Showing papers in "Microbiology in 1966"

The Aerobic Pseudomonads a Taxonomic Study

Abstract: SUMMARY A collection of 267 strains, representing many of the principal biotypes among aerobic pseudomonads, has been subjected to detailed study, with particular emphasis on biochemical, physiological and nutritional characters. A total of 146 different organic compounds were tested for their ability to serve as sources of carbon and energy. Other characters that were studied included : production of extracellular hydrolases; nitrogen sources and growth factor requirements H-chemolithotrophy; denitrifying ability; pigment production; ability to accumulate poly-p-hydroxybutyrate as a cellular reserve material; biochemical mechanisms of aromatic ring cleavage; and nature of the aerobic electron transport system. The resultant data have revealed many hitherto unrecognized characters of taxonomic significance. As a consequence, it has become possible to recognize among the biotypes examined a limited number of species which can be readily and clearly distinguished from one another by multiple, unrelated phenotypic differences.

The Crabtree Effect: A Regulatory System in Yeast

Abstract: SUMMARY: When Saccharomyces cerevisiae is growing exponentially on glucose or fructose as carbon plus energy source, and in the presence of air, the glucose degradation proceeds mainly via aerobic fermentation. When the yeast is growing on mannose or galactose, degradation proceeds simultaneously via respiration and fermentation. This situation results from a repression of the of the respiratory enzymes synthesis by high fermentation rates. This regulatory system, called the “Crabtree effect”, consists actually of a repression of an energy source (respiration) by another energy source (fermentation). Various yeast strains were tested; the regulatory system was present in about 50% of them.

An Index to Deoxyribonucleic Acid Base Compositions of Bacterial Species.

Abstract: SUMMARY: This paper consists of a reference list of bacterial species for which deoxyribonuclieic acid base compositions are known. Culture-collection strain numbers have been included wherever possible. The compilation may also provide a basis for the inclusion of these data into species descriptions.

The heat resistance of bacterial spores at various water activities.

Abstract: SUMMARY: The heat resistance of the spores of six species of bacteria varied with water activity (aw) at which the spores were heated, although the magnitude of the changes differed greatly between species. At all aw values there was an approximately linear relation between the logarithm of the number of viable spores and the time of heating. The slopes of these straight lines were used to describe the observed death-rates as the time (D value) required to decrease the population by one log. unit. For all six species the greatest heat resistance was manifest at aw values of about 0.2–0.4, the maximum D values at 110° now varying from about 2 to 24 hr. At aw values less than 0.2 the heat resistance decreased; for spores rigorously dried over P2O5 (0.00 aw) the D values at 110° now varied between about 30 sec. and 30 min. When the spores were heated at aw values above 0.4 the resistance of 4 species decreased considerably, being lowest at 1.00 aw; with spores of Bacillus coagulans and B. stearothermo-philus the heat resistance decreased less at the high aw values; at 1.00 aw their D values were slightly greater than at 0.00 aw. At the high aw values the D values at 110° varied from less than 0.1 sec. for Clostridiuum botulinum type E to about 40 min. for B. coagulans and B. stearothermophilus. The Q10 for thermal death was about 10 at high aw values, decreasing to about 2 at aw values below 0.3. Under very moist conditions spores of B. stearothermophilus were about 50,000 times more heat resistant than were spores of C. botulinum type E; but at aw values less than about 0.5 this ratio fell to about 10. The convergence of this ratio resulted from more than a 100,000-fold increase in the resistance of the type E spores, and only a 20-fold increase in the resistance of the spores of B. stearothermophilus.

Deoxyribonucleic acid base composition in the genus Pseudomonas.

Abstract: SUMMARY The base compositions of deoxyribonucleic acids extracted from aerobic pseudomonads were determined by examination of the buoyant density of each sample in caesium chloride (CsCl) gradients. A collection of 165 strains, representing many of the principal biotypes among aerobic pseudomonads, was subjected to this examination. The similarities and differences in the base compositions of the genetic material have been compared with the taxonomic arrangements suggested by the comparison of phenotypic (largely nutritional and enzymic) features. The data on base composition of the deoxyribonucleic acids of the various cultures support, for the greater part, the conclusions of Stanier, Palleroni & Doudoroff (1966) and of Redfearn, Palleroni & Stanier (1966). Data are also presented on pseudomonads not included in the latter studies.

Adansonian Classification of Mycobacteria

Abstract: SUMMARY: An Adansonian classification of mycobacteria has been done by using 94 characters. Fifty-nine strains of slowly growing mycobacteria were classified into five groups: (1) Mycobacterium tuberculosis and M. bovis (2) M. kansasii; (3) M. avium, 16 strains of non-photochromogens from human sources, 6 strains of non-photochromogenic mycobacteria from soil sources, and scotochromogens from human sources (M. aquae); (4) 2 strains of non-photochromogens from human sources; (5) 1 strain of non-photo-chromogen from human source. The third group seemed to consist of three subgroups: (3, i) non-chromogens from soil sources; (3, ii) Mycobacterium avium and some non-photochromogens, which were inseparable from M. avium; (3, iii) some non-photochromogens from human sources resembling M. avium (but separable from it) and scotochromogens from human sources. Slowly growing non-photochromogenic mycobacteria from soil sources (subgroup 3, i) were considered to form a new species, M. terrae. A description of this species is given. Seventy-eight strains of rapidly growing mycobacteria were classified into seven groups: (6) 6 strains of miscellaneous species, Mycobacterium marinum, M. balnei, M. platypoecilus, M. ranae and M. piscium; (7) M. thermoresistibile (sp.nov.); (8) M. phlei; (9) M. aurum (sp.nov.); (10) M. fortuitum and group IV rapid growers; (11) M. parafortuitum; (12) M. smegmatis. These groups seemed to form independent species. Mycobacterium thermoresistibile is a new species capable of growing at 52°. Mycobacterium aurum is a new species consisting of rapidly growing scoto-chromogenic mycobacteria with urease, nicotinamidase and pyrazina-midase and some strains also with acetamidase and allantoinase.

Some criteria for the recognition of Nocardia madurae (Vincent) Blanchard.

Abstract: SUMMARY: A combination of characters for the description and identification of strains of Nocardia madurae, based on the examination of 44 strains, is presented. Although nearly all the 44 strains were received from medical laboratories, a few were isolated from soil. Some of the distinguishing properties of N. madurae are compared with those of N. asteroides, N. caviae, N. brasiliensis, N. pelletieri and Streptomyces somaliensis.

Chemistry of Hyphal Walls of Phytophthora

Abstract: SUMMARY: Hyphal walls of two phytopathogenic moulds, Phytophthora cinnamomi and P. parasitica, were isolated essentially free from cytoplasmic contamination. They have a complex chemical structure consisting of polysaccharide, protein and lipid. D-Glucose was the main monosaccharide detected in acid hydrolysates. Chromatographic evidence suggested the presence of small amounts of mannose (0.6%), glucosamine (0.3%) and traces of galactosamine and ribose. Glucans constituted nearly 90% of the wall but only about a maximum 25% of the wall could be regarded as cellulose I on the basis of solubility, resistance to hydrolysis and X-ray diffraction. Most of the wall glucan exhibited chemical and physical properties unlike typical cellulose. The spectrum of amino acids commonly found in fungal walls was detected; hydrolysates also contained hydroxyproline and two minor unidentified ninhydrin-positive components. Protein comprised 3-5% of the wall. A small amount of lipid (1-3%), mostly of the bound type, was found, and also traces of phosphorus, and compounds with absorption maxima at 263 mμ. Hyphal walls of Phytophthora cinnamomi and P. parasitica differed only slightly in quantitative composition.

Some strains in search of a genus--Corynebacterium, Mycobacterium, Nocardia or what?

Abstract: SUMMARY: In a continued search for a more suitable generic location for the species tentatively designated Mycobacterium rhodochrous (Overbeck) Gordon & Mihm, strains of some species of Corynebacterium, both animal and plant pathogens, were found to have the same morphology and the same, or nearly the same, physiological properties as strains of the species provisionally labelled M. rhodochrous. Additional tests and observations applied to the strains of the species M. rhodochrous resulted in a pattern of approximately 30 different characteristics which distinguished the species. Among the newly studied properties was the ability to utilize glucose oxidatively. Because strains of the type species of the genus Corynebacterium ferment glucose, the assignment of the glucose-oxidizing strains tentatively named M. rhodochrous to the genus Corynebacterium is not proposed.

Concentrations of nicotinamide nucleotide coenzymes in micro-organisms.

Abstract: The dynamics of varying ATP concentration was studied in the cells of the thermophilic strain of Bacillus brevis 224 synthesizing a neutral exoprotease. Some irregularities during the primary and secondary growth of the culture corresponded to the changes in the amount of ATP. A sharp decrease (by a factor of ca. 100) in the level of ATP pool was detected in the bacterial cells after 2.5 hours of their exponential growth; their growth ceased and the synthesis of protease was depressed. A decrease in the rate of the enzyme synthesis coincides with an increase in the concentration of ATP in the cells.

A comparative study of Pseudomonas pseudomallei and Bacillus mallei

Abstract: SUMMARY A comparative study of many strains of Pseudom,onas pseudomallei and Bacillus mallei has shown that these two species are very similar with respect to their nutritional and biochemical properties, thus confirming earlier claims of a relationship between them, based on such criteria as pathological and serological properties. P. pseudomallei is in all respects a typical and nutritionally highly versatile member of the genus Pseudomonas. In view of this fact we propose that B. mallei should also be placed in the genus Pseudomonas, even though it is a permanently non-motile bacterium. The ecology and possible evolutionary relationships between the two species are discussed in the light of the present findings.

The Crabtree Effect and its Relation to the Petite Mutation

Abstract: SUMMARY: Some yeast strains are able to give rise to “petite” mutants upon treatment with euflavine while some other strains do not give rise to cytoplasmic respiration-deficient mutants. Nevertheless euflavine mimics the effect of the petite mutation in those strains which are unable to give petite mutants. There is a correlation between the presence of the Crabtree effect in a yeast strain and its ability to give petite mutants.

Thiosulphate metabolism and rhodanese in Chromatium sp. strain D.

Abstract: SUMMARY: Suspensions of Chromatium D oxidized thiosulphate completely to sulphate (in the light) under anaerobic conditions in the presence of carbon dioxide. During the oxidation, intracellular sulphur accumulated transiently and sulphate production followed a biphasic pattern. Using inner-35 S-thiosulphate, the initial burst of sulphate production, which accounted for about half of the total yield, occurred principally at the expense of the inner (SO3-) atom of thiosulphate; there was no intracellular accumulation of labelled sulphur. The radioactivity from outer-35S-thiosulphate accumulated transiently within the organisms and was transferred to sulphate at a rate which was similar to the second phase of sulphate production; most of the outer (S-) atom therefore passed through the stage of endogenous sulphur. Extracts of the organism catalysed the cyanolysis of thiosulphate to give sulphite and thiocyanate. An assay for this enzyme, rhodanese, based on the spontaneous reduction of 2,6-dichlorophenol-indophenol by sulphite was developed. The enzyme was also detected in extracts of Athiorhodaceae. The enzyme was partially purified from extracts of Chromatium D and resolved into two active fractions. It is concluded that endogenous sulphur is an intermediate in the oxidation of thiosulphate by Chromatium D and that the cleavage of the S—S bond in the molecule is a key step in the oxidation process. Rhodanese, which catalyses this type of reaction, may be concerned in this cleavage.

Loss of antibiotic resistance in Staphylococcus aureus resulting from growth at high temperature.

Abstract: SUMMARY: Fifty strains of Staphylococcus aureus resistant to penicillin or tetracycline or both were examined for loss of these two resistances as the result of growth at 43-44°. Twelve strains showed a loss of penicillin resistance under the experimental conditions, and of these twelve, three showed a loss of tetracycline resistance. The two resistances were lost independently; in strains in which both resistances were lost most of the sensitive variants had lost one or other resistance but not both. However, penicillin resistance was lost only in strains that were also tetracycline-resistant and vice versa. All strains in which a loss of resistance occurred had similar phage-typing patterns and all belonged to the ‘52, 52A, 80, 81 complex’ of strains. Not all strains in the complex, however, showed a loss of resistance. Both penicillin and tetracycline resistance were transduced into suitable sensitive recipients. The results showed that the heat-sensitivity of the transduced resistance was the same as in the donor in which the transducing phage was propagated. The results are consistent with the hypothesis that these two resistances are carried by two separate plasmids, at least in certain strains of S. aureus. Nine multiply-resistant strains of Staphylococcus aureus were examined for loss of resistance to antibiotics other than penicillin and tetracycline as the result of growth at elevated temperatures. These other antibiotics included streptomycin, erythromycin, novobiocin, oleandomycin, neomycin and bacitracin. In no case was any loss of resistance observed.

The Structure and Infective Process of a Pseudomonas Aeruginosa Bacteriophage Containing Ribonucleic Acid

Abstract: SUMMARY: The electron microscope shows that there are a number of different morphological types of bacteriophages which grow on Pseudomonas aeruginosa. Some are conventional ones with contractile or non-contractile tails, but the most interesting is a tail-less phage containing RNA. The structure of both conventional and RNA phages is described. It is shown that the RNA phage probably infects the cell via polar pili. Intracellular multiplication and lysis by the RNA phage is followed in thin sections of infected cells. In the early stages, the nuclear region is much reduced and dense granular areas appear. These subsequently differentiate into crystalline aggregates of virus particles; at the same time a large bulge, identical to that found associated with spheroplast formation, appears. The crystals continue to increase in size until the spheroplast ruptures and lysis occurs.

Diurnal Changes in the Concentrations of Micro-organisms in the Rumens of Sheep Fed Limited Diets Once Daily: WITH AN APPENDIX ON THE KINETICS OF RUMEN MICROBES AND FLOW

Abstract: SUMMARY: The pattern of change of concentration of different groups of microorganisms in the rumen was found to be characteristic of the group and little affected by the time of day, the nature of the diet, or the host animal. The dilution rate of rumen liquor and the rate of change of concentration of several groups of micro-organisms were measured at intervals following feeding; this allowed calculation of the apparent specific growth rate. The changes in concentration of the ophryoscolecid ciliate protozoa, the selenomonads and the oval organism described by Eadie could be explained as the resultant of the changes in dilution rate due to the act of eating and in growth rate in response to incoming nutrients. Rates of change in concentration greater than could be accounted for on the basis of growth and dilution alone were found with the peptostreptococci, the polymastigate flagellate protozoa and the holotrich ciliate protozoa. It is suggested that the peptostreptococci underwent lysis or engulfment by other organisms and that the polymastigates became sequestered, probably close to the rumen wall. The concentration changes of the holotrichs were more difficult to understand, but it would appear that little division took place for some 18 hr after feeding, followed by several divisions in quick succession. The oscillospirae showed two peaks in concentration; no explanation can be offered for this.

The Fluorescent Staining of Bacteriophage Nucleic Acids

Abstract: SUMMARY: The staining of viral nucleic acids with acridine orange and their subsequent examination under the fluorescence microscope permits the determination of the type and strandedness. Since the existing procedures are complicated, modifications have been devised which simplify them and avoid the use of the fluorescence microscope, an ordinary ultraviolet lamp being substituted. Also, it has been found that certain post-staining treatments cause colour changes which are related to the strandedness and type of nucleic acid and hence are valuable confirmations of the normally used nuclease sensitivity tests. The new procedures were tested for a wide range of specimens including double-stranded ribonucleic acid, but emphasis has been placed on the identification of bacteriophage nucleic acids.

DNA homology and taxonomy of Pseudomonas and Xanthomonas.

Abstract: SUMMARY: The relatedness between several nomen species of the Pseudomonas-Xanthomonas group and some other organisms was numerically fixed through DNA homology and DNA base composition. For Pseudomonas the numerically analysed strains proposed by Lysenko as neotypes were used. The mean % (G+C) was in the range 60-67.5. 14C-DNA from either Pseudomonas fluorescens or P. putida was hybridized with DNA from 17 different species centres and the DNA homology was in the range 50-100%. Genetic species differentiation in the genus Pseudomonas seems justified. In three border cases (P. iodinum, P. diminuta and P. atlantica) DNA homology was only 28-50%, so the inclusion of these organisms in the genus Pseudomonas is uncertain. The species centres P. pavonacea and P. rubescens are omitted from the genus Pseudomonas because of their very low DNA homology and aberrant DNA base composition. Twenty-eight nomen species of Xanthomonas all form a narrow group in the range 63.5-69% (G+C). With two exceptions DNA homology with a median strain Xanthomonas pelargonii was always over 75% and frequently nearly complete. 14C-DNA from P. fluorescens hybridized with Xanthomonas-DNA to the same extent as with the pseudomonads proper. The Xanthomonas cluster overlapped perfectly with part of the Pseudomonas group. It is proposed therefore to gather all xanthomonads in a single genetic species P. campestris. This is such a dense cluster that the preservation of separate species names for the border cases seems undesirable. About one half to two-thirds of Pseudomonas- and Xanthomonas-DNA is identical. The genera Rhizobium, Azotobacter and Azomonas appeared to be rather closely related to Pseudomonas since they shared some 40-50% of their DNA. The genus Serratia appeared to be more closely related to Pseudomonas than to Escherichia. The genera Gluconobacter, Acetobacter, Serratia and Escherichia shared some 20-30% DNA with Pseudomonas, but Bacillus-DNA was almost entirely different. From a comparison between DNA homology and taximetric similarity, it appeared that most pseudomonads would not contain unused genes. The advantages of a classification based on % (G+C) and DNA homology are obvious.

The sterol requirement of Phytophthora cactorum

Abstract: SUMMARY: Several sterols and related substances were tested for ability to promote sexual reproduction in Phytophthora cactorum. These compounds were classified as active (oospores formed), partially active (oogonia and antheridia formed, but no oospores), or inactive (no oogonia). Quantitative differences between active substances were noted in respect of the numbers of oospores produced and the time of their appearance. The most active substances tested were 29-isofucosterol and β-sitosterol. Loss of activity was associated with shortening of the side chain of the sterol molecule or change in its configuration, absence of a double bond in the B ring or of a hydroxyl group at position 3 on the A ring.

The Survival of Escherichia coli sprayed into Air and into Nitrogen from Distilled Water and from Solutions of Protecting Agents, as a Function of Relative Humidity

Abstract: SUMMARY: The survival in air as a function of relative humidity (RH) and aerosol age is reported for Escherichia coli (strains B and Jepp) and for Serratia marcescens (strain UK 8) sprayed from suspensions in distilled water and in solutions of dextran and of raffinose. The survival in nitrogen (> 99.9%) of E. coli (strains B, Jepp and commune) is given as a function of RH, when sprayed from suspension in distilled water and in raffinose solution. The results show that E. coli in the aerosol was subject to at least three stresses, an air stress, an RH stress, and a collection stress. The air stress accounted for loss of viability at low RH and the RH stress occured at high RH and is expressed as RH ranges in which E. coli rapidly lost viability. The survival, especially at high RH, depended upon the composition of the collecting fluid. At high RH a range of RH was found in which the bacteria were unstable when collected in phosphate buffer. Addition of raffinose (chosen as a typical protecting agent to the spray fluid and the addition of M-sucrose to the collecting fluid eliminated the instability for E. coli (commune) and decreased it for the other two strains.

Approach to an Improved Taxonomy of the genus Agrobacterium

Abstract: SUMMARY: With a view to an improved taxonomy of the genus Agrobacterium, 45 strains including representatives of all nomen-species, were used to investigate the following features: base composition and compositional distribution of pure deoxyribonucleic acid (DNA); type of flagellation; 3-ketoglycoside formation; phytopathogenicity for tomato and Datura It is proposed to limit the genus Agrobacterium to two, or possibly three, species: (I) Agrobacterium radiobacter and its phytopathogenic variety A radiobacter var rumefaciens; (2) A rhizogenes; and (3) possibly A pseudotsugae More work on the latter two species is required before they can definitely be accepted as separate species of this genus The DNA of all the strains of the former two species has a Tm value in the narrow range of 938°-95 The corresponding with an average molar guanine + cytosine (GC) content of 595–628% The variance σ of the compositional distribution of the DNA molecules ranges between 0 and 088% with an average of GC) The only available strain of A pseudotsugae, with 677% GC, was mpletely out of this range and its chromosomal DNA was clearly different from that of the other two species All strains of Agrobacterium proper were peritrichous, frequently with 5–6 flagella All 8 strains of A radiobacter and 24 of 28 strains of the variety ‘tumefaciens’ converted lactose into 3-ketolactose; all the other strains were negative in this respet Several arguments are advanced to include the strain A stellulatum and A gypsophilae from this genus The relationship between Agrobacterium and some other genera is shown graphically in a plot of mean similarity vermus DNA base composition

Phosphomannans and Other Components of Flocculent and Non-Flocculent Walls of Saccharomyces cerevisiae

Abstract: SUMMARY: Preparations of flocculent and of non-flocculent cell walls were obtained from flocculent and non-flocculent cells of a strain of Saccharomyces cerevisiae. Flocculent walls contained 46% glucan, 43% mannan, 0.4% P, 1.1% hexosamine, 0.79% non-hexosamine N; non-flocculent walls contained 47% glucan, 44% mannan, 0.3% P, 1.2% hexosamine and 0.98%non-hexosamine N. Mannose-6-phosphate was identified as the principal phosphorus compound present. The mannose residue formed part of the cell-wall mannan and the phosphate was also linked by a second, labile, ester bond to an unidentified site. The degree of phosphorylation of the mannan varied from 1 phosphate to 19 mannose residues in non-flocculent cells to 1 phosphate to 13 residues in flocculent cells.

Biosynthesis of the Antibiotic Nisin by Whole Streptococcus lactis Organisms

Abstract: SUMMARY: A reaction mixture is described consisting of a buffered solution of amino acids, salts, growth factors and glucose in which freshly harvested washed Streptococcus lactis incorporated radioactive tracers and synthesized nisin. Rapid nisin synthesis started after a delay of 30-60 min. but bacteria pre-incubated in the reaction mixture synthesized nisin without delay although the rate of protein synthesis remained the same as that of freshly harvested bacteria. Although growing S. lactis is sensitive to penicillin and mitomycin these antibiotics had no effect on nisin synthesis by washed organisms. Actinomycin D inhibited uptake of tritiated uridine immediately and inhibited nisin synthesis after a delay of about 60 min. Antibiotics which interfere with protein synthesis, e.g. chloramphenicol, puromycin and terramycin also interfered with nisin synthesis. The inhibition was immediate and occurred irrespective of whether the antibiotics were added at the beginning of an experiment or after 50 min. Nisin synthesis was more sensitive than protein synthesis. The data suggest that nisin synthesis occurs by a mechanism similar to that of protein synthesis.

Observations on the Adsorption of Caulobacter Bacteriophages containing Ribonucleic Acid

Abstract: SUMMARY: Caulobacter bacteriophages containing ribonucleic acid have been found to attach to pili of their hosts. Only when the phage is actually lytic for a given host can the phage+pilus complexes be observed; non-specific complexes are not formed. Removal of the pili from the host by shear treatment before phage adsorption resulted in effective inhibition of phage adsorption. While swarmer caulobacters frequently possessed pili which were located at the flagellated pole of the organism, stalked caulobacters were almost always devoid of these structures. Adsorption experiments with segregated populations of caulobacters indicated that stalked caulobacters adsorbed RNA phages very poorly, while in swarmer populations and unsegregated cultures the RNA phages were efficiently adsorbed.

Distribution of Cell Size in Growing Cultures of Bacteria and the Applicability of the Collins-Richmond Principle

Abstract: SUMMARY: Theoretical cell-size distributions for populations of growing cells are calculated for different models of cell growth and for different degrees of variability in size of cells at division. From these computations, it is concluded that the coefficient of variation (c.v.) is almost independent of the relationship of growth rate to cell size. It is 20% if there is no variability in the cell size at division. For a case typical for enteric rod-shaped bacteria, the variability in cell size at division is about 10% and the calculated c.v. in cell size of the population in this case increases to 22-23%. Calculations based on the microscopic observations of others are in the range of 20-25%. It is proposed that the c.v. of the size distribution serve as a standard in assessing the accuracy of the electronic instruments that size bacteria. Evidently, only the higher moments of the population cell size distribution contain information bearing on the growth dependence of the organisms on their size. It is pointed out that this means that the Collins-Richmond principle must be applied only to precise and accurate data.

Effert Of Lactoperoxidase and Thiocyanate on the Growth of Streptococcus pyogenes and Streptococcus agalactiae in a Chemically Defined Culture Medium

Abstract: SUMMARY: A chemically defined culture medium was used to study the effect of Parified lactoperoxidase and thiocyanate on the growth of several cultures of Streptococcus pyogenes and S agalactiae While not inhibited by either component alone, S pyogenes growth was completely inhibited when both components were present in the medium The growth inhibition was annulled completely by glutathione, thioglycollic (mercaptoacetic) acid of catalase S pyogenes glyceraldehyde phosphate dehydrogenase was inhibited by lactoperoxidase when hydrogen peroxide was present The inhibition was annulled with cysteine and glutathione which suggested this dehydrogenase to be a possible site of inhibition The inhibition was Postulated to be a peroxidatic conversion of essential enzymic sulphydryl groups to inactive disulphide groups, thus interfering with the energy metabolism up of S pyogenes With S agalactiae cultures a delay in growth inhibition up to 6 hr resulted instead of complete growth inhibition Catalase neutralized this effect The extent of growth inhibition was greatest in those strains which were unable to adapt to an oxidative pathway for their energy supply In becoming independent of the fermentative pathway, the cultures were no longer as sensitive to peroxidase, thioeysnate and hydrogen peroxide The necessity for thiocyanate in the is inhibitory system is not yet clear Thiouracil and thiourea were ineffective replacements for thiocyanate

Some Properties of Three Related Viruses: Andean Potato Latent, Dulcamara Mottle, and Ononis Yellow Mosaic

Abstract: SUMMARY: Three similar and apparently previously unrecorded viruses were studied and found to be most like viruses of the turnip yellow mosaic group. Andean potato latent virus (APLV) was obtained from primitive cultivated potatoes collected in the high tropical Andes, dulcamara mottle virus (DMV) from Solanum dulcamara L. growing near Rothamsted, and Ononis yellow mosaic virus from Ononis repens L. growing in many parts of England. All three viruses are readily transmitted by sap inoculation; APLV and DMV are transmitted through the seed of infected plants; DMV is transmitted by the flea beetle Psylloides affinis Paykull. Plants infected by one of the viruses are not protected against infection by the others. Purified preparations of these viruses have many common properties. Each virus has isometric particles 25-30 mμ in diameter, indistinguishable in appearance from one another and from the particles of turnip yellow mosaic virus. Preparations of each contain mainly two types of particles with sedimentation coefficients of about 115S and 55S, corresponding to infective nucleoprotein particles and non-infective “empty” particles respectively. Each contains nucleic acid with a molar base composition of about G 16% A 22% C 33% U 29%. The three viruses are serologically related; antisera titres are 8-128 times greater with homologous than with the heterologous viruses. No serological relationship was found between these viruses and turnip yellow mosaic, wild cucumber mosaic, cocoa yellow mosaic, squash mosaic and red clover mottle viruses. Plants infected with APLV or DMV when sprayed with solutions of 2-thiouracil or 6-azauracil produced fewer nucleoprotein particles and more “empty” protein particles, than plants sprayed with water.

The oxidation of fatty acids by spores of penicillium roqueforti.

Abstract: SUMMARY: The ability of washed spores of Penicillium roqueforti to oxidize fatty acids decreased markedly with age but was restored by adding specific sugars and amino acids. Only the C6 to C12 fatty acids were oxidized to the corresponding methyl ketone with one less carbon atom. The yield of methyl ketone between pH 5.5 and 7.0 decreased progressively from a maximum of 75% from octanoic acid to zero from myristic acid. The small amounts of metabolic carbon dioxide evolved greatly stimulated the oxidation of C10 and C12 fatty acids. The addition of sodium azide, 2,4-dinitrophenol (DNP) and certain divalent metallic ions, but not chloramphenicol, inhibited the oxidation of fatty acids. Oxidation was preceded by a lag period which was lengthened by increasing the fatty acid concentration or by decreasing the concentration of spores. Since cell-free extracts of spores were able to oxidize fatty acids, the lag phase with whole spores appears to be due to the absence of active transport systems. This is also indicated by the elimination of the lag phase by pre-incubation with octanoic acid but not by pre-incubation with glucose or casamino acids. The possible significance of methyl ketone formation in fatty acid metabolism is discussed.

The relationship of F type piliation and F phage sensitivity to drug resistance transfer in R+F- Escherichia coli K 12.

Abstract: SUMMARY: Resistance factors (R factors), of the kind which confer sensitivity to F specific phage as well as promoting conjugation in enterobacteria determine the production of a pilus similar to the specific pilus seen on F- bacteria. R factors, however, unlike F, also determine the production of a repressor of function: this means that in an established R+ culture, only a small proportion of the bacteria can conjugate, be infected with F phage, or produce the pilus. Under conditions where repression is lifted, the three characters, conjugation, F phage sensitivity and production of the pilus, are coordinately de-repressed.

Observations on the Effects of a Chromosome Duplication in Aspergillus Nidulans

Abstract: SUMMARY: During a study of genetic factors affecting the morphology of Aspergillus nidulans a novel and characteristic variant was observed among the progeny of crosses involving certain morphologically normal parents. This type, which had a diminished linear growth rate, segregated in constant proportion; it was designated ‘crinkled’. It carried a duplication for a chromosome segment as a result of an unequal translocation in one parent. Crinkled colonies showed vegetative instability and sectored types which, in varying degree, approached normal morphology and growth rate. These revertants probably arose by loss of a variable part of the chromosome segment carried in duplicate. The loss occurred from either the translocated or untranslocated segment.