- Volume 29, Issue 4, 1962

SUMMARY: The establishment and components of the rumen ciliate population in a series of young animals has been followed using intra-ruminal inoculation with rumen material, and for comparison purposes the ciliate population in a number of adult ruminants has been examined. The fact that the ciliates Polyplastron multivesiculatum, Eudiplodinium maggii and Epidinium spp., though not host specific, did not form a stable mixed population was noted and experiments were carried out to examine the antogonism between certain of these organisms. The cause of the antagonism was not determined but cannibalism, food competition, or gross bacterial change did not seem to be responsible. It was found that the population of an adult animal could be changed by inoculation but the relationship between the ciliates appeared to be in some way affected by the host. It is concluded that inter-relationships of the type described may play an important role in determining the components of a particular rumen microfauna.

SUMMARY: The enzymic mechanism of D-and L-lactate catabolism was the same in several strains of Acetobacter and Gluconobacter. This was taken to indicate a close relationship between these groups. Both isomers were broken down by way of pyruvate and acetaldehyde to acetate. Identical reactions were carried out by two sets of enzymes of a different nature and localization, one particulate, the other soluble. All strains contained a constitutive, soluble pyruvate decarboxylase which required thiamine pyrophosphate and Mg++. When grown on lactate, a pyruvate decarboxylase was also present in the particulate fraction. No evidence was found for a pyruvate oxidase system. Acetaldehyde was oxidized by a particulate oxidase system and by NADP-and NAD-linked dehydrogenases. This last enzyme was activated by coenzyme A and glutathione. The particulate pyruvate decarboxylase was not very tightly bound to the particles, as it could easily be detached by washing with buffer. The oxidase systems could not be removed under these conditions.

SUMMARY: A sensitive method for the assay of μg. amounts of megacin is described. Sensitive organisms adsorb megacin and the saturation concentration is similar to bactericidal concentrations. The death of megacintreated organisms is, however, not coincident with adsorption but can be delayed or prevented by incubation at low temperature. Post-adsorption death is in fact proportional to the incubation temperature. Bactericidal amounts of megacin transform protoplasts of sensitive organisms to empty spherical ghosts and also appear to disrupt the permeability barrier of whole organisms. Megacin does not, however, degrade isolated or intact cytoplasmic membranes.

SUMMARY: The cultural, biochemical and morphological characteristics of six cultures of Simonsiella and four cultures of Alysiella are described. The multicellular filaments of both Simonsiella and Alysiella, originally termed ‘disk-bacteria’, are ribbon-like, non-sporing, non-branching, aerobic and Gram-negative. They are greater than 2 μ wide, exhibit gliding motility on solid media and ferment carbohydrates. The family Simonsiellaceae fam.nov. is proposed to include the genus Simonsiella Schmid and the genus Alysiella Langeron. Amended descriptions of the species Simonsiella crassa Schmid and of Alysiella filifornis (Schmid) Langeron are given.

SUMMARY: Four methods were employed to study the immediate fate of staphylococci within leucocytes after phagocytosis. These were: (a) The method of Cohn & Morse where leucocytes and staphylococci were mixed in tubes and kept agitated. Periodically samples were removed and lightly centrifuged to sediment the leucocytes. Plate counts were made on the lysed leucocytes to measure the intracellular organisms, the supernatant to measure the extracellular population, and a non-centrifuged sample to determine the total number of viable cocci present. (b) Concentrated suspensions of leucocytes and staphylococci were packed together by brief centrifugation to permit rapid phagocytosis without antibodies then diluted in cold Hanks solution to stop further phagocytosis. The suspension was then rapidly passed through a Servall centrifuge with the continuous flow attachment to remove excess extracellular organisms. The infected leucocytes were placed in suspension and samples removed and treated as in the previous procedure. (c) Leucocytes and staphylococci were placed in plastic chambers containing a number of small coverslips. The cells were allowed to sediment and adhere to the coverslips, then washed to remove most of the extracellular organisms. Coverslips were removed at intervals and attached leucocytes lysed to liberate intracellular cocci which were enumerated by plate counts. Companion coverslips were washed, fixed, and stained in order to count the number of leucocytes present. The extracellular staphylococcal population was estimated by making plate counts on the tissue culture medium in the chambers. (d) Suspensions of infected leucocytes were diluted and placed in a series of Petri dishes. The cells were permitted to settle and attach to the glass. Periodically the plates were washed and melted trypticase soy agar was added. After incubation the plate counts afforded an estimation of the viable cocci remaining within the leucocytes at each sampling.

The results obtained with these procedures were in fairly good agreement with each other. It was found that Staphylococcus aureus (18-Z and Smith strains) survived in significant numbers within monocytes and polymor-phonuclear leucocytes of normal rabbits for several hours. Little destruction of this organism during the first hour after phagocytosis could be demonstrated.

SUMMARY: It was found that Staphylococcus aureus usually survived within monoeytes of normal rabbits for several hours without multiplication, but were eventually destroyed. However, there was variation in the intracellular behaviour in leucocytes of different rabbits in that cells from some donors began the slow destruction of the staphylococci shortly after phagocytosis.

In many of these experiments streptomycin was incorporated in the tissue-culture medium to suppress the extracellular multiplication of staphylococci. Interference by streptomyein with the intracellular be-haviour of staphylococci was considered as minimal on the basis that the intra ellular survival was not influenced by different concentrations of the drug in the tissue-culture medium nor did incubation of the cells in the antibiotic before infection alter the subsequent survival of the organisms.

SUMMARY: Organisms of the phytoflagellate Prymnesium parvum Carter undergo swelling and lysis in the presence of ammonia or acetic acid. The lytic activity was pH-dependent and increased as the concentration of undis-sociated weak electrolyte in the suspension medium was increased. The kinetics of swelling were followed with the aid of an electronic particle coounter and by microscopic examination. In the presence of ammonia or acetic acid, the rate of swelling as well as the final volume of the Prym-nesium organisms were a function of external osmotic pressure and of temperature. It is suggested that the swelling and lysis are osmotic in nature and depend on the intracellular accumulation of weak electrolytes by a ‘pump’ driven by differences between environmental and intracellular pH values. The similarities between this phenomenon and concentration of weak electrolytes in mammalian erythrocytes and other cells is discussed. Differences in the morphology and lysis of Prymnesium by ammonia and acetic acid were found which suggest the existence of intracellular compartments maintained at different pH values.

SUMMARY: Strains of Salmonella typhimurium Q1, lysogenized with type A phages, were superinfected with the heterologous free phages of the same group. This produced lysis (productive or vegetative development) and prophage change (either prophage substitution or double lysogenization) in a constant pattern. Prophage change was frequently detected when lysis was absent. Certain of the phages were aggressive, producing active lysis and prophage change in many of the heterologous lysogenic strains, others were intermediate and some were non-aggressive. In general, aggressive phages in prophage form conferred a good degree of immunity on the host bacterium, while non-aggressive phages did not: but to this rule there were exceptions. In most cases, immunity to lysis and immunity to prophage change ran an approximately parallel course, but again there were exceptions. Some strains, with certain superinfections, were immune to lysis but not to prophage change, while others showed greater resistance to prophage change than to lysis. The reaction to superinfection split the series into two groups. Superinfection of a lysogenic organism of either group with phage of the same group produced—if there was any prophage change—prophage substitution: superinfection of a lysogenic organism of one group with phage of the other group produced double lysogenization. Each group of phages had therefore its own site of attachment to the bacterial chromosome. Immunity appeared to be due neither to defective adsorption nor to steric interference, but to repressers with specific characters which varied from strain to strain.

Summary: It is the first occasion in this series of lectures in which the major part of the problem under discussion concerns the work of the lecturer himself. This is rather like entering the confessional in public, and you will forgive me, I know, for having provided myself with a few lantern slides in order to darken the room from time to time. A diffieulty that became very real to me in preparing this lecture was to recall my actual processes of thought at the time of this work 21 years ago. So much has happened since which has a direct bearing on it that it is extremely difficult to cast out things which have since become, so to speak, part of my phenotypic constitution. However, I will try to be strictly honest and if things in fact did not occur in the way in which, in the light of the present knowledge, they ought to have occurred, this is not my fault. I am instructed to discuss the interplay of theory, experiment, models and chance in my work; this means that I really have to be frank!

SUMMARY: Foamy virus has occurred in 40–60 % of vervet, rhesus and cynomolgus monkey kidney tissue cultures, but has been absent from Erythrocebus patas cultures. Factors influencing its passage in tissue culture have been investigated. The virus is sensitive to ether and chloroform. Ultra-centrifugation indicated a particle size of greater than 70μ. No hacmag-glutination or haemadsorption could be demonstrated with erythrocytes from a variety of animals. No reduction in titre resulted from eleven months’ storage of a serum-free suspension at −20°. Stability at other temperatures was determined.

SUMMARY: Spores of Bacillus larvae White germinate and make initial vegetative growth best in a limited range of low redox potentials, but later growth and sporulation occur best aerobically. Different media needed for best results with each phase of development of the bacillus are described. Spores of B. larvae germinate in the mid-gut contents of honey-bee larvae up to 2 days old. The vegetative forms then migrate and become closely applied to, but do not penetrate, the mid-gut epithelium. Most organisms seem to be voided with the contents of the intestine when an infected larva defaecates shortly before it pupates. A few organisms are presumably left in the intestine and probably invade the tissues of the larva as it pupates.

SUMMARY: The lethal effect of cold shock on Aerobacter aerogenes suspensions depended on the time of exposure to low temperature, the growth phase, the concentration of bacteria, the diluent. No death occurred when weak suspensions of susceptible bacteria (about 108/ml.) in buffered saline (pH 6.5) were rapidly cooled to 0° and immediately warmed to 20°, but loss of viability was progressive during 1 hr. at 0°. Bacteria harvested from defined medium at intervals during the exponential growth phase varied in sensitivity to chilling but were more susceptible than stationary phase organisms. While growing in partially synchronized culture the sensitivity of bacteria did not increase significantly during the division lag phase. The viability of dense suspensions (about 1010 bacteria/ml.) in buffered saline was little affected by chilling for 1 hr. at 0°, irrespective of the growth phase. A bacteria-free filtrate from a chilled concentrated suspension of exponential-phase organisms substantially protected a dilute suspension from the lethal effect of chilling. Substances found in protective filtrates were amino acids, adenosine triphosphate and nucleic acid constituents. When added to the diluent in which susceptible bacteria were chilled, a mixture of amino acids afforded some protection; small amounts of adenosine triphosphate had no effect. Other substances found to protect susceptible bacteria were sucrose (0.3 M), magnesium or calcium ions (5 x 10−3M) and, to a much smaller extent, spermine (10−5M). The present results support the suggestion that the lethal effect of chilling is at least partly due to interference with the functioning of a bacterial permeability control mechanism.

SUMMARY: Streptococci isolated from horse faeces and corresponding to the description of Streptococcus equinus Andrewes & Horder (1906) were found to belong to the serological group D. The group D antigen was produced by all the strains examined, but was not always extractable from whole organisms by HCI or formamide; broken organisms, however, always gave group D antigen. Collections of S. equinus and S. bovis strains were found to be physiologically similar, but distinguishable.