados com distância genética de pelo menos 2%. A divergência encontrada dentro desse grupo é semelhante à observada entre Potamotrygon spp. Segundo as premissas para barcoding COI e a distribuição alopátrica de três clados em P. aiereba indicam que esse grupo pode ser um complexo de espécies. O rio Negro é conhecido por sua pesca ornamental, e na calha Solimões-Amazonas, esses animais são utilizados como fonte de proteína e sofrem com a pesca comercial. Em vista disso medidas de conservação para esta espécie devem ser tomadas em nível local, considerando cada rio separadamente, ao invés de empregar escalas regionais maiores.

The virtosome-a novel cytosolic informative entity and intercellular messenger.

Studies on a range of prokaryote and eukaryote cells and tissues have shown that a newly synthesized DNA/RNA-lipoprotein complex is released in a regulated manner. This complex, termed a virtosome, is a novel cytosolic component of eukaryote cells. The released virtosomes can readily enter other cells where they can modify the biology of the recipient cells. Such modifications include immunological changes and transformation from normal to cancer cells. The virtosomes form a normal component of the circulating nucleic acids in plasma and serum currently used for clinical diagnostic purposes. Given the transformative powers of virtosomes released from tumour cells, the presence of such a complex in human plasma could readily offer the basis of an alternative mechanism for the initiation of metastases.

Genetic structure of tree and shrubby species among anthropogenic edges, natural edges, and interior of an atlantic forest fragment.

Two species, Psychotria tenuinervis (shrub, Rubiaceae) and Guarea guidonia (tree, Meliaceae), were used as models to compare the genetic structure of tree and shrubby species among natural edges, anthropogenic edges, and a fragment interior. There were significant differences between two genetic markers. For isozymes, P. tenuinervis presented greater heterozygosity (expected and observed) and a higher percentage of polymorphic loci and median number of alleles than G. guidonia. For microsatellites, there was no difference in genetic variability between the species. Only P. tenuinervis, for isozymes, showed differences in genetic variability among the three habitats. There was no genetic structure (F (ST) < 0.05) among habitats in both plant species for both genetic markers. Isozymes showed great endogamy for both plant species, but not microsatellites. The forest fragmentation may have negative effects on both spatial (among edges and interior) and temporal genetic variability.

Genetic structure and affinities of the Corsican population (France): classical genetic markers analysis.

The frequencies of 19 classical genetic markers for a total of 54 alleles were studied in a sample of 1,164 individuals born and residing in five different regions of Corsica. The results, which are also discussed in the context of the Mediterranean populations, show the existence within Corsica of a certain genetic differentiation between north and south which follows the linguistic subdivision differentiation. Compared to the other Mediterranean populations, Corsica also appears to be greatly differentiated from the populations of regions such as France and Tuscany, regions which have had great political and cultural influence. The Mediterranean population most comparable to Corsica is Sardinia. Despite their common origin, however, they do not prove to be absolutely identical. The genetic characteristics of Corsica and their relationship with the Mediterranean populations are interpreted in terms of demographic and matrimonial structure, isolation, and genetic drift.