Cobalamin producers and prokaryotic consumers in the Northwest Atlantic

Cobalamin availability can influence primary productivity and ecological interactions in marine microbial communities. The characterization of cobalamin sources and sinks is a first step in investigating cobalamin dynamics and its impact on productivity. Here, we identify potential cobalamin sources and sinks on the Scotian Shelf and Slope in the Northwest Atlantic Ocean. Functional and taxonomic annotation of bulk metagenomic reads, combined with analysis of genome bins, were used to identify potential cobalamin sources and sinks. Cobalamin synthesis potential was mainly attributed to Rhodobacteraceae, Thaumarchaeota, and cyanobacteria (Synechococcus and Prochlorococcus). Cobalamin remodelling potential was mainly attributed to Alteromonadales, Pseudomonadales, Rhizobiales, Oceanospirilalles, Rhodobacteraceae, and Verrucomicrobia, while potential cobalamin consumers include Flavobacteriaceae, Actinobacteria, Porticoccaceae, Methylophiliaceae, and Thermoplasmatota. These complementary approaches identified taxa with the potential to be involved in cobalamin cycling on the Scotian Shelf and revealed genomic information required for further characterization. The Cob operon of Rhodobacterales bacterium HTCC2255, a strain with known importance in cobalamin cycling, was similar to a major cobalamin producer bin, suggesting that a related strain may represent a critical cobalamin source in this region. These results enable future inquiries that will enhance our understanding of how cobalamin shapes microbial interdependencies and productivity in this region.     

Selective intra-lysosomal concentration of niobium in kidney and bone marrow cells: a microanalytical study

Niobium is used as an alloy in the industrial and biomedical fields. The concentration of the toxic element in organs of a number of animal species has been defined by using radioactive niobium (⁹⁵Nb). However, tissue lesions induced by niobium have only been studied at the light microscopy level. In this study, we used an electron probe X-ray analyzer equipped with a transmission electron microscope to define the localization of this element in kidney and bone marrow cells. Results demonstrated that niobium is located in the lysosome and that this element coprecipitates with phosphate. In kidney, lysosomes and precipitates are eliminated in the tubular lumen. In contrast, precipitates appear to be eliminated more slowly from the lysosomes of bone marrow macrophages. These processes therefore correspond to one of the mechanisms by which lysosomes eliminate certain toxic mineral elements and thus play a role in the more general process of the body's defenses.     

Organization of the genes necessary for hydrogenase expression in Rhodobacter capsulatus. Sequence analysis and identification of two hyp regulatory mutants

A 25kbp DNA fragment from the chromosome of Rhodobacter capsulatus B10 carrying hydrogenase (hup) determinants was completely sequenced. Coding regions corresponding to 20 open reading frames were identified. The R. capsulatus hydrogenase-specific gene (hup and hyp) products bear significant structural identity to hydrogenase gene products from Escherichia coli (13), from Rhizobium liguminosarum (16), from Azotobacter vinelandii (10) and from Alcaligenes eutrophus (11). The sequential arrangement of the R. capsulatus genes is: hupR2-hupU-hypF -hupS-hupL-hupM-hupD -hupF -hupG -hupH -huoJ -hupK -hypA-hypB-hupR1-hypC -hypD -hypE -ORF19 -ORF20 , all contiguous and transcribed from the same DNA strand. The last two potential genes do not encode products that are related to identified hydrogenase-specific gene products in other species. The sequence of the 12 R. capsulatus genes underlined above is presented. The mutation site in two of the Hup^? mutants used in this study, RS13 and RCC12, was identified in the hypF gene (deletion of one G) and in the hypD qene (deletion of 54 bp), respectively. The hypF gene product shares 45% identity with the product of hydA from E. coli and the product of hypF from R. leguminosarum. Those products present at their N-terminus a Cys arrangement typical of zinc-finger proteins. The G deletion in the C-terminal region of hypF in the RS13 mutant     

The electrophoretic polymorphism of bacterial esterases

Abstract: The specific activities of esterases and certain other molecular properties including immunospecificity indicate that the electrophoretic variations of these enzymes in bacterial populations are the result of allelic variations at specific gene loci. The esterase polymorphism of Enterobacteriaceae and some other species isolated from man or animals demonstrates that esterases can distinguish between bacteria at the species or subspecies level, both by their biochemical properties and by their electrophoretic differences. The esterase data complement DNA hybridization studies and agree with ribosomal DNA polymorphism, especially for delineating a phylogenetically distinct group of highly pathogenic strains in Escherichia coli . A two-dimensional electrophoretic profile obtained by establishing a direct correspondence between homologous esterase bands resolved by independent runs of isoelectric focusing and standard electrophoresis considerably improves the detection of allelic variations, whereas protein titration curves (electrophoresis in pH gradient) can be used to demonstrate the real electrophoretic homogeneity of allozymes or evalue their molecular relationship in terms of apparent amino acid substitutions. This overview establishes that esterases, by their significant electrophoretic polymorphism, are reliable molecular markers for systematics and epidemiology, and are suitable enzyme systems for studying population genetics and phylogeny.     

Seasonal incidence and ecology of the tick Ixodes ricinus (Acari: Ixodidae) on grazing pastures in Western France

A longitudinal survey was carried out during a 2 year period in Western France to assess the infestation level of grazing pastures byIxodes ricinus ticks. Four farms were visited once a month and each of the grazing pastures was sampled in the centre and at the border using the blanket dragging method. A total of 3562I. ricinus (34 adults, 900 nymphs and 2628 larvae) were collected and the infestation was significantly higher during the first year (p<0.0001). The infestation level byI. ricinus varied between grazing pastures and farms. Grazing pastures in the vicinity of forest were more infested than the others, all through the study. The seasonal distribution of ticks showed peaks, with low fluctuations between farms, years and stages. Tick abundance could not be related to vegetation, but only to the vicinity of woods.