The effect of Cd2+ and a combination of Cd2+ with non-inhibiting levels of metals like Ca2+, Zn2+ and Hg2+ on the uptake of ammonia and phosphate by Anacystis nidulans IU625 (ATCC 27144) was investigated. Increasing concentrations of Cd2+ resulted in the subsequent inhibition of both NH4+ and PO43- uptake. The uptake kinetics was studied by monitoring short-term uptake rates at varying substrate levels. The values for Vmax (maximum uptake capacity) and Km (half saturation constant) were obtained using the double reciprocal plot. The NH4+ uptake as such, was found to be more sensitive to the heavy metal than the PO43- uptake as fairly low levels of Cd2+ were sufficient to inhibit the process significantly. However, the uptake kinetics for both NH4+ and PO43- was altered if Cd2+ was present in combination with other divalent cations such as Ca2+, Zn2+ and Hg2+. Zn2+ acted antagonistically to Cd2+ toxicity. Similarly, the Ca2+-Cd2+ combination protected against inhibition by Cd2+ ions. Hg2+ behaved differently: the Cd2+-Hg2+ combination resulted in increased inhibition.
Fatty acid synthases were isolated from six representative strains of corynebacteria and their properties were investigated. All synthases were multifunctional proteins (type I synthase). Fatty acid synthases of Corynebacterium glutamicum CNF 016 and Brevibacterium ammonia-genes CNF 096 produced not only saturated fatty acids (palmitic and stearic acids) but also oleic acid. On the other hand, synthases of Corynebacterium diphtheriae CNF 017, Corynebacterium xerosis CNF 010, Corynebacterium equi CNF 002, and Corynebacterium fascians CNF 006 synthesized exclusively saturated fatty acids. The Km values for acetyl-CoA of the enzymes from Corynebacterium glutamicum CNF 016, Brevibacterium ammoniagenes CNF 096, Corynebacterium diphtheriae CNF 017, Corynebacterium xerosis CNF 010, Corynebacteriumequi CNF 002 and Corynebacterium fascians CNF 006 were 1.3μM, 11μM, 24μM, 80μM, 53μM and 220μM, respectively. There were almost no differences among the six strains of corynebacteria in the Km values of other substrates. The results suggest that the properties of fatty acid synthase are useful for the taxonomic characterization of corynebacteria.
Plasma membranes were isolated from the acellular slime mold Physarumpolycephalum at different developmental stages in macrocyst formation and the protein composition was analyzed by polyacrylamide gel electrophoresis. Turnover of membrane protein was also studied by pulse-chase experiments with 32S-methionine. Surface proteins on the plasma membrane which were labeled by the lactoperoxidase-catalyzed iodination of intact plasmodia were also labeled with Concanavalin A, indicating that these components are glycosylated. The glycoproteins of the plasma membrane of vegetative plasmodia were largely conserved during the development of macrocysts. However, the relative amounts of these proteins showed significant changes and a few components were transiently accumulated in the plasma membrane. These facts suggest that the morphogenic events are accompanied by alterations in protein composition in the plasma membrane.
The kinetics of L-alanine-induced spore germination of Bacillus subtilis was studied in a very low range (<6μM) of concentration of L-alanine (ALA), where departure from Michaelis-Menten kinetics is frequently observed. For this purpose, a very sensitive method for measuring germination was devised based on the fact that a DNA repair-deficient mutant, UVSSP42-1, produces spores extremely sensitive to ultraviolet (UV) radiation, and the spores acquire normal UV resistance upon germination. After UV irradiation at an appropriate fluence, germination percentage was calculated from the survival of spores. Germination as low as 0.1% could be measured with sufficient accuracy for kinetic analysis. In a range of ALA concentration of 1.75 to 6μM, a double logarithmic plot of germination rate against ALA concentration gave a straight line with a slope of about 3. It may be assumed that binding of three molecules of ALA per receptor is required to trigger germination.
Forty-three strains of Gluconobacter species were examined for the electrophoretic comparison of six enzymes, namely, glucose-6-phosphate dehydrogenase (NADP-dependent, EC 220.127.116.11), 6-phosphogluconate dehydrogenase (NADP-dependent, EC 18.104.22.168), glucose dehydrogenase (NADP-dependent, EC 22.214.171.124), alcohol dehydrogenase (NAD-dependent, EC 126.96.36.199), aldehyde dehydrogenase (NADP-dependent, EC 188.8.131.52), and catalase (EC 184.108.40.206). From the electrophoretic patterns of the enzymes, these organisms were unequivocally divided into two groups, Groups I and II. There was no relation between the two groups; the similarity value was 0%. Group I consists of organisms with a high guanine-plus-cytosine content of DNA ranging from 58.1 to 62.8mol%, a range of 4.7mol%. Group II is composed of organisms with a distinctly lower guanine-plus-cytosine content of DNA ranging from 54.2 to 57.6mol%, a range of 3.4mol%. Such a grouping was supported earlier by a DNA-DNA hybrid experiment. On the basis of the electrophoretic patterns of the enzymes and the DNA-DNA hybridization, we propose a new species, Gluconobacter cerinus, sp. nov., nom. rev., for the organisms classified in Group II.
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Edited and published by : Applied Microbiology, Molecular and Cellular Biosciences Research Foundation/Center for Academic Publications Japan Produced and listed by : TERRAPUB, Center for Academic Publications Japan/Shobi Printing Co., Ltd. (-Vol.60,No12), Center for Academic Publications Japan/InternationalAcademic Printing Co., Ltd.(-Vol.54,No1)