- Volume 9, Issue 3, 1953

SUMMARY: Serological typing has been used to study competition between five strains of Rhizobium trifolii in growth and nodulation with four species of host. Although a proportion of non-reacting antigenic variants appears to have been encountered, the serological method remains uniquely suitable for studies of this kind.

Irrespective of host species or level of inoculum the population of bacteria in the tube of seedling agar approached a maximum of approximately 4 × 106 viable cells per ml. No consistent relationship was found between host species and the proportion of the several strains of rhizobia in the population outside the plant. The relative frequency of strains was, however, markedly affected by level of total inoculum and time of growth after inoculation. Some strains grew better at first but reached a lower maximum than others which fared better at higher population levels, whether from a heavier inoculum or prolonged growth. The population on the root surface itself failed to reflect any marked host influence in the balance between strains.

The proportions of strains found in the nodules were unrelated to their representation in the root’s external environment. Each host exercised a specific selective effect in this regard.

SUMMARY: Seven strains of acetic acid bacteria were separated into two well-defined groups on nutritional criteria. One group grew relatively poorly in media containing amino-acids andglucose, but grew well when lactate replaced glucose. In the presence of glucose and lactate, but not of glucose alone, ammonia was utilized as the sole source of nitrogen. With one exception, this group required no added growth factors for growth in a denned medium.

The second group grew well when glucose, but not lactate, was supplied as the chief source of carbon and/or energy. Casein acid hydrolysate was a suitable source of nitrogen, but ammonia, as a sole source of nitrogen, failed to support growth even when lactate waspresent, except to a limited extent when the growth period was prolonged to 7 days. All members of this group required added nicotinate, panto-thenate and p-aminobenzoate.

SUMMARY: The ciliate population of the large intestine of the horse shows large, daily variations. The ventral colon is the site where the ciliate fauna varies most. Two species, Cycloposthium edentatum and C. dentiferum, became established in the large intestine after passage through the stomach and small intestine. The introduction of new species into the ventral colon caused significant changes in the fauna of that part of the gut.

SUMMARY: Under the conditions prevailing during the early stages of certain highly aerated penicillin fermentations, lard oil and oleic acid appear to be oxidized only slowly, or not at all, by suspensions of washed mycelium of Penicillium chrysogenum. Lard oil and oleic acid are both oxidized rapidly, however, under the conditions present at 48 hr. and after. The optimum pH for oxidation of lard oil by suspensions of washed mycelium c. 48 hr. old is 8·1 and for oleic acid, c. 6·4, but oxidation of both lard oil and oleic acid was apparent at the pH prevailing during the early stages of the fermentation (5·5–6·0).

Mycelium from shaken flask fermentations (conditions of relatively low aeration) appeared to oxidize lard oil only slowly even during the later stages of the fermentation although oleic acid, which is the principal product of hydrolysis of lard oil, was oxidized rapidly.

The results suggest that enzymes involved in the oxidation of lard oil and oleic acid may be present only in relatively low concentration in young mycelium and be synthesized as growth takes place. The ability to oxidize lard oil also appears to be favoured by conditions of high aeration during growth.

SUMMARY: Paper chromatograms of hydrolysates of 118 micro-organisms were examined in a study of the distribution of α, ε-diaminopimelic acid and other amino-acids. A method for the identification of α, ε-diaminopimelic acid is described. Diaminopimelic acid was found in nearly all the bacteria examined, except for the Gram-positive cocci, Streptomyces spp., and Actinomyces spp. It was also found in blue-green algae but in no other algae, nor in fungi, yeasts, plant viruses, or protozoa.

Each species examined showed a different amino acid composition. β-Alanine and α- and γ-aminobutyric acids were sometimes found, often in several species of the same genus. Seven unidentified ninhydrin-reacting spots were recorded; none of them had the wide distribution of diaminopimelic acid.

SUMMARY: Phage lysates of a salmonella strain can transduce flagellar characters from that strain to a second strain which absorbs the phage. Non-motile strains treated with lysates o other strains produced stable motile forms detected as spreading swarms in semi-solid agar.

O strains of known species produced swarms with the H antigens characteristic of theirown species, and the species of previously untypable O isolates could be inferred from the H antigens of their induced swarms.

The production of swarms by O strains when treated with lysates of other O strains divided nine Salmonella typhimurium O strains into six interacting groups; there are therefore at least six non-homologous genetic factors, mutation of any of which may cause absence of flagella, thus masking other genes which control H antigenic specificity.

Two flagellated but non-motile strains produced motile forms when treated with lysates of other strains, or of each other. At least two genes concerned with locomotor function are thus recognized. All the motile derivatives of one O strain spread very slowly through semi-solid agar; the ability to spread rapidly could be transduced to them by a second exposure to a lysate.

In exceptional instances two flagellar characters were simultaneously transduced: three O strains sometimes acquired a flagellar antigen from the donor strain at the same time as the H character; another O strain sometimes acquired simultaneously flagellation and the slow-spreading character.

There are therefore many distinct genes controlling the presence, antigenic character and function of the flagella. They may form part of an ordered gene array in which pairs of genes which are sometimes simultaneously transduced by a single phage particle are presumably closely linked.

SUMMARY: A steroid fraction obtained from lemon juice was found to be an essential metabolite for Paramecium aurelia, var. 4, stock 51.7 (s), in axenic culture. This steroid is closely related to, or is identical with, either β-sitosterol or γ-sitosterol.

SUMMARY: High cell densities reached in cultures of Desulphovibrio desulphuricans (Hildenborough strain), grown in a medium of glucose, peptone, yeast extract and salts were due to the presence of a non-sulphate-reducing anaerobic contaminant whose presence was detectable only in special conditions. The relevance of this to previous studies on the Hildenborough strain is discussed and certain quantitative data are corrected.

SUMMARY: In the use of an organism for assay of folic acid those compounds which affect the utilization of folic acid should be determined. With Tetrahymena pyriformis (geleii), it is shown that thymine (or thymidine), glycine, p-amino-benzoic acid, creatin and vitamin B12 diminish the requirement for folic acid. Pteroic acid, p-aminobenzoylglutamic acid, 5-methylcytosine, p-hydroxybenzoic acid, carbamylaspartic acid and ribonucleic acid have no effect on the requirement, while cholesterol and cortisone increase the requirement.

SUMMARY: Isotherms of the absorption of polymyxin E by Bacillus subtilis, Pseudomonas denitrificans and Streptococcus faecalis after 20 min. contact with the antibiotic were determined. Tested on seven different bacteria, the maximum amounts of polymyxin E absorbed showed that the polymyxin-sensitive bacteria were capable of absorbing much greater quantities of the antibiotic than resistant organisms. When the bacteria were suspended in buffer solutions, the ultraviolet spectra of their supernatant fluids showeda maximum absorption at 260 mμ.; purines and pyrimidines contribute to this maximum. Addition of polymyxin E to suspensions of sensitive bacteria caused an immediate increase in the height of this maximum. Similar treatment of resistant organisms caused very little immediate increase in the amount of 260 mμ. absorbing material released. On prolonged incubation of untreated and polymyxin E treated cells there was a steady increase in the amount of 260 mμ. absorbing cell solutes released into the suspension media. Within the pH range 4·4–7·6 no optimum pH value was found for the polymyxin E absorption process or for the cellular release mechanism. The absorption isotherms of polymyxin E obtained with cell-wall preparations derived from sensitive and resistant bacteria showed that cell walk derived from sensitive organisms bound more polymyxin E than cell-wall preparations from resistant organisms. On treatment of sensitive bacteria with concentrations of polymyxin E less than those required for 99 % killing in 20 min. at 25°, there was a linear relationship between the amounts of 260 mμ. absorbing material released and the percentage of cells killed. Complete saturation of sensitive organisms with the antibiotic was not necessary to kill the cells. The amounts of polymyxh E. required for 99·5 % killing corresponded closely to those suflicient for the formation of a closely packed monolayer within the bacterial cell wall. It is suggested that, at these bactericidal concentrations, polymyxin E combines with and thereby disorganizes the structures responsible for the maintenance of osmotic equilibrium within the cell wall.

SUMMARY: Tobacco mosaic virus reached higher concentrations when inoculated tobacco leaves were placed in a solution containing 10 g./l. sucrose and 0·2 g./l. calcium phosphate than when in water. Detached leaves in water usually produced momvirus than leaves left onthe plants. Other sugars and phosphates also increased virus production. Sugar and calcium phosphate sometimes separately increased the concentration of the virus, but the response was usually greatest to both together. The increase varied with the nutritional state of the plants from which the leaves me and some other environmental conditions. Virus concentration, and the effect of sucrose and calcium phosphate in increasing it, was greater when leaves were in the light than in the dark. Conditions which increased virus concentration also increased the total carbohydrates of the leaves.

SUMMARY: Quantitative studies have been carried out on the survival of bacteria on drying from the frozen state. Attention has been confined mainly to one species of vegetative bacteria, viz. Bucterium coli, of which several different strains were examined. When suspended in a phosphate buffer (pH 7·6) and dried from the frozen state (−35), it was found that the percentage of organisms surviving varied widely with the strain used. With a given strain, it was found tht a well-defined relationship existed between the concentration of organisms in the suspension before drying and the percentage of viable survivors recovered after reconstituting the dried product; the more dilute the suspension thelower the percentage of organisms surviving. When a low concentration of organisms was suspended in the cell-free Altmte obtained from a higher concentration of the same organisms, the percentage of viable organisms recovered approximated to the figure to be expectedfor the higher concentration of organisms. The dependence of percentage survival on the concentration of organiamS in the suspension being dried was shown to be due to soluble material derived from the organisms themselves. On freezing alone, percentage survival wasindependent of the concentration of organisms in the suspension; the material affords protection during the drying stage of the process only. The protective effect of the material during freeze-drying was enhanced by the addition of glucose, especially during prolonged secondary drying.

SUMMARY: To approach reproducibility of mass cultures as sources of enzymes, the growthrequirements of two mesophils belonging to BaciUus lichenifmis and B. Circulans, and three thermophils belonging to B. liehenifomis, B. circulans and B. steurothemmphilus, were determined in metal-buffered media.

The mesophilic B. lichenifmis required glycerol or glucose, also alanine, aspartate, glycine, glutamate, arginine, histidine and lysine. Cytidylic acid or guanylic acid further increased growth; adenosine was inactive. The thermophilic B. lichenifomis required forgood growth either glycerol, gluconate, or glucose, also succinate or glutamate; glutamate was replaceable by the combination of arginine + histidine + proline. In glycerol media, either dl-malate alone, or citrate plus either acetate or fumarate supported growth; neither acetate nor fumarate were effective by themselves. In the absence of intermediatesof the citric acid cycle, sodium bicarbonate or a combination of protogen + acetate allowed growth. With acetate present, protogen was replaceable by thiamine.

The B. stearothmmophilus strain utilized glucose or sucrose; thiamine, biotin nicotnic acid were required. A combination of arginine + histidine + isoleucine increased growth. The carbohydrate requirement appeared absolute.

The thermophilic B. circulans required glutamate or a combination of succinate + arginhe + histidine; these sufficed for moderate growth. Supplementation with glycerol, sucrose, gluconate or glucose increased growth. Further addition of acetate decreased the lag phase. For the mesophilic B. circulans, either glucose or gluconate were suitable substrates; thiamine, biotin, riboflavin, and ‘reduced sulphur’ were required.

SUMMARY: The Carbondale yeast stock contains cultures which are characterized by the delayed fermentation of galactose. Long-term adaptation to galactose results from gene-mutation followed by the selection of the mutant in the presence of galactose. The original non-fermenter and the derived fermenter mutant contain no galactozymase and possess no selective advantage over each other when grown in glucose. Three different methods (variance analysis, fluctuation-redistribution tests, and chemostat experiments) which have been used with success in the detection of spontaneous mutations showed that the mutation to ability to ferment galactose did not occur spontaneously in these stocks. Exposure of non-dividing non-fermenter cells of the long-term fermenter to galactose induced the mutation to the fermenter type in a small but relatively constant number of cells, while exposure to glucose, ribose or lactose was ineffective; dividing cells were not susceptible to themutagenic action of galactose. Prolonging the exposure of the cells on galactose agar plates increased the number of mutations. It is inferred that the induction of the mutationresults from the impingement of galactose on the gene-surface thus modelling the gene-surf'ace into a mirror-image of the substrate.

SUMMARY: Untreated cells of three Gram-negative and four Gram-positive bacteria were resistant to lysis by crude and crystallbe trypsin. The resistance of the Gram negative organisms to lysis by trypsin was abolished by heating suspensions for 5 min. at 100° the rates and extent of lysis of the three organisms by crude trypsin were comparable. After maximal lysis of heated suspensions of Bacterium coil and Pseudomonas fluorescens, by crude trypsin, examination of the residual material in the electron microscope showed that cel walls were the principal components. When heated suspensions of Micrococcus lysodeikticus, Bacillus megaterium and Staphylococcus aurm were incubated with crude or crystalline trypsin, slow lysis occurred and the extent of lysis was less than that observed for the Gram-negative bacteria. Electron microscopic examination of trypsin-lysed cells of B. megMum showed incomplete digestion of cytoplasmic contents. Heated and autochved cells of Streptococcus faecalis were resistant to digestion with trypsin.

Cell-wall suspensions of B. meguterium were rapidly lysed on incubation with crystalline lysozyme. Heated cells of M. lysodeikticus were only partially lysed by lysozyme, but the subsequent addition of trypsin resulted in a rapid dissolution of the cell bodies. Although treatment of heated B. megaterium cells with lysozyme resulted in turbidity increases, the enzyme completely digested the cell wall leaving coagulated protoplasmic bodies. The protoplasmic bodies were rapidly lysed by crude trypsin.

SUMMARY: To test the capacity of different staphylococci to acquire resistance to bacteriophage in vitro, twenty phages were grown on solid medium and in fluid medium with their propagating strains of Staphylococcus aureus, different phage types and patterns beingrepresented.

Resistant secondary growth never appeared among staphylococci of the 3 A group and often appeared among members of the 6/47 group. Some members of the 29/52 group acquired resistance readily, and others never became resistant, Cross-resistance to other phages wa oornmonly acquired. Secondary growth was shown to be resistant or sensitive to the phage, or to yield a mixture of resistant and sensitive colonies.

With the exception of propagating strain PS69, all staphylococci which became resistant to phage acquired lysogenicity for the sensitive parent strain. All but one of the staphylococci which had acquired resistance to a phage appeared to be capable of absorbing that phage. A substance which caused non-specific inhibition of phage lysis on agar mediumwas present in phage lysates of a staphylococcus that had shown sensitive secondary growth. These results am discussed with reference to phage typing and to the possibilities of therapy by phage.

SUMMARY: Four analogues of pteroic acid and one of pteroylglutamic acid were tested for their ability to stimulate growth of Streptococmfaecalis R in the absence of pteroic acid or to inhibit growth in its presence. The four analogues of pteroic acid were inactive in either respect, but 2-deamhopteroylglutamk acid was inhibitory. Inhibition of the or anism wasmost marked in the presence of pteroic acid, and became relatively more efficient as the concentrations of inhibitor and growth factor were increased. Inhibition was much less marked in the presence of rhizopterin or Leucovorin, the relative efficiency decreasing in comparable conditions. Pteroylglutamic acid had an intermediate position and showed a competitive relationship.

Lactobacillus cmei was similarly inhibited when growth was supported by either pteroylglutamic acid or Leucovorin, but was less pronounced in the presence of the latter. On the other hand, the analogue could substitute for pteroylglutamic acid in stimulating the suboptimal growth supported by a mixture of thymine and a purine in the absence of added folic acid.

Several other organisms whose growth is independent of exogenous folic acid were unaffected by the analogue.