- Volume 20, Issue 2, 1959

SUMMARY: Antibacterial tests with mycobacteria were carried out in rocked JL tubes (Monod). The medium used was Sauton medium+1% (w/v) Tween 80. It took 48 hr. to get a reproducible value for the ID 50 dose (50% inhibition dose) with tubercle bacilli of human type, and 8 hr. with the avian type.

SUMMARY: The incorporation pattern of 14C from [14C]glucose by the fungus Zygorhynchus moelleri has been investigated. The following substances became labelled in incubation periods of 6 sec. to 30 min.: the monophosphates of glucose, fructose, sedoheptulose, ribose, maltose, glycerol, gluconic acid, glyceric acid, enolpyruvic acid and guanosine; the diphosphates of fructose, glucose, glyceric acid, adenosine, uridine, inosine and guanosine; the triphosphates of adenosine and uridine; uridinediphosphoglucose and uridinediphosphoribose; free maltose and fructose; aspartic acid, glutamic acid, alanine, valine, tyrosine, proline, histidine, threonine, citrulline and glutamine; malic acid, citric acid, succinic acid, fumaric acid and glyceric acid. A small percentage of the 14C was present in unidentified substances. The kinetics of the incorporation of 14C, first into uridinediphosphoglucose, then into maltose phosphate, and finally into free maltose, suggests this sequence of compounds for the biosynthetic pathway of maltose formation.

The main effects of starvation of the cells by shaking them in phosphate buffer for 24 hr. were an increased % incorporation of 14C into maltose and the sugar phosphates, and a decreased % incorporation into amino acids, organic acids and nucleotides. The addition of a small amount of ammonia to starved cells increased the absolute rate of incorporation of 14C from labelled glucose into soluble cellular constituents; however, while the % of the total soluble 14C found in the nucleotides was markedly increased when ammonia was added, the % in the sugar phosphates decreased. In the presence of azide, the incorporation of 14C by starved cells into maltose and the nucleotides was severely inhibited and the incorporation into amino acids was somewhat increased. Thus, one of the most important results of starvation was to prevent incorporation of 14C into the nucleotides, organic acids and amino acids, while the addition of ammonia overcame the effects of starvation and promoted nucleotide synthesis. Ammonia had very little effect on the cells in the presence of azide.

A kinetic study of the sequence in which 14C was detected in these compounds indicated that glucose was metabolized by both the glycolysis and the oxidative pathways, and later by the tricarboxylic acid cycle.

SUMMARY: Sodium-rich yeast was prepared by aerating a yeast suspension in m-NaCl for a period of 60 min. This yeast contained then on the average 0·070–0·075 m- equiv. Na/g. dry wt. On incubating it with glucose, xylose or lactose in water, 0·1 m-KCI or 0·1 m-NaCl it lost some of its sodium, in the last case against an apparent concentration gradient. It appears that this movement of Na ion is of a diffusion character as evidenced by the effect of temperature, by incubation without metabolizable substrates and by the use of metabolic inhibitors; however, the possibility of an active contribution to this efflux cannot be excluded. The movement of Na+ out of the cell was shown to be connected with considerable changes of cell volume effected above all by changes of osmotic pressure of the medium, sodium being lost as a 0·06m-0·10m solution. A discussion of these phenomena is presented.

SUMMARY: Single ascospores which gave rise to temporarily self-fertile cultures were found in Neurospora crassa. Genetical and cytological evidence suggested that these ascospores were disomic for the chromosome containing the mating-type locus, the disomy having arisen following partial desynapsis at meiosis and unequal distribution of univalents. At some time after germination, the nuclei reverted to the haploid state. If the disomic ascospore had been heterozygous at the mating-type locus, two sorts of haploids might occur and fertility probably resulted from mating between these.

SUMMARY: Colonies of Aspergillus glaucus arising from single asexual spores or hyphal tips of the same or different homokaryon clones often vary in their adaptability to new environments. This shows itself as differences in the percentage survival and mean lag period of inocula taken from colonies growing on a normal medium when transferred to one containing a poison such as mercuric chloride, or unfamiliar sugar sources, e.g. arabinose, galactose, lactose and xylose.

The differences in adaptability to these new media between homokaryon clones are characteristically nuclear in origin, while those between colonies of the same clone are characteristically cytoplasmic. The nuclear system might be formally regarded as epistatic to the cytoplasmic system involved in these adaptive changes.

Selection for the cytoplasmic differences can produce marked changes in the adaptability of the asexual spores of single colonies, even though the selection technique is such that colonies in the direct line of selected descent are at no time exposed to the new media.

The changes in adaptability to mercuric chloride are independent of those for adaptability to the new sugars and only the latter shows any correlation with changes in rate of growth. There is therefore evidence of two or possibly three cytoplasmic systems with much the same properties of variation but independent in action and transmission.

SUMMARY: A methionine-requiring mutant of Neurospora crassa incorporated 35SO4 into methionine. This incorporation represents net synthesis of methionine by the mutant. It is quite likely that methionine synthesis proceeds by the normal pathway in the mutant. Not all of the normal proteins can be synthesized when methionine supplies are limiting, accounting for the inability of the mutant to begin growth without a long lag even though methionine can be synthesized.

SUMMARY: Virulent and avirulent strains of Leptospira icterohaemorrhagiae did not grow from inocula of fewer than 107 organisms/ml. in Korthof medium, but did grow when FeCl3 or preparations containing iron porphyrins were added. With added FeCl3 or haematin growth was somewhat slower than when the iron porphyrin-containing preparations were added.

SUMMARY: An obligately anaerobic sulphate-reducing vibrio (NCIB 8382) isolated from soil from Singapore differs from known species of sulphate-reducing bacteria. The organism is relatively large, with one or two flagella, Gram-negative, lacks hydrogenase and pigments characteristic of Desulphovibrio desulphuricans, though an insoluble cytochrome is present. It grows with lactate or pyruvate, but is unable to metabolize acetate, propionate or butyrate; it reduces sulphate, sulphite or thiosulphate but not tetrathionate. Sporulation is rare but has been observed. The name Desulphovibrio orientis is proposed for this organism.

SUMMARY: The true capsular polysaccharide of Streptococcus bovis contains galactose, glucose, rhamnose and an uronic acid as constituent sugars, whereas those of Leuconostoc mesenteroides and L. dextranicum contain only galactose and glucose in about equal proportions. Contamination of the capsule with dextran, not easily removed by simple washing of the harvested organisms, may occur with all species when grown in sucrose or in glucose media. This contamination is minimized when a glucose medium is inoculated with a glucose culture many times removed from a sucrose-containing medium.

SUMMARY: In cultures of the flagellate Ochromonas malhamensis the rate of growth is determined by the concentration of cyanocobalamin up to a limit at which a maximum growth rate is achieved. In organisms grown exponentially with different rate-limiting concentrations of cyanocobalamin, the amounts of protein and nucleic acids were approximately proportional to the rates at which the organisms had grown. With increasing growth rate the concentrations of riboflavin, nicotinic acid, pantothenic acid and chlorophylls increased. Carbohydrate showed little change, whereas fat and ‘free’ amino-nitrogen diminished in concentration as the growth rate increased. In cultures of O. malhamensis grown with limiting or near-limiting concentrations of cyanocobalamin and with increasing concentrations of chloramphenicol, the rates of division declined asymptotically to a low value corresponding with 500 μg. chloramphenicol/ml. culture medium. Inhibition of growth caused by the antibiotic was annulled by increasing the concentration of cyanocobalamin in the culture medium.

SUMMARY: The Adansonian method of classification, in which all features are given equal weight in deducing similarity between strains, has been applied to staphylococci. Staphylococcus aureus, S. saprophyticus and S. roseus are natural groups, but S. lactis and S. afermentans are not, for individual strains of these ‘ species ’ are as different from each other as from the three previous species. The group as a whole is divided into two main branches which might be regarded conveniently as two genera, Staphylococcus and Micrococcus.

SUMMARY: The making of models for taxonomic purposes and their use is described, and the fidelity with which they can represent the taxonomic relations between bacteria is discussed. These models are particularly useful for teaching purposes.

SUMMARY: The fixation of tetanus toxin by nervous tissue (Wassermann-Takaki phenomenon, 1898) has been re-investigated. Fixation is greatly dependent on the concentration of toxin and of receptor. Toxin is fixed in preference to toxoid, but its toxicity does not appear to be markedly diminished by fixation. A biological assay of the toxin receptor in nervous tissue and its components has been devised. The receptor activity is not due to a cerebroside, as thought by Landsteiner & Botteri (1906), but to some substance (present mainly in grey matter) that tends to associate with it.

SUMMARY: The fixation of tetanus toxin by the receptor in nervous tissue is highly specific in so far as tetanus toxic protein (and toxoid to a much smaller extent), and apparently nothing else, is adsorbed from solutions of ionic strength greater than 0·15. At lower ionic strengths certain other proteins may be adsorbed by a mechanism that is probably different. The specific adsorption of toxic protein has been used as the basis of a chemical method of assay of the receptor which depends on the estimation of the amount of protein adsorbed under prescribed conditions by the unknown amount of receptor from a fixed amount of crude tetanus toxin.

SUMMARY: The tetanus toxin receptor in nervous tissue appears to be a ganglioside (mucolipid, strandin, containing: fatty acid, sphingosine, glucose, galactose, acetylgalactosamine, acetylneuraminic acid and amino acid (?) residues). The water- soluble ganglioside occurs in nervous tissue in the form of labile water-insoluble complexes with cerebrosides and sphingomyelins. The solubility of the complexes in water increases with increasing ganglioside content, but decreases when calcium is incorporated. Standing with ganglioside inactivates the toxin.

SUMMARY: Protoplasts were released from Micrococcus lysodeikticus by the action of lysozyme in media containing sucrose, NaCl or mixtures of these. Empirical corrections by two methods were made for the effect of refractive index on the optical density of the protoplast suspensions measured at 500 mμ. With the assumption, valid for some similar systems, that the optical density of a protoplast suspension is inversely proportional to the protoplast volume, the protoplasts were shown to behave as osmometers at osmotic pressures above the threshold for lysis and to follow a van’t Hoff-Boyle law. The osmotically-inactive volume in a standard stabilizing medium containing m-sucrose + 0·05m-NaCl (osmotic pressure 37·8 atm.) was c. 76 %. Protoplasts formed in hypotonic media were more resistant to osmotic explosion than those formed at higher medium concentrations and subsequently diluted.

SUMMARY: Splash dispersal (first studied by Faulwetter, 1917a, b) is characteristic of many bacterial plant pathogens and slime-spored fungi. The mechanism of splash has been studied in the laboratory under simplified conditions with water drops falling from known heights on to thin films of a suspension of conidia of Fusarium solani spread on horizontal glass surfaces. The resulting splash droplets were caught, counted and measured by the naphthol green B slide method (Liddell & Wootten, 1957). Both the total number of droplets produced and of those carrying spores increased as the film thickness decreased, and as the size and velocity of the incident drop increased.

One incident drop 5 mm. in diameter falling on a horizontal film of spore suspension 0·1 mm. thick on a glass surface produced over 5200 splash droplets of which over 2000 carried one or more spores. The sizes of splash droplets ranged from 5μ about 2400μ, and their size distribution was of the log probability type. The median diameter was 70μ for all droplets, and 140 μ for droplets carrying spores. The medium horizontal distances travelled by these droplets in still air was 10 and 20 cm. respectively. Increasing the film thickness to 0·5 and 1·0 mm. reduced the total resulting droplets to 3500 and 2100 (1600 and 500 carrying spores), respectively. Neither median diameter nor median distance of horizontal travel were much altered by varying the diameter of incident drop or film thickness. Droplets of diameters between 164 and 655μ tended to travel further than either smaller or larger droplets. Small spores such as those of Gloeosporium album, Colletotrichum lindemuthianum and Nectria cinnabarina were even more readily picked up from suspension than the macroconidia of Fusarium solani.

The number of droplets deposited per unit area on a horizontal plane decreased rapidly with increasing distance from point of impact, and in still air few droplets travelled beyond 70 cm.

Splash on a twig bearing conidial fructifications of Nectria cinnabarina produced 2000 spore-carrying droplets, and the sequence of events is shown by high-speed photography.

A splash droplet consists of an intimate mixture of liquid from both the incident drop and the surface film. The larger splash droplets contain spores if either the incident drop or the surface film is a spore suspension. Both raindrops falling at terminal velocity and drops falling more slowly from vegetation may operate the splash dispersal mechanism. Splash in rain or drip from trees may act as a complete dispersal mechanism in still air, or as a ‘take-off’ mechanism leading to dispersal by wind. Both functions are important in plant epidemiology.

SUMMARY: Several strains from Escherichia coli NCTC 8196 were isolated from discrete colonies. They were grown in liquid media in the presence of proflavine, and then in its absence. The distribution of resistance was measured by the number of organisms able to multiply at different concentrations of proflavine. Some strains were also grown in the presence of proflavine on plates, and the resistance of broth cultures from them was measured on gradient plates. The results cannot be explained on the assumption that the resistance was determined solely by specifically induced adaptation.

SUMMARY: Experiments were performed to demonstrate the production in Escherichia coli of spontaneously occurring mutants resistant to proflavine. The fluctuation test of Luria & Delbriick (1943) suggested that such mutants arise. This was confirmed by a modification of the technique of Lederberg & Lederberg (1952). By this method of indirect selection by replica plating, two separate first- step mutants were isolated; from one of these was isolated a second-step mutant, and from this a third-step mutant. The resistance of the third-step mutant was about 100 times greater than that of the original sensitive strain. By the same technique, two first-step mutants to chloramphenicol resistance were isolated. None of the 6 mutants had come into contact with either drug until the time of testing. Crossresistance between proflavine and chloramphenicol was shown by 5 of the 6 mutants; the sixth showed an increase in proflavine resistance though not in resistance to chloramphenicol.