Urea production and turnover following the addition of AMP, CMP, RNA and a protein mixture to a marine sediment

The potential of adenosine 5'-monophosphate (AMP), cytidine 5'-monophosphate (CMP), 1 6 s ribosomal RNA, and a protein (bovine serum albumin) to serve a s substrates for bacterial urea production was evaluated in a defaunated, anoxic marine sediment. AMP, CMP and RNA stimulated urea production and urea turnover, but CMP to a lesser degree than AMP and RNA. The increase in urea production and turnover rates took place immediately after AMP, CMP, and RNA were added to the sediment. The rapid response in urea production and turnover rates suggests that the necessary uptake mechanisms and enzymes to utilize the substrates were present constitutively. Addition of the protein mixture did not result in any measurable changes in the urea pool size, urea turnover rate, or urea production rate during the 165 h of incubation. However, an ~ncreased and continuous net NH,' production in the protein-amended sediment relative to the control sediment indicated that the added protein mixture was accessible for bacterial degradation. The results showed that purines and pyrirnidines were substrates for the bacterial urea production in the marine sediment, whereas protein was not important for urea production.