- Volume 25, Issue 1, 1961

SUMMARY: The physiological properties of a collection of rapidly growing acid-fast bacilli were analysed according to a simple mathematical method proposed by Sneath. Closer relationships were observed between Mycobacterium smegmatis and M. phlei than between either of them and M.fortuitum; all three species form natural groups. On the basis of the Adansonian classification two other small groups were found which probably are new species. Some unnamed strains which could not be included in any of the groups mentioned above were placed in the classification and collectively labelled irregular branch. A key for the rapid identification of the specific groups is described.

SUMMARY: The lengths of organisms of Escherichia coli B/r grown in continuous culture in a glucose salts medium were measured over a wide range of population densities at 22° and 37°. In some cases the cultures were exposed to continuous gamma radiation at dose rates of 600 r./hr. at 22° and of 1000 r./hr. at 37°. The average length of the forms and the distribution with respect to length depended upon the temperature, population density and radiation dose rate. The growth rate was almost independent of population density over the range in which the average length of organism showed such a marked dependence. No significant differences in growth rate were observed as between unirradiated and irradiated cultures. Changes in average length of organisms are regarded as phenotypic responses to changes in growth conditions, some conditions favouring division and others inhibiting division amongst short organisms.

SUMMARY: By suitable adjustment of growth conditions in continuous cultures, organisms of Escherichia coli B/r with average lengths covering a wide range were produced and studied. From X-ray survival data it was concluded that radiosensitive sites were distributed along the length of an organism at intervals of 1–1·5 µ, whilst nuclear staining by the HCl-Giemsa method showed chromatinic bodies at an average spacing of 1·2µ,. Thus each nuclear body appeared to be a radiosensitive site. Lysozyme treatment did not reveal evidence of transverse membranes apart from those at visible ‘waists’. It was concluded that the longer organisms arose by the inhibition of the terminal stages of division. This inhibition did not affect the multiplication of the nuclear and cytoplasmic components, although there was considerable aggregation of nuclear material in irradiated organisms.

SUMMARY: A procedure is given for the detection of imidazole compounds accumulated in the mycelium of adenine mutants of Neurospora crassa. Of five such compounds detected, four have been tentatively identified. The distribution of these imidazoles among the mutants investigated allows a correlation between the adenine loci and the steps of purine biosynthesis.

SUMMARY: A wild strain of the multinucleate plasmodial myxomycete Physarum poly- cephalum was isolated in pure culture and grown on a medium consisting of 1 % (w/v) Tryptone, 1% (w/v) glucose, 0·15% (w/v) yeast extract, 0·3% (w/v) CaCO3, inorganic salts and a small amount of chick embryo extract. The organism may be grown with this medium either as a single large plasmodium on surface culture, or as a suspension of tiny plasmodia in submerged culture. From an initial inoculum of 1 ml. of a 3-day culture, the average plasmodial yield in a submerged culture was about 80 mg. dry weight/20 ml. medium at 72 hr. Growth occurred only in the presence of small amounts of an unidentified factor which was present particularly in chick embryo extract and foetal calf serum. An isolate of P. polycephalum was grown continuously on this medium for over four years without an appreciable decrease in growth rate. Under proper conditions a suspension of tiny plasmodia from shaken culture will fuse to form a single large surface plasmodium which exhibits synchronous mitosis.

SUMMARY: The survival characteristics of washed stationary phase Aerobacter aerogenes organisms suspended in buffered sodium chloride solution and stored at room temperature, or at 37° with aeration, depended on the medium used for growing the bacteria. Populations of bacteria harvested from tryptic meat broth or tryptone glucose medium remained almost completely viable for longer periods than bacteria from a simple ammonium salt + mannitol medium in which carbon was limiting. Analyses of washed freeze-dried preparations of freshly harvested bacteria showed that the amounts of protein, carbohydrate and ribonucleic acid present varied according to which of the above media was used for growth. During the initial stages of storage at 37°, when the viability of the population remained apparently unchanged, a progressive loss in bacterial dry weight occurred, due to degradation of these cell constituents. Endogenous glycogen was degraded and oxidized; bacteria which contained glycogen survived well. However, the addition of glucose to suspensions stored under aerobic or anaerobic conditions did not favour survival. Utilization of substances made available by degradation of various endogenous macromolecular constituents may be an important factor concerned with the survival of bacteria in unfavourable environments.

SUMMARY: Syntrophism was demonstrated between strains of Lactobacillus plantarum and Streptococcus faecalis in a chemically defined medium which lacked phenylalanine and pteroylglutamic acid (PGA); however, the presence of p-aminobenzoic acid (PABA) was essential. Enumeration of the two organisms in syntrophic growth was found to be possible by the use of Trypticase soy agar + 0·25% (w/v) glucose at pH 9·0 as a selective medium for S. faecalis. It was found that S. faecalis predominated in the early stages of the syntrophic growth, but that L. plantarum eventually predominated. Characterization by a bioautographic technique of the phenylalanine-active factor synthesized by S. faecalis and required by L. plantarum indicated that the factor was not identical with phenylalanine or shikimic acid. Micro-biological assays of the culture fluid from cultures of L. plantarum indicated that three types of folic acid compounds were synthesized: (1) oxygen-stable compounds which supported the growth of Pediococcus cereviseae; (2) oxygen-labile compounds which supported the growth of P. cereviseae; (3) oxygen-stable compounds which supported the growth of S. faecalis but not of P. cereviseae.

SUMMARY: A close relationship has been found between the baking activity of dried yeast and the yeast cell volume after reconstitution; other things being equal, the cell volume is in turn dependent upon the permeability of the cell wall. It appears that the total observed loss of activity occasioned by drying yeast may be attributed to increased cell-wall permeability.

SUMMARY: The sodium and potassium contents of cells of 32 strains of non-halophilic bacteria were determined after growth in a standard medium of low salt content. The salt tolerance of each strain was assessed by determining the lowest water activity at which growth occurred in sodium chloride medium. Among the strains examined the potassium contents varied about fivefold and were positively correlated with salt tolerance.

SUMMARY: The introduction of sodium acetate-2-14C into a bovine rumen resulted in the in vivo labelling of the rumen gases and volatile fatty acids. The relative isotope concentration in substrate and products indicated that a maximum of 5·6% of the methane and 11% of the carbon dioxide in rumen gas might have been derived from the methyl carbon of acetate when the substrate was added to the rumen 18 hr. after the animal had been fed a normal ration. A maximum of 3·2% of the methane and 4·2% of the carbon dioxide might have been derived from the methyl carbon of sodium acetate-2-14C when this substrate was introduced into the rumen immediately after the animal had been fed. The addition of sodium acetate-1-14C to the rumen 18 hr. after feeding indicated that 2% of the methane and 10% of the carbon dioxide was derived from the carboxyl carbon of the substrate. Most of the derived radioactivity of the volatile acids of the rumen was found in the butyric acid fraction, although smaller amounts appeared in propionic acid and the volatile fatty acids with a chain length of greater than 4 carbons.

SUMMARY: Yeasts belonging to the genera Candida and Trichosporon have been isolated in small numbers from the rumen of fistulated cows. Similar yeasts were not found on samples of feed material. The yeasts present fell into two groups dependent on the diet of the cow from which they were isolated.

SUMMARY: The yields of three antigens of Pasteurella pestis (fraction I, antigen 4, V antigen) in continuous flow culture over a range of temperature and pH values have been determined quantitatively. The production of some other antigens was followed qualitatively. The production of fraction I, V antigen and antigen 4 was greatest at 37° and little or none at 28°. The production of antigen 4 required an environmental pH below 6·9. The production of antigen 5 showed oxygen dependence at 28° but not at 37°. In transitions from one antigenic state to another the amounts of some antigens in the organism passed through maxima. Selection against types with the V and fraction I antigens occurred during growth at 37°, but not at 28°. Selection against types with antigen 4 did not occur.

SUMMARY: Addition of formalin (40% formaldehyde) to a concentration of 5–10% (v/v) to a bacterial culture before flagellar staining may change the shape of the flagella as seen in the stained preparation. With many bacteria, if not a majority, the formalin has no effect on the flagellar shape. The coiled, the straight, the small-amplitude and the typical undulant flagellar shapes evidently are mainly due to formalin fixation. The effect of formalin on flagellar shape may have taxonomic significance and should be recorded. Formalin fixation is advantageous in flagellar staining in that it kills the bacteria and makes for nicer preparations, especially when the bacteria are capsulated.

SUMMARY: A total of 171 cultures of Brucella, mostly isolated in this country from milk and foetal material, was examined for sensitivity to thionin blue as well as to basic fuchsin and thionin, and for agglutination in monospecific sera. Standard strains of Brucella abortus, B. melitensis and B. suis grew in the presence of thionin blue in the concentration studied. Three groups of B. abortus were found, however, which were sensitive to thionin blue. These were: (a) strains resembling the vaccine strain B. abortus strain 19; (b) dye sensitive strains (B. abortus type II Wilson), (c) a previously undescribed group. Cultures of this last group required added CO2 for growth, grew on basic fuchsin and were virulent for guinea-pigs. The significance of these results is briefly discussed.nce of these results is briefly discussed.

SUMMARY: A purified preparation of the ‘amine’ which accumulated in the medium during the growth of a strain of Saccharomyces cerevisiae (yeast 47) under conditions of partial biotin-deficiency contained two compounds, one of which was chromatographically and electrophoretically identical with synthetic 5-aminoimidazole. Both compounds gave identical colours on diazotization and coupling in the Bratton & Marshall reaction and on treatment with the Pauly imidazole reagent. The other, and major, component of purified ‘amine’ was shown to be 5-aminoimidazole riboside by its conversion to the free base and ribose on incubation with a bacterial nucleosidase. Synthetic 5-aminoimidazole gave analytical figures for formate, NH3-N and total-N similar to those previously obtained for purified ‘amine’. Evidence was obtained that resting organisms of a mutant Escherichia coli converted ‘amine’ and synthetic 5-aminoimidazole to 5-amino-4-imidazole-carboxamide. One of the adenine derivatives which accumulated instead of ‘amine’ and hypo-xanthine in a medium supplemented with aspartate was tentatively identified as thiomethy ladenosine.

SUMMARY: Endospores of Bacillus cereus Frankland and Frankland strain R (which is able to grow under highly alkaline conditions) germinated at a higher pH value than spores of an alkali-sensitive strain, Mu-3055. Spores of B. circulans Jordan strain Ru 38 (able to grow at pH 11·0) germinated at pH 11·0. Spore germination at any pH value was generally followed by outgrowth to the vegetative rod. Outgrowth of germinated spores of B. cereus R at pH 10·0 and of those of B. circulans Ru 38 at pH 11·0 took place at 30° but not at 37°. Growth from a vegetative inoculum of B. cereus R at pH 10·0 or 10·3 took place more readily at 30° than at 37°. The ability of the vegetative forms of both bacterial species to grow under alkaline conditions was transmitted through the endospore.

SUMMARY: Single organisms of Klebsiella pneumoniae were repeatedly selected for resistance on streptomycin agar yielding a population with increased resistance clearly different from that of the parent strain. These two strains were grown together and when retested a uniform population was found to be present with streptomycin resistance intermediate between the initial two.

Two strains of Klebsiella pneumoniae, one the type-strain, the other a chloramphenicol-resistant mutant with a different colonial appearance, were grown together and the mixture sampled at intervals. The two populations became progressively more alike until within six hours they were indistinguishable. The resulting uniform population was intermediate in sensitivity to chloramphenicol and the colonies could no longer be assigned easily to either parental type on morphological grounds. When the two strains were separated by a collodion membrane, this diminution of variation did not occur.

The results cannot be explained by overgrowth of one strain by the other. It is suggested that something analogous to inbreeding is taking place.