Steward, G. F.. MBARI,
Long, R. F.. University of California, San Diego,
Azam, F. University of California, San Diego,

Bacteria are intimately involved in every aspect of the functioning of aquatic food webs. As a consequence, one of the most fundamental and common measurements in studies of aquatic microbial ecology is bacterial growth rate. Several different approaches have been developed based on incorporation rates of radiolabeled substrates, frequency of dividing cells, or cellular RNA content. The most popular are incorporation rate measurements using tritiated thymidine (3H-TdR) or leucine (3H-Leu), because they are sensitive, relatively simple, and direct. However, they also pose logistical difficulties due to strict regulations governing purchase, transport, use and disposal of radioactivity. A promising new approach we have been exploring employs the thymidine analog bromodeoxyuridine (BrdU) as a substrate for DNA synthesis. Monoclonal antibodies against BrdU allow non-radioactive measurements of DNA synthesis by immunoassay. Tests in seawater and freshwater suggest that this method can serve as an economical substitute for 3H-TdR for measuring bacterial productivity. BrdU-labeling could also allow measurements of productivity at the single cell level by flow cytometry or immunofluorescence microscopy. Ultimately, this could lead to spatially explicit measurements of cell specific growth rates which are needed to understand how bacteria interact with and process organic matter which is heterogeneously distributed at the microscale.
Day: Wednesday, Feb. 3
Time: 09:30 - 09:45am
Location: Hilton of Santa Fe
Code: SS38WE0930H