- Volume 17, Issue 3, 1957

SUMMARY: A proportion of wild-type strains of >Escherichia coli unable to recombine with >E. coli K12 F − mutants can ‘infect’ them with the sex-differentiating character known as F. Of these strains, not all infect the same >E. coli K12 F − mutants and the ease of transfer of F varies among them, suggesting that there are different F agents. This is supported by the finding that there are great variations in the transfer of unselected markers in crosses in which the only known difference is the origin of the F factor possessed by the F + parent.

Colicinogenicity and F are frequently associated and all of nine strains producing colicin I possess F, but they are not identical, since the two properties have been separated by treatment with cobalt chloride.

SUMMARY: The modes of sporulation of Micromonospora chalcea, the parasitic Actinomyces odontolyticus and of stages in the primary mycelium of a strain of Streptomyces are compared. All produce spores singly on short side-branches, but the characters of the parasitic Actinomyces appear to be neotenic and degenerate, whereas those of the Streptomyces are primitive, and show signs of affiliations with a variety of different genera.

SUMMARY: Two new species of the genus Nocardia (Trev.) have been isolated from the soil of chalk grassland. One of these, Nocardia calcarea n.sp., fixes atmospheric nitrogen in culture in amounts of 2–4·5 mg. N/g. glucose, sucrose or mannitol present in the medium. The second species, N. cellulans n.sp., decomposes cellulose in culture and fixes atmospheric nitrogen in culture using glucose, sucrose, mannitol and cellulose as carbon source; amounts of 12 mg. N fixed/g. cellulose decomposed were recorded. The properties of nitrogen fixation and cellulose decomposition have not previously been recorded for this genus. The two organisms are described.

SUMMARY: Cell-free extracts of Mycobacterium smegmatis contain an inorganic polyphosphatase and a ‘polyphosphate-AMP-phosphotransferase’. The latter enzyme, which synthesizes adenosine triphosphate from adenosine-5-monophosphate and inorganic polyphosphate, has a pH optimum of about 6·3, and is stimulated by Mg. It does not appear to be attached to cell particles, and a slight purification may be effected by ammonium sulphate precipitation.

With a tracer technique it was shown that cellular inorganic polyphosphate is probably not the sole precursor either of lipid phosphorus or of nucleic acid phosphorus in M. smegmatis. The rapid accumulation of insoluble polyphosphate caused in M. smegmatis and M. phlei but not M. tuberculosis, by a number of organic substances, particularly alcohols, was studied. This accumulation takes place even after inoculation into a fresh nitrogenous medium, when polyphosphate normally decreases.

SUMMARY: The nucleic acids were isolated from Aerobacter aerogenes by extraction of mechanically disintegrated organisms with 0·14 m-sodium chloride at pH 7·5. Upon subsequent isolation, about 80 % of the deoxyribonucleic acid (DNA) originally contained in the organisms was obtained, but only about 50% of the ribonucleic acid (RNA). The loss of RNA was mainly due to enzymic degradation. By extraction of A. aerogenes with 1 % sodium cholate at 60°, enzymic degradation was virtually eliminated and a good yield of both DNA and RNA obtained. They were relatively undegraded and both showed evidence of the presence of hydrogen bonds. The amounts of the purine and pyrimidine bases in both types of nucleic acid were determined. The DNA and RNA from the normal streptomycin-sensitive strain of A. aerogenes differed significantly in base composition from the corresponding nucleic acids from a strain which had been trained to grow in 5 % (w/v) streptomycin.

SUMMARY: The ‘bulging factor’, a new antibiotic with a chemical nature related to streptothricin, is produced by a Streptomyces strain and was isolated as reineckate and picrate. A study on its mode of action resulted in the development of a plate technique for assaying bulging factor activity. Evidence is presented in support of a theory about the existence of an active water-excreting mechanism in fungi susceptible to the bulging factor.

SUMMARY: Washed suspensions and cell-free extracts of Proteus vulgaris decarb- oxylate leucine, valine, norvaline, isoleucine, and α -amino- n -butyric acid. The system differs from most bacterial decarboxylases in being optimally active near pH 7 and in not requiring acid conditions for its formation. The system is adaptive (inducible); the presence of either leucine, valine or isoleucine will simultaneously induce decarboxylase activity against each of the five amino acids listed above. No additive effects were found when two amino acids were offered to the system simultaneously. Pyridoxal phosphate is required as coenzyme at least for valine and leucine decarboxylation ; the affinity between apo- and co-enzyme is greater during decarboxylation of valine than leucine.

SUMMARY: Suspensions of Bacillus subtilis form dl-alanine when incubated with pyruvate and ammonia. When leucine and valine are formed from the analogous keto acids, only the l-isomer is found. Since B. subtilis has a racemase active for alanine but not for valine or leucine, it is possible that the l-alanine may be the primary product and which is then racemized.

Suspensions of Bacillus subtilis and of some other organisms can synthesize certain amino acids from ammonia and the corresponding keto-acids (Fair-hurst, King & Sewell, 1956). When alanine is formed from pyruvate by B. subtilis, the racemic dl-mixture is produced. The present paper gives evidence in support of this finding (mentioned by Fairhurst et al. 1956, but not in detail) and discusses the mechanism of the reaction.

Summary: Spores of Didymella lycopersici and of six soil fungi were introduced separately into small quantities of soil spread in a film over a microscope slide. Direct observations were made, following which the soil from the slides was used for plate counts at stages before and after spore germination, when mycelium had developed, and after fruiting. It was found that as soon as spores germinated numbers obtained by plating decreased in the case of four of the seven fungi tested and did not increase as mycelial development progressed but reflected immediately the occurrence of sporulation.

Summary: A series of experiments with culture media was carried out dealing with: (1) the action of different salts and their interaction in the medium; (2) the relation of the nitrogen source to the action of the salts; (8) the effect of the carbon source; (4) the proportionate influence of the salts in the medium; (5) the rate of growth. The results showed that this fungus grew well at 26° with an initial pH value of 7·0–8·0 and a growth period of 6–7 days. Statistical analysis of the results showed: (a) that under the given conditions an aqueous medium containing: 4%(w/v) glucose; 0–048 m-K2HPO4 ; 0·012 m-MgSO4.7H2O; 0·025 m-(NH4)2SO4; 2p.p.m. Zn, Fe and Mn, produced optimal growth measured as mg. dry wt.; (b) a balance did not exist between KCl, K2HPO4 and MgSO4; (c) a balance did not exist between the concentration of glucose and (NH4)2SO4; (d) a balance existed between K2HPO4 and (NH4)2SO4; (e) this fungus could only utilize KNO3 or Ca(NO3)2 to a negligible extent, while the best source found for nitrogen was (NH4)2SO4; the most available phosphorus source was K2HPO4; (f) the rate of growth followed a sigmoid curve in a nutritionally optimal solution but in the minimal solution used the onset of decline in dry weight was delayed; (g) the importance of a balanced solution is that in suitable media the buffering action of the phosphate controls the onset of acidity inimical to growth.

SUMMARY : A psychrophilic species of the genus Pseudomonas was found to be capable of growth in a simple defined medium with any one of a number of carbon sources. The growth requirements were the same at 0° and 20°. The organism vigorously oxidized glucose to gluconic and 2-ketogluconic acids. Rates of O2 uptake were measured over the range 0–40° and compared with similar measurements on P. aeruginosa. Under the experimental conditions values of Q O2 for the psychrophile were higher than those for P. aeruginosa at all temperatures, including those above 30° at which temperatures the psychrophilic organism does not grow. The values of Q O2 and their temperature coefficients were dependent on conditions of cultivation. It is concluded that the systems involved in the oxidation of glucose and gluconic acid by the two organisms may not be greatly different in those physical properties which determine their temperature relations.

Summary: Polysaccharides obtained from twelve previously unextracted Shigella strains were hydrolysed and analysed chromatographically to determine their hexose constituents. The polysaccharides extracted from eight strains of the Flexner group (NCTC strains 3, 4833, 8205, 8206, 8201, 8207, 2245 and 4839), all contained the same hexose constituents, namely glucosamine, glucose and rhamnose. Shigella shigae (NCTC 8005) polysaccharide contained glucosamine, galactose and rhamnose. S. sonnei (NCTC 8220) polysaccharide contained glucosamine, galactose and glucose. S. schmitzi (NCTC 8218) polysaccharide contained glucosamine, galactose, glucose and rhamnose. S. alkalescens (NCTC 7925) polysaccharide contained glucosamine, galactosamine, glucose and galactose.

Summary: Pure cultures of Ankistrodesmus spp. showed continual morphological fluctuation when growing in complex organic media, and to a lesser (though detectable) extent in mineral media. Clonal populations were no less variable. In mineral media, variation of A. braunii was associated with the stationary phase of growth only, but in the complex organic test medium was seen in logarithmic phase as well. The normal processes governing cell morphogenesis are described for A. braunii. Their normal sequence is disrupted by increasing osmotic pressure of the medium in reverse of their normal order in time and of their hypothetical serial coupling to the metabolism concerned with cell growth. The final uncoupling, that of growth from initiation of cell division, is also accomplished by a wide range of C-N heterocyclic ring structures in very low concentration, which may indicate that nucleic acid metabolism is the system concerned at this point in the sequence.

Summary: A series of comparative studies was made of soil yeasts in a yellow-brown earth originally under forest but now under pasture. Of six solid acid media used for primary isolations, an agar medium containing 4 % (w/v) glucose and 1 % (w/v) peptone gave the highest yeast counts. Two soil-extract agars and a modified Czapek-Dox agar gave slightly lower counts; a third soil-extract agar inhibited all but one yeast species and gave a much decreased count. The addition of a surface active agent to glucose peptone agar did not increase the count. Acid broth enrichment cultures gave a distorted picture of the species pattern shown by primary cultures on solid media. Prolonged mechanical shaking of soil dilutions before culturing, and the addition of a surface active agent to the diluent did not affect the yeast pattern seen, quantitatively or qualitatively.

Summary: Catalase and peroxidase were markedly decreased in quantity in molybdenum-deficient felts of Neurospora crassa. Addition of molybdenum aseptic- ally and in vivo to mats deficient in molybdenum restored the activities of the two enzymes and the yield of mycelium to the amounts in the control treatments. Infiltration of hydrogen peroxide to growing felts, deficient in molybdenum, after 3 days of growth, resulted in a partial reconstitution of catalase to 18 % and peroxidase to 50 % of the control levels after a further 2 days growth but the weight of mycelium remained unchanged. There was no positive correlation between the activity of either enzyme at various stages of purification and its molybdenum content as determined by a radioassay method. The purified enzymes were not activated by molybdenum. The effect of molybdenum deficiency on the two iron- containing enzymes is probably indirect, resulting from a decrease in the activity of molybdenum-dependent flavoproteins which produce hydrogen peroxide, the common substrate for catalase and peroxidase.

Summary: Diverse enzyme changes were obtained in Neurospora crassa grown at deficient, optimal and toxic levels of Mo, Cu and Fe. These included mutual antagonisms between the metals, single effects of one element or additive ones of more than one element. Cytochrome c oxidase content, enhanced by Cu treatment, was decreased by increasing Mo; the reverse relationship was obtained with nitrate reductase. Cytochrome c and nitrite reductases, however, were depressed by amounts both of Cu and Mo which were toxic to growth; the effects were additive. Single effects were as follows: TPNH diaphorase and acid phosphatase were depressed by Cu and Mo excess respectively; the iron enzymes and the two diaphorases were more active when Fe was increased from deficiency to sufficiency level. High iron concentrations increased nitrate reductase but depressed the nitrite system. Molybdenum is shown to inhibit acid phosphatase competitively in vitro, presumably by forming a molybdo-phosphate addition compound with the substrate. Cu dispersed this complex and restored the enzyme activity to normal. Vanadate or tungstate had a similar effect to molybdate in depressing the enzyme but Cu was found to reverse the inhibition.

Thus it appears that antagonisms between metals in nutrition experiments may be related to their effects on certain enzymes as illustrated here for Cu, Mo and Fe in Neurospora.

Summary: A study of the nutritional requirements of the trypanosomid flagellate Strigomonas (Herpetomonas) oncopelti has led to the development of a chemically defined growth medium containing methionine, thiamine, nicotinamide, p-amino-benzoic acid, glucose, salts and trace metals. Fractionation and analysis of organisms grown in this defined medium supplemented with trace amounts of various 14C-labelled substrates has thrown light upon the ability of growing organisms to utilize carbon derived from glucose, acetate, a number of amino acids, purines and pyrimidines for the synthesis of cellular components.

Summary: The action of 2:7-diamino-9-phenyl-10-ethyl phenanthridinium bromide (ethidium bromide) on the parasitic flagellate Strigomonas oncopelti has been studied. The drug is irreversibly active only against growing organisms. Addition of the drug to cultures of organisms in the logarithmic phase of growth did not result in an immediate inhibition of growth but in a progressive decrease in growth rate; at least a doubling in number of organisms always occurred before multiplication finally ceased. During the period of growth in the presence of drug the deoxyribonucleic acid content of the organisms fell to half its normal value whilst the ribonucleic acid remained approximately constant. Conditions have been determined which permit the synthesis of nucleic acids and proteins by washed suspensions of S. oncopelti and the effect of ethidium bromide on these processes has been studied. The drug rapidly inhibits DNA synthesis whereas RNA and protein synthesis continue for a period of 2–3 hr. after the addition of drug. A study has been made of the uptake of 14C-labelled ethidium bromide by organisms under conditions which will or which will not permit nucleic acid synthesis. The uptake of drug is of two types: (i) an initial rapid uptake which occurs in the absence of nucleic acid synthesis and which does not affect the subsequent growth of organisms; (ii) an additional uptake by growing organisms which appears to follow the course of RNA synthesis and which results, eventually, in an inhibition of growth.