Movile Cave is an unusual, isolated ecosystem which harbours a complex population of microorganisms, fungi and endemic invertebrates. In the absence of light and with no fixed carbon entering the cave, life is sustained by non-phototrophic microorganisms such as sulfur and methane oxidisers. Also present are methylotrophs that use one-carbon compounds such as methanol and methylated amines as their sole source of carbon and energy. Produced during putrefaction, methylated amines are likely to be major degradation products in Movile Cave. Further to being methylotrophic substrates, they are also a nitrogen source for many non-methylotrophic bacteria. The role of methylated amines as carbon and nitrogen sources for Movile Cave bacteria was investigated using a combination of DNA stable isotope probing and cultivation studies. Both, well-characterised and novel methylotrophs were identified: Methylotenera mobilis dominated 13C-monomethylamine SIP enrichments, while members of Catellibacterium, Cupriavidus and Altererythrobacter were also active. Cultivation studies consolidated SIP results in obtaining the first methylotrophic isolates from the genera Catellibacterium and Mesorhizobium. Pathways for monomethylamine (MMA) metabolism were investigated using new PCR primers designed to target gmaS, the gene for gammaglutamylmethylamide synthetase, a key enzyme of the recently characterised indirect MMA oxidation pathway. This pathway is also present in bacteria that use MMA only as a nitrogen source, while the well-characterised, direct MMA oxidation pathway involving methylamine dehydrogenase (mauA) is found only in methylotrophs. gmaS was present in all MMAutilising isolates, while mauA was found only in some methylotrophs, suggesting the indirect pathway is the major mode of MMA oxidation both in methylotrophs and non-methylotrophs from Movile Cave. Preliminary gmaS surveys revealed a high diversity of gmaS-containing bacteria. The roles of N2 fixers and nitrifiers were also investigated. Both bacterial and archaeal ammonia oxidisers were found to be active; however, sulfur oxidisers appeared to be the dominant autotrophs in Movile Cave.
|Publisher||University of East Anglia|
|Source Sets||Ethos UK|
|Type||Electronic Thesis or Dissertation|
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