[Fine structure of the cytoplasmic membrane of Bacillus stearothermophilus and Bacillus coagulans].
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Increasing concentrations of ethylene glycol (EG), 1,2-propylene glycol (PG) or 2,3-butylene glycol (BG) lower the heat resistance of B. subtilis SJ2 and B. stearothermophilus 1518 spores, and there is a linear relationship between logarithm of decimal reduction time (D) and glycol concentration. D120 degreesc values of B. subtilis spores in 0.02M, pH 7.0 phosphate buffer containing 20 per cent (w/w) EG, PG and BG are respectively 1, 0.7 and 1.1 min compared to 1.5 min in buffer alone. Corresponding values for B. stearothermophilus spores are 2, 2.4 and 3 min compared to 3.2 min. The type of glycol has little effect upon temperature coefficient z for destruction of the B. subtilis spores (average 6.9 degrees C). On the contrary, in the case of B. stearothermophilus, z increases when the number of carbons increases in the glycol molecule (from 7 to 15 degrees). The thermodynamic parameters which characterize the activation of the spore destruction reaction cannot lead to a general conclusion about a possible mechanism of destruction in the presence of chemical compounds belonging to an homologous series: the two behave diversely, and there is no "isokinetic temperature".
Parameters of heat denaturation and intrinsic fluorescence of barnase and its close homologue, binase, in the pH region 2-6 have been determined. Barnase heat denaturation (pH 2.8-5.5) proceeds according to the "all-or-none" principle. Barnase denaturation temperature is lower than that of binase and this difference increases from 2.5 degrees C at pH 5 to 7 degrees C at pH 3. Enthalpy values of barnase and binase denaturation coincide only at pH 4.5-5.5, but as the pH decreases the barnase denaturation enthalpy decreases significantly and in this respect it differs from binase. The fluorescence and CD techniques do not reveal any distinctions in the local environment of aromatic residues in the two proteins, and the obtained difference in the parameters of intrinsic fluorescence is due to fluorescence quenching of the barnase Trp-94 by the His-18 residue, which is absent in binase. Secondary structures of both native and denaturated proteins also do not differ. Some differences have been found in the barnase and binase electrostatic characteristics, revealed in the character of the dipole moment distribution.
A higher efficiency of B. subtilis cells transformation by B. natto DNA is true for every concentration of DNA and is not due to the helping effect known for streptococci, strain Challis. In competition experiments for DNA uptake unlabelled B. natto and B. subtilis DNAs when added to transforming H3-DNA reduced the radioactivity of the samples by a factor of three and two, respectively. A conclusion is drawn that a higher rate of B. natto DNA penetration to the B. subtilis cells results in a higher efficiency of their transformation.
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