Taylor, L. T. Monterey Bay Aquarium Research Institute, taylor@mbari.org
Preston, C. M. Mraine Science Institute, preston@lifesci.lscf.ucsb.edu
DeLong, E. F. Monterey Bay Aquarium Research Institute, delong@mbari.org

Fluorescently labeled, rRNA targeted oligodeoxynucleotide probes are useful for phylogenetic identification of single microbial cells, using fluorescent in situ hybridization (FISH) formats. However, oligodeoxynucleotide probes frequently lack sufficient sensitivity. Oftentimes, 50% or less of naturally occurring picoplankton are visualized using single fluor oligonucleotide probes and standard epifluorescence microscopy. To improve this situation, we modified a previously reported method using multiply labeled, rRNA targeted polyribonucleotide probes. Polyribonucleotide probes homologous to marine "Group 1" and "Group 2" planktonic archaea, and planktonic bacteria, were synthesized and optimized for group specificity and sensitivity. FISH was performed on filtered seawater samples. Dual labeling experiments confirmed specificity and improved sensitivity in natural samples. Depth profiles of archaea in "slot blot" experiments with extracted rRNA, showed similar trends to those determined with FISH using polyribonucleotide probes. Routine enumeration of marine "Group 1" archaea was achieved to depths of 3000 m, and in a full year time series in Monterey Bay. Planktonic "Group 1" archaeal cells had a distinct morphology, were larger than indicated by DAPI staining, and were abundant (up to 200, 000 /ml) at depths below 80 m. Further, the archaeal population was dynamic, occassionally reaching high cell densities (30, 000 /ml) in coastal surface waters.
Day: Monday, Feb. 1
Time: 04:45 - 05:00pm
Location: Sweeney Center
Code: SS41MO0445S