- Volume 54, Issue 2, 1968

SUMMARY: The survival of Escherichia coli K12 HfrC sprayed from distilled water into a nitrogen atmosphere as a function of aerosol age and of storage relative humidity (RH) is demonstrated. The survival pattern was typically that of E. coli, i.e. marked instability in a region at high RH and better stability at low RH. The results of changing the RH from the storage RH to 10 % or 30% are described. Comparison of survival in nitrogen with that in air showed air to be slightly toxic, the toxic component being oxygen or a trace of some contaminant in it. Glycerol and raffinose were slightly protective as additives at high RH; at low RH glycerol was toxic, but raffinose was highly protective. It was discovered that E. coli K12 HfrC carried a temperate phage and that this phage was not activated by the processes involved in aerosol experiments. The synthesis of phages T3 and μ2 by E. coli K12 HfrC, collected from the aerosol, was examined. Phage production and viability were similar, and hence it is concluded that in a nitrogen atmosphere loss of viability was not caused by DNA inactivation, DNA synthesis inhibition or inhibition of cell-wall division, but by failure of RNA synthesis, protein synthesis or energy production.

SUMMARY: An organism was isolated in pure culture from germinating seeds of Psychotria nairobiensis Brem. By standard bacteriological techniques the organism was considered to belong to the Chromobacterium lividum group. It was shown to fix nitrogen. By using an antiserum prepared against one strain, four strains were found to be serologically identical and showed some cross-reaction with Agrobacterium tumefaciens. An immunofluorescence technique was used in a search for these organisms in the seed embryo, leaf nodules and other tissues of a number of leaf-nodulated Rubiaceae and Myrsinaceae including Psychotria nairobiensis, Ardisia crispa and a non- nodulated species of Myrsinaceae, Ardisia elliptica. From the results obtained it is concluded that this serotype of Chromobacterium lividum is present in the leaf-nodulated members of these families of plants.

SUMMARY: A study was made of the binding of aflatoxin B1 and its toxic effects on Bacillus megaterium NRRL B-1368. After a 12 hr incubation period, 5 μg. aflatoxin B1m1. inhibited growth of the test organism 95 %. Viable organisms decreased from 3·8 ⨯ 107/ml. in the controls to 5·0 ⨯ 104/ml. in a growth medium containing 50 μg. aflatoxin B1/ml., after 4 hr. of incubation. Viability was not significantly decreased, however, when the organisms were incubated with the same concentration of toxin either under nitrogen, or at 5°, or in the presence of bacteriostatic concentrations of tetracycline. Binding experiments showed that 4·0 ⨯ 109 organisms/ml. took up approximately 7.0 μg. aflatoxin B1/ml. After five aqueous washes of the organisms, 20-25% of the toxin remained bound to them. The tightly bound toxin was removed by ultrasonic treatment of the organisms and chloroform extraction of the macerate. Removal of cell walls by lysozyme following toxin uptake released 23% of the initially bound toxin, and osmotic rupture of the protoplasts an additional 7%. Toxin was also taken up by intact and by ruptured protoplasts. Removal of nucleic acids from the membranes did not alter their capacity to bind aflatoxin B1.

SUMMARY: Cell walls were prepared from various species of the genus Pseudomonas which are resistant to ethylenediaminetetra-acetic acid (EDTA). The cell walls were analysed and comparisons made with the walls of EDTA-sensitive pseudomonads. The walls had none of the structural features which appeared to characterize EDTA-sensitive pseudomonads. Lipopolysaccharide was not extracted from the walls of resistant organisms by EDTA at pH 9.2. The wall of P. iodinum contained almost no lipid or protein but consisted mainly of glycosaminopeptide and material which resembled a teichoic acid. It is proposed that this organism be removed from the genus Pseudomonas. The walls of P. diminuta, P. maltophilia, P. pavonacea and P. rubescens had compositions broadly characteristic of Gram-negative bacteria. The four species are not obviously related. Glycolipids were present in the walls of P. diminuta, P. maltophilia and P. rubescens. An ornithine-containing lipid was isolated from P. rubescens and partly characterized. A small amount of this lipid was also present in P. maltophilia. The wall of P. maltophilia was distinctive in its wide range of monosaccharide components, including an unidentified neutral sugar of high mobility on paper chromatograms.

SUMMARY: The use of a conditional probability model for the identification of bacteria is illustrated by a pilot study on a group consisting mainly of bacteria of the family Enterobacteriacae. It is shown that such models may be untrustworthy unless more stringent criteria are used about the basic data and about the results than is normally the case in studies of this kind, including the present one.

SUMMARY: The distribution of [14C]-L-cysteine and [14C]iodoacetic acid in mycelium and sclerotia of Sclerotium rolfsii Sacc., and the effect of disodium ethylene-diaminetetraacetic acid (Na2EDTA), trans-1, 2-diaminocyclohexane-N, N, N´, N´-tetraacetic acid (Chel. C.D.), potassium iodate and phenylthiourea on the formation of sclerotia by S. rolfsii were studied. [14C]-labelled iodoacetic acid accumulated specifically in the sclerotia, whereas [14C]-L-cysteine was equally distributed throughout the mycelium. Accumulation of iodoacetic acid at specific sites was observed even before the formation of the sclerotia. Most of the radioactivity of the fungal mycelium grown on [14C]iodoacetic acid was found in the cell-free extract, 93° of the radioactivity of the extract being associated with the ammonium sulphate-precipitated fraction. Na2-EDTA, Chel. C.D. and potassium iodate at 10-3M also induced sclerotial formation. The effect of Na2EDTA was eliminated by the addition of 3 × 10-5M-Cu2+, but not by Fe2+, Zn2+, Co2+, Mn2+, Ca2+ nor Mg2+. Phenylthiourea (10-3M) initiated sclerotial formation but inhibited further development and melanogenesis. It is suggested that sclerotial formation in S. rolfsii is induced by inactivation of a -SH + Cu2+-containing protein entity which acts as a repressor of sclerotial formation.

SUMMARY: A survey of 91 strains of Streptococcus salivarius showed that 72 could be classified as type I or II. Only type I strains reacted with group K antiserum. The component responsible for type specificity is a cell-wall polysaccharide composed in each case of galactose, glucose, rhamnose and a trace of glucosamine. However, differences in polysaccharide structure are indicated by differences in the rate of release of soluble carbohydrate by dilute acid. Soluble cell-wall products were obtained by digesting wall with a Streptomyces enzyme preparation and used for serological studies. Galactose was the most effective monosaccharide inhibitor of both type I and type II precipitation. Further investigation suggested that type I specificity depends on the grouping O-β-D-galactopyranosyl-(I → 6)-D-galactose.

SUMMARY: The rate of germination of populations of spores of Bacillus coagulans decreased as germination progressed, late-germinating spores exhibiting a delay or decreased probability of germination. Delayed germination was not due to changes occurring in the environment during germination. Colonies formed by delayed individuals had a similar morphology to those produced by the rest of the population. Delayed individuals constituted not more than 5% of the total spore population. In a sample containing 17 delayed individuals, 14 gave spore populations with initial germination rates like that of the parent population, while three yielded populations which germinated at much slower rates. Delayed germination still occurred in spore populations grown from single colonies of the parent population. It was concluded that the spore populations were heterogeneous with regard to germination; reasons for the heterogeneity are discussed.

SUMMARY: Large dilutions of bacterial suspensions were made at 45° in a buffered complex medium containing agar. The tubes of medium with the serial dilutions of bacteria were solidified by cooling; subsequent incubation at 37° permitted bacterial growth in discrete colonies. The density of colonial growth was enumerated by comparison with a set of prepared standards calibrated by the pour-plate technique. A large range (log10 2·5 to 10·5) of colony counts was covered in only four test tubes without any prediction of the approximate count. The method has advantages of speed, economy of reagents and apparatus, as well as range and precision.

SUMMARY: Suspended tissue cultures of R I-resistant Solanum tuberosum infected with race 4 sporangia of Phytophthora infestans developed toxicity in the culture fluid when tested after 10 days against a zoospore suspension of P. infestans. The toxic material was extracted into ether and salicylic, vanillic and p-hydroxybenzoic acids were identified in the toxic fraction by thin-layer chromatography, gas-liquid chromatography and mass spectrometry. Quantitative estimates of the amounts of material present in the toxic fraction allowed a mixture to be made which closely simulated the natural toxic material. Use of pure materials allowed an analysis of the behaviour of the zoospores with variation in dosage.

SUMMARY: The acid-resistant and heat-resistant alga Cyanidium caldarium yields cell-wall preparations which are unusually rich in protein (50 to 55‥) and contain only small amounts of polysaccharides (hemicellulose, 12 to 14 ‥ cellulose, 3 to 4‥). At least 13 amino acids are present in the cell walls, but diamino-pimelic acid, muramic acid and amino sugars are absent. It is suggested that Cyanidium is more closely related to the green rather than the blue-green algae.

SUMMARY:Clostridium tetanomorphum grew in medium containing yeast extract when supplied with glutamate, histidine, glucose, maltose or pyruvate. Measurements of Q H 2 values and specific activities for two enzymes, phosphofructokinase and β-methylaspartase indicated that the glucose and glutamate fermentations were inducible. With glucose, the onset of active glucose metabolism was delayed in preference for energy sources provided by yeast extract. The inhibitory mechanism which was responsible for this delay did not appear to be a typical enzyme repression but rather a catabolite inhibition. No significant changes in the cobalamin content of the organisms accompanied growth with different substrates.

SUMMARY: A relatively rapid and reliable method is described for producing axenic cultures of soil-borne blue-green algae, of the blue-green algal endophytes of certain cycads, and the blue-green endophyte of the angiosperm Gunnera chilensis Endl. It was based on the micro-manipulation of hormogonia and akinetes, from which axenic cultures were propagated. Micromanipulation was done during growth in impure culture on an agar medium. The technique was used to obtain axenic cultures of fifteen soil isolates, the endophytes of the cycads Macrozamia lucida (Linnaeus) Johnson, Encephalartos altensteinii Lehm., and Bowenia serrulata Bull, and the endophyte of Gunnera chilensis Endl. The soil isolates have been tentatively identified as species of the genera Nostoc, Anabaena, Calothrix, Scytonema, Wollea, Microchaete, and Oscillatoria.

SUMMARY: Thymidine kinase (EC 2.7.1.21), an enzyme that catalyses the phosphorylation of thymidine to thymidine-5’-phosphate in the presence of adenosine triphosphate and Mg2+, was not detected in cell-free extracts of Neurospora crassa, Aspergillus nidulans, Saccharomyces cerevisiae or Euglena gracilis. Deoxyribonucleic acid was not specifically labelled in Neurospora crassa grown in the presence of [14C]thymidine, [14C]thymidine monophosphate or [14C]thymidinetr iphosphate. Instead, the isotope was incorporated into both types of nucleic acid in a ratio which approximated the mole ratio of ribonucleic acid to deoxyribonucleic acid. It is considered that the absence of thymidine kinase prevents the specific incorporation of thymidine into deoxyribonucleic acid in intact cells of Neurospora crassa.