Fuhrman, J. University of Southern California, fuhrman@usc.edu
Ouverney, C. University of Southern California, ouverney@scf.usc.edu

For many years, microbiologists have asked if most countable cells are active. Unfortunately, confusion has resulted because activity is measured by several methods with different detection thresholds; also, some methods may not always work. Microbes in nature have a variety of physiological states and undoubtedly display a spectrum of activity - from dead to rapidly growing. If a detection method has a high threshold and measures only the fastest growing portion, the erroneous conclusion is that only a small fraction of the cells are active at all. However, highly sensitive and generally applicable methods, such as autoradiography with trace additions of mixed amino acids, show that the majority of native marine microbes have some activity. For example, our recent results from the Western Mediterranean showed that 73-86% of DAPI-countable bacteria take up amino acids, agreeing with studies elsewhere. Published work from our lab shows that autoradiography results coincide with those from universal 16S rRNA probes. Recently we have developed the ability to use autoradiography in conjunction with phylogenetic group-specific 16S rRNA probes of individual cells to measure the activity of particular subsets of native marine communities. This powerful approach permits detailed analysis of community structure and activity.
Day: Monday, Feb. 1
Time: 02:00 - 02:15pm
Location: Sweeney Center
Code: SS41MO0200S