Nitrogenase activity in the rhizosphere of sugarcane (Saccharumofficinarum Linn.), and its associated soil was measured by reduction of acetylene. Zero order kinetics and first order kinetics of acetylene reduction (C2H2→C2H4) were used to describe the activity of N2 fixers from these soils. Arranged in descending order of nitrogen-fixing (acetylene-reducing) potential, the sites examined were highland (arable), mesic meadow, peat polygon trough, transition zone between mesic meadow and peat polygon trough, lowland (flooded with water) and virgin flooded land. On most of the land, sugarcane has been under cultivation for centuries. In total, 9 acetylene reducers were isolated, the remaining being oligonitrophiles. In addition to using the saturation kinetic values to describe the activity of dinitrogen fixers, first order kinetics of several potential energy substrates were also compared. Carbohydrate concentrations (glucose, maltose, arabinose, mannose and raffinose) between 25 and 100μg/ml were used since the Michaelis-Menten plot indicates that between this range first order kinetics were measured. The results indicated that various carbohydrate additions had different effects on C2H2 reduction. Because of the relatively high temperature requirements for Azotobacterchroococcum development, tropical areas appear more favorable for a higher incidence of this bacterium. Optimal temperatures for acetylene reduction were between 25°-30°. Acetylene reduction was pH-dependent, the optimum occurring between pH 6.4-7.5. Nitrogenase activity was almost completely inhibited by air and anaerobic conditions, and was optimum at around pO2 0.06atm. The reduction of 2, 3, 5-triphenyl tretrazolium chloride to triphenyl formazan has been used to estimate the dehydrogenase activity of Azotobacter strains in vivo. A significant correlation has been obtained between isocitrate dehydrogenase reactions and the oxygen uptake of a number of isolates; the production of the formazan was used as an index of endogenous respiration. A similar relationship was also obtained between dehydrogenase reactions and bacterial numbers. A relationship between acetylene reduced per gram of organic carbon utilized and the dehydrogenase reactions has been recorded. This investigation also proposes an index for quick screening of nitrogen fixation in Azotobacter.
The white rot decay of coconut fibres caused by pure cultures of the basidiomycetes Trametes versicolor (L. ex Fr.) Lloyd and Stereumrugosum (Pers. ex Fr.) Fr. was strongly inhibited by the previous inoculation of cellulolytic fungi belonging to the ascomycetes and Fungi imperfecti. Generally, the total white rot decay was hardly or moderately inhibited when the basidiomycete was inoculated first. The cause of this biological inhibition is discussed. Another aspect of the present study is the toxicity of copper and zinc ions on the white rot decay of coir caused by the basidiomycetes mentioned. The effect of copper and zinc ions on coir degradation in non-sterilized soil is also demonstrated.
The model tested in this report is that bacterial cells form colonies by chance and the probability of cells forming visible colonies in a time interval is determined by a parameter λ of a colony forming equation previously presented. An isolate from soil was used for a single population test. Cells in a freshly cultivated or starved population of the organism on parallel plates showed no significant departure from the value expected from the equation in increases in the number of colonies during successive time intervals. Mixed populations in soil and river samples showed similar colony forming behavior.
The infectivity of Rhizobium trifolii 4S (infective strain on white clover) was lost in 50% of the surviving cells when the cells were incubated in broth medium without shaking at 35° for 7 days. The plasmid DNA extracted from 4S strain and non-infective strains (A1, spontaneous mutant obtained from 4S, and strain H1 and H2 obtained by the incubation of high temperature) were separated by 0.7% agarose gel electrophoresis. Rhizobium trifolii 4S had three plasmids with molecular weights of 210, 280 and 350Md. However, only two plasmids of 280 and 350Md were detected from the non-infective strains A1, H1 and H2.
The DNA-DNA homologies were determined among 14 strains of 13 species in the genus Thiobacillus. DNA from Thiobacillus versutus (synonym "Thiobacillus rapidicrescens") THI 041 and THI 024 did not react with DNAs from other species of facultatively chemolithotrophic Thiobacillus. This supports our previous conclusion, based on chemotaxonomic and physiological characteristics, that "T. rapidicrescens" is a new species. Both strains of Thiobacillus sp. THI 011 and Thiobacillus sp. THI 051, which were isolated from an activated sludge enriched with thiocyanate, were considered to be new species. Thiobacillusacidophilus THI 061 was closely related to "Thiobacillus organoparus" THI 071 in their DNA-DNA homology, and THI 071 was considered to be a strain of T. acidophilus. "Thiobacillus delicatus" THI 091, Thiobacillus perometabolis THI 023, and Thiobacillus intermedius THI 101 were regarded as three distinct species on the basis of DNA-DNA homology and phenotypic characteristics. Homologies were low among "Thiobacillus denitrificans" THI 151, Thiobacillusthioparus THI 111, Thiobacillus neapolitanus THI 121, and Thiobacillusferrooxidans THI 135. Therefore, these organisms were considered to be separate species. The DNA-DNA homologies supported the classification of the species in the genus Thiobacillus on the basis of the ubiquinone system in the respiratory chain, composition of cellular fatty acids, DNA base composition, and nutritional characteristics.
The effect of Cd2+ (4ppm) and a combination of Cd2+ with the non-inhibitory levels of metals like Ca2+ (150ppm), Zn2+ (2ppm), and Hg2+ (0.04ppm) on the uptake of nitrate by Anacystis nidulans IU 625 (ATCC 27144) was investigated. The NO3- uptake kinetics was studied by monitoring short-term uptake rates at different NO3- levels (1-20mM). The values for Vmax (0.8μmol/μg protein/hr) and half saturation constant for uptake (Km 3.03mM) were obtained employing the double reciprocal plot. A 4ppm level of Cd2+ inhibited 50% of the NO3- uptake rate (at saturating NO3- level) compared to Cd2+-less control. Cd2+ inhibition of NO3- uptake (Km 5.88mM) was alleviated as a result of competitive interaction by either Ca2+ (Km 4.34mM) or Zn2+ (Km 4.08mM). Hg2+ ions, however, interacted synergistically with Cd2+ (Km 12.5mM). There was no change in the uptake capacity (Vmax 0.8μmol/μg protein/hr) for NO3- under various treatments.
The relationships among 36 strains of 17 Saccharomyces species were studied by comparing ten enzymes electrophoretically. Twelve of the 13 strains of Saccharomyces cerevisiae tested produced rather similar patterns, but one distiller's yeast previously classified as Saccharomycesformosensis differed in fructose-1, 6-bisphosphate aldolase (EC 18.104.22.168). Three Saccharomyces uvarum strains split into two categories with quite different enzyme patterns. One included strains previously named Saccharomyces carlsbergensis and was similar to S. cerevisiae in its enzyme patterns. The electrophoretic patterns of S. cerevisiae, S. bayanus, S. chevalieri, S. diastaticus, and S. italicus were nearly identical. Strains of Saccharomyces delbrueckii, S. fermentati, S. rosei, and S. saitoanus, belonging to the so-called Torulaspora group, had similar electrophoretic patterns which were readily distinguishable from those of S. cerevisiae. The patterns of Saccharomyces bailii, S. bisporus, S. florentinus, and S. rouxii, belonging to the so-called Zygosaccharomyces group, differed from each other and from the S. cerevisiae and Torulaspora strains.