Investigations into the mechanisms and ecological controls of cryptic methane cycling




Cunningham, Christian

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Methylotrophs, microorganisms that consume C1 compounds, play important roles within the environment for cycling of nutrients and filling diverse ecological niches. This research aimed to analyze the functionality and diversity of methylotrophs within marine environments with a focus on those specifically able to metabolize methane. Previous work had focused on freshwater isolates or mixed communities. We grew Methyloprofundus sedimenti WF1 under four different initial methane concentrations and sampled them over time for methane and pmoA transcript abundance. This gene encodes for an enzyme involved for the first step of methane oxidation and therefore the transcript abundance is suggested to correlate with methane oxidation activity. Transcript abundance was correlated with methane concentration within each methane treatment. Correlations within but not between treatments suggested that transcript abundance correlates with methane oxidation activity. Additionally, a novel culturing method using fluorescence activated cell sorting was utilized for the cultivation of methylotrophic bacteria from core samples taken from Oso Bay, TX wetlands. Isolates were sequenced for whole genome sequencing and characterized for the metabolic potential and their phylogenetic relationships. Three of the four isolates were identified as potentially new species within Methylophaga and the fourth was identified as Methylobacterium organophilum. One of the isolates within Methylophaga had genes necessary for complete denitrification, which had only previously been observed within Methylophaga nitratireducenticrescens JAM1. The use of the key methanol dehydrogenase gene mxaF was analyzed for its phylogenetic accuracy. The gene formed similar topologies within the genus Methylophaga but lacked congruency when compared across the phylum Proteobacteria. This study expands on the understanding of the correlation of methane oxidation activity and transcript abundance as well as the diversity of capabilities within the group Methylophaga from the marine environment.



FACS, methane, Methanotroph, Methylotroph, Single cell sorting, Transcript abundance