Multiple Bacteriocin Production by Leuconostoc mesenteroidesTA33a and Other Leuconostoc/Weissella Strains

Leuconostoc (Lc.) mesenteroides TA33a produced three bacteriocins with different inhibitory activity spectra. Bacteriocins were purified by adsorption/desorption from producer cells and reverse phase high-performance liquid chromatography. Leucocin C-TA33a, a novel bacteriocin with a predicted molecular mass of 4598 Da, inhibited Listeria and other lactic acid bacteria (LAB). Leucocin B-TA33a has a predicted molecular mass of 3466 Da, with activity against Leuconostoc/Weissella (W.) strains, and appears similar to mesenterocin 52B and dextranicin 24, while leucocin A-TA33a, which also inhibited Listeria and other LAB strains, is identical to leucocin A-UAL 187. A survey of other known bacteriocin-producing Leuconostoc/Weissella strains for the presence of the three different bacteriocins revealed that production of leucocin A-, B- and C-type bacteriocins was widespread. Lc. carnosum LA54a, W. paramesenteroides LA7a, and Lc. gelidum UAL 187-22 produced all three bacteriocins, whereas W. paramesenteroides OX and Lc. carnosum TA11a produced only leucocin A- and B-type bacteriocins. Received: 11 April 1997 / Accepted: 10 June 1997     

Microzooplankton and macrozooplankton glutamate dehydrogenase as indices of the relative contribution of these fractions to ammonium regeneration in the Gulf of Maine

Ammonium regeneration by micro- (35–153 µm) andmacrozooplankton (> 153 µm) was determined in the Gulfof Maine by measuring the activity of the excretory enzyme glutamatedehydrogenase (GDH) in various size fractions. GDH maxima weregenerally observed to correspond to the depth of the chlorophyllmaximum as previously reported in the Gulf of Mexico and inthe vicinity of the Nantucket Shoals. GDH activity of the microzooplanktonwas considerably lower than the macrazooplankton, suggestingthe microzooplankton made only a minor contribution (1–11%) to the total ammonium regenerated. These results were confirmedby biomass estimates made from counts of individual species.Ammonium excretion by both zooplankton fractions was estimatedto supply 5–31 % of the nitrogen requirements for primaryproduction, with an estimated 59–63% supplied by the verticaltransport of nitrate (new nitrogen) into the euphoric zone.     

Exemplars and the reproduction of everyday life: The Amherst affair

Frederick Errington is Aaaociate Professor of Anthropology, at Keene State College, New Hampshire. Deborah Gewertz is Professor of Anthropology, at Amherst College, Massachusetts.     

Direct plasmid transfer from replica-plated E. coli colonies to competent B. subtilis cells. Identification of an E. coli clone carrying the hisH and tyrA genes of B. subtilis

Summary We have cloned the hisH tyrA wild-type genes of Bacillus subtilis with the aid of the chimeric plasmid pBJ194, which replicates both in B. subtilis and Escherichia coli. Primary cloning was done in E. coli. The original E. coli clone, carrying the recombinant plasmid (pGR1) which complements hisH tyrA mutants of B. subtilis, was selected directly from a mixture of plated E. coli clones by replicaplating these clones onto minimal agar plates without tyrosine spread just before with competent B. subtilis cells. After overnight incubation clusters of small colonies had developed exclusively in the E. coli [pGR1] colony prints.The Tyr⁺ minicolonies were shown to be B. subtilis carrying pGR1 because (i) their appearance depended linearly on the number of B. subtilis cells plated, (ii) they produced extracellular protease and amylase and (iii) plasmids could be reisolated from the minicolonies and used to transform B. subtilis recE4 tyrA1 both to Cm^r and Tyr⁺.Plasmid pGR1 transfer through replica plating was compared with plasmid transfer in liquid. Both systems depended on transformable B. subtilis strains and were sensitive to DNAseI. However, whereas integration of the tyrA ⁺ gene into the chromosome and concomittant loss of plasmids occurred frequently during regular plasmid transformation of Rec⁺ B. subtilis, this was a rare event during plasmid transfer through replica plating.