The calcium-dipicolinic acid (Ca-DPA) complex in the spores of Bacilluscereus T is believed to play an important role in the phenomenon of heat resistance. Studies were carried out to determine whether calcium was present in the form of a complex with DPA. Ca and DPA are known to be released into the medium following germination. The presence of Ca-DPA complex in the spores can be established, if Ca and DPA are released in the same ratio in which they are present in the spores. This was studied by preparing spores having different Ca-DPA ratio, and subsequently determining the ratio in which they were released during germination. The present results indicate that the Ca-DPA ratio during the release was the same as in the spores. Attempts were also made by increasing the Zn concentration in the medium to see whether Zn could replace Ca in Ca-DPA complex. The results obtained show that Zn is not taken up by the spores in the presence of Ca.
Synthesis of alkaline phosphatase in Aspergillus flavus is markedly inhibited by chlorinated hydrocarbons whereas acid phosphatase and invertase are unaffected. Cellulase production and growth of Trichodermaviride are inhibited by DDT, Lindane, Endrin, and Heptachlor. Amylase formation by A. oryzae is significantly decreased in the presence of insecticides.
Effect of alternating current (50Hz) on the growth of Escherichia coli B was examined. Current intensity affected the length of lag time depending on the inoculum size, shaking rate during cultivation, and composition of culture medium. In the cell number of inoculum less than 108 cells/ml, lag time was prolonged with an increase of the current intensity. On increasing the cell number of inoculum, effect of the current on lag time decreased. It appears that electric current affects the relationship between the length of lag time and inoculum size. Intensified current had a lethal effect on the cells in a small inoculum size during cultivation. On the other hand, the current had little or no effect on the growth rate and extent of the growth once the growth began. The current had greater effect on the cells cultivated at a lower shaking rate. Supplementation of a certain nutrient such as yeast extract into the medium weakened the effect of the current. Composition of the medium might have changed by exposure to the current. In the present examination, a stimulative effect of electric current on the growth was not observed.
The mechanism of inhibition by lipid A, various fatty acids, or their derivatives on the transport activities of membrane vesicles from Escherichiacoil was studied. Various fatty acids and lauryl alcohol dramatically enhanced the proton permeability of membrane vesicles, potently inhibited the uptake of triphenylmethylphosphonium ion by the membrane vesicles, and severely inhibited the uptake of serine driven by an artificial membrane potential introduced by K+-diffusion via valinomycin. Lipid A and methyl laurate also acted similarly to fatty acids although to a lesser extent. It was also found that the inhibition of transport activities by lipid A and fatty acids was partially recovered by the addition of bovine serum albumin. Bovine serum albumin removed fatty acid from fatty acid-treated membrane vesicles and reduced the proton permeability compared to the treated membrane vesicles. These results indicated that lipid A, fatty acids, and their derivatives acted as proton conductors of membrane vesicles. The proton potential (interior negative) produced by electron transport systems or by K+-valinomycin was abolished in the presence of these compounds. For this reason, neither succinate nor amino acids could be accumulated by membrane vesicles in the presence of lipid A, fatty acids, or their derivatives.