The dependence of the turbidity in yeast suspensions treated with various amounts of cetyltrimethylammonium bromide (CTAB) on the percentage of killed cells provides a means for the determination of the germicidal effect. Empirical equations which describe the observed relationship between turbidity and mortality were derived, and turbidity measurements necessary to estimate the killed fractions of the sample were described. The time course of the germicidal action of CTAB upon yeast cells was observed by using this method. The turbidity change thereby observed can be accounted for by the change in cell volume resulting from the cell degeneration. Some observations on different microbes treated with various germicides suggest that the present method may be applicable to other kinds of germicides and microbes.
The base composition of DNA (GC content) from 62 strains of yeasts and yeast-like fungi was studied. They are widely distributed from 26 to 64%. Most species of Saccharomycetaceae exhibited low GC content of 26-42.5%, but Lipomyces starkeyi and Naganishia globosus showed rather high values of 45.5% and 47.5%, respectively. In Cryptococcaceae, the GC content ranged from 30 to 64%. Yeasts belonging to Cryptococcus and Rhodotorula exhibited high GC content of 46-56% and 47.5-64%, respectively. In the genera of Torulopsis, Candida and Trichosporon, GC contents were widely distributed, namely, 34.5-52.5% in Torulopsis, 30-60% in Candida, and 32.5-59% in Trichosporon. Brettanomyces bruxellensis and Kloeckera apiculata exhibited low GC content of 35% and 30%, respectively. Trigonopsis variabilis showed rather a high value of 44%. Sporobolomyces salmonicolor, a ballistosporous yeast, exhibited a high GC content (57%). Of the yeast-like fungi, Tremella fuciformis and Aureobasidium pullulans showed high GC content of 54.5% and 51.5%, respectively. Meanwhile, Dipodascus albidus and Geotrichumcandidum exhibited low GC content of 33% and 40.5%, respectively.A phylogenetic relationship between the yeasts exhibiting a high GC content and Heterobasidiomycetes was discussed. A taxonomic significance of urease activity was found to be correlated to the GC content.
Although 6-phosphogluconate dehydrogenase (decarboxylating) (EC 18.104.22.168) has not been detected in Leuconostoc mesenteroides B07, the NAD-linked dehydrogenase catalyzing only oxidation of 6-phosphogluconate was purified from this organism. Basal properties of the dehydrogenase was studied and the dehydrogenation product was isolated and identified as 2-keto-6-phosphogluconate.
The course of growth of several bacteria in the heat-killed cell suspension of the respective strains was traced by counting the viable cell numbers. 1) The mean generation time of Escherichia coli was dependent on the concentration of the heat-killed cells. The maximum growth rate, mean generation time of 35min, was attained at the concentration of 25×109 or more heat-killed cells per ml. The mean generation time was comparable to that in the casamino acids-salt mixture medium. Final cell number attained was about 1% of that of the heat-killed cells initially supplied. The ratios of the number of viable cells to the heat-killed cells were fairly constant over a wide range of the concentration of the heat-killed cells, but they were smaller in lower concentration. The mean generation time and final yield increased in the medium supplemented with either glucose or ammonium chloride, and particularly, the effect of ammonium chloride on the reduction of the mean generation time was prominent. 2) Similar experiments were carried out with 9 other species of bacteria using suspensions of 2 to 3×109 heat-killed cells per ml. Some bacteria grew in their own heat-killed cell suspensions fairly rapidly after a short lag period. By contrast, Achromobacter liquefaciens failed to grow in its heat-killed cell suspension. The final yields of viable cells per unit number of heat-killed cells supplied were different from species to species. Among them, Arthrobacter simplex and Pseudomonas aeruginosa were the highest, and one new cell was produced at the expense of 13 to 14 heat-killed cells, while the others needed as many as 300 to 2, 000 heat-killed cells. 3) The effect of addition of glucose, ammonium chloride, sodium glutamate or inorganic salts on the growth and the final yield of several bacteria grown in their heat-killed cell suspension was studied. Most bacteria responded to ammonium chloride and sodium glutamate, and their final yield more or less increased, whereas they did not show any appreciable response to glucose. Growth of Serratia marcescens was completely suppressed by glucose. Phosphate was not effective in increasing the final yield of all the bacteria tested. The growth of some bacteria was much increased by the addition of salt mixture other than phosphate.
The activated sludge tested contained about 1011 bacterial cells per g of dry matter. The bacterial strains isolated from the activated sludge were classified into 21 groups by their morphological and physiological properties. Depending upon the floc-forming activities, the representative 12 strains which seemed to be dominant in number were distinguished into the following three types: (A) Floc former as cultured singly, (B) floc former as cultured in combination with strains other than type A, and (C) restrainer of floc formation if combined with type B. The bacteria isolated and the original sludge showed only a weak activity in oxygen consumption with glucose, but the sludge and some of bacteria belonging to types B and C consumed large or noticeable amounts of oxygen with peptone.
The determination studies were carried out on 12 representative bacteria which were isolated from activated sludge (1), and the following species were identified; Pseudomonas stutzeri (No. 46), Alcaligenes faecalis (No. 32), Pseudomonas diminuta (No. 2), Achromobacter pestifer (No. 18 and No. 27), Pseudomonas fragi (No. 3), Achromobacter superficialis (No. 5), Flavobacteriumlutescens (No. 9), Pseudomonas sp. (No. 11), and Brevibacterium ammoniagenes (No. 1 and No. 19). Among them, floc-forming bacteria were Ps. stutzeri (No. 46) and Al. faecalis (No. 32), the former being new as floc-forming bacteria. Floc-inhibiting strains were Ps. diminuta (No. 2), Pseudomonas sp. (No. 21), and Achromobacter pestifer (No. 27). The bacteria which formed flocs in mixed culture were the other seven strains.
Using rab values, rates of oxygen transfer into sulfite solution, as an index for establishing aeration-agitation, the fermentative production of inosine was scaled up from a flask culture to a 50-k1 tank culture. By applying the optimum condition for the production of inosine obtained with small scale fermentors, the yield of inosine obtained with a 50-k1 fermentor was approximately the same as that from small-scale fermentors. With due consideration to cotton plugs as a barrier of oxygen transfer, the advantage of using rab values for aeration-agitation index and for scale-up of aerobic fermentation was discussed.
Escherichia coli cells, which were obtained at the logarithmic phase of growth, were highly susceptible to a cold shock with viability as a criterion. The presence of bivalent cations in cold buffer, to which cells were squirted, protected the cells from the cold shock. Among cations examined, magnesium was the most effective. When high concentrations of magnesium sulfate (10-1M, final) were added to shocked cells immediately after the shock, their viability increased markedly to the level of unshocked cells. This recovery gradually decreased upon incubation of shocked cells in chilled buffer in the absence of a magnesium ion. After an incubation for 120min, no significant increase in viability was observed by the addition of magnesium. Two critical temperature zones in the cold shock were demonstrated with E. coli. When the temperature of the cell suspension before the shock was lowered by 10°, both critical temperature zones moved to lower temperature sides approximately by 10°. A rapid chilling by 7-10° or by 17-27° had a remarkable lethal effect.
Cell-free extracts were prepared from four types of Escherichia coli cells; cells grown aerobically with glucose, cells grown aerobically without glucose, cells grown anaerobically with glucose, and cells obtained after aeration of the anaerobically grown cells. Examination of the activities of about 20 enzymes in these extracts showed that glucose and oxygen in growth environment generally do not significantly influence the level of enzymes in fermentative pathways. The presence of oxygen during the growth increased the level of formate dehydrogenase, NADH oxidase system, and several enzymes in the tricarboxylic acid cycle, particularly isocitrate dehydrogenase and succinyl-CoA synthetase. The presence of glucose during the growth repressed the level of several enzymes in the glyoxylate cycle, particularly isocitrate lyase and citrate synthase. When thick suspensions of the cells grown anaerobically with glucose were aerated in a glucose-free incubation mixture for 4hr, initial low activities of about 10 enzymes increased to the level of cells grown aerobically in the absence of glucose, without accompanying significant cell multiplication.
The name Cunninghamella brunnea spec. nov. has been given to a new phaeosporous merosporangiferous Mucorales isolated from ‘Usar’ soils (pH 8.0-9.0), Lucknow, India. The new species is characterized by the presence of large greyish-brown spores and the absence of vesicles and oil-globules in the hyphae. This species is considered to have evolved as an ecological specialization in response to high temperature and intense solar radiation conditions prevailing in these soils.
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