Biomedical subjects
Publications and source records attributed to V R Srinivasan.
Methylanthranilate inhibited the germination of spores of aerobic bacilli without affecting growth and sporulation. The inhibition of germination could not be reversed by removal of methylanthranilate.
A cellobiose-utilizing bacterium isolated from sugar cane bagasse and identified as a strain of Alcaligenes faecalis (ATCC 21400) produced an inducible beta-glucoside-splitting enzyme. The enzyme was purified by a series of streptomycin and ammonium sulfate fractionations and by Sephadex and diethylaminoethyl column chromatography. The final preparation was purified 130-fold, with a recovery of about 10% of the initial enzyme activity. The enzyme had a wide pH range, with optimal activity at pH 6.0 to 7.0. The enzyme was stable in solution at pH 6.5 to 7.8 when kept at 30 C for 2 hr, but it was destroyed by temperatures above 55 C. At 58 and 60 C, the time required to inactivate 90% of the initial activity was 16 and 6.5 min, respectively. An activation energy of 9,500 cal/mole and a K(m) of 1.25 x 10(-4)m were obtained by using p-nitrophenyl beta-glucoside as a substrate. The K(i) value and hydrolysis of cellobiose by the enzyme indicated a high affinity of the enzyme for the cellobiose. The enzyme had its specificity on beta-glucosidic linkage and the rate of hydrolisis of glucosides depended upon the nature of the aglycon moiety. The inactivation studies showed the presence of sulfhydryl groups in the enzyme. The activity of the enzyme was easily destroyed by the Cu(++) and Hg(++) ions. The Michaelis-Menton relationship and the rate of heat inactivation indicated the presence of one type of noninteracting active site in the bacterial beta-glucosidase. Molecular weight of the enzyme was estimated by gel filtration (Sephadex G-200) and sucrose density gradient, and a value of 120,000 to 160,000 was obtained.
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A cellulose-decomposing aerobic and mesophilic bacterium has been isolated from soils of sugar cane fields. The terminal dilution method was adapted to isolate a single clone of cellulolytic organism from closely related contaminants. The cultural and physiological characteristics of the isolate were studied, and the organism was identified as a member of the genus Cellulomonas. The isolate excreted cellulase into the menstruum, and it hydrolyzed various cellulosic materials producing cellobiose as the final breakdown product in the menstruum. When sugar cane bagasse was properly treated with alkali and heat, the organism could decompose up to 90% of the initial substrate within 5 days. Amino acid analysis of the cell crop revealed a high content of lysine, and the essential amino acid pattern compared favorably with that of Food and Agricultural Organization reference protein.
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Stahly, D. P. (University of Illinois, Urbana), V. R. Srinivasan, and H. Orin Halvorson. Effect of 8-azaguanine on the transition from vegetative growth to presporulation in Bacillus cereus. J. Bacteriol. 91:1875-1882. 1966.-The guanine analogue, 8-azaguanine (azaG), was found to inhibit sporulation of Bacillus cereus strain T when added to proliferating cells, but not to inhibit when added after the transition to presporulation. When azaG was added to vegetative cells, the growth rate was reduced, but no immediate bactericidal effect was demonstrated. Azaguanine was shown to be incorporated solely into ribonucleic acid (RNA). All of the natural purine bases and nucleosides were found to prevent azaG inhibition by blocking incorporation of the analogue into the RNA. Addition of a subinhibitory level of C(14)-azaG to proliferating cells resulted in an increase in incorporation paralleling the increase in number of cells. At the time of transition from growth to presporulation, a rapid removal of the azaG label from the cells occurred in the absence of net RNA breakdown. If differentiation was inhibited by increasing the concentration of azaG, then no expulsion took place. Instead, at the end of growth, net incorporation ceased, and a steady-state condition was established in which incorporation equaled breakdown. No azaG degradative enzymes are present in presporulating cells. The possibility is discussed that an increase in the ratio of natural purines to azaG occurred at the time of transition, and that the natural purine derivatives then were reincorporated into RNA preferentially to azaG. The data are consistent with the hypothesis than an increased rate of RNA turnover occurs at the time of transition from vegetative growth to presporulation. Addition of phosphate buffer (pH 7.0, 0.1 m) to azaG-inhibited vegetative cells caused reversal of inhibition, the reversal being accompanied by expulsion of the azaG. At least a partial explanation of this effect is that phosphate causes a decrease in the azaG intracellular pool size.
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The authors report two cases of isolated splenic tuberculosis treated since 1989 in Nizam's Institute of Medical Sciences. One case presented as pyrexia of unknown origin (PUO) and another with idiopathic thrombocytopenic purpura (ITP). Both were found to have splenic tuberculosis after splenectomy. Pre operative diagnosis could not be made in these cases. Splenectomy followed by antituberculous chemotherapy cured the condition in both the cases. The authors underline the diagnostic difficulties, essentially related to the rarity of this condition inspite of the progress in modern imaging.