Phosphorus plays a crucial role in biology, and so microorganisms have developed many ways of obtaining phosphorus including the catabolism of aminoalkylphosphonates. Previous studies have led to a model of phosphonate use only as a phosphorus source by phosphorus starved marine microorganisms. However, a small number of terrestrial bacteria can use specific phosphonates as a carbon or nitrogen source when not phosphorus starved, but this possibility has not been investigated in marine organisms. Enrichment cultures confirmed that phosphonates are bioavailable phosphorus sources for marine bacteria and also that AMPA, 2AEP, OH2AEP and PnAI can support growth as nitrogen sources even in the presence of phosphate. Twelve isolates from these cultures grew using 2AEP as the sole nitrogen source despite exogenous phosphate addition. Cell-free extracts showed that four isolates catabolised PnAcHyde to produce Pi and an aldehyde, characteristic of a PhnX enzyme. The remaining isolates catabolised PnAc to release Pi and acetate, characteristic of a PhnA enzyme. While these enzymes are known to be involved the degradation of 2AEP under phosphorus starvation this is the first demonstration of marine bacteria capable of phosphate-insensitive 2AEP catabolism by these enzymes. Another isolate used OH2AEP and 2AEP as nitrogen sources even with exogenous phosphate addition. OH2AEP degradation enzymes, induced by OH2AEP, produce an aldehyde, Pi and ammonium, consistent with the proposed HpnWX pathway. The aldehyde could not be identified. A collection of inhibition, product and cofactor studies showed that 2AEP catabolism is carried out by an unusual PhnWA pathway. Therefore marine microorganisms can use some aminoalkylphosphonates as nitrogen sources regardless of Pi concentrations, despite the current model of marine phosphonate catabolism excluding this possibility. This is achieved using a mixture of characterised and previously undescribed C-P cleavage pathways. As such we need to reconsider the importance of aminoalkylphosphonates to microbial nutrition and marine biogeochemistry.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:676275 |
| Date | January 2014 |
| Creators | Chin, Jason |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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