METHYLATED AMINE-UTILISING BACTERIA AND MICROBIAL NITROGEN CYCLING IN MOVILE CAVE

Wischer, Daniela (2014) METHYLATED AMINE-UTILISING BACTERIA AND MICROBIAL NITROGEN CYCLING IN MOVILE CAVE. Doctoral thesis, University of East Anglia.

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Abstract

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.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Mia Reeves
Date Deposited: 29 Jan 2016 11:37
Last Modified: 29 Jan 2016 11:37
URI: https://ueaeprints.uea.ac.uk/id/eprint/56877
DOI:

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