Culture supernatant fluids of 50 phosphate‐dissolving bacteria isolated from rhizospheres of crop plants were examined for IAA, gibberellins and cytokinins. These bacteria possessed phytase activity and 27 could dissolve rock phosphate. Twenty bacteria synthesized all 3 types of plant hormones, 43 produced IAA, 29 formed gibberellins and 45 cultures produced cytokinin‐like substances. Of the 50 bacteria tested 28 decomposed IAA. Plant growth inhibitors were detected in cultures of some isolates. The ecological significance of these rhizosphere bacteria and their mode of action when used as inoculants is considered.
F. GONZÁLEZ, M.E. FÁREZ‐VIDAL, J.M. ARIAS AND E. MONTOYA. 1994. Acid phosphatase and alkaline phosphatase from vegetative cells of Myxococcus coralloides D were purified by two chromatographic steps. The molecular weights were estimated by gel filtration and SDS‐PAGE. Optimum pH, stability, optimum temperature and thermal inactivation studies were made for both enzymes. EDTA and other chelating agents inhibited alkaline but not acid activity. Mg2+ activated the alkaline phosphatase, while the acid phosphatase was inhibited by fluoride. Both enzymes degraded a number of phosphomonoesters, but were unable to hydrolyse either polyphosphates or cAMP. The Km values of the acid and alkaline phosphatases for p‐nitrophenylphosphate were 5.0 times 10‐3 mol ***l‐1 and 1.5 times 10‐3 mol l‐1, respectively.
A substance that significantly depresses liver catalase values when injected into mice has been isolated from biochemical mutants of yeasts and staphylococci with impaired respiration. This is considered as an important argument in support of the Warburg hypothesis on the origin of cancer cells.
The effects on plant growth of "bacterial fertilizers" prepared from Azotobacter spp. and phosphate-solubilizing bacteria ("phosphobacteria") have been the subject of much controversy. Cases where no plant-growth stimulation occurred may often be accounted for by the failure to establish the bacterial inocula in the rhizosphere. Three factors that may influence inocula establishment, i.e. soil fertility, manuring, and interactions between Azotobacter and "phosphobacteria," were examined in pot experiments, designed for statistical analysis, in two neutral-alkaline soils, using lavender plants (Lavandula spica L.). During the experiments the numbers of Azotobacter and "phosphobacteria" were counted. Dry weights of roots and shoots were recorded after 16 weeks of growth. At the end of the experiments there were always more Azotobacter and "phosphobacteria" in the rhizospheres when plants were inoculated with both groups of organisms together than when they were inoculated singly. Addition of 2% farmyard manure to the richer soil enhanced this effect. Plant growth was greatest when seedlings were inoculated with both Azotobacter and the "phosphobacteria".
A wine-making Saccharomyces cerevisiae yeast strain isolated in our laboratory produces two different killer toxins, each one encoded by one dsRNA plasmid. One toxin has the same specificity as the one produced by strain M437 described by Naumov, but the dsRNA plasmid which encodes it migrates slightly faster in poly acrylamide gel electrophoresis. The other toxin has not been previously described, and is encoded by a dsRNA fraction which migrates at a lower rate than the × fraction of M437. These two dsRNA plasmids can be maintained separately in different yeast strains.
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