T7 RNA Polymerase Functions In Vitro without Clustering

Many nucleic acid polymerases function in clusters known as factories. We investigate whether the RNA polymerase (RNAP) of phage T7 also clusters when active. Using ‘pulldowns’ and fluorescence correlation spectroscopy we find that elongation complexes do not interact in vitro with a Kd<1 µM. Chromosome conformation capture also reveals that genes located 100 kb apart on the E. coli chromosome do not associate more frequently when transcribed by T7 RNAP. We conclude that if clustering does occur in vivo, it must be driven by weak interactions, or mediated by a phage-encoded protein

In situ predatory behavior of Mysis relicta in Lake Michigan

Selectivity coefficients (W′) and predation rates on Lake Michigan zooplankton were determined for Mysis relicta during spring through fall using an in situ method. W′ values indicated the following ranked order of prey preference: Cladocera > copepod copepodites and copepod nauplii > adult diaptomids and cyclopoids. With few exceptions, W′ values for different prey categories remained fairly constant despite greatly changing relative abundances of prey. Predation rates and prey selectivity were similar in most cases to those determined in laboratory studies. Ingestion rates (percent dry body weight · day −1 ) were correlated to total prey biomass (r = 0.38) and to effective prey biomass (r = 0.85), where the weighting factors were overall mean selectivity coefficients for the different prey categories. This result suggested that seasonally varying composition of prey caused much of the variation in ingestion rates among experiments. Feeding trials performed at the same depth with daytime and nighttime assemblages of zooplankton indicated that Cladocera may escape heavy Mysis predation at night by migrating from the metalimnetic-hypolimnetic interface into the epilimnion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42918/1/10750_2004_Article_BF00008105.pd