X-ray diffraction studies of outer membranes of Salmonella typhimurium.

X-ray diffraction studies were carried out on the outer membranes of various strains of Salmonella typhimurium. Ten distinct diffraction peaks which seem to be caused by protein assemblies were observed for most strains. Three small-angle reflections were used to determine an average structure of the protein assembly in the outer membrane of mutant HN202. An electron density distribution of the averaged assembly was obtained by means of the Fourier-Bessel transform. It has a diameter of about 100A, in agreement with the results of electron microscope observations (Smit, Kamio, and Nikaido (1975) J. Bacteriol. 124, 942--958), and exhibits a low electron density region at its center, suggesting the presence of a pore, as predicted on the basis of transmembrane transport experiments (Nakae (1976) J. Biol. Chem. 251, 2176--2178).     

Change in the H2 photoproduction capability in a synchronously grown aerobic nitrogen-fixing cyanobacterium,Synechococcus sp. Miami BG 043511

Synchronously growing cells of nitrogen-fixing Synechococcus sp. Miami BG 043511 were harvested periodically and the capability for hydrogen photoproduction in closed vessels was measured under hydrogen production conditions. The capability for hydrogen photoproduction in cells was correlated with that of cellular carbohydrate content. Cells with a high carbohydrate content exhibited a high capacity for hydrogen production and those with low carbohydrate content exhibited low capacity for hydrogen production. Nitrogenase activity at the onset of incubation did not coincide with a capability for the cells to produce hydrogen during the subsequent incubation period. Interestingly, when cells with a high capacity for hydrogen photoaccumulation were incubated, alternate periods of hydrogen and oxygen accumulation were observed at 12 hour intervals. About 0.5 ml of hydrogen per ml of cell suspension was accumulated in flasks during the initial 12-h incubation period. These observations indicate that the use of synchronous culture can be one of the ways of provide materials suitable not only for basic studies but also for applied aspects of hydrogen photoproduction.     

Phase transitions of the purple membrane and the brown holo-membrane X-ray diffraction,circular dichroism spectrum and absorption spectrum studies

The phase transition of the purple membrane observed by differential scanning calorimetry (Jackson, M.B. and Sturtevant, J.M. (1978) Biochemistry 17, 911–915) has been investigated by X-ray diffraction, circular dichroism and absorption spectrum, in comparison with the phase transition in the brown holo-membrane. The two-dimensional crystal of bacteriorhodopsin transformed into two-dimensional liquid around 74–78°C in the purple membrane and around 50–60°C in the brown holo-membrane. The X-ray diffraction patterns obtained at 78°C for the purple membrane and at 60°C for the brown holo-membrane exhibit several broad peaks. Analysis of the pattern suggests that bacteriorhodopsin molecules aggregate in trimers even above the phase transition temperature. The negative circular dichroism band in the visible region is still present at 80°C in the purple membrane and at 60°C in the brown holo-membrane, but becomes negligibly small at 70°C in the brown holo-membrane. The 560 nm absorption peak due to bacteriorhodopsin changes its position and height drastically around 80°C in the brown holo-membrane as in the purple membrane. X-ray diffraction studies have been made on membranes of total lipids extracted from the purple membrane. No indication of the phase transition has been found between ?81°C and 77°C.     

Advances in soil microbial ecology and the biodiversity

Recent studies on the colony formation of soil bacteria opened the way to categorize soil bacteria into colony forming curve (CFC) groups of different growth rates. A bacterial culture collection comprising organisms from every CFC group is called an ecocollection. Outlines of ECs of paddy soil 1992 and grassland soil 1987 and 1992 were described. Phylogenetic studies by 16S rDNA sequencing showed a great diversity of culture strains of the ecocollections (EC). A set of alternative concepts was proposed; the active and the quiescent forms of bacterial cells in soil. The former is able to be cultivated and thus counted by the plate method, while the latter is not unless it transforms into the former. Based on the results several points required for extensive cataloguing of soil bacteria were noted.     

The effect of sodium bicarbonate on a single dose of diethylcarbamazine therapy in patients with bancroftian filariasis in Kenya

An attempt was made to examine the effect of a combination of diethylcarbamazine citrate (DEC-C) and sodium bicarbonate (NaHCO₃) on the pharmacokinetics of diethylcarbamazine (DEC), side-reactions and reduction of the microfilarial density of patients with Wuchereria bancrofti infection at a hospital in Nairobi, Kenya. The microfilariae carriers received DEC-C at 6 mg/kg or 3 mg/kg with or without NaHCO₃ at 75 mg/kg body weight. The patients treated with a combination of drugs showed alkaline urine for 4 h post-treatment, while patients treated with DEC-C alone showed acidic urine. Although no significant difference was detected in the DEC half-life value and other pharmacokinetic parameters between patients treated with DEC-C (6 mg/kg) plus NaHCO₃ (75 mg/kg) and those treated with DEC-C (6 mg/kg) alone, the general tendency was that in patients receiving NaHCO₃ the first-order elimination rate constant decreased and serum elimination half-life and area under the serum concentration-time curve values increased. There was a significant difference between the mean values of the first-order absorption rate constant, the first-order elimination rate constant, and the time to maximum serum concentrations for the patients receiving DEC-C at 3 mg/kg plus NaHCO₃ at 75 mg/kg and those for the group receiving DEC-C at 6 mg/kg alone. There was no difference in frequency and severity of the side-reactions between patients receiving DEC-C at 6 mg/kg plus NaHCO₃ at 75 mg/kg, DEC-C at 3 mg/kg plus NaHCO₃ at 75 mg/kg, and DEC-C at 6 mg/kg alone. During the initial 5 days post-treatment, there was no significant difference in reduction of microfilarial density among these three groups. In the field, an attempt was made to examine the possibility of increased antifilarial effect using a combination of DEC-C and NaHCO₃. The patients were examined for microfilariae, given DEC-C at 6 mg/kg with or without NaHCO₃ at 75 mg/kg, and examined for microfilariae again 1 year later. Although the cure rate was the same among the groups, the percentage reduction in microfilarial density of the patients receiving DEC-C plus NaHCO₃ was significantly greater than those of patients receiving DEC-C alone. A combination of DEC-C with NaHCO₃ will be of practical value in a single dose of DEC-C for the mass-treatment of bancroftian filariasis.