- Volume 7, Issue 3-4, 1952

SUMMARY: Thirty-eight methods or modifications of methods for removing trace metals from nutrient media were tested, using Aspergillus niger as test organism to indicate deficiencies.

The most marked symptoms of Zn and Fe deficiencies were obtained after treatment by the Al2O3 or dithizone + oxine methods, of Cu and Mn deficiencies by the Al2O3 method, and of Mo deficiency by Nicholas's method which involves co-precipitation with sulphides of Cu and Pb. Four strains of A. niger differed in their trace element requirements. Shake cultures of A. niger gave less growth in complete medium than did surface cultures, while in deficient media this was reversed. Sucrose peptone and broth media were only partially purified by the Al2O3 treatment. Deficiencies of Fe, Zn and Cu were obtained for Chlorella vulgaris, and of Fe and Zn for Torulopsis utilis, as detected by growth response. Apart from decrease of growth, trace metal deficiency symptoms in Penicillium roqueforti were not very obvious.

SUMMARY: Optimum conditions for acetate oxidation by acetate-adapted cells of Bacterium coli and experiments dealing with the inhibition of this oxidation are described. Quantitative relationships in isotope experiments between precursor and product implicate at least succinate, fumarate and malate in the cyclic mechanism of acetate oxidation by this organism. The involvement of additional compounds in the oxidation of acetic acid is not excluded by these experiments. However, compounds more oxidized than acetate, such as glycollate and glyoxylic acid, are shown not to be involved in the oxidation of the C2-fatty acid.

SUMMARY: Strains of Rhizobium from a wide variety of host plants were found to possess either a complete or a reduced life cycle. In the former, which was characteristic of strains from certain wild legumes and garden flowers, the bacteroids within the nodule were branched and septate; the free-living stages included small Bacterium-like forms which were responsible for infection of the host plant, and large, occasionally Gram-positive forms resembling Bacillus, which produced both specialized, coceoid swarmers and resistant endospores. The reduced cycle was commonly found in Rhizobium from cultivated field crops. The bacteroids were single cells of irregular outline; the free-living stages were reduced to the Bacteriumlike stage alone, sometimes so actively motile as to perform the function of swarmers. This condition is regarded as degenerate and due to a parasitic habit. The mode of formation of the endospores, which differs in detail from that of Bacillus, is described. The morphology of various stages in the life cycle and a slight tendency to Gram-positivity render it apparent that Rhizobium is a specialized genus of Bacillaceae. probably related to the plant parasitic B. polymyxa group, with which it also has biochemical affinities.

SUMMARY: A Perspex housing for a binocular microscope is described and the method is given for the production and maintenance of sterility inside it.

SUMMARY: The assay of inositol has been developed using Kloeckera brevis B 768 and a strain of Schizosaccharomyces pombe. In the assay of Difeo Bacto yeast extract it was necessary to supplement the basal medium with an inositol-free preparation from yeast extract. A new assay design has been proposed and the results treated statistically.

SUMMARY: The growth of Bacterium coli on agar media containing bile salts is conditioned by a number of factors. The proportion of total cells able to grow on a medium not containing bile salts rapidly declines at temperatures of incubation above 43°. On a medium containing bile salts and lactose a distinctly inhibitory effect is observed at 37; with most strains this effect is still more pronounced at 44°. Some brands of bile salts are appreciably more inhibitory than others. Inclusion of phosphate in a bile salts medium introduces a markedly inhibitory factor, the severity of which varies with the strain of organism; some strains are virtually unable to grow on such a medium.

When a culture of Bact. coli is suspended in water containing only small concentrations of inorganic salts an increasing proportion of the population becomes attenuated so that the cells are unable to grow on bile salts lactose agar at 44. An occasional strain may also exhibit sensitiveness to the presence of neutral red. This attenuating effect may be largely decreased if, before the inoculum is mixed with the bile salts and agar, it is subjected to a short period of incubation with lactose broth. This treatment has been made the basis of a technique for obtaining a colony count of Bact. coli which is applicable to polluted waters.

SUMMARY: Agglutinins against Salmonella pullorum and Salm. typhi (strain O 901) were induced in hens by intravenous inoculation with killed suspensions and were transferred to the yolks of their eggs. This transference of antibody continued throughout a laying season of about 280 days, and the relationship between the agglutinin titres of sera and yolks was not close. The titres of yolks seldom rose above 160 even when those in the serum were 2500 and 5120, whereas the agglutinin levels of developing ovules from hens naturally infected with Salm. pullorum were about the same in the related sera.

The sera and egg yolks of hens vaccinated with killed Salm. pullorum or infected with Salm. gallinarum contain a non-agglutinating antibody. The titres of nonagglutinating antibody in sera and in related egg yolks were about equal when hens were inoculated intravenously; very little antibody was demonstrable in fresh egg yolks after intramuscular or subcutaneous administration. Hens infected with Salm. gallinarum by the mouth yielded high yolk titres of agglutinating and non-agglutinating antibodies and these titres were maintained at a high level throughout the experimental period of 474 days. The results suggest that some of the antibody in egg yolk is formed in the follicular epithelium of the developing ovule or in the yolk material itself.

A passive immunity to Salm. pullorum is transferred from vaccinated hens to their chicks by the egg yolks and antibodies pass from yolk to embryonic serum from about the 11th day of incubation. The titres in the serum of the newly hatched chick are about the same as in the egg yolk before intubation and they decrease rapidly during the first 3 days and have almost disappeared by the 17th day; from the 8th day until the 17th day non-agglutinating antibodies alone are demonstrable. Antibodies are absorbed from the yolk through the vitelline and hepatic portal circulations and little or none is transferred by the yolk stalk and the chick’s intestine.

SUMMARY: The reproductive processes occurring in mycobacteria were studied in mycelial strains of avian tubercle bacilli and the developments recorded by phase-contrast microscopy. Three main developments were traced: (1) Disintegrating mycelial branches release micro-rods (as small as 0·2 μ.), which later elongate into bacillary forms. (2) Parts of some mycelia produce filamentous sprouts which grow into entangled nests of filaments, and finally give rise to spherical colonics of short rods. (3) Some mycelial branches become swollen and very dense. Later they become more transparent and parallel rows of filaments are revealed lying orientated along the length of the branches. The typical morphology of orientated and non-orientated growth is explained with reference to the modes of development. Growth is preceded by a stage of mycelial proliferation, which is mainly non-acid-fast, but results in microeolonies of the normal acid-fast rod. The relation between some atypical structures and L-forms is discussed.

SUMMARY: Ten antibiotics have been included in this study; eight of them were metabolic products of fungi isolated from soils of the Bagshot Sand type. Their stability in Bagshot Sand soils and in a neutral garden loam has been investigated. Some were more stable than others, the rate of inactivation varied from soil to soil, but all exhibited a fair degree of stability in some of the soils. Four types of inactivation could be distinguished: (1) The natural pH of the soil was sometimes that at which the antibiotic was intrinsical unstable; this was noted specially with albidin, frequentin, gliotoxin, penicillin and viridin. (2) Inactivation caused by some form of biological activity, indicated by less rapid inactivation in heattreated than in untreated soil, was observed with griseofulvin, mycophenolic acid and patulin. (3) Adsorption on the soil was noticeable only in the case of streptomycin, the only basic antibiotic studied: acid-washed sand was able to bind appreciable quantities of this antibiotic, (4) Some other form of inactivation, probably chemical in nature, was concerned in the inactivation of gladiolic acid, penicillin and streptomycin.

SUMMARY: Pleuropneumonia-like organisms (PPLO) of human origin are very susceptible to the deleterious action of soaps. There was no significant difference in the antibacterial action of soaps containing 2% hexachlorophene and an ordinary-hand soap, on the pleuropneumonia-like organisms tested. The great susceptibility of these organisms to soap probably masks any action which the hexachlorophene contained in the medicated soaps might have on PPLO. The deleterious action of soaps on pleuropneumonia-like organisms is bactericidal.

SUMMARY: Four different antigenic types of coagulase were identified. Antisera were prepared in rabbits against three of these, and a specific antiserum against the fourth was found in a normal human. The coagulases of all but two of the human strains examined were inhibited by one or other of two of these antisera and in a few cases by both; in addition antibodies of the same type were present in the sera of the majority of a group of normal adults. The coagulases produced by thirty-five animal strains were inhibited by the other two antisera, but further work is needed on the coagulases found in animal strains.

SUMMARY: The ‘B’ virus (strain no. 1) of the 68th rabbit passage has been successfully transmitted to Swiss albino mice and carried through ten passages in this species by intracerebral inoculation. This virus produced symptoms of irritability and involvement of the central nervous system in these mammals. Paralysis occurred in mice from the 6th to the 10th passages. Virus-bearing material from the 10th intracerebral mouse brain passage upon being injected intradermally into unvaccinated rabbits produced paralysis but had no effect on rabbits previously immunized against ‘B’ virus.

SUMMARY: The effect of heat, HgCl2 and cetrimide on decarboxylase systems of some typical lactic acid bacteria and coliform organisms has been investigated. The enzymes appeared to be reversibly inactivated by heat, for the cultures in milk and in broth retained considerable decarboxylase activity after having been heated to 100 for 60 min. Furthermore, decarboxylation continued after sterilization of the cultures with HgCl2, and with cetrimide.

SUMMARY: Bacterium coli was killed rapidly when shaken with glass beads. The bacteria were killed before they were disintegrated. The effect on this process of size of bead, speed of shaking, density of suspension, and size of container were investigated and optimal conditions for bacterial destruction were ascertained.

Two serologically unrelated strains of nodule bacteria produced two different polysaccharides, only one of which precipitated with antiserum to its parent bacterium. Both polysaccharides interfered with the multiplication of two bacteriophages in liquid cultures of the two bacterial strains, each of which was susceptible to only one of the two bacteriophages. One polysaccharide was slightly more effective than the other in interfering with multiplication of both bacteriophages: one phage was much more susceptible than the other to the interfering action of both polysaccharides. Crystallized pancreatic ribonuclease interfered with multiplication of bacteriophages much more strongly than did the polysaccharides. Neither the polysaccharides nor ribonuclease destroyed the phage particles.

Cellulolytic iodophilic cocci have been isolated in significant numbers from rabbit caecal contents. Seven strains of the anaerobic Gram-positive cocci have been isolated on seven separate occasions from rabbits obtained from different sources and maintained on various diets. No other cellulolytic bacteria have been observed in cultures inoculated with high dilutions of caecal contents, suggesting that the isolated cocci are the most important agents of cellulose digestion in the caecum.

Of the carbohydrates tested the caecal cocei utilize only cellulose and cellobiose. The products of cellulose fermentation include acetic acid, succinic acid, a trace of formic acid, ethanol, CO2 and H2.

Spore trapping by the Petri dish method showed the incidence of airborne Cladosporium herbarum spores, which fluctuated markedly from day to day, to be similar in Central London and in an outer suburb throughout the year.

Many strains of Corynebacterium diphtheriae carry phages capable of lysing other strains. Diphtheria phages are type-specific and do not lyse strains which are serologically unrelated but susceptibility to a phage may vary among different members of the same serological type and this can be used to differentiate subtypes of different biological behaviour. Phage-resistant mutants are readily selected in diphtheria cultures and the resistant mutants frequently have characteristics quite distinct from those of the parent strain, e.g. virulent organisms have been isolated from a number of avirulent strains. It is suggested that the possibility of converting avirulent strains to virulent ones may be of importance epidemio-logically and that the phage selection of mutants may account for the wide variety of serological types isolated from patients. Some strains found to be resistant to type-specific phages have been shown to be lysogenic and when subjected to ultraviolet irradiation liberate phage particles which are capable of lysing susceptible strains of the same serological type. The diphtheria phages investigated are thermolabile. difficult to filter, of fairly large size and give rise to small plaques of lysis with susceptible strains.

Examination of the action of a series of surface-active polyoxyethylene ethers on the growth of the avirulent strain of Mycobacterium tuberculosis, H37 Ra, showed that one member, the ether of 2,2′-dihydroxy-5, 5′-di-tert-octyldiphenyl-methane (D4), inhibited this strain but not the virulent variant H37 Rv. This type of differential inhibition has been observed with a commercial surface-active mixture, ‘Triton A20’ (Dubos & Middlebrook, 1948). Lengthening of the polyoxyethylene chains of D4 led to loss of its inhibitory property. Both D4 and ‘Triton A20’ could induce resistance in H37 Ra, and cross-resistance to D4 of a strain resistant to ‘Triton A20’ was observed; this cross-resistance suggested that a compound closely related to D4 was the active constituent of ‘Triton A20’. The resistant strains grew in a microscopically amorphous pattern, like their parent strain.

The growth of four other avirulent strains of tubercle bacilli was inhibited, like that of H37 Ra, by D4, while two slightly virulent strains grew freely in this detergent, like H37 Rv. One factor common to the strains naturally insusceptible to D4, but absent from those inhibited, is the ability to produce some degree of microscopic ‘cord’ pattern, and this property may have some connexion with the cause of the differential inhibition by D4. Surface activity also probably plays a part.