Project description:Although N2 fixation can occur in free-living cyanobacteria, the unicellular endosymbiotic cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A) is considered to be a dominant N2-fixing species in marine ecosystems. Four UCYN-A sublineages are known from partial nitrogenase (nifH) gene sequences. However, few studies have investigated their habitat preferences and regulation by their respective hosts in open-ocean versus coastal environments. Here, we compared UCYN-A transcriptomes from oligotrophic open-ocean versus nutrient-rich coastal waters. UCYN-A1 metabolism was more impacted by habitat changes than UCYN-A2. However, across habitats and sublineages genes for nitrogen fixation and energy production were highly transcribed. Curiously these genes, critical to the symbiosis for the exchange of fixed nitrogen for fixed carbon, maintained the same schedule of diel expression across habitats and UCYN-A sublineages, including UCYN-A3 in the open-ocean transcriptomes. Our results undersore the importance of nitrogen fixation in UCYN-A symbioses across habitats, with consequences for community interaction and global biogeochemical cycles.
Project description:Triplets of Lactobacullus plantarum strains were isolated from nine contrasting habitats. Without any passage through other culture media, isolation and cultivation were on model media that strictly reproduced the chemical and physical conditions and stressors of the habitats of origin. Here, we demonstrated how L. plantarum regulates and shapes its transcriptome in response to contrasting habitats. Firstly, multivariate clustering analysis of transcriptional data (RNA-Seq), complemented with metabolomics and phenomics, grouped the strains according to the habitats of origin. Subsequently, selected strains from each habitat switched to repeated cultivation on MRS medium and transcriptomes homogenized into a unique cluster. Adaptation to this common medium mainly relied on activation of genes for phage- and prophage-related proteins and transposases. Finally, the comparison of growth across model media and with respect to MRS medium showed that 44% of the overall 3,112 gene transcripts changed depending on the specific habitat. Regulation and shaping of transcriptomes mainly concerned carbohydrate acquisition, pyruvate catabolism, proteolytic system and amino acid, lipid and inorganic ion transport and metabolism, with contrasting responses for contrasting habitats. Pathways reconstruction demonstrated how the large genome size of L. plantarum imparts transcriptome and metabolic flexibility as the basic mechanism for a nomadic lifestyle.
Project description:Members of the bacterial phylum Spirochaetes are primarily studied for their commensal and pathogenic roles in animal hosts. However, Spirochaetes are also frequently detected in anoxic hydrocarbon-contaminated environments but their ecological role in such ecosystems has so far remained unclear. Here we provide a functional trait to these frequently detected organisms with an example of a sulfate-reducing, naphthalene-degrading enrichment culture consisting of a sulfate-reducing deltaproteobacterium Desulfobacterium naphthalenivorans and a novel spirochete Rectinema cohabitans. Using a combination of genomic, proteomic, and physiological studies we show that R. cohabitans grows by fermentation of organic compounds derived from biomass from dead cells (necromass). It recycles the derived electrons in the form of H2 to the sulfate-reducing D. naphthalenivorans, thereby supporting naphthalene degradation and forming a simple microbial loop. We provide metagenomic evidence that equivalent associations between Spirochaetes and hydrocarbon-degrading microorganisms are of general importance in hydrocarbon- and organohalide-contaminated ecosystems. We propose that environmental Spirochaetes form a critical component of a microbial loop central to nutrient cycling in subsurface environments. This emphasizes the importance of necromass and H2-cycling in highly toxic contaminated subsurface habitats such as hydrocarbon-polluted aquifers.
2018-05-17 | PXD005624 | Pride
Project description:Rokubacteria in northern peatlands: habitat preferences and diversity patterns
Project description:High resolution Mass Spectrometry and Peptides identification uncovered ancestral giant insect viruses motifs within Histone-4 peptides in human liver cells. These peptides did not match any human sequence. This finding consolidates the dogma that molecular patterns are universal and suggests that metazoan cellular structures possibly share an evolutionary link with ancient giant viruses.
Project description:Environmental parameters drive phenotypic and genotypic frequency variations in microbial communities and thus control the extent and structure of microbial diversity. We tested the extent to which microbial community composition changes are controlled by shifting physiochemical properties within a hypersaline lagoon. We sequenced four sediment metagenomes from the Coorong, South Australia from samples which varied in salinity by 99 Practical Salinity Units (PSU), an order of magnitude in ammonia concentration and two orders of magnitude in microbial abundance. Despite the marked divergence in environmental parameters observed between samples, hierarchical clustering of taxonomic and metabolic profiles of these metagenomes showed striking similarity between the samples (>89%). Comparison of these profiles to those derived from a wide variety of publically available datasets demonstrated that the Coorong sediment metagenomes were similar to other sediment, soil, biofilm and microbial mat samples regardless of salinity (>85% similarity). Overall, clustering of solid substrate and water metagenomes into discrete similarity groups based on functional potential indicated that the dichotomy between water and solid matrices is a fundamental determinant of community microbial metabolism that is not masked by salinity, nutrient concentration or microbial abundance.