In:
Applied and Environmental Microbiology, American Society for Microbiology, Vol. 70, No. 11 ( 2004-11), p. 6363-6369
Abstract:
Within grazed pastures, urine patches are hot spots of nitrogen turnover, since dietary N surpluses are excreted mainly as urea in the urine. This short-term experiment investigated 13 C uptake in microbial lipids after simulated deposition of cattle urine at 10.0 and 17.1 g of urea C m −2 . Confined field plots without or with cattle urine amendment were sampled after 4 and 14 days, and soil from 0- to 5-cm and 10- to 20-cm depths was analyzed for content and composition of phospholipid fatty acids (PLFAs) and for the distribution of urea-derived 13 C among individual PLFAs. Carbon dioxide emissions were quantified, and the contributions derived from urea were assessed. Initial changes in PLFA composition were greater at the lower level of urea, as revealed by a principal-component analysis. At the higher urea level, osmotic stress was indicated by the dynamics of cyclopropane fatty acids and branched-chain fatty acids. Incorporation of 13 C from [ 13 C]urea was low but significant, and the largest amounts of urea-derived C were found in common fatty acids (i.e., 16:0, 16:1ω7 c , and 18:1ω7) that would be consistent with growth of typical NH 4 + -oxidizing ( Nitrosomonas ) and NO 2 − -oxidizing ( Nitrobacter ) bacteria. Surprisingly, a 20‰ depletion of 13 C in the cyclopropane fatty acid cy17:0 was observed after 4 days, which was replaced by a 10 to 20‰ depletion of that in cy19:0 after 14 days. Possible reasons for this pattern are discussed. Autotrophic nitrifiers could not be implicated in urea hydrolysis to any large extent, but PLFA dynamics and the incorporation of urea-derived 13 C in PLFAs indicated a response of nitrifiers which differed between the two urea concentrations.
Type of Medium:
Online Resource
ISSN:
0099-2240
,
1098-5336
DOI:
10.1128/AEM.70.11.6363-6369.2004
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2004
detail.hit.zdb_id:
223011-2
detail.hit.zdb_id:
1478346-0
SSG:
12
