Cloning of genes that suppress an Escherichia coli K-12 alanine auxotroph when present in multicopy plasmids.

To facilitate molecular analyses of a previously uncharacterized gene involved in alanine synthesis, attempts were made to clone the wild-type allele of this gene, alaA, with a mini-Mu plasmid element used for in vivo cloning. Seventy-six independent Ala+ plasmids were isolated and characterized. Physiological, enzymological, and restriction endonuclease analyses indicated that three different genes, none of them alaA, were cloned. These genes were avtA+, which encodes the alanine-valine transaminase (transaminase C); tyrB+, which encodes the tyrosine-repressible transaminase (transaminase D); and a previously undescribed gene, called alaB, which encodes an alanine-glutamate transaminase.     

Investigation of the angular distribution and energy spectrum of fast ions produced during irradiation of targets by short laser pulses in the SOKOL-P facility

Results are presented from experimental investigations of the angular distributions and energy spectra of fast ions produced in deuterium polyethylene targets under irradiation by picosecond laser pulses with intensities of up to 2 × 10¹⁸ W/cm² in the SOKOL-P facility. The parameters of ion fluxes were measured by time-of-flight spectrometers based on semiconductor detectors.     

Fate of transforming DNA following uptake by competent Bacillus subtilis. I. Formation and properties of the donor-recipient complex

Following uptake by competent Bacillus subtilis, transforming DNA is converted to two distinct slowly sedimenting molecular forms which possess little transforming activity (eclipse). A few minutes after uptake is initiated, a physical complex of donor and recipient DNA begins to form. The recovery of donor transforming activity following eclipse, and the appearance of recombinant activity, previously reported by Venema, Pritchard &; Venema-Schröder (1965), is shown to be due to changes occurring in the donor—recipient complex. This complex exists transiently in a form with low recombinant-type transforming activity. This transient form may be one in which the donor and recipient components are joined non-covalently. The donor-recipient complex is shown to be a heteroduplex structure in which the donor moiety has an approximate molecular weight of 750,000.     

Foraging Efficacy of a Larval Parasitoid in a Cotton Patch: Influence of Chemical Cues and Learning

Plant-herbivore chemical signals and behavioral plasticity may enhance parasitoid host-foraging efficacy in the field; however, no studies have quantified the potential benefits from these factors under field-type conditions. The effect of plant-herbivore signals and learning on the foraging efficacy of Microplitis croceipes was quantified by directly observing and recording total and sequential duration of various foraging behaviors relative to 5 randomly placed herbivore-damaged and host-infested cotton plants and 20 undamaged and non-host-infested plants. Microplitis croceipes spent significantly more time searching (flying and antennation) on host infested versus uninfested plants. Antennation time was significantly and negatively correlated with successive host stings. Contrary to expectations of increased duration, flight time remained constant throughout the foraging bout, which may indicate that there was some learning associated with flight. These results suggest that plant-herbivore chemical signals and learning enhances the foraging efficacy of M. croceipes.