- Volume 52, Issue 2, 1968

SUMMARY: Fourteen previously unstudied strains of the genus Desulfovibrio and eight thermophilic strains of the genus Desulfotomaculum were allotted to species on the results of physiological and biochemical tests.

On DNA base composition the Desulfovibrio strains fell clearly into three groups, corresponding to Dv. salexigens, Dv. desulfuricans and Dv. vulgaris. NaCl-dependence appeared to be a constant and unique feature of Dv. salexigens strains, and ‘sulphate-free’ growth on pyruvate a constant characteristic of Dv. desulfuricans, although one strain of Dv. vulgaris also dismuted pyruvate. Fumarate dismutation showed no species correlation. ‘Sulphate-free’ growth on choline was often minimal and the test appeared to be of little value. A high degree of resistance to Hibitane was not a constant characteristic of Dv. salexigens.

The thermophilic strains showed great uniformity in DNA base composition, Hibitane resistance and ‘sulphate-free’ growth, and were all classified as Desulfotomaculum nigrificans.

SUMMARY: A process is described for preparing suspensions of Mycobacterium lepraemurium from livers of infected mice, free from traces of host tissue. The organisms doubled in length when incubated in ‘elongation medium’ for 12-14 days but did not multiply. Analyses of normal and elongated organisms were made for lipid, phosphorus, nucleic acids, hexosamines, neutral sugars and α-amino nitrogen. A doubling of dry weight occurred during elongation, and there was a net synthesis of each of the components measured. Lipid and neutral sugar more than doubled, phosphorus, nitrogen and total nucleic acid rather less than doubled and hexosamine and DNA increased by about one third.

SUMMARY: Twenty-one soil samples from sites in West Scotland where alder (Alnus glutinosa) has not grown for many years were examined for the presence of the alder root-nodule endophyte by observing the production of nodules on test plants which were grown (a) in water culture and their roots inoculated with an aqueous suspension of a soil sample, or (b) in the soil itself. Twelve of the samples gave positive results, most of the remaining samples were at pH < 4. Ten samples from sites free from bog myrtle (Myrica gale) were similarly tested for the corresponding endophyte; 8 of these gave positive results. To explain these results it seems necessary to assume either that infective bodies of the endophyte can survive in soils for long periods, though not grow; or that the endophytes can grow saprophytically in soils and thus are not near-obligate symbionts.

SUMMARY: Sarcina ventriculi possesses a hydrogen-producing mechanism similar to that present in the coli-aerogenes group of bacteria. Formate is converted to hydrogen and carbon dioxide by formate hydrogenlyase and S. ventriculi is thus the only organism outside the coliform group known to possess this system. Formate dehydrogenase has also been demonstrated in the intact S. ventriculi organisms with both methylene blue and benzylviologen as hydrogen acceptors, but with extracts activity was only observed with benzylviologen. Hydrogenase activity was present in whole organisms and extracts of S. ventriculi. Hydrogenlyase, hydrogenase and, to a lesser extent, formate dehydrogenase activities in S. ventriculi are extremely sensitive to inhibition by oxygen. It is important support for the postulated mechanism of action of formate hydrogenlyase in the coliform bacteria that S. ventriculi also possesses the enzymic components deemed necessary for this activity, namely formate dehydrogenase (benzylviologen) and hydrogenase.

SUMMARY: The growth rates of nine yeasts, conventionally classified as ‘osmophilic’ and six yeasts, conventionally classified as ‘non-osmophilic’ were measured at 30° in media adjusted to known water activities with polyethylene glycol. The organisms were less tolerant of low water activities (aw ) in the presence of polyethylene glycol than in the presence of sugars. There was no significant difference between average minimal water activities supporting growth of the two groups of yeasts in polyethylene glycol, although differences in sugar tolerance were conspicuous. There was good correlation, however, between quantitative water relations of the organisms in polyethylene glycol and qualitative observations of ability to grow at specified sugar concentrations. The osmophilic organisms grew about half as fast as the non-osmophilic organisms at their respective optimal water activities. The osmophils had relatively broad water activity optima; the non-osmophils had sharp optima. Neither group of yeasts had a general requirement for a water activity lower than that of the basal medium (0.997 aw ) in order to grow, although there were two osmophilic strains which would not grow in the basal medium at 30°. The adjective ‘osmophilic’ is considered to be inaccurate; until the physiology of these yeasts is better understood we propose that they be designated simply as ‘sugar tolerant’. The quantitative results have provided a basis for selecting sugar tolerant organisms for biochemical and physiological investigations.

SUMMARY: Biochemical procedures for the differentiation of fungi in general and pathogenic fungi in particular have been slow to develop because many such organisms possess a sufficiently varied morphology to allow of considerable subdivision by that means alone. When, however, one considers organisms with a very reduced morphology, such as yeasts, the picture is very different and biochemical procedures have long been standard. Dependence on morphology for the identification of filamentous fungi has several disadvantages, of which slowness and lack of precision are the two most important. It is not desirable in medicine to have to wait several months till a particular identifiable structure is produced and there are a few pathogenic fungi which remain permanently nondescript. The lack of precision is best shown by the plethora of synonyms and ill described ‘species’ that have long plagued mycology.

The capacity of fungi to utilize various compounds and the chemical nature of their structure have both been used as methods of differentiation. The former method has been successfully used to show differences between morphologically similar organisms in several genera such as Microsporum, Trichophyton and Madurella. This method has also proved of the utmost value in distinguishing those aerobic Actinomycetes which are responsible for mycetoma from one another. Tests commonly used are the ability to degrade compounds such as casein, tyrosine, xanthine and urea or the lack of ability to grow in the absence of certain amino acids or vitamins or the ability to assimilate a particular compound such as dulcitol, erythritol, lactose or sucrose. Chemical analysis of fungi has not yet progressed so far but differences have been demonstrated, and the detection of arabinose and di-aminopimelic acid in the cell walls of Actinomycetes appears to be on the verge of becoming standard technique.

SUMMARY: α-Methylmethionine is a potent growth-inhibitory analogue of methionine producing an immediate effect on the growth rate of Escherichia coli at very low concentrations. Under certain conditions inhibition was transient, apparently due to an adaptation by the organisms. The analogue did not repress the synthesis of the methionine-forming enzymes but mimicked methionine as a feedback inhibitor of homoserine-O-trans-succinylase, acting on the enzyme at even lower concentrations than did methionine itself. Comparison of the effects on enzyme activity and growth rate leads to the conclusion that such enzyme inhibition is the basis of the effect of analogue on growth. Certain other compounds related to methionine also inhibited homoserine-O-trans-succinylase and of these D-methionine, DL-homocysteine and N-acetylmethionine probably caused inhibition after conversion to L-methionine.

α-Methylmethionine markedly inhibited the formation of infective phage after irradiation of E. coli HfrH(λ); methionine annulled the effect and allowed phage development to occur. The analogue was not incorporated into proteins in place of methionine, nor did it interfere with the incorporation of added methionine. Protein synthesis was inhibited by the analogue only when the process was dependent on methionine formation.

SUMMARY: The base composition of purified DNA from 18 species of the genus Candida was determined from the denaturation temperature, Tm. A great genetic heterogeneity was found with a mean molar guanine+cytosine (% GC) composition ranging from 35.1-57.6%.

Candida albicans, C. tropicalis, C. clausenii and C. stellatoidea showed essentially identical base composition 35.1-35.7% GC. The highest values (54.1-57.6% GC) were noted for C. catenulata, C. brumptii and C. zeylanoides. These three species also showed a compositional distribution of their DNA distinctly higher than the other species examined. The taxonomic and phylogenetic affinity between C. catenulata, C. brumptii and C. zeylanoides and the C. albicans group must on the basis of these investigations be seriously reconsidered. The rest of the species examined showed a wide range of mean % GC between the two clusters already mentioned. A variable degree of genetic affinity between these species and the C. albicans group cannot be excluded on the basis of the present examinations. Knowledge of DNA base compositions would appear to be of definite significance in the taxonomy of yeasts.

SUMMARY: Changes in Mycobacterium phlei due to B2h lysogeny were studied by the replica plating method. The changes could be divided into three categories: mutation to slow growth and small colony size; mutation to relative but complex nutritional requirements; and finally mutation to thiamine deficiency (thi−). A segregant clone obtained in the thi− mutant showed the characteristics of slow-growing small colony variants. Change in the bacterial host could be related to the type of integrated phage.

SUMMARY: A mutant of Chlamydomonas reinhardii with abnormal cell division is described. Cultures of the mutant consist of cells with between one and about seven nuclei. The number of pairs of flagella per cell is the same as the number of nuclei, except in large moribund cells which lack flagella. Pyrenoid division lags behind nuclear division in some cells. The expression of the mutation is modified by the age of the culture, pH of the environment or by the presence of certain other mutations. Genetic analysis is slightly complicated by the presence of multinucleate gametes, but it is shown that cytokinesis deficiency is inherited as a single gene mutation which maps close to the ac 29 locus on linkage group VI.

SUMMARY: Results of studies are reported on the carbohydrate metabolic capabilities of cells of Staphylococcus aureus grown in human serum at varied percentage iron-saturations of its contained siderophilin; on the production by such cells of coagulase, hyaluronidase, staphylokinase, and haemolysins; and on the effectiveness of some antibiotics as growth inhibitors under similar in vitro growth conditions. Cocci grown in serum at a normal serum iron level and percentage of iron-saturation show a significant reduction in their endogenous respiration, in their capacity to attack lactate, a complete loss of ability to oxidize formate, and a several-fold increase in anaerobic glycolytic capacity as compared to those cocci grown in serum containing unchelated free ionic iron. These metabolic changes, in conjunction with an observed increased rate of acid production and rate of glucose utilization by the growing culture of ‘low-iron’ cells versus the ‘high-iron’ cells, indicate an increased dependence upon glycolytic rather than oxidative energy production processes by the iron-restricted cells. The strain of S. aureus employed in these studies, although characterized by conventional methods as a producer of coagulase, hyaluronidase, haemolysins, and staphylokinase, did not elaborate any of these pathogenesis-linked factors at detectable levels when grown in normal serum. Coagulase, alone, was found at ‘high-iron’ levels. The amount of dimethoxyphenyl penicillin required to inhibit growth of our S. aureus strain grown in serum increased with increasing percentage of iron saturation of the siderophilin while the effectiveness of a given inhibitory concentration of kanamycin and chloramphenicol was indifferent to any variation in the iron-saturation value.

SUMMARY: The influence of post-irradiation growth inhibition on survival and absolute yields of prototrophic mutants has been studied in Escherichia coli B/R, u.v.-irradiated in the lag and logarithmic phases of the growth cycle. Without post-irradiation growth inhibition, survival and yields of mutants were higher for logarithmic phase cells. Post-irradiation growth inhibition reduced yields of mutants from both types of cells to similar extents and markedly increased the survival of logarithmic phase cells, both after small and large u.v. doses. In the case of lag phase cells, a survival increase mediated by post-irradiation growth inhibition, could only be observed by giving a large u.v. dose or by inhibiting repair of damage occurring after plating for colony formation. Post-irradiation growth inhibition was observed to have two effects–one tending to increase survival and another tending to enhance lethality. The results indicate that observable effects of post-irradiation growth inhibition on survival and induced mutation in E. coli B/R and whether or not such effects are correlated depend upon a number of factors. These include: (1) relative amounts of repair occurring during growth inhibition and during subsequent growth; (2) heterogeneity of the population with respect to growth phase, intrinsic repair ability and amount of damage; and (3) relative contributions of increased repair and increased killing–both mediated by post-irradiation growth inhibition.

SUMMARY: The development in culture of a stromatal rind of Sclerotinia fructicola was studied with a light microscope and the surfaces of stromata of the brown rot fungi grown on agar cultures and on fruits were examined with a Stereoscan electron microscope. The hyphae on the surface of some stromata retained their shape, while on other stromata a crust of thickened, collapsed hyphae developed over the outside. In some places rounded cells were seen below the gaps in the crust. The deposit of a melanin-like pigment around and in the walls of exposed stromatal hyphae may possibly increase the resistance of these hyphae to drying and be of importance in survival of the brown rot fungi.

SUMMARY: The isolation from a perianal abscess of a Haemophilus species requiring for growth the presence of X-factor but not V-factor is recorded. Two other similar strains were isolated from normal faeces. The properties of these isolates are given and compared with those of previously described species of the genus Haemophilus having the same growth requirements. The isolates form a homogeneous group resembling Haemophilus influenzae-murium.

SUMMARY: Good correlation between pectin methyl-trans-eliminase (PTE) activity and the ability to macerate plant tissue slices was found in fractions obtained from culture filtrates of the fungus Sclerotinia fructigena by gel filtration on dextran gel, or by ion-exchange chromatography. The presence of two isoenzymes was indicated, one of which was markedly activated by sodium polypectate or potato extract. Endo-polygalacturonase and α-L-arabinofuranosidase activities were not correlated with macerating ability. Negligible amounts of PTE were, however, detected in extracts of apple fruitlets rotted by S. fructigena; the pH optima of the enzyme components in the culture filtrates differed greatly from the pH of apple tissue. For this and other reasons PTE would appear to have little, and at most very localized, significance in the infection of apple fruits by S. fructigena.

SUMMARY: Bacillus fastidiosus, an aerobic spore-forming bacterium able to utilize uric acid or allantoin as sole source of carbon and nitrogen, has been re-isolated and its fine structure described. Anatomical features of vegetative cells are similar to those of other members of the genus Bacillus. The mature endospore has typical core and cortical regions. The spore coat is highly laminated and surrounded by a tight-fitting exosporium to which conspicuous exosporial hairs are attached.

SUMMARY: Magnesium-limited mixed cultures, each containing two microbial species, were produced by exchange of small numbers of organisms between magnesium-limited chemostat cultures of Aerobacter aerogenes, Pseudomonas fluorescens, Bacillus subtilis, B. megaterium, Staphylococcus epidermis and Torula utilis. The fate of each species in these mixed cultures was determined following cross-inoculation. Gram-negative organisms invariably outgrew the Gram-positive ones, but the ability of B. subtilis and B. megaterium to outgrow each other, or to outgrow the yeast, depended on the inoculum size. This dependence resulted from the presence of specific extracellular products in the Bacillus cultures which stimulated their growth and uptake of magnesium. The concentration of these extracellular growth-promoting substance(s) in magnesium-limited cultures of B. subtilis varied with population density. Thus, when the magnesium concentration in the medium was decreased from 0.9 to 0.15 μg./ml. (thereby causing the steady-state population density to be decreased to one-eightieth the initial value), B. subtilis could no longer maintain itself against proportionately low concentrations of T. utilis. But addition of extracellular fluids from dense magnesium-limited B. subtilis cultures to magnesium-limited T. utilis cultures enabled small numbers of the Bacillus now to outgrow the yeast. From these two observations it is concluded that magnesium assimilation by B. subtilis is more dependent on extracellular substance(s) than is magnesium assimilation by either T. utilis or the Gram-negative organisms. Modification of the basic theory of microbial growth in a chemostat culture, to take account of product-stimulated substrate-assimilation, is suggested.