- Volume 19, Issue 1, 1958

SUMMARY: A mieroconidial non-colonial heterokaryon of Neurospora crassa was produced from a inacroconidial colonial and a macroconidial non-colonial homo-karyon. The macroconidial colonial strain was found to have the genetic constitution mieroconidial (m) (the pem of Barratt & Gamjobst, 1949) suppressor of mieroconidial (su m); col-1 and the other m+ su m+; col-1+. The dominance relationships of m, sum and col-1 with their wild type alleles and the particular nuclear ratio in which they are present determine the mieroconidial non-colonial phenotype of this heterokaryon, As a further consequence of the dominance relationships between col-1 and its wild-type allele, only one of the two pleiotropic effects of the mutant gene is expressed in the heterokaryon. The enormous discrepancy between the estimates of the nuclear ratio by two different plating methods is shown to be due to an almost complete suppression of one type of homokaryotic colony by the other.

SUMMARY: An influenza A strain, Ryan, isolated in Melbourne in 1954 contains on a particle basis about 20% filaments. By using the electron microscope for particle counting, the efficiency as haemagglutinin of Ryan ‘long’ filaments (particles in which length: width ⩾ 6) was estimated to be about 6 times greater than that of spheres of PR 8 virus. Allantoic fluid preparations of Ryan virus have high values for the ratio (log) EID50:AD and estimates indicate that a maximum of 6 ‘long’ filaments are equivalent to one EID50, compared with 18 particles in the case of PR 8 virus or 14 particles in the case of a mutant strain of Ryan virus which exists almost exclusively as spheres. Compared with virus PR 8 spheres (16 particles: AD), spherical particles present in filamentous Ryan preparations have a low efficiency as haemagglutinin (29 to 38 particles:AD). These particles are formed before the ‘long’ filaments, and in fluids harvested 21 hr. after inoculation when the proportion of ‘long’ filaments is very low, about 9 spherical particles constitute 1 EID50. For the purpose of subsequent chemical examinations filaments were isolated and concentrated by a process involving specific adsorption to and elution from red cells, followed by 3 cycles of differential centrifugation. The ratio of filaments: spheres in such preparations is about 50:50. ‘Purified’ filaments weigh about 30 times as much as the spherical particles present and account for over 95 % of the total weight present in purified preparations.

SUMMARY: The amount, type and properties of nucleic acid have been estimated in the two end fractions, Ryan supernatant (Ryan Sup.) and Ryan final filaments (Ryan F.F.) of a purification procedure applied to allantoic fluid preparations of filamentary Ryan virus. Ryan Sup. consists of 80 % spherical particles and 20 % short filaments (length:diameter < 6). Analysis indicates an average nucleic acid content of 0·75 % (PR 8 = 0·91 %). The value of the ratio, adenine+uracil: guanine + cytosine for the nucleic acid of A strains of influenza virus varies between 1·22 and 1·28. The value for Ryan Sup. is 1·20; for a mutant strain of Ryan virus which exists almost exclusively as spheres, the value is also 1·20.

The ratio of filaments to spherical particles in Ryan F.F. is about 50:50. On a dry-weight basis, Ryan F.F. contains about 0·25 % RNA. There may be small amounts of DNA present. On a particle basis, the residual filamentary structures contain about eight times as much RNA as do PR 8 spheres. The value of the above ratio of bases however is about 0*9. Treatments of filaments with diethyl ether releases a soluble complement-fixing antigen (CFA) which on purification is found to have the same nucleic acid content per unit of CF activity as does soluble CFA isolated from either PR 8 or Ryan Sup. viruses. In each case the value of the above ratio of bases is about 1·25. On a particle basis filaments in Ryan F.F. contain 3 to 4 times as much soluble CFA as does PR 8 virus so that the residual RNA in Ryan F.F. must closely correspond in properties to RNA from the potential host cell which has a value for the above ratio of about 0·6. Exposure of Ryan F.F. to ribonuclease or to a procedure which degrades the filamentary form to smaller spherical units does not affect the amount or properties of the associated RNA.

A tentative scheme is proposed for the formation of virus particles of Ryan F. preparations. It is postulated that most of the spheres present in such preparations arise by fragmentation of the tip of forming filaments where there is a relative concentration of viral type RNA. The filaments which are found in the allantoic fluid thus represent only part of the original filamentary structures. This concept implies that filaments break more readily at those places where there is an enrichment of viral type nucleic acid.

SUMMARY: Two species of Mallomonas (Chrysophyceae), M. insignis Penard and M. akrokomos Pascher ex Ruttner manuscript were investigated with optical and with electron microscopes. Carbon replicas have now made it possible to learn how the scales fit together in the armour and in particular how the tail, in each species, is constructed. Direct electron micrographs in conjunction with Teplicas have given much additional information about the scales. Developmental stages of M. insignis have been noted.

SUMMARY: Myxococcus xanthus lyses not only in old cultures but also when suspended in solutions of monovalent cation salts. This lysis is slow at 37° and lower temperatures, but is very rapid at 45° and 60°. Organisms in distilled water do not lyse at any temperature. Lysis is more rapid at high pH values, in broth or in solutions of monovalent cation salts; it is optimal in c. 0·03 m solutions of the salts. During lysis the cell wall weakens and empty spherical protuberances develop at the ends or in the middle of the organism. Finally, the dense material of the protoplasm disappears except for an occasional granule, and only single or paired spherical ghosts remain.

SUMMARY: Some pairs of genetically marked strains of Vibrio cholerae when grown together and plated under selective conditions give rise to greater number of colonies than either strain plated alone; in the case of other pairs in which this phenomenon did not occur, large number of presumptive recombinants were obtained when one of the strains was made lysogenic with a particular phage. Although the small number of markers made it impossible to do mapping studies, the evidence is strongly suggestive of recombination, probably phage-mediated transduction.

SUMMARY: The infra-red absorption spectra of 76 strains of lactobacilli representing 11 different species were examined. With only a few exceptions, the spectra could be grouped into 5 distinct spectral types, each corresponding to a Lactobacillus species or a group of related species. From a study of acetic acid extracts, it has been found possible to relate spectral differences to the relative concentrations of nucleic acids and carboxylate groups in the different organisms.

SUMMARY: Electron micrographs of cell walls of the unicellular green flagellate Plaiymonas subcordiformis revealed no evidence of a fibrous construction. A preparation of walls was isolated, hydrolysed, and analysed by paper chromatography. The major components indicated were galactose and a uronic acid; glucose was not detected. It was concluded that the cell walls of this alga are not composed of cellulose.

SUMMARY: A lethal oedema-producing toxin has been made in vitro in serum cultures of Bacillus anthraeis which is identical with the toxin originally recognized in vivo. Toxin is produced by the attenuated immunogenic Sterne strain as well as by the virulent N.P. strain. Previous non-recognition of the toxin in cultures was due to its early appearance and rapid disappearance under ordinary growth conditions. A toxin-destroying mechanism was demonstrable in organisms from cultures grown for more than a few hours. Attempts to maintain the toxin concentration or to increase it by addition of various nutrilites to batch culture failed; only by continuous culture have the organisms been kept in their toxigenic growth phase. Traces of the toxin appear in cultures in tryptic meat broth; these are increased by the addition of large molecular constituents of serum which appear to play an important role in toxin production.

SUMMARY: Aqueous extracts of Aerobacter sp. and Escherichia coli have been found to cause excystment of viable sterile cysts of Schizopyrenus russelli. The factors which cause excystment are thermostable. With the aid of paper partition chromatography of the aqueous extract of Aerobacter sp., it has been found that part of the excystment-inducing activity is due to the presence of amino acids, some of which have been identified. Amino acids, sugars, purines, pyrimidines, nucleosides, nucleotides and organic phosphates have been tested for their ability to induce excystment. It has been found that some amino acids and a few nucleotides can cause excystment. The effect of pH, concentration and time on excystment with amino acids has been studied.

SUMMARY: Silage made in the laboratory at 22°, 30° and 40° from five specimens of grass was examined after 1, 2, 3 and 8 days and 6 months- The dominant bacteria on fresh grass were obligate aerobes which died rapidly in a closed silo. Bacteria capable of anaerobic growth were represented irregularly and often weakly on grass. This can account for much of the variation in the composition of bacterial populations in silage. Organisms that developed extensively in much of the silage were the Klebsiella group, Lactobacillus, Streptococcus, Leuconostoc, Pediococcus, Clostridium and Bacillus. Each proceeded to multiply soon after silos were closed; all stopped growing at about the same time. The rate of growth and the concentration of viable organisms reached were determined by properties of the herbage. Gram-negative organisms were restrained at 40°, Clostridium and Bacillus at 22°. The multiplication phase was short; it could be completed by the third day at all three temperatures. Cessation of growth could not be attributed to the accumulation of acids. Much acid was formed after all the main groups had reached the phase of decreasing viable count. When the lactic acid fermentation was not vigorous the decreases in pH value were most rapid at 40° and slowest at 22°.

SUMMARY: Freshly isolated and old stock strains of Streptococcus bovis originating from the rumen will produce dextran at 37° in liquid sucrose-containing media. For good yields the presence of CO2 in some form is necessary. The CO2 may be provided as HCO3− at the start or during the life of the culture or by incubation in a CO2 atmosphere. The dextran has [α]20 D +187° to +190° and is similar chemically to the leuco- nostoc dextran save that branching of the αl → 6 linked anhydro-glucose chain is rarer. With some strains practically no dextran is formed in H2 as gas-phase or in a closed system without HCO3− from which air is excluded. Other strains seem to have a limited power of producing dextran under these conditions, possibly because their action is not entirely homofermentative. Tween 80 will partially replace CO2 even with the first kind of strain. Highest yields of dextran, up to 80 % of the anhydro- glucose provided, are obtained when the life of the culture is prolonged by repeated neutralization and when additional sucrose is supplied. This is best achieved by the continuous neutralization obtained when solid CaCO3 is present in the culture. Dextran production is always accompanied by accumulation of fructose in the culture liquid together with a reducing fructose-containing disaccharide. Dextran can sometimes be produced in a simple liquid sucrose + proteose peptone medium with no phosphate buffering. Other things being equal, the presence of CO2 or HCO3− does not greatly increase the yield of bacterial protein in sucrose media.

SUMMARY: The effect of area:volume ratio and composition of medium on the accumulation of diazotizable amine (‘amine’) and hypoxanthine by yeast 47 growing in biotin-deficient medium are reported. The ‘amine’, isolated from culture filtrates by mercury precipitation and separation on ion exchange resins, gave the Pauly reaction for imidazoles: on acid hydrolysis it yielded ribose, glycine, ammonia and formic acid, but no phosphate. These properties are consistent with the view that the ‘amine’ is 5-amino-imidazole riboside or a closely related compound. When the growth medium contained 500μg. l-aspartic acid/ml., instead of ‘amine’ and hypoxanthine, substances accumulated which on hydrolysis yielded adenine as the only purine. ‘Amine’ accumulation by yeast 47 may be a symptom of a derangement of purine metabolism resulting from a biotin-conditioned block in aspartate synthesis.

SUMMARY: The flagellate Ochromonas malhamensis requires vitamin B12 and responds only to those natural forms of the vitamin which are active also for higher animals. The relation between the rate of growth and the concentration of cyano- cobalamin is described by an equation of the form of an adsorption isotherm. The ‘inactive’ analogues, pseudovitamin B12 and Factor A, were taken up by O. malhamensis to about the same degree as cyanocobalamin, and inhibited competitively the growth response to cyanocobalamin, apparently by blocking a cell mechanism for ‘ binding ’ the vitamin.

SUMMARY: Didymium nigripes has been grown in two-membered cultures with Aerobacter aerogenes as its bacterial associate. All phases of the developmental cycle were observed, including spore germination, myxamoeboid growth, plasmodium formation and growth, and fruiting. Both spores and myxamoebae have regularly yielded clonal populations displaying normal development terminating with the appearance of fruits. Efficiency of plating determinations showed that spores and myxamoebae were 100 % viable under the proper conditions. Greatly decreased spore viability was encountered when plasmodia were permitted to fruit in the presence of the metabolic products of their bacterial associate. Plasmodium formation was inhibited by the presence of 2 % (w/v) glucose or 0·2 % (w/v) brucine. However, the myxamoebae grew normally under these conditions.

SUMMARY: Infectivity titrations and electron microscopic spray counts were performed on purified preparations of adenovirus type 5. The number of virus par- ticles/5,0 % infective units varied from 10 to 100 with different preparations.

SUMMARY: Harposporium anguillulae Lohde was isolated in pure culture from an infected nematode and its behaviour on culture media under various conditions is described. The life history of the fungus in the nematode host has been investigated and the infection traced back to germinating conidiospores in the oesophagus. Two other Harposporium spp. were also isolated and it is shown that their mode of infection is similar to the one described for H. anguillulae. Because of these findings a new theory for the mode of infection is proposed and its significance in the ecology of the fungus discussed.

SUMMARY: The oxidation of ammonia by Nitrosomonas europaea is accelerated in mineral liquid media by the addition of small amounts of com steep liquor or its ‘ash’. The amount of nitrite produced in such cultures usually exceeds the controls by 6–7 times after 6 days. However, in the following days nitrite-production becomes slower and after 14 days the controls have reached the same nitrite concentration as the com steep liquor cultures. Concomitant with the accelerated nitrite-production hydrogen-ion concentration in the cultures increases considerably and may attain values as low as pH 6·3 after 14 days, as compared with c. 7·8 in the controls. The effect of com steep liquor stimulation is more pronounced the smaller the inoculum used. Microscopical examination of slides immersed in cultures during incubation shows that N. europaea adheres to the glass surface only in cultures without com steep liquor. The stimulatory factor in solutions of the ‘ash’ of com steep liquor was not removed by dialysis nor by treatment with cation exchange resins. When the solutions were centrifiiged both washed sediment and supernatant fluid were active. A possible explanation of the com steep liquor effect is that colloidal matter in the solutions absorbs ammonia or any other nutrient in the medium in a way more favourable for their utilization by the organism.