| Summary: | Methylated amines, such as trimethylamine (TMA) and trimethylamine N-oxide, are nitrogenous compounds that are thought to be ubiquitous in the marine environment. TMA is a product of the anaerobic degradation of quaternary amines, such as glycine betaine and choline. Through a set of complex chemical and biological interactions, methylated amines play a role in regulating the planet’s climate. Microbial degradation of methylated amines is thought to be a sink for these compounds in the marine environment, however some of the key genes and enzymes responsible for the degradation of methylated amines are unknown. Using Ruegeria pomeroyi DSS-3 as the model organism, the key enzymes for the uptake and catabolism of trimethylamine N-oxide were identified and it was discovered that these genes and enzymes are highly expressed in the seawater, as revealed by the re-analysis of a number of recent metatranscriptomic and metaproteomic datasets. Again using R. pomeroyi as the model organism, it was shown that trimethylamine and trimethylamine N-oxide can be oxidised to CO2 to generate reducing equivalents and ATP. The generation of this reducing power results in a number of physiological benefits which are further discussed in detail. It was determined that bacteria possessing trimethylamine monooxygenase, the key enzyme required for the oxidation of TMA could also oxidise the reduced sulfur compound, dimethylsulfide, when supplemented with methylated amines. The ecology of methylated amine-utilising bacteria was investigated using a newly designed primer set targeting the trimethylamine N-oxide demethylase. The results are presented in detail within. The key genes and enzymes essential for the catabolism of the quaternary amine, choline were also discovered, again using R. pomeroyi as the model organism. The occurrence of genes required for the catabolism of choline are widespread among certain groups of marine bacteria known to interaction with eukaryotic biota, suggesting that this compound may be an essential nutrient for these organisms.
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