- Volume 10, Issue 1, 1954

SUMMARY: Spermine was found to inhibit the growth of various micro-organisms. The most susceptible were Staphylococcus aureus and Staph. albus, Neisseria gonorrhoeae and N. meningitidis, and to a lesser degree Bacillus anthracis. The Enterobacteriaceae were relatively resistant. The action of spermine was enhanced by an increase in pH of the medium. The antibacterial effect was bactericidal; it was slowed but not prevented by a decrease in temperature from 37 to 6°. The nutrients of various media influenced the action of spermine.

SUMMARY: A series of four factorial experiments with culture media was carried out dealing with (1) the action of individual salts and their interactions in the medium, (2) the relation of the nitrogen source to the action of the salts, (3) the effect of the ratio of the carbon source and (4) the proportionate influence of the salts in the medium. Statistical analysis of the results has shown (a) the composition of the culture medium which produces optimal growth under given conditions, (b) that a suitable balance of salts in the medium, while conducive to good growth, is not of over-riding importance to this fungus, and (c) that ammonium nitrate serves as the key nutrient in the balance of salts which produces optimal growth measured as milligrams of dry weight.

Summary: A new species of Debaryomyces has been isolated from the air. It is characterized by a four-spored ascus, the production of a pellicle, lack of pseudomycelium,and the ability to assimilate glucose, sucrose, maltose and galactose but not lactose. It has been named Debaryomyces marama.

Summary: An organism with a new type of polar monotrichous flagella is described. The flagella have a very short wavelength which is very characteristic. The organism liquefies gelatin and oxidizes ethanol to acid. All other common differential tests were negative. The name Pseudomonas diminuta n.sp. is suggested.

SUMMARY: The basis of variation in morphological appearance of first cultures of Fusarium oxysporum f. gladioli, isolated from diseased roots and corms of prematurely yellowed Gladiolus plants, was investigated. The occurrence of mutations is considered to be far too infrequent to account for the wide range of variability of the fungus in culture, and the existence of heterocaryons of mixed morphologically distinct genotypes is considered.

Cytological studies show that each microconidium contains one nucleus which is derived by mitosis from the single nucleus of the conidiophore. Hyphal tip cells contain an average of seven nuclei whilst the cells behind, in the older parts of the hyphae, contain only one nucleus each or, more rarely, two. Anastomoses between germ tubes from conidia of different morphological variants occur very frequently and may provide a means whereby heterocaryons are formed.

Synthesis of heterocaryotic cultures is achieved by simultaneous inoculation of plates containing plain water agar medium. Hyphal tips were separately removed from the mixed colonies thus produced and analysed by single-sporing the resulting colonies. Media varying in carbon content and in carbon/nitrogen ratio proved to have a selective action upon one or other of the homotypes constituting a heterokaryon of two known morphologically distinct variants. By use of such media, it was shown that the ratios of nuclei homotypic for ‘flat sporodochial’ and ‘aerial microconidial’ variants was altered according to the relative concentrations of carbon or nitrogen in the culture medium.

A discussion follows on the bearing of these results on the reliability of hitherto important taxonomic criteria in a classification of these fungi. The isolates of F. oxysporum f. gladioli include a wide range of morphological variants which may be included in Snyder & Hansen’s F. oxysporum. The existence of neterocaryons between taxonomic variants and their plasticity under various cultural conditions, poses the question of their status in any satisfactory classificatory system.

SUMMARY: Colour Mutants Of The Tomato Pathogen, Corynebacterium Michiganense, Provided An opportunity to Determine the nature Of this micro-organism’s pigments, and the effect of mutation and nutrition thereon. The major pigments of C. Michiganense are carotenoids. The parent and mutant strains show distinct qualitative differences in pigment synthesis. The naturally occurring yellow parent type produces cryptoxanthin and lycopene. A pink mutant forms lycopene and spirilloxanthin. A red back-mutant produces only lycopene. An orange mutant synthesizes crypto-xanthin, β-carotene and canthaxanthin. Carotenoids were not detected in the colourless mutants.

Carotenoid synthesis in the yellow strain of C. michiganense is affected by thiamine in a manner similar to that previously described for C. poinsettiae: cryptoxanthin and lycopene are synthesized only at relatively high thiamine concentrations. The formation of lycopene, relative to spirilloxanthin, in the pink mutant is favoured by high thiamine concentrations. Similarly, the red strain forms appreciably more lycopene at higher thiamine concentrations than at lower. The formation of carotenoids in the orange strain appears not to be influenced by external thiamine concentration, possibly because this culture synthesizes an excess of the vitamin. No other nutritional factor which was examined caused detectable alterations in colour of the cells.

SUMMARY: A marine Stichococcus sp. was found to require a growth factor present in small quantities in natural sea water. Probably the same factor was produced in the medium by a bacterium with which the alga was associated when isolated. The factor could be removed from sea water by activated charcoal, and could be replaced by crystalline vitamin B12 (cobalamin).

The marine alga used in this investigation was collected in Great South Bay, Long Island, N.Y., by Mr J. H. Ryther (1954) and was purified as described below. There is some doubt as to the identity of the alga, which is a unicellular form about 2. wide and 26 . long. It has been tentatively assigned by the present author to the genus Stichococcus, and may be identical with S. cylindricus Butcher (1952) .

SUMMARY: The capsules of bacteria and of Cryptococcus neoformans are invisible under the phase-contrast microscope. They can be made visible through addition of a number of proteins at a certain, usually very narrow, pH range lying on the acid side of the isoelectric point of the proteins. The pH range at which the reaction occurs shifts with the isoelectric point of the protein used. The optimal pH range depends, on the other hand, upon the capsular substance of the micro-organism. The non-specific capsular reaction is elicited through a salt-like combination of several proteins with the bacterial capsule, leading to precipitation at a pH value on the alkaline side of the isoelectric point of the bacterial surface and on the acid side of the isoelectric point of the proteins. The reaction is reversible; it disappears on changing the pH. The non-specific capsular reaction at an inter-isoelectric pH zone of the bacterial surface and of the proteins is not a ‘swelling’ reaction. A swelling of the capsule might occur with some bacteria as a secondary phenomenon on the alkaline side of the reaction zone. The reaction occurs in a broader zone in members of the genus Bacillus where it reveals a distinct shrinkage of the capsule at the acid side of the reacting zone.

SUMMARY: A group of variant strains of the slime mould, Dictyostelium discoideum, was collected, all of which cannot accomplish the complete morphogenetic cycle; instead some stop at intermediate stages. They have been termed ‘morphogenetically deficient’. In many cases a mixed population of two deficient strains can achieve synergistic development even to the production of normal fruiting structures with viable spores. The nature and intensity of the synergistic response is a function of the proportions of the partners in the mixture. No recombinant types have been found among the spores obtained from the mixtures. The comparative patterns of response have been ascertained when the deficient stocks are paired in all possible combinations. Finally, an antagonistic interaction between two deficient strains is described.

SUMMARY: The methyl red (mr) reactions of eighteen strains of coliform bacteria were investigated. Two different media were used, glucose phosphate peptone broth and a liquid defined medium. In the glucose phosphate peptone medium the MR test was found to vary with the brand of peptone used, but the defined inorganic salt + glucose medium gave constant results throughout. After 5 days of incubation at 30° in a glucose phosphate peptone medium twelve substrains selected from each of three strains showed a maximum pH difference of 0·2 unit. When the test strains were inoculated into two batches of this medium made up on different days, pH differences up to 0·6 unit were obtained between the two batches.

SUMMARY: Two different organisms were dried in normal rabbit serum and in the presence of specific antibody. Reconstitution of the dried products showed that the presence of antibody did not affect the viability, agglutinability or the absorptive capacity of the bacteria.

SUMMARY: The nutritional requirements of eight strains of Clostridium parabotulinum type A were studied. Five strains required for optimum growth the three vitamins, biotin, thiamine and p-aminobenzoic acid, one strain showed additional demands for nicotinic acid and pyridoxin, whilst two non-toxigenic strains required biotin and p-aminobenzoic acid. Biotin could be replaced by oleic acid and a number of Tweens, p-aminobenzoic by folic acid, citrovorum factor or a mixture of thymine and purines.

All the strains tested showed good growth in a medium containing at least 2·5% casein hydrolysate (Difco), equivalent to about 0·18% N. The casein hydrolysate could be replaced by a mixture of amino acids, of which the following nine were essential: tryptophan, threonine, valine, leucine, isoleucine, methionine, arginine, phenylalanine and tyrosine. The last three acids were required in unusually large amounts. Growth in chemically define medium was followed by a rapid lysis. In spite of optimum growth, the toxin titre in the defined medium was about 50,000 LD50 doses/ml., i.e. approximately ten times less than that obtained in complex media.

SUMMARY: A study has been made of some 300 facultative anaerobic strains, isolated by Heald, Krogh, Mann, Appleby, Masson & Oxford (1953) from the rumen of a hay-fed sheep. The 120 streptococcal isolates all belonged to Lancefield’s serological group D. 82% had fermentation and other reactions similar to Streptococcus bovis; 6% resembled Str. faecalis and the remainder (12%) were unclassifiable by existing schemes. Str. faecalis could also be isolated from old hay fed to the sheep. Staphylococcal isolates were all coagulase-negative, and eleven out of twelve conformed to subgroup 2 in the classification of Shaw, Stitt & Cowan (1951) . The coliform isolates were mostly of the true intestinal type. A few strains resembled Aerobacter cloacae, but A. aerogenes was not encountered. The large Gram-negative sarcina-like organism, previously detected in rumen contents by Baker, Nasr, Morrice & Bruce (1950) and by Moir & Masson (1952) , has been isolated in pure culture and named Sarcina bakeri. It ferments only glucose.

Summary: When the avirulent strain of Mycobacterium tuberculosis H37 Ra was repeatedly subcultured in a liquid medium containing low concentrations of ‘Triton A20’ or other chemically similar non-ionic surface-active polyoxyethylene ethers, the morphology changed from the amorphous growth pattern characteristic of avirulent tubercle bacilli to the formation of microscopic ‘cords’ similar to those shown by virulent strains such as H37Rv. Once developed, the cord-forming property of H37 Ra persisted when cultures were transferred to liquid medium devoid of surface-active agent, even when such transfer was made after passage through mice; after further subcultures, however, a tendency to reversion was apparent. No difference in virulence was detected between cord-forming H37 Ra and the unmodified strain when tested in mice.

Previous work had indicated that a lower member of the polyoxyethylene ether series, the dimer ‘D4’, inhibited amorphous-growing avirulent tubercle bacilli, including H37 Ra, but not the growth of naturally cord-forming strains, exemplified by the virulent H37 Rv and attenuated strains derived from it. The growth of cord-forming avirulent organisms, developed from H37 Ra in the present experiments, was also found to be relatively unaffected by D4.

Summary: Submerging leaves in water soon after they are inoculated with viruses can prevent infection, and for studying factors that affect the rate of virus multiplication leaves should not be placed in solutions until a day after inoculation.

The rate at which viruses multiply in tobacco leaves is decreased by spraying with solutions of thiouracil, but less so than by floating leaves in the solutions. The physiological state of floated leaves affects the extent to which thiouracil impedes virus multiplication; least virus is produced in the presence of thiouracil when the condition of leaves otherwise most favours virus formation. Multiplication of virus can be checked at any time by thiouracil, but is most affected when leaves contain little virus; multiplication is resumed when thiouracil is removed. Thiouracil impedes the multiplication in tobacco of all viruses tested, but not of a tobacco necrosis virus in French bean or broad bean mottle virus in Vicia faba.

When mixed with inocula, thiouracil can prevent infection from occurring, both in tobacco and French bean. It also affects the growth and appearance of both plants. These effects, unlike the impedance of virus multiplication in tobacco, are not counteracted by an excess of uracil. Tobacco leaves in which tobacco mosaic virus is multiplying develop necrotic spots and rings when treated with thiouracil, and local lesions can be made evident by spraying inoculated leaves. Necrotic lesions also occur on V. faba infected with broad-bean mottle virus and treated with thiouracil.

Summary: A strain isolated from a human source is described and is proposed as the type for the species Staphylococcus aureus Rosenbach in place of the one chosen by Shaw, Stitt & Cowan (1951) which has some characters of animal strains.

Summary: Various aspects of the nutrition of four fungi which commonly inhabit percolating filters treating sewage have been studied. Sepedonium n.sp., a predominating fungus, required organic sources of nitrogen while Fusarium aqueductum, Geotrichum sp., and Trichosporon cutaneum were able to utilize ammonium salts; F. aqueductum was also able to utilize nitrate. Geotrichum sp. and F. aqueductum needed no external supply of vitamins, T. cutaneum required thiamine and Sepedonium sp. required thiamine and biotin for optimum growth. The pH range for optimum growth was narrow (pH 7 to 8·5) for Sepedonium sp. while the ranges for the other fungi were much wider (pH 3 or 4 to 9).

Zn, Ca, Mn and probably Fe and Cu were required by Sepedonium sp., which was the only one of the four fungi inhibited by concentrations of Zn above the optimum in media partially deficient in other elements. Mn, Fe or Cu when added with Zn counteracted the inhibitory action, while Ca increased it.