Project description:Thiamine is often undetectable in ocean surface waters where Pelagibacter cells are numerically abundant. Despite this, Pelagibacter cells are missing de novo thiamine synthesis pathways. We show that an eogenous source of the thiamine precursor HMP is required for thiamine synthesis in Pelagibacter and that this precursor is abundant in the Sargasso sea. Batch cultures of P. ubique were grown in a defined arificial seawater media. Three cultures were given no thiamine amendment, and three other cultures received an excess concentration of thiamine. Cultures were harvested for microarray analyses just prior to and after thiamine limitation for the purpose of observing differences in gene expression related to thiamine limitation.
Project description:Although hydrogen sulfide is toxic to most organisms, a fish, Poecilia mexicana, has adapted to survive in environments with high levels of hydrogen sulfide. The epigenetic changes in response to this environmental stress were examined by assessing DNA methylation alterations in the nucleated red blood cells (RBC) in the fish. In addition to collecting wild males and females from sulfidic and non-sulfidic environments, wild males and females in these environments were collected and moved to a non-sulfidic environment in the laboratory and propagated for two generations in a non-sulfidic environment. We compared epimutations between sexes and field and laboratory populations. The F0 generation sulfidic wild fish were compared to the non-sulfidic wild fish and found to have significant differential DNA methylation regions (DMRs) in the RBC DNA. The F2 generation laboratory fish were also compared between the sulfidic and non-sulfidic populations, and a significant number of DMRs were also identified. The DMRs have stable generational inheritance in the absence of the sulfidic environment. The DMRs in the F0 generation wild fish had an over 80% overlap with the F2 generation laboratory non-sulfidic environment propagated fish. This is one of the first examples of epigenetic generational stability after the removal of an environmental stressor. The DMR associated genes were found to be relevant to sulfur toxicity and metabolism processes.
Project description:Ammonia-oxidizing archaea (AOA) have been reported at high abundance in much of the global ocean, even in environments such as pelagic oxygen minimum zones (OMZs), where conditions seem unlikely to support aerobic ammonium oxidation. Due to the lack of information on any potential alternative metabolism of AOA, the AOA community composition might be expected to differ between oxic and anoxic environments, indicating some difference in ecology and/or physiology of the AOA assemblage. This hypothesis was tested by evaluating AOA community composition using a functional gene microarray that targets the ammonia monooxygenase gene subunit A (amoA). The relationship between environmental parameters and the biogeography of the Arabian Sea and the Eastern Tropical South Pacific (ETSP) AOA assemblages was investigated using principal component analysis (PCA) and redundancy analysis (RDA). In both the Arabian Sea and the ETSP, AOA communities within the core of the OMZ were not significantly different from those inhabiting the oxygenated surface waters above the OMZ. The AOA communities in the Arabian Sea were significantly different from those in the ETSP. In both oceans, the abundance of archaeal amoA gene in the core of the OMZ was higher than that in the surface waters. Our results indicate that AOA communities are distinguished by their geographic origin. RDA suggested that temperature was the main factor that correlated with the differences between the AOA communities from the Arabian Sea and those from the ETSP. Physicochemical properties that characterized the different environments of the OMZ and surface waters played a less important role than did geography in shaping the AOA community composition.