- Volume 15, Issue 1, 1956

Summary: Genes controlling carbohydrate fermentation in Saccharomyces often control the fermentation of more than one carbohydrate. The gene MZ has at least five different manifestations involving its ability to respond to five different carbohydrate inducers for the production of a single enzyme; a series of multiple alleles of MZ differ from one another in ability to respond to the different inducers. The gene DX controls the fermentation of dextrin and glycogen. The gene ST controls the fermentation of starch; some starch-positive cultures are Schardinger-dextrin-positive. The gene SU controls the production of a constitutive enzyme which splits both sucrose and raffinose.

Summary: Cysteine was formed from sulphate, sulphite and thiosulphate as inorganic sulphur sources, by acetone-dried powders of Aspergillus nidulans mycelium. Added pyridoxal was obligatory for cysteine synthesis with sulphate or sulphite, and this synthesis was further enhanced by the addition of sodium pyruvate and sodium glutamate. Concomitant accumulation of cysteine sulphinic acid and utilization of glutamic acid was demonstrated. With thiosulphate, considerable synthesis of cysteine occurred in the absence of supplements, but was much enhanced by the addition of serine. Cysteine sulphinic acid did not accumulate with thiosulphate as the inorganic sulphur source. Parathiotrophic mutants, produced by ultraviolet irradiation, were used in the further elucidation of the biosynthetic mechanisms involved. Two reaction sequences: sulphate →sulphite →cysteine sulphinic acid →cysteine; and thiosulphate →cysteine-S-sulphonic acid →cysteine probably take place in the mould.

Summary: Different pathways of terminal oxidation exist in killer and sensitive stocks of Paramecium aurelia, variety 4, stock 51.7. The killers contain an active succinoxidase system which is absent, or present only in small concentrations, in the sensitives. The succinoxidase system might therefore either be necessary for the maintenance of the cytoplasmic particle ‘kappa’ or is intrinsically associated with it.

Summary: During the course of adaptation to the mouse lung of the Rob strain of influenza B,‘pure’ clones of virus were isolated from bronchial washings at succeeding passages by the limiting infective dilution technique in chick embryos. The clones were studied for various in vitro and in vivo properties. A progressive dominance was obtained in the virus population of virus particles causing extensive pulmonary consolidation. Those particles which produced extensive consolidation became resistant to inhibition of heated virus haemagglutinin by sheep mucin. A complete correlation was found between the appearance of resistance to sheep mucin inhibitor and a decrease of enzymic activity on sheep mucin.

From the heterogeneous population of particles found in the early course of mouse passage a virus was isolated which exhibited all of the tested properties of the adapted virus. In comparison to a non-pathogenic virus form, these properties included: (a) the production of extensive pulmonary consolidation, high mortality of mice, and multiplication of virus on serial mouse passage; (b) the production of a more rapid growth rate, and the ability to multiply to a greater extent; (c) the inability of heated virus haemagglutinin to be inhibited by sheep mucin and ovomucin; (d) a decrease of enzymic activity on sheep mucin and mouse lung inhibitors under certain experimental conditions; and (e) a high position in the fowl red cell receptor gradient.

The above data offer presumptive evidence that one of the processes operative in the adaptation process of Rob virus to the mouse lung is a selection of mutants found in the unadapted heterogeneous virus population.

Summary: The nutritional patterns of 28 typed and untyped strains of Acetobacter spp. ranged between extremes with predominant lactate (lactaphilic) or glucose (glycophilic) metabolism. Typical lactaphilic strains did not require exogenous supplies of growth factors and gave rise to new ninhydrin-reacting substances when cell suspensions were incubated in solutions of proline, glutamate and aspartate. Under similar conditions, glycophilic strains yielded no new ninhydrin-reacting substances and required added nicotinate, pantothenate and, in some cases, p-amino-benzoate for growth.

All strains utilized ammonium sulphate as sole source of nitrogen for growth. Under such circumstances, most lactaphilic strains grew readily when lactate provided the only source of energy and carbon: other organic acids, even to be partially effective as substitutes for lactate, required the simultaneous presence of glucose. Glycophilic strains utilized ammonium sulphate as sole source of nitrogen for growth slowly and to a limited extent in glucose medium, the degree of growth being increased by the presence of certain organic acids. Characteristically, glycophilic strains required certain sugars or sugar alcohols for growth, but were little or not at all stimulated by lactate.

Summary: The cultural and biochemical characteristics of 38 strains of Chromobacterium are described. They are non-sporing aerobic Gram-negative rods which produce a violet pigment and possess both polar monotrichous and peritrichous flagella. They produce little acidity from carbohydrates and utilize citrate.

Two main groups of strains were distinguishable, a mesophilic and a psychrophilic group. The former usually ferment glucose anaerobically, are markedly proteolytic, facultatively anaerobic, and give a positive egg-yolk reaction, but do not hydrolyse aesculin. The psychrophilic organisms produce acid from glucose but only aerobically, are poorly proteolytic, strictly aerobic, and hydrolyse aesculin but do not produce an egg-yolk reaction.

Chromobacterium viscosum Grimes, C. iodinum Davis and C. ianthinum Gilman have been re-examined; they should be excluded from the genus. The nomenclature of the genus is confused. Proposals have therefore been made to the International Committee on Bacteriological Nomenclature that the mesophilic species should be called Chromobacterium violaceum and the psychrophilic species C. lividum, and neotype strains have been suggested.

SUMMARY: Some strains of Chromobacterium exhibit either polar or mixed polar and peritrichous flagellation according to the conditions of culture. Polar and lateral flagella differ in the site of insertion, the wavelength, ease of staining, and in antigenic composition. Peritrichous flagellation is greatest in young cultures on solid media and is least in liquid media. The peritrichate flagella disappear in old agar plate cultures, leaving polar flagellated organisms.

SUMMARY: Washed suspensions of certain bacteria can synthesize alanine from pyruvate and ammonia. This has been studied in detail in Bacillus subtilis. Several other amino acids can be formed from the corresponding keto-acids, but synthesis was most rapid in the case of alanine. Notably, glutamic acid is formed from keto-glutarate relatively slowly, whilst oxalacetate fails to give aspartate. Pyruvate can accept an amino group from a number of amino acids by transamination (but aspartic and glutamic acids are less effective than ammonia itself). It is possible that the reductive amination of pyruvate may proceed directly rather than through transamination from some other primary amino-acceptor.

SUMMARY: Sex incompatible (F −) strains of Escherichia coli have a lower acid agglutination point, a stronger affinity for a basic dye and a greater stability in broth cultures as compared with F + strains of corresponding phenotype. These findings indicate a correlation between some surface properties and sex compatibility. These surface properties and the F + state are transmitted infectively from F + to F − strains at the same time. Screening for cultural behaviour of infected strains yields results fully consistent with screening for sex compatibility.

SUMMARY: Mutants of Fusarium oxysporum f. pisi (cause of pea wilt), distinguished from the parent types by their different morphology, pathogenicity and nutritional requirements, were obtained by ultraviolet irradiation. Pairs of mutants with different nutritional requirements (auxotrophs) formed balanced heterokaryons on non-supplemented medium. Most of the auxotrophs were less pathogenic than the wild-types, whereas heterokaryons between the mutants were not.

Single conidia of a heterokaryon between an auxotroph from race 1 and one from race 2 of Fusarium oxysporum gave a small proportion (3 in 108) of colonies which were able to grow on non-supplemented medium. These three prototrophs were presumably diploid because vegetatively they gave new strains with various combinations of colour, nutritional requirements, actinomycete tolerance and pathogenicity.

The results indicate that, in fusaria, heterokaryosis plays a part in variation of virulence and that Fusarium oxysporum, which has no known sexual stage, has a system similar to the parasexual cycle described by Pontecorvo for certain other Fungi Imperfecti, that permits the segregation and recombination of genetic factors outside the sexual stage.

SUMMARY: Four strains of Salmonella typhimurium avirulent for mice were found to be capable of acting as gene acceptors in transduction experiments. An attempt was made to transduce virulence to three strains, using a typical mouse-virulent strain of S. typhimurium as donor. Two of the strains which are adenine-dependent were successfully made virulent by transduction and simultaneously became adenine-independent. The other strain M206, whilst possessing the typical antigenic structure of S. typhimurium and being non-exacting nutritionally, was not made virulent by transduction.

SUMMARY: A droplet of a suspension of Halobacterium halobium in a concentrated brine when left to dry on a collodion-covered grid yields a useful preparation for electron microscopy. Two strains, one red and one pink, were examined. Both strains have polar tufts of flagella. The cell wall contains a single layer of hexagonally arranged globular particles. Halobacterium halobium has these characteristics in common with Spirillum spp., but unlike the true Spirillum spp. it is rod-shaped.

Electron microscopical examination showed that the gas vacuoles observed by Petter (1931, 1932) to be a feature of pink strains of H. halobium actually were smaller but much more numerous than the optical microscope revealed. Stereo-pictures show that these vacuoles did not collapse upon desiccation of the bacteria.

SUMMARY: Five strains of Candida albicans were isolated from the following vegetable sources: flowers of Ulex sp. (two strains), leaves of Myrtus communis, a sample of ‘hongo’ and a sample of sour red wine. The five strains show the characteristic properties of Candida Albicans including pathogenicity for rabbits. These isolations do not prove that the organism has a saprophytic free-living stage; only that it can at least survive outside and animal host for an appreciable time.

SUMMARY: Only 30–50 % of the cell-bound penicillinase of Bacillus cereus NRRL 569 is neutralized by antiserum prepared against the exo-penicillinase. The unneutralizable fraction is not decreased by cell disintegration which liberates a proportion of the cell-bound enzyme into solution. Absence of neutralization cannot therefore be explained by the existence of a mechanical barrier which prevents access of antibody; it has in fact been shown to be due to the presence of another type of penicillinase, not liberated from the cells, which is enzymically similar to, but immunologically and physico-chemically distinct from, the exo-enzyme. This cell-bound penicillinase has been separated from the exo-enzyme by fractional precipitation with ammonium sulphate. It is inducible by penicillin, like the exo-enzyme, and is present in cells of the constitutive mutant strain, 569/H.

SUMMARY: Chlamydomonas moewusii is a unicellular, haploid, heterothallic alga. Suspensions containing a high proportion of active gametes are readily obtainable. The species is obligately photo-autotrophic. Organisms grown in light lose sexual activity when incubated in darkness, and only regain it when illuminated. Organisms of both mating-types require light for sexual activation. This reaction appears independent of the presence or absence of CO2. It was not found possible to replace the effect of light by the addition of any chemical or natural extract to the medium. By the use of a simple device, changes in the sexual activity of a given suspension were followed experimentally. The sensitivity of organisms to light remained approximately constant during an experimental run of 1–2 hr. Mating activity of organisms transferred to darkness remained constant for a few minutes (‘dark lag’) before decreasing. The length of the dark lag was a function of the duration of previous illumination. The dark lag of plus organisms was shorter than that of minus organisms under comparable conditions. After the lag period, decline of activity in darkness was approximately exponential. Rates of loss of activity between 10° and 3° were measured, and half-life values calculated, for each mating-type. The rate of loss of activity was approximately the same for both mating-types. Loss of sexual activity was somewhat accelerated by anaerobiosis. Resumption of sexual activity on re-illumination followed a short period of persistent inactivity (‘light lag’). The length of the light lag was not dependent on the duration of the preceding dark period. At 25°, the lower threshold of white light was 10 f.c. for minus organisms, 50 f.c. for plus organisms. At 300 f.c., minus organisms were reactivated between 12·5° and 35°, plus organisms between 17·5° and 30°. The action spectrum of photoactivation exhibited two peaks, around 450 and 680 mμ., thereby resembling the absorption spectrum of the chloroplast. Phenylurethan (6 × 10−4 m) reversibly inhibited photosynthesis and photoactivation of sexuality, while respiration and the mating process itself were affected to a much lesser degree. It is postulated that mating activity is controlled by an intracellular hormone, activated at the plastid during illumination, and operative at the flagella.

Summary: Desulphovibrio desulphuricans (E1 Agheila Z), in lactate + sulphate media, required 10 mµmole Fe/ml. for optimal growth; no absolute iron requirement was demonstrable in pyruvate + sulphate media but iron up to 20 mµmole/ml. stimulated growth. In a sulphate-deficient pyruvate medium, in which this strain can grow, iron was not required nor did it stimulate growth. Organisms grown with limited iron formed limited amounts of cytochrome c 3, and in the absence of iron were markedly deficient in this; their content of hydrogenase was reduced to a lesser extent and their content of desulphoviridin was only halved. Iron-deficient organisms were able to reduce sulphate only slowly. Less than 1 % of the iron added to cultures was accounted for as cytochrome c 3, though only some 6 % of this iron remained in solution after growth.

Summary: Increased production of perithecia by Chaetomium globosum in the neighbourhood of a physical barrier which impedes the growth of the colony is associated with a locally increased concentration in the medium of organic phosphates excreted by the organism, caused by unequal diffusion of these compounds owing to the presence of the barrier.

Summary: Teepol, a modern anionic detergent, has been investigated and used in culture media for organisms of the coli-typhoid group, in substitution for bile salts. Media containing 0·1 % Teepol and an indicator of the sulphonphthalein group have been found to possess advantages over MacConkey’s medium. While bile salts as marketed are costly and variable in their bacteriological properties, Teepol is cheap and reliable.

Summary: Spirillum lunatum has been shown to possess a life cycle in which there is an alternation between a vegetative and a microcyst stage. Microcyst formation may occur from the spiral vegetative cell by:(1) fusion of two entwined organisms to form one or more microcysts; (2) the production of a protuberance at some point along the organism into which the entire organism is gradually absorbed; (3) the gradual shortening and rounding of the organism to form an oval to spherical body. Microcyst formation begins, in a typical broth culture, at c. 24 hr. after inoculation and the majority of the organisms are in the microcyst stage after a 4-day incubation period. When microcysts from an old culture are inoculated into fresh media, they germinate to form the spiral vegetative organism. Germination occurs by either unipolar or bipolar emergence of the germ tube.