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A nonradioactive assay of bacterial productivity optimized for oligotrophic pelagic environments
Author(s) -
Nelson Craig E.,
Carlson Craig A.
Publication year - 2005
Publication title -
limnology and oceanography: methods
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.898
H-Index - 72
ISSN - 1541-5856
DOI - 10.4319/lom.2005.3.211
Subject(s) - context (archaeology) , productivity , thymidine , pelagic zone , biology , environmental chemistry , ecology , chemistry , biochemistry , in vitro , paleontology , economics , macroeconomics
The measurement of bacterial production is a cornerstone of research in aquatic biogeochemistry and microbial ecology, yet the standard radioisotope‐based techniques are threatened by increasing logistical obstacles. The two primary goals of this study were (1) the development of a reliable nonradioactive assay of bacterial productivity interpretable in the context of previous 3 H‐thymidine ( 3 H‐TdR)—based metrics, and (2) maximizing the sensitivity of the assay to allow routine measurement of bacterial productivity in open‐ocean and low‐productivity environments. We optimize existing methods for immunochemical detection of the incorporation of the thymidine analog 5‐bromo‐2′‐deoxyuridine (BrdU) to present a functional assay of community bacterial productivity comparable to radioisotope‐based assays in economy and field implementation and capable of consistently detecting bacterial production rates within the range of 0.1 to 10 pmol BrdU L −1 h −1 . A standardization procedure provides complete separation of radioisotopes from the working methodology and gives statistically consistent results between calibrations with no degradation of the labeled DNA standards. Immunoassayed BrdU incorporation rates were highly correlated with parallel measurements of 3 H‐TdR incorporation rates spanning a range of 0.1 to 10 pmol L −1 h −1 ( r = 0.96, n = 20, P < 0.001). Model II linear regression (BrdU = 0.65[ 3 H‐TdR] + 0.12) yielded a conversion factor not significantly different from that reported previously comparing incorporation rates measured using radioisotope protocols ( 3 H‐BrdU = 0.69[ 3 H‐TdR] − 0.81). The assay is interpretable in the context of 3 H‐TdR—based measures of production, providing continuity as a nonradioactive measure of bacterial production in low‐productivity aquatic ecosystems.