Abstract
The significance of dissolved combined amino acids (DCAA), dissolved free amino acids (DFAA), and dissolved DNA (D-DNA) as sources of C and N for marine bacteria in batch cultures with variable substrate C/N ratios was studied. Glucose, ammonium, alanine, and phosphate were added to the cultures to produce C/N ratios of 5, 10, and 15 and to ensure that phosphorus was not limiting. Maximum bacterial particulate organic carbon production (after 25 h of incubation) was inversely correlated with the C/N ratio: with the addition of identical amounts of carbon, the levels of production were 9.0-, 10.0-, and 11.1-fold higher at C/N ratios of 15, 10, and 5, respectively, relative to an unamended control. The bacterial growth efficiency increased from 22% (control cultures) to 44 to 53% in the cultures with manipulated C/N ratios (C/N-manipulated cultures). Net carbon incorporation from DCAA, DFAA, and D-DNA supported on average 19, 4, and 3% (control cultures and cultures to which only phosphate was added [+P cultures]) and 5, 4, and 0.3% of the particulate organic carbon production (C/N-manipulated cultures), respectively. In the C/N-manipulated cultures, a 2.6- to 3.4-fold-higher level of incorporation of DCAA, relative to that in the control cultures, occurred. Incorporation of D-DNA increased with the substrate C/N ratio, suggesting that D-DNA mainly was a source of N to the bacteria. Organic N (DCAA, DFAA, and D-DNA) sustained 14 to 49% of the net bacterial N production. NH4+ was the dominant N source and constituted 55 to 99% of the total N uptake. NO3- contributed up to 23% to the total N uptake but was released in two cultures. The studied N compounds sustained nearly all of the bacterial N demand. Our results show that the C/N ratio of dissolved organic matter available to bacteria has a significant influence on the incorporation of individual compounds like DCAA and D-DNA.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Kroer N., Jørgensen N. O., Coffin R. B. Utilization of dissolved nitrogen by heterotrophic bacterioplankton: a comparison of three ecosystems. Appl Environ Microbiol. 1994 Nov;60(11):4116–4123. doi: 10.1128/aem.60.11.4116-4123.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Paul J. H., Deflaun M. F., Jeffrey W. H. Mechanisms of DNA utilization by estuarine microbial populations. Appl Environ Microbiol. 1988 Jul;54(7):1682–1688. doi: 10.1128/aem.54.7.1682-1688.1988. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Turk V., Rehnstam A. S., Lundberg E., Hagström A. Release of bacterial DNA by marine nanoflagellates, an intermediate step in phosphorus regeneration. Appl Environ Microbiol. 1992 Nov;58(11):3744–3750. doi: 10.1128/aem.58.11.3744-3750.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]