Biosorption capacity of genus Dictyota facing organochlorine pesticide pollutions in coastal areas of the Lesser Antilles

International audienceMeasurements of chlordecone, an organochlorine insecticide with high persistence in natural environments, have been carried out on several species and genus of macroalgae in Guadeloupe and Martinique. These data were statistically compared to determine the ability of the genus Dictyota to accumulate chlordecone, compared to other collected macroalgae. The comparisons were conducted between phylogenetic groups (Rhodophyta, Phaeophyta and Chlorophyta), and between sites (Guadeloupe vs Martinique). Concentrations of chlordecone measured in Dictyota spp. samples were significantly higher than the other groups regardless to the site. Phaeophytes are generally characterized by a higher capacity for biosorption of contaminants. In this study, however, only the Dictyota spp. samples followed this pattern. Therefore, this genus is of interest in cases of phycoremediation of the chlordecone

Genomic Mysteries of Giant Bacteria: Insights and Implications

Bacteria and Archaea are traditionally regarded as organisms with a simple morphology constrained to a size of 2-3 µm. Nevertheless, the history of microbial research is rich in the description of giant bacteria exceeding tens and even hundreds of micrometers in length or diameter already from its early days, for example, Beggiatoa spp., to the present, for example, Candidatus Thiomargarita magnifica. While some of these giants are still being studied, some were lost to science, with merely drawings and photomicrographs as evidence for their existence. The physiology and biogeochemical role of giant bacteria have been studied, with a large focus on those involved in the sulfur cycle. With the onset of the genomic era, no special emphasis has been given to this group, in an attempt to gain a novel, evolutionary, and molecular understanding of the phenomenon of bacterial gigantism. The few existing genomic studies reveal a mysterious world of hyperpolyploid bacteria with hundreds to hundreds of thousands of chromosomes that are, in some cases, identical and in others, extremely different. These studies on giant bacteria reveal novel organelles, cellular compartmentalization, and novel mechanisms to combat the accumulation of deleterious mutations in polyploid bacteria. In this perspective paper, we provide a brief overview of what is known about the genomics of giant bacteria and build on that to highlight a few burning questions that await to be addressed

Cave Thiovulum (Candidatus Thiovulum stygium) differs metabolically and genomically from marine species

Abstract Thiovulum spp. (Campylobacterota) are large sulfur bacteria that form veil-like structures in aquatic environments. The sulfidic Movile Cave (Romania), sealed from the atmosphere for ~5 million years, has several aqueous chambers, some with low atmospheric O 2 (~7%). The cave’s surface-water microbial community is dominated by bacteria we identified as Thiovulum .We show that this strain, and others from subsurface environments, are phylogenetically distinct from marine Thiovulum .We assembled a closed genome of the Movile strain and confirmed its metabolism using RNAseq. We compared the genome of this strain and one we assembled from public data from the sulfidic Frasassi caves to four marine genomes, including Candidatus Thiovulum karukerense and Ca .T. imperiosus, whose genomes we sequenced. Despite great spatial and temporal separation, the genomes of the Movile and Frasassi Thiovulum were highly similar, differing greatly from the very diverse marine strains. We concluded that cave Thiovulum represent a new species, named here Candidatus Thiovulum stygium. Based on their genomes, cave Thiovulum can switch between aerobic and anaerobic sulfide oxidation using O 2 and NO 3 - as electron acceptors, the latter likely via dissimilatory nitrate reduction to ammonia. Thus, Thiovulum is likely important to both S and N cycles in sulfidic caves. Electron microscopy analysis suggests that at least some of the short peritrichous structures typical of Thiovulum are type IV pili, for which genes were found in all strains. These pili may play a role in veil formation, by connecting adjacent cells, and in the motility of these exceptionally fast swimmers.info:eu-repo/semantics/publishe