A slow growing nitrogen-fixing strain ofVigna radiata var.aureus (mung bean)Rhizobium which expressed nitrogenase activity in a synthetic medium was isolated from its native population. Mutants with decreased and increased nitrogenase activity were derived from this strain by treatment with acridine orange and ethidium bromide. These mutants were tested for symbiotic effectivity invivo. The effectivity of mutants with decreased nitrogenase activity in the culture medium was lower than the parent strain; however, the effectivity of mutants with higher nitrogenase activity did not increase above that of the parent. This suggests that the plant is perhaps a limiting factor in the full expression of rhizobial nitrogenase in the nodules.

Carboxin prevents the growth of yeast by inhibiting protein synthesis; the resumption of growth in the presence of this chemical appears to be primarily due to a cellular alteration affecting carboxin entry into the cells.

The pattern of release of extracellular cellulase during the germination ofTrichoderma reesei spores has been examined. The four enzymes namely, filter paper degrading enzyme, Β-1,4 endoglucanase, Β-glucosidase and xylanase appear sequentially in the culture broth during germination of the spores. The order of enzyme appearance is not altered by the type of carbon source in the germination medium. Measureable quantities of filter paper degrading enzyme is detected only after the outgrowth has occurred. A possible mechanism of spore germination and induction of the enzymes by insoluble cellulose is suggested.

Azospirillum brasilense, an associative diazotrophs from sorghum roots grows autotrophically on NH₄⁺ and CaCO₃. NH₄⁺ a is also oxidized to NO₂^- and then denitrified. Addition of malate to the autotrophic medium enhances both NH₄⁺ oxidation as well as NONH₂^- dissimilation. The incomplete nitrification linked denitrification results in a rapid loss of nitrogen from the growth medium. The bacterium also shows assimilatory NO₃^- and NO₂^- reductases and fixes nitrogen at 50 μg N/ml of NH₄⁺ NO₃^- or NO₂^-