- Volume 11, Issue 3, 1954

Summary: The early stages in the oxidation of naphthalene by five micro-organisms were investigated. In all the organisms. d-trans-1:2-dihydro-1:2-dihydroxy-naphthalene. salicylic acid and catechol appeared to be intermediate oxidation products. Washed cells grown on naphthalene oxidized α- and β-naphthol, but whether these compounds are true intermediates remains undecided.

SUMMARY: Live rod-shaped bacteria incubated on a medium containing 3 % urea grow but do not divide. They thus become much longer than dead bacteria lying among them, and the numbers of each kind can easily be counted in an electron microscope. This urea method gives accurate results and has several advantages over colony-counting methods. The significance of various interesting differences in the. counts given by the two methods is discussed. Slope cultures at 18 hr. gave live counts of over 95 % by the urea method.

SUMMARY: A method is described for obtaining mutants of Chlamydomonas moewusii with impaired motility. Thirteen distinct mutants with paralysed flagella were isolated, and eleven of these were obtained in both mating types by crossing with wild type. No sexual activity was elicited in M. 1060 (minus). No allelism was detected among the remaining twelve mutants. In M. 1002 plus, the locus for paralysis appears to be very closely linked with that of mating type. In certain mutants, paralysed plus gametes, when paired with wild-type minus, recovered motility after some hours. Recovery is attributed to the passage of motility factors across the protoplasmic bridge linking the paired gametes. Paralysed minus cells may act as donors of such factors when paired with paralysed plus cells of an unlike mutant strain. The pairs formed by mating genetically dissimilar gametes are considered as heterokaryons, which can be used to provide information on the identity or non-identity of genes associated with paralysis. The role of a number of transmissible factors in normal flagellar activity is thereby implicated.

Summary: An investigation of the rate of increase of spontaneous mutants and the subsequent increase in mutant proportion in a bacterial culture revealed discrepancies between the observed results and those expected on the assumption that mutant and parent grew with equal rates. These discrepancies could not be accounted for in terms of a selective difference between established mutants and their parents since, when the two were mixed together in reconstruction experiments, they fared equally well for hundreds of generations. Rather the discrepancies indicated a difference between parents and new mutants. The data were consistent with the hypothesis that the mutation occurred independently among one of four mutable units (nuclei) and that the mutant nucleus was dominant over its sister non-mutant nuclei in the heterocaryon so formed. As a consequence, a delay of two generations ensued before the mutant unit segregated into the homocaryotic ancestor of a mutant clone. This process delayed the onset of an increase in mutant numbers after mutation. The accurate prediction of the pseudo-equilibrium level of mutants, based on verifiable assumptions of periodic selection, mutation and segregation lag, is added evidence for the occurrence of a two-generation delay before the increase of the mutant clone. This phenomenon, called segregation lag, is a source of error in the calculation of mutation rate by methods involving the numbers of mutants found in bacterial cultures. Furthermore, because bacteria may be multinucleate, the rate of mutation/bacterium/generation is not the same as the rate of mutation mutable unit (nucleus)/generation.

SUMMARY: Histidine-independent (h+) mutants induced in histidine-requiring (h−) cultures by ultraviolet light have a delay in the onset of logarithmic increase that is about two generations longer than the delay shown by marked unirradiated h+ bacteria present at the same time. This extra delay is interpreted as being due to the segregation of one from four nuclei which are present, on the average, in growing h− organisms. The same assumption accounts for the extra delay observed in spontaneous h+ mutants. These and other results are discussed in relation to the site of mutation and to the various types of delay that can retard the onset of growth of a mutant clone. It is concluded that in the mutation from h− to h+, the h+ condition is dominant in the heterocaryon, that whatever phenotypic delay exists is short, and that cell division is not required to pass through it.

SUMMARY: By combining nucleus and cell-wall studies on the same bacterial cells, it was demonstrated that many mitosis-like configurations are actually divided by cross-septa. The results do not signify the absence of classical mitotic figures, but they do show that a nuclear study by itself is not sufficient to establish the existence of such configurations in the bacterial cell.

Summary: Proteus vulgaris and Salmonella typhi require for growth at temperatures above normal complex nitrogenous substances additional to the media suitable for growth at normal temperature.

SUMMARY: A simple method for purification of tryptophan desmolase from Neurospora crassa in a good yield is described. No difference could be detected between the tryptophan desmolase extracted from a back-mutated strain of mutant C 83 and that from the wild-type strain. Michaelis constants with respect to the substrates indole and serine and the co-factor pyridoxal phosphate were measured as the basis for possible differences. It is shown that the concentration of tryptophan desmolase in the organism can be determined by genes other than those which induce a tryptophan requirement. Crosses of a histidine-requiring mutant to wild type yielded mutant progeny with 2 to 3 times the normal activity and progeny with no detectable activity under certain conditions. The lack of activity appears to be due to the production of an inhibitor.

Summary: The effect of phenol, mercuric chloride, fluoride, bisulphite, azide, malonate, 2:4-dinitrophenol and cyanide on respiration and penicillin production was studied using suspensions of washed penicillin-producing mycelium of Penicillium chrysogenum in Warburg flasks. Inhibition of penicillin production by phenol and by mercuric chloride closely followed the inhibition of respiration. Both fluoride and bisulphite inhibited penicillin production to a greater extent than respiration. Malonate was without effect on respiration or penicillin production, possibly because the pH was too high to allow a sufficient concentration of undissociated acid. Penicillin production was inhibited by 2:4-dinitrophenol at concentrations which had little effect on respiration, suggesting that phosphate bond energy is utilized in penicillin formation. Penicillin production was extremely sensitive to cyanide. A concentration of 0·000002 m-KCN, which caused no significant inhibition of respiration, depressed the rate of penicillin production to c. 25% of normal. Maximum rates of penicillin production and respiration are dependent on cyanide-sensitive systems but an alternative, relatively cyanide-stable system allows both respiration and penicillin production to proceed at c. 25% of the maximum rate.

Summary: Nocardia opaca Waksman & Henrici can use certain long chain saturated aliphatic hydrocarbons and many vegetable oils as sole carbon and energy source in presence of simple mineral salts. Long chain saturated aliphatic acids (e.g. myristic, palmitic and stearic) can similarly serve.

The same general morphological development is obtained on all these compounds but the initial mycelial phase is more pronounced on oily substrates (particularly hydrocarbons) than on water soluble or insoluble solid substances. Granules are demonstrable inside the cells. These granules are more intensely stained with fat and polysaccharide reagents than the rest of the cell. Well-defined electron dense bodies are also observed which behave similarly to the ‘mitochondria’ described by Mudd, Winterscheid, DeLamater & Henderson (1951) in Mycobacterium thamnopheos under intense electron bombardment.

Summary: Experiments have been carried out on the kinetics of induced synthesis of lysine decarboxylase in washed suspensions of Bacterium cadaveris. The enzyme is produced when glucose and lysine are present simultaneously. Lysine analogues tested as inducers were inactive. In anaerobic synthesis the rate of formation of new enzyme is directly proportional to the degree of saturation of the enzyme by its substrate; in aerobic synthesis a maximal rate is found even when the enzyme is almost totally unsaturated. The pH curve for enzyme synthesis corresponds closely with that for enzyme activity. Adapted cells undergo de-adaptation when incubated with glucose in the absence of lysine; this is due to the effect of cadaverine on the co-enzyme. The bearing of these results on current theories of enzyme induction is discussed.

SUMMARY: Two coryneform organisms (A1032 and A1062) isolated from the skin mucus of Arctic cod, are described in detail. Strain A1032 may be a new species; strain A1062 is a strain of Corynebacterium erythrogenes.

Three carotenoid pigments, all with very similar absorption spectra, were found in both strains. Two of these pigments were identified as neoxanthin and sarcina-xanthin. The third pigment has not been described previously and has been named corynexanthin; it is characterized by an extremely high adsorptive power. The three pigments occur in different relative amounts in the two strains. Diphenylamine has no qualitative effect on the pigments produced, but does tend slightly to inhibit the amount produced.

Strain A 1062 on certain media (notably blood agar base, Oxoid), produces large amounts of coproporphyrin III and smaller amounts of pentacarboxy-, tricarboxy-, and dicarboxy-porphyrins. Strain A 1032 does not produce porphyrins.

SUMMARY: Pancreatic ribonuclease inhibits the multiplication of a Rhizobium bacteriophage in liquid bacterial cultures by preventing permanent combination between phage and host. The addition of ribonuclease after phage has already combined with the bacteria does not prevent phage from multiplying, but it does decrease the rate of multiplication; the enzyme also interferes with multiplication of the bacteria. Experiments with ribonuclease in conjunction with chymotrypsin suggest that phage and bacteria unite in the presence of ribonuclease but that the union is only transitory and ends by the release of still active phage. In the presence of chymotrypsin, however, the phage becomes inactive during this transient union.

SUMMARY: Chlamydomonas dysosmos is capable of normal photosynthetic growth, and of heterotrophic growth in darkness on acetate, pyruvate or lactate. An ultraviolet-induced mutant (D. 2075) was isolated which behaved like an obligate photo-autotroph. In the presence of 2:4-dinitrophenol (5 × 10−5 m) or sodium azide (1 × 10-5 m), the wild-type organism similarly behaved in growth experiments like an obligate photo-autotroph. Mutant cells oxidized all added acetate to CO2. Wild-type cells oxidized a portion of the substrate, and utilized some of the energy so released for the assimilation of the remainder. There are indications that in the wild type the assimilation of acetate commences only after a period of acetate oxidation. The mutant is believed to be impaired in its ability to effect oxidative assimilation.

Summary: The coliform population in the rumens of twelve calves of ages 10–105 days was never greater than 106/g., and consisted mostly of Escherichia coli and intermediate types. Only one well-capsulated strain of Aerobacter aerogenes was isolated, whereas such capsulated strains could be isolated with ease from the rumen of a starch-fed sheep. An unidentified small catalase-negative Gram-negative rod, which readily produced ammonia from urea, was isolated from the rumen contents of two of the older calves, at a dilution of 10−4.

Summary: A substance produced by Pseudomonas aeruginosa (P. pyocyanea) which antagonizes the activity of streptomycin and dihydrostreptomycin, and which will itself inhibit bacterial growth in low concentrations, has been isolated in a crystalline form.

The antagonist at 0·01 μg./ml. was capable of antagonizing the action of 1000 times its weight of dihydrostreptomycin against Bacillus subtilis or B. pumilus. It was much less active against Escherichia coli. Growth of B. subtilis and B. pumilus was inhibited by less than 1 μg. antagonist/ml. under conditions which required a concentration of 6 μg. dihydrostreptomycin sulphate/ml. to inhibit growth.

A method of assay of antagonist activity, capable of assaying solutions containing 0·01 μg. antagonist/ml., was developed. It was a cup-plate method which depended on the production of zones of exhibition. Plates poured with seeded nutrient agar containing an inhibitory concentration of dihydrostreptomycin were used, and the samples of antagonist were placed on the surface of the agar in fish spine beads. The zones of exhibition developed during incubation of the plates and the potency of the samples could be determined from a comparison with zones produced by a standard preparation on the same plate.

The antagonist was produced by most strains of Pseudomonas aeruginosa under favourable conditions. Its production in fluid culture depended on vigorous aeration, but too high an aeration rate or foaming of the culture produced low yields. Strains of other organisms which were examined, for example, Staphylococcus aureus, Escherichia coli, Serratia marcescens, Bacterium bodenheimer, streptococci of Lance-field’s Group D, Bacillus subtilis and B. pumilus, did not produce antagonist.

The antagonist was extracted from fluid culture by n-butanol; the butanol was removed by distillation in an atmosphere of nitrogen, and the residue fractionated by precipitation from benzene solution by addition of light petroleum. The success of the fractionation was dependent on obtaining an initial butanol extract containing at least 100 μg. antagonist/mg. total solids. This in turn was dependent on the use of a simple chemically defined culture medium for production, and the choice of a strain of Pseudomonas aeruginosa which produced a high yield of antagonist. The crystalline antagonist has the formula C17–18H23–24NO2 and a molecular weight of the order 300–400. It is stable in the dry crystalline state, but readily oxidized in solution. It is soluble in ethanol and butanol, less soluble in benzene, and relatively insoluble in light petroleum. Its maximum solubility in water at room temperature at pH 7·0 is c. 10 μg./ml.; at pH 9·0 it is 20–30 μg./ml.

Summary: The properties (Michaelis constants, rates of inactivation at 100°, temperature coefficients and pH/activity relationships) of the extracellular penicillinase formed by a strain of Bacillus subtilis when growing in casein hydrolysate (= ‘basal’ enzyme) have been compared with those of the enzyme formed by the organism when growing in the same medium after addition of 1 unit benzylpenicillin/ml. (= ‘induced’ enzyme); no differences between the two preparations were detected. Similarly, no immunological or other differences were found between the basal and induced penicillinases of B. cereus, strain 569. However, the B. subtilis penicillinase was significantly different from the B. cereus penicillinase in the value of its Michaelis constant and the shape of its pH/activity curve; it was also quite distinct immunologically.

Summary: The fluorescent materials present in human and cat hair as a result of infection with Microsporon canis, M. audouini and Trichophyton schoenleini were extracted with dilute ammonia. Paper chromatography and electrophoresis showed that the principal fluorescent material was common to all these infections and that further fluorescent substances were present in the extract from T. schoenleini infected hair. Chemical properties and absorption spectra of the extracts have been examined.

SUMMARY: A new species of the genus Alcaligenes is described which is able to produce gas from nitrate.