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UTILIZATION OF DISSOLVED NITROGEN BY HETEROTROPHIC BACTERIOPLANKTON: EFFECT OF SUBSTRATE C/N RATIO
Citation:
Jorgensen, N., N. Kroer, AND R. Coffin. UTILIZATION OF DISSOLVED NITROGEN BY HETEROTROPHIC BACTERIOPLANKTON: EFFECT OF SUBSTRATE C/N RATIO. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/006, 1994.
Description:
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. lucose, 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. aximum bacterial particulate organic carbon production (after 25h 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. he bacterial growth efficiency increased f rom 22% (control cultures) to 44 to 53% in the cultures with manipulated C/N ratios (C/N-manipulated cultures). et 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. n 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. ncorporation of D-DNA increased with the substrate C/N ratio, suggesting that D-DNA mainly was a source of N to the bacteria. rganic N (DCAA, DFAA, and D-DNA) sustained 14 to 49% of the net bacterial N production. H., was the dominant N source and constituted 55 to 99% of the total N uptake. O, contributed up to 23% to the total N uptake but was released in two cultures. he studied N compounds sustained nearly all of the bacterial N demand. ur 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.