- Volume 5, Issue 3, 1951

SUMMARY: An internal organization is revealed in resting spores of Bacillus spp. by brief treatment at room temperature with n-HNO3 or, more effectively, a mixture of n/3-HNO3 (or HCI) with 0·1 % potassium permanganate. Two distinct steps are involved: the first initiates the reaction without visible changes in the spore; the second is an instantaneous process which abolishes the refractility of the spore and allows staining of the contents. These differentiating procedures have no observable effect on vegetative cells, and the spore's response to them is abruptly abolished with the onset of germination. They are ineffective on heat-killed spores and are inhibited, under certain conditions irreversibly, by 0·5–1 % sodium fluoride. Differentiating reagents probably act indirectly by stimulating abnormal chemical activity of the spore.

Three structures, interpreted as the outer spore membrane, nucleus and cytoplasm, can be distinguished in treated spores. Differentiation does not alter the size or the shape of the spore but shrinks the cytoplasm away from the membrane and, in permanganate-containing mixtures, changes the configuration of the nucleus. The extent of these rearrangements varies with the temperature at which differentiation is carried out. The nucleus is on the outer surface of the cytoplasm and connected with it by a short narrow stalk. The nucleus gives a positive Feulgen reaction. Nucleus and cytoplasm of spores differentiated with n/3-HNO3 or HCI containing 0·1% of KMnO4 are soluble in phosphate buffers at pH 6·3–7·6 and m/16 sodium acetate at pH 7·4. Nucleus and cytoplasm are insoluble in these solutions after differentiation with n-HNO3, but the nucleus of spores treated in this way is destroyed by trypsin in phosphate butter.

The existence of a second, inner, spore membrane, jointly surrounding nucleus and cytoplasm, is postulated. This layer is believed to be the seat of the spore's bright retractility and imperviousness to stains.

The huge spores of Metobacterium polyspora react like Bacillus spores to differentiating reagents and permit direct observation of the act of transformation from the featureless to the differentiated aspect of the spore.

The proportion of lysogenic cultures in five species of salmonella examined varied from 84% in Salmonella thompson to 0% inS. pullorum.

When estimating the amount of phage present in lysogenic cultures of S. thompson it was possible to obtain a plaque count approximately equal to the number of bacteria present in these cultures when the susceptible culture used for determining the counts was used relatively dilute. When used less dilute the counts were lewer and equal to those obtained when the bacteria were killed by heating to 56 for 30 min. This lower figure is an estimate, of the free phage in the culture.

Plaque size varied inversely as the amount of bacteria in the susceptible culture. When lysogenic cultures were used for counting a related phage, plaque size was diminished by partial interference.

Two types of relationship were noted between the growth rate of bacteria and phage in artificially induced lysogenie cultures of S. thompson. In one, the number of free phage particles was always directly related to the number of viable bacteria present; in the other, the phage particles increased rapidly in number during the logarithmic phase of bacterial multiplication and then decreased rapidly due presumably to their absorption by the bacteria.

The active infection of the lysogenic cultures with an unrelated phage usually resulted in an increased-yield of the phage with which the culture was latently infected. In one instance the latent infection was transformed into an active one.

All the artificially induced resistant variant strains of S. thompson were lysogenic. It was impossible to make some cultures permanently resistant to two different phases as the resulting cultures were unstable and soon showed signs of active infection. Others were made with a difficulty not experienced during the making of singly resistant strains. Most of these were latently infected only with the first phage to which they had been made resistant: others carried both phages.

By the use of seven phage preparations, forty-one of fifty smooth strains of Salmonella thompson were classified into eleven types. The remaining nine strains were insusceptible to all the test phages; mouse passage did not render them susceptible. Acquired phage resistance was responsible for many of the strains being regarded as different phage types. A study of phage-resistant variants cast doubt on the complete validity of Bail's cross-resistance tests. The danger of using lysogenie cultures for the propagation of phages for the study of phage mutation were noted. Most of the S. thompson phages were fully active against strains of S. cholerae-suis but not for other Salmonella sp. that were tested.

Magnesium exerts a specific function in (a) the formation of the Gram complex, and the activation of cell division in certain Gram-positive bacteria, and (b) activation of bacterial growth. Of a series of divalent metallic ions, only manganese is capable of partially replacing magnesium in the above processes.

SUMMARY: The growth of bacteria in chemically-defined media containing mixtures of amino-acids is less dependent upon the magnesium concentration than in simple media composed of saits, glucose or glycerol and a single source of nitrogen. In the more complex chemically-defined media growth initially increases rapidly with, and then becomes independent of, the magnesium concentration. Gram-positive bacilli jail to grow when the magnesium content of the medium is less than 0·66 p.p.m., whereas this amount of magnesium is almost sufficient to maintain maximum growth of the Gram-negative bacteria. In addition, a deficiency of magnesium (i.e. c. 1–5 p.p.m.) inhibits the cell division of the Gram-positive rod-shaped organisms, and results in the formation of filamentous cells.

SUMMARY: The chains which are formed when rod-shaped Gram-positive bacteria are grown in media containing low concentrations of magnesium, undergo fission when exposed to the action of lysozyme. This effect is not produced by various other hydrolytic enzymes including the carbohydrases, cellulase and hyaluronidase, Fracgmentation of the filameatous forms of the Gram-positive organisms, however, is not produced by lysozyme.

A crude preparation obtained from mechanically disintograted Clostridium welchii cells resembled lysozyme in its action on the magnesium-deficient organisms.

SUMMARY: The growth requirements of a strain of Schizosaccharomyces octosporus were studied by auxunographic and tube tests. The organism grows satisfactorily on a glucose + mineral salts medium containing asparagine and ammonium sulphate, provided also that inositol, pantothenic acid, nicotinic acid, biotin, histidine, methionine and adenine are added. Complex interactions between adenine and guanine were found, and for this reason S. octosporus cannot be regarded as a suitable test organism for the assay of adenine.

SUMMARY: Pyrnvie acid accumulates in aerated cultures of Aerobacter aerogenes during logarithmic growth and disappears rapidly in the stationary phase. The amount accumulated depends upon the carbon source utilized, being greatest with glucose and malic acid and least with acetic acid, of the compounds studied. For aerated washed suspensions of cells trained to metabolize glucose, malate, fumarate or succinate respectively the rates of pyruvate production for various substrates are in the order: rate in malate > fumarate > succinate > acetate. Only cells trained to metabolize acetate produce pyruvate from acetate as fast as from suecinate and fumarate. When ammonium sail solution is added to these suspensions accumulation of pyruvate ceases.

Rates of pyruvate production at various substrate concentriation by washed suspensions accord with a kinetic scheme in which pyruvate appears as a transitory intermediate in a reaction sequence. Results are not compatible with the existence of the tricarbosylic acid cycle in bacteria.

SUMMARY: In this blender the container and cutter assembly can be removed for heat sterilization. A cotton-wool gland maintains sterility during blending.

SUMMARY: The life cycle in Sporocytophaga closely resembles that of the non-sporing eubacteria.

The haploid microcyst germinates, the resulting cell containing two paired chromosomes reproducing vegetatively. An autogamous fusion and subsequent reduction division precede the maturation of the microcyst.

Sporocytophaga differs from Myxococcus by the absence of fruiting body formation, and in the details of its nuclear cycle. These bacteria may possibly be regarded as the ancestors of the higher myxobacteria.

SUMMARY: From a study of the mode of production of the l-phase from the bacillary phase and of the reversion of the l-phase into bacilli, by phase-contrast microscopy and in stained preparations, it appears that the l-cycle is a process of regeneration in bacteria.

SUMMARY: An examination of freshly isolated Haemophilus pertussis strains for agglutinability, growth requirements, haemagglutination, virulence for mice, alum precipitability and protective properties shows that each of these characters varies quantitatively, and furthermore that they vary independently. The presence of one strongly marked character is no indication that another character will be strongly marked or even present. Not all strains necessarily have the character to be expected in freshly isolated strains; one or possibly more may be missing. On subculture of the strains on Bordet-Gengou media the order in which these characters degenerate or are lost and the rate at which they are lost differs with the strain. Agglutinability and agglutinogen content vary considerably in freshly isolated strains, and therefore the expression ‘agglutinates to titre’ cannot be considered as a criterion of a Phase I organism. The obvious complexity of the serology of organism within ‘Phase ’ suggests that this term has served its useful purpose and should now be dropped as a description of a certain type of strain. The term ‘Smooth’, which indicates the possession of the antigenic components commonly associated with the pathogenic state of the organism, is preferable.

SUMMARY: A modification of the Hirst & Pickels photoelectric densitometer and its application to work on influenza virus haemagglutination are described. The methods used are believed to reduce to a minimum the inherent margin of error of virus and serum antibody assays based upon the haemagglutination reaction. In order to make full use of data thus obtained precise assessment of the significance of differences of titre is essential, and for this purpose two simple statistical tests have been applied and their application illustrated by an example.

SUMMARY: Cultures of Aspergillus niger partially deficient in zinc produce much larger quantities of acid per unit of glucose used than do normal cultures. This fact has been the basis of the current suggestion that zinc plays a part in the utilization of carbohydrate by fungi. The experiments described here show that partial deficiencies, not only of zinc but also of iron, copper, manganese, phosphorus, magnesium and potassium all had a similar effect on the production of acid by a strain of A. niger. It would appear that the effect of zinc on the way in which carbohydrate is utilized is not a specific effect and indicates no more about the role of zine than about the role of any other inorganic nutrient.

SUMMARY: Using a defined medium capable of purification free from trace elements the relationship between the latter and streptomycin production by Streptomyces griscus was investigated. Zinc and copper were essential for antibiotic production in as much as they were essential for growth. In the case of iron, approximately five times as much was required for antibictic production as for growth alone. It was not possible to demonstrate that manganese was essential for either growth or antibiotic production.

SUMMARY: The finding of a pleuropenumonia-like organism associated with infertility and epididymitis in a dog led to the examination of throat and vaginal swabs from all the animals in a breeding kennel. Pleuropneumonia-like organisms were isolated from the majority of samples. Strains differed in colonial appearances, and a classification into types based on these differences was confirmed by the serological demonstration that each type was antigenically distinct. Nearly all the strains belong to one of three types, provisionally called α, β and γ. Each type was regarded as a distinct species of the pleuropneumonia group, and its biological properties were studied.

SUMMARY: Representative strains of the pleuropneumonia group, originally isolated from animals, grew well on a basal medium containing infusion broth, peptone, yeast extract and agar when this was further enriched with horse serum. The serum could be replaced by an ethereal extract of egg-yolk and fractionation of this suggested that cholesterol might be the active substance promoting growth. Growth was obtained when cholesterol (0·01 mg./ml.) was added to the basal medium, together with starch or bovine albumin. Addition of the acetone-insoluble fraction of egg-yolk with cholesterol gave better results, growth of six of the eight strains tested being equal to that on serum agar; the lecithin and kephalin fractions after purification were less effective. No growth was obtained when starch, bovine albumin or the acetone-insoluble lipid was added to the medium without cholesterol. Cholestanol and stigmasterol were as effective as cholesterol in promoting growth. Oleic acid in high concentrations (> 0.05 mg./ml.) inhibited growth. Both lipid and protein fractions of serum appeared to be concerned in its ability to promote growth.

SUMMARY: An organism was isolated from soil, which grew in a basal mineral medium with either 3-methylglucose or 3-methylfructose as sole source of carbon. The bacterium is a member of the coli-aerogenes group, intermediate type 1. Grown in presence of either methyl-sugar, under suitable conditions, washed suspensions of the organism oxidize either 3-methylglucose or 3-methylfructose. Under anaerobic conditions, the two methyl-sugars are broken down with the formation of hydrogen, carbon dioxide and acid. The ability to attack 3-methylglucose or 3-methylfructose was acquired by growth in presence of either of the two methyl-sugars but not in the presence of glucose.

SUMMARY: In certain strains of Rhizobium spp., tiny spherical swarmers, with a central nucleus and one or occasionally two flagella, are released from the cell lumen of specialized large bacilli, the barred forms, of which the bars are modified crosswalls. The swarmers exhibit appearances suggestive of conjugation.

In other strains true swarmers are not produced; their function is performed bysmall motile cells produced by normal cell division.