Exploring sterol function in the bacterium Gemmata obscuriglobus

Armitage, Emily
Unlike eukaryotic cells, bacterial cells generally lack membranes that enclose their nucleus, do not contain organelles, and lack cellular compartmentalization altogether. However, members of the Planctomycete-Verrucomicrobia-Chlamydiae (PVC) bacterial superphylum challenge the traditional view of eukaryotes vs. prokaryotes as they contain some of these eukaryotic-like features. An interesting bacterium in this group, Gemmata obscuriglobus, has been shown to have a complex endomembrane system, highly condensed nucleoid region, and segregated transcription and translation. G. obscuriglobus has also been found to produce sterols, which are essential for structure and function of membranes in eukaryotic cells. Sterols only have been detected in a subset of bacteria, however the function remains enigmatic. To explore the function of sterols in G. obscuriglobus, our lab has developed a chemical approach using the drug terbinafine to begin to determine sterol function. We have shown that sterol depletion by terbinafine causes replication defects, suggesting sterols are necessary for survival, the first instance in a bacterium. We are conducting RNA sequencing on treated vs. untreated cells to determine the global effect of sterol depletion. This will allow for the identification of genes responding to sterol depletion. I will conduct quantitative real time polymerase chain reactions on the best hits to verify the RNA sequencing reads. We will utilize a recently developed genetic approach to further elucidate the RNA sequencing best hits function in response to sterol depletion. There may be a relationship between the eukaryotic-like features of G. obscuriglobus and sterol synthesis, and understanding bacterial sterol function could elucidate this.
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