Project description:Monitoring microbial communities can aid in understanding the state of these habitats. Environmental DNA (eDNA) techniques provide efficient and comprehensive monitoring by capturing broader diversity. Besides structural profiling, eDNA methods allow the study of functional profiles, encompassing the genes within the microbial community. In this study, three methodologies were compared for functional profiling of microbial communities in estuarine and coastal sites in the Bay of Biscay. The methodologies included inference from 16S metabarcoding data using Tax4Fun, GeoChip microarrays, and shotgun metagenomics.
Project description:<p>Particulate organic matter (fecal pellets) from zooplankton has been demonstrated to be important nutrient sources for the pelagic prokaryotic community. Significantly less is known about the chemical composition of the dissolved organic matter (DOM) produced by these eukaryotes and its influence on pelagic ecosystem structure. Zooplankton migrators, which daily transport surface-derived compounds to depth, may act as important vectors of limiting nutrients for mesopelagic microbial communities. In this role, zooplankton may increase the DOM remineralization rate by heterotrophic prokaryotes through the creation of nutrient rich “hot spots” that could potentially increase niche diversity. To explore these interactions, we collected the migratory copepod Pleuromamma xiphias from the northwestern Sargasso Sea and sampled its excreta after 12-16 h of incubation. We measured bulk dissolved organic carbon, dissolved free amino acids via high performance liquid chromatography and dissolved targeted metabolites via quantitative mass spectrometry (UPLC-ESI-MSMS) to quantify organic zooplankton excreta production and characterize its composition. We observed production of labile DOM, including amino acids, vitamins and nucleosides. Additionally, we harvested a portion of the excreta and subsequently used it as the growth medium for mesopelagic (200m) bacterioplankton dilution cultures. In zooplankton excreta treatments we observed a four-fold increase in bacterioplankton cell densities that reached stationary growth phase after five days of dark incubation. Analyses of 16s rDNA amplicons suggested a shift from oligotrophs typical of open ocean and mesopelagic prokaryotic communities to more copiotrophic bacterial lineages in the presence of zooplankton excreta. These results support the hypothesis that zooplankton and prokaryotes are engaged in complex and indirect ecological interactions, broadening our understanding of the microbial loop.</p>
Project description:Unfolded protein accumulation in the lumen of endoplasmic reticulum (ER) induced by cold exposure is termed UPRER. Some mammals hibernate to overcome cold winter. We investigated whether hibernating bats are under UPRER and activate Akt, Nrf2, and NF-κB signaling pathways that are critical for cell survival against cold. Results of Western blotting showed that several UPRER marker proteins such as PERK and ATF4 had a higher abundance in torpid than in active bats. Cellular redistribution of GRP78 and a lower degree of binding between PERK and GRP78 were also seen in torpid bats, suggesting the occurrence of UPRER. Results also showed that torpid bats had a higher amount of p-Akt (Ser473), a higher ratio of p-Akt (Ser473)/Akt, a lower amount of Keap1/Nrf2 and NF-κB (p65)/I-κBα complexes, and a higher degree of NF-κB (p65) nuclear translocation than active bats, indicating simultaneous activation of Akt, Nrf2, and NF-κB during hibernation. Evidence of such activation was not observed in fasted, cold-treated, or normal mice. Using PPI network and IPA analyses, we examined the proteomes of liver and liver mitochondria of bats and found a global metabolic adjustment and survival adaptation in response to UPRER in hibernating bats. Our data provide the first molecular evidence of a complex cross talk involving Akt, Nrf2, and NF-κB via the PERK-EIF2-ATF4 regulatory axis under UPRER in bats to ensure their survival during hibernation.