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The biology of candidate divison OP3

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Resteu,  Anastasia
IMPRS MarMic, Max Planck Institute for Marine Microbiology, Max Planck Society;

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Citation

Resteu, A. (2016). The biology of candidate divison OP3. Master Thesis, University of Bremen, Bremen.


Cite as: https://hdl.handle.net/21.11116/0000-0001-C33B-1
Abstract
Methanogenic cultures growing on limonene have been previously established from wastewater treatment plant sludge. The most abundant members of the microbial community were candidate division OP3, Deltaproteobacteria, Bacteroidetes, Firmicutes, as well as Archaea. Studies of the cultures suggested a syntrophy between multiple species of Bacteria and Archaea for the remineralization of limonene, and a possible predatory lifestyle of OP3. Genes associated with a type IV secretion system have been detected in the OP3 genome, and OP3-like cells have often been found attached to larger cells. This project focused on the transcriptomics of free-living OP3 cells and of those attached to the potential prey in order to identify the key virulence genes. Several predicted genes expressed exclusively in free-living cells have been identified. A highly expressed potential operon encoding a type IV secretion system was found in all of the OP3 cells. A second focus of the study was monitoring the metabolic activity of the enrichment cultures and the changes in the abundance of certain microbial groups. The OP3 abundance and methane production, used to measure metabolic activity, were inversely proportional in the initial stages of the incubation, suggesting a negative effect of OP3 on the major players involved in methanogenesis or in the production of the substrate for methanogenesis. A substantial overall increase in the relative abundance of OP3, and a perpetual decrease in that of other bacteria may indicate predator-prey relationship between them.