- Volume 21, Issue 2, 1959

SUMMARY: Freeze-dried preparations of certain organisms may suffer considerable mortality during reconstitution to the wet state. For Vibrio metchnikovi the mortality was greatly decreased by rehydration with small volumes of water, or with various volumes of relatively concentrated solutions of some solutes. Within certain limits, slow dropwise addition of water resulted in higher viable counts than did rapid addition of the same volume of water. In preliminary tests Mycoplasma mycoides and two coliphages were also affected by the volume of water used for rehydration, but no significant effects were observed with nine other bacteria. Comparisons of rehydration at several temperatures showed greatest destruction at 37° for V. metchnikovi, but at 0° for three other bacteria. The importance of rehydration rates and of exposure to hypotonic solutions is discussed.

SUMMARY: Infection with bacteriophage increased the electrophoretic mobility of pea nodule bacteria (Rhizobium leguminosarum) at pH 7, suggesting an alteration of the bacterial surface. This seemed to occur at about the middle of the latent period. .

SUMMARY: The synthesis of cellulose by Acetobacter on media based on blackstrap molasses was studied. Methods are described for the determination of cellulose, and of growth as cell-N, in static culture. Different carbohydrate substrates were compared for cellulose production by Acetobacter acetigenum strain EA-I; hydrolysed molasses was found to give the largest yields. In media based on this substrate growth and cellulose production both reached their maximum values with a sugar concentration of 7·9 % (w/v) after 40 days’ growth at 26–29°. The maximum conversion (18 %) of sugar to cellulose, however, was obtained with 1·5 % (w/v) sugar. Cellulose synthesis ceased when growth stopped, even when the sugar in the medium was not exhausted, indicating that cellulose was synthesized only by the actively growing organism. The cellulose produced/mg. cell-N and % cellulose in the pellicles decreased with increased sugar concentration in the medium. Other Acetobacter strains were examined in this medium; the cellulose yields varied over a wide range, equivalent to conversions of 1·9–23·5 %.

SUMMARY: Growth and cellulose production by Acetobacter acetigenum strain EA-I was limited by nitrogen concentrations below 0·01 % (w/v) in glucose defined medium. Ammonium sulphate and asparagine + glutamic acid (50% of each) were equivalent as nitrogen sources when compared on a nitrogen weight basis over the range 0·001–0·1 %-N; at higher concentrations ammonium sulphate decreased growth and cellulose synthesis, while asparagine+glutamic acid became stimulatory. When used as adjuncts in glucose defined medium, acetate, citrate and succinate at suitable concentrations increased growth and cellulose synthesis, by as much as 20–30-fold under the most favourable conditions. Ethanol stimulated growth but did not increase cellulose synthesis. The addition of calcium or magnesium carbonate to defined medium inhibited growth. The influence of glucose concentration in defined medium on growth and cellulose synthesis was relatively slight in the absence of succinate; in the presence of 0·084 m-succinate the cultures showed a much greater response to glucose concentration, with a maximum cellulose yield that was 7·6 times greater than the maximum in the absence of succinate, and was associated with a 1 ·9-fold increase in growth. In hydrolysed molasses medium the addition of succinate decreased growth and cellulose synthesis; slightly increased cellulose yields were obtained when ethanol and calcium carbonate were added.

SUMMARY: Mycobacterium smegmatis was grown on Lemco agar in the presence and absence of acetate and fumarate. Fumarate was oxidized rapidly by fumarate- grown organisms. Lemco-grown and acetate-grown organisms oxidized fumarate at an increasing rate after a lag period and this adaptation was inhibited by chloramphenicol. Disrupted bacterial preparations oxidized fumarate rapidly, irrespective of the growth medium. Acetate-grown organisms oxidized acetate at more than twice the rate of fumarate-grown and Lemco-grown organisms. There was slight adaptation to acetate oxidation by acetate-grown organisms but greater adaptation by Lemco-grown and fumarate-grown organisms. Acetate was oxidized by disrupted bacterial preparations. The evidence for the existence of acetate and fumarate permeases is discussed.

SUMMARY: The propagation of Eperythrozoon coccoides in embryonated hen eggs inoculated by the yolk sac and intravenous routes is recorded. Fourteen continuous serial passages were made in the yolk sac and sixteen passages were made after intravenous inoculation into the chick embryo. The mortality among infected embryos was low; splenic enlargement was the only lesion detected. Once the strain had become established. E. coccoides was seen in blood smears taken from some eggs after each passage. Yolk sac or blood from infected embryos proved to be infective for mice on each occasion they were examined; 10−6 dilutions of yolk sac were also infective. E. coccoides was preserved for short periods at − 30° in mouse and chick- embryo blood, but not in yolk sac. The organism was also preserved in mouse blood and chick-embryo tissues at −79°. The presence of 10% (v/v) sterile glycerol appeared to increase the stability of E. coccoides in chick-embryo tissues stored at −79°.

SUMMARY: The formation of acetoin was studied with 44 strains of the genus Acetobacter, when growing on a medium containing dl-lactate as the main carbon source. Most of the strains produced only limited amounts of acetoin. However, strains of the species A. rancens, pasteurianum and ascendens converted most of their substrate into acetoin, up to 74 % of the theoretical amount. The influence of the substrate concentration and of the degree of aeration was studied.

The Voges-Proskauer positive substance was isolated from large-scale fermentations, purified and definitely identified as acetoin. It was present chiefly in the laevo- rotatory form. Young resting cells oxidized d( —)- lactate, l( + )- lactate, sodium pyruvate, acetoin and diacetyl, often nearly to completion. Cell-free extracts synthesized acetoin from pyruvate optimally at about pH 7. More than 99 % of the enzyme activity was located in the soluble enzyme fraction. Thiamin pyrophosphate stimulated COa and acetoin production from pyruvate. Evidence is presented that acetoin may arise both from the acetaldehyde and from the a-acetolactate pathway.

SUMMARY: Previous workers have shown that the flagellation of certain bacteria is variable, becoming lateral or polar according to age and conditions of culture. In view of these findings, and because of the morphological and biochemical similarity of the organisms, Lysenko (1958) has equated Pseudomonas noctuarum with Serratia marcescens. It is now suggested that Pseudomonas noctuarum would be better placed in the genus Aeromonas, and that it is similar to an organism provisionally named A. margarita. It is further suggested that all members of the genus Aeromonas could be regarded as non-chromogenic species of the genus Serratia.

SUMMARY: Four morphologically different types of the bifid bacteria can be distinguished, and a classification of these bacteria on morphological basis agrees rather well with earlier groupings based on biochemical and serological characteristics. Morphological features may thus have a taxonomic value as regards the bifid bacteria. A comparison of the morphological characteristics of the bifid bacteria with those of representatives of the genera Corynebacterium, Actinomyces, Propioni- bacterium, Butyribacterium and Lactobacillus revealed that three out of four morphological subtypes showed closest resemblance to the genus Butyribacterium, whereas the fourth subtype (the one referred to in the literature as Lactobaci llus bifidus var. pennsylvanicus) may be related to Actinomyces. Thus, the designation Lactobacillus bifidus for these bifid bacteria seems clearly wrong.

SUMMARY: Some strains of Group D streptococci are capable of coagulating cit- rated rabbit plasma. This reaction is not due to citrate utilization but to a specific agent elaborated by the organisms; this agent is probably enzymic in nature. The addition of 5 units heparin/ml. to the citrated rabbit plasma inhibits coagulation by streptococci and makes the reaction more specific for staphylococci.

SUMMARY: Cultures of 351 miscellaneous Gram-negative rods including 54 pseudomonads were tested for their capacity to break down arginine rapidly by Møller’s qualitative technique, by a new qualitative method, and by a quantitative technique which uses standardized washed suspensions. All but 5 of the pseudomonads gave positive results by both qualitative techniques. Among the other organisms tested, positive results were given by Aeromonas strains, some Cloaca strains, some Salmonellas, and, in the case of the new qualitative technique, by 5 strains among other groups. With the quantitative technique 50 % of the arginine was broken down in 2 hr. by all but one of the pseudomonads as compared with only four strains among the other groups. The arginine was broken down completely by 49 of the 54 pseudomonads, but by no other organisms. The ability to break down arginine rapidly is a useful taxonomic feature for pseudomonads and the qualitative tests may have practical value in the identification of strains which do not produce pigment.

SUMMARY: An irreversible cessation of growth, accompanied by the death of the growing tips and. the appearance of an intense brown pigment, is a regular feature of aged clones of Aspergillus glaucus. The frequency of this phenomenon, referred to as ‘vegetative death’, varies between clones of similar age and between identically maintained lineages of the same clone. It also varies with the method of propagation and with the other factors which affect the speed of ageing.

The heterokaryon and related tests show that vegetative death is cytoplasmic in origin while its segregation in the asexual progeny of colonies with mixed cytoplasms, and its infective spread via hyphal anastomoses, clearly define it as mutational in origin. Vegetative death involves a qualitatively different kind of cytoplasmic change from that previously found in the earlier stages of ageing.

In common with some other cytoplasmic mutants, those responsible for vegetative death suppress their wild type counterparts in cytoplasmic mixtures even though they are incapable of continued survival except in such mixtures. In this respect they differ from the generally reported behaviour of mixtures of mutant and wild type nuclei in heterokaryotic association. It is suggested, however, that the behaviour of either may be atypical, since most of the heterokaryons investigated will have been chosen for their stability, while a cytoplasmic mutant which was not suppressive is unlikely to be recognized and isolated by present techniques.

SUMMARY: Examination of the antibiotic powers towards bacteria and moulds of 150 strains of yeasts from the British National Collection of Yeast Cultures has revealed that whereas none exhibited marked antibacterial properties certain of them inhibited the growth of moulds. Strains of Candida pukherrima, when grown on a malt+yeast-fpeptone+glucose agar medium inhibited the growth of strains of certain Mucor, Fusarium and Penicillium spp. The inhibition was due to pulcherriminic acid, a derivative of the red pigment, puleherrimin, formed by Candida pulcherrima. It inhibited growth of the moulds completely at 5000 p.p.m. and partially at 500 p.p.m.

SUMMARY: The spore wall of Bacillus subtilis is composed largely of structural protein, in contrast to the peptide+amino sugar + sugar complex of the wall of vegetative cells. Alanine, glutamic acid, α ε-diaminopimelic acid, glucosamine, muramic acid, glucose, ribitol compounds and O-ester groups are the principal constituents of the vegetative cell walls. All of the compounds characteristic of the peptide+amino sugar+sugar complex have been detected in the spore wall preparations but they account only for a minor part of the spore wall. The walls of the vegetative bacteria have a high phosphorus content and contain appreciable amounts of a ribitol phosphate polymer. Spore walls and vegetative cell walls differ also in the nature of their N-terminal amino acids; glycine is the principal N-terminal amino acid of the spore wall protein whereas alanine is the main amino acid found in the wall of vegetative cells.

SUMMARY: The rate of division of lysogenic bacteria in infected animals can be estimated by superinfecting the bacteria with a suitable mutant of the prophage before inoculation. Since, as shown by other workers, the mutant phage is usually stable and does not multiply during bacterial growth, the proportion of bacteria carrying the mutant steadily falls in a predictable manner in each bacterial generation. Comparison of the proportions of superinfected bacteria present at the start and at the end of a known period therefore gives the number of bacterial generations occurring in a known time. It is assumed that there is no selection either for or against superinfected bacteria.

Mice were inoculated with Escherichia coli strain K12, lysogenized by phage λb and superinfected by phage λhc. The proportion of superinfected bacteria in the spleen did not usually change in the 30 hr. following inoculation. Hence, this strain of bacteria cannot produce viable progeny in the spleen.

The behaviour of the superinfecting phage differed in two ways from that described by previous workers. First, only part of the adsorbed phage was recovered after induction by ultraviolet radiation. Second, the proportion of bacteria which yielded superinfecting phage sometimes fell very rapidly when superinfected overnight cultures were diluted in a medium which allowed bacterial multiplication. This phenomenon is referred to as ‘unstable superinfection’.

SUMMARY: The infectivity of nucleic acid preparations made by disrupting tobacco mosaic virus with phenol was increased, relative to that of intact virus, by keeping test plants in darkness or at 37° for some time before they were inoculated. The differences in susceptibility to infection of leaves in different physiological states was too great to be explained by differences in the ability of leaf extracts to inactivate nucleic acid preparations in vitro. The spontaneous inactivation of the preparations in vitro was not prevented by inhibitors of ribonucleases and most additions to the preparations increased the rate of inactivation. Not all the inactivations are readily explicable on the assumption that the minimal infective unit is a pure nucleic acid built up solely from nucleotides. Leaf sap and saliva are reasonably assumed to inactivate because they contain ribonuclease; also, inactivations by formaldehyde phenylglyoxal, and thiaminase in the presence of thiamine, may well reflect reactions with known components of nucleic acids. However, it is less easy to invoke such actions to explain the inactivation by spermine, ‘interferon’, some oxidizing agents, leaf mitochondria in the presence of some other substances, and the greater rate of inactivation in vacuo than in air. Although nucleic acid seems essential for infectivity, it seems prudent to suspend judgement about the precise chemical identity of the minimal infective unit.

SUMMARY: A large collection of Staphylococcus aureus strains of human origin was examined for ability to inhibit the growth of Corynebacterium diphtheriae on the surface of solid media. Inhibition with the formation of a sharply-defined zone was produced by members of S. aureus Type 71, by certain closely-related strains, and by very few others. A small number of strains gave a wider hazy zone of inhibition. Both types of zone were produced by agents which diffused through agar, but not through cellophan, and killed C. diphtheriae. The two sorts of agent differed in their spectrum of activity for other corynebacteria. Strains of S. aureus which produced sharp zones of inhibition of C. diphtheriae also had a weak inhibitory activity against strains of S. aureus which were non-inhibitors or producers of hazy zones, but not on others which produced sharp zones. Ability to give rise to hazy zones persisted indefinitely in culture, but ability to produce sharp zones was regularly lost in culture after a few months. Loss of activity was accompanied by a widening of the susceptibility of the staphylococci to lysis by typing phages.