- Volume 12, Issue 3, 1955

SUMMARY: The hypothesis that the fungicide 2-heptadecyl-2-imidazoline might owe its effectiveness to interference with the synthesis of histidine or purines was tested in experiments with Sclerotinia fructicola. The toxicity of the fungicide was significantly decreased by guanine, xanthine, or xanthosine; a number of other related compounds and histidine had no effect.

Annulment of the action of 2-heptadecyl-2-imidazoline by either xanthine or guanine was competitive. The inhibition index for 2-heptadecyl-2-imidazoline/ xanthine was 0·000581, while that for 2-heptadecyl-2-imidazoline/guanine was 0·000832. Attempts to demonstrate the accumulation of the purine precursor 5-amino-4-imidazolecarboxamide in culture filtrates of Sclerotinia fructicola grown in the presence of the fungicide were negative.

SUMMARY: An apparently lysogenic strain of Xanthomonas pruni was isolated. A series of experiments was performed to determine whether the isolate was lysogenic or whether it was a case of pseudolysogenesis. The results indicated that it was a true case of lysogenesis. The phage released by the lysogenic organism differed from the one used in its selection. The possible origin of this new phage and its lysogenic host is discussed.

SUMMARY:Screening tests on the inhibition of growth of phage T2r+ and of its host, Escherichia coli strain b, by a number of enzyme inhibitors, showed that only arsenite, borate and cyanide inhibited the phage at concentrations which were without effect on the phage alone, on its adsorption to bacteria, or on bacterial growth. In single-step experiments, the inhibitory effect of arsenite and cyanide on phage multiplication was maintained for several hours, whereas borate merely lengthened the latent period by a few minutes without decreasing the final titre. Arsenite was still effective as an inhibitor when added half way through the latent period.

SUMMARY:The isolation from soil of three strains of oxalate-decomposing organisms different from other known oxalate-decomposing organisms is described: only one strain was studied in detail. This organism grew in concentrations of potassium oxalate up to 2 % (w/v) with an optimum of c. 1 % (w/v). Growth was preceded by a lag period of c. 18 hr. which was not decreased by addition of yeast autolysate, bicarbonate or formate. Of several other substrates tested only glycol-late, dl-lactate. pyruvate, dl-malate and succinate supported growth. Washed cell suspensions oxidized oxalate and the gas exchanges observed corresponded with an assimilation of some of the oxalate used. The oxidizing powers of washed cells varied somewhat with the carbon source used for growth.

SUMMARY:Desulphovibrio desulphuricans (strain El Agheila Z) oxidized malate, fumarate, succinate, lactate and pyruvate quantitatively to acetate in cultures containing excess sulphate. Polysaccharide accumulated in old cultures.

Cell suspensions harvested from malate media yielded theoretical amounts of sulphide and CO2 from malate, fumarate or succinate+excess sulphate. Succinate was formed transiently during malate oxidation. Various inorganic sulphur-containing anions, methylene blue or oxygen acted as alternative hydrogen acceptors to sulphate for malate oxidation. In the absence of sulphate, malate was metabolized yielding acetate, CO2 and succinate in the molar ratio 3 malate → 2 succinate + 2CO2+ acetate; in hydrogen, malate or fumarate were partly reduced to succinate. Malate or fumarate accelerated the reduction of sulphate, but not dithionite, in hydrogen. Suspensions treated with cetyltrimethylammonium bromide formed fumarate and lactate + CO2 from malate. Fumarate was formed via a reversible fumarase: lactate was formed via a decarboxylase system independent of cozymase, Mn++, cocarboxylase or codecarboxylase.

Cell suspensions harvested from lactate media yielded theoretical amounts of sulphide and CO2 from lactate or pyruvate+ excess sulphate. In the presence of arsenite, pyruvate was formed from lactate; pyruvate formation was demonstrated with another strain.

Suspensions of strain California 43:63 harvested from lactate media reduced fumarate in H2 quantitatively to succinate; crotonate, maleate or acetylene-dicarb-oxylate were not reduced; malate was reduced slowly.

Hence the reaction sequence: succinate ⇌ fumarate ⇌ malate ⇌ lactate ⇌ pyruvate ⇌ acetate probably takes place in these bacteria: a reversible succinate ⇌ fumarate system may form a link between sulphate reduction and the oxidation of organic compounds or hydrogen.

SUMMARY: Fourteen strains of the Azotobacter agile-A. vinelandii group were classified into one or the other of the above species by morphological, cultural and growth characteristics. The groups were then surveyed by a study of oxidative reactions of whole cell suspensions on some intermediates of the tricarboxylic acid (TCA) cycle: acetate, malate, succinate, α-ketoglutarate and citrate.

All strains grew readily in a nitrogen-free medium. Organisms that were morphologically large rods or ovoid cells produced a green water-soluble pigment in an iron-deficient medium, and did not utilize mannitol or nitrate in the absence of another carbon or nitrogen source. Strains composed of smaller rods also produced the green pigment, and would utilize mannitol and nitrate. The first group was classified as Azotobacter agile, and the second as A. vinelandii.

Q O2(N)values on the TCA substrates tested did not indicate group variation. However, 15–24 hr. cells of the Azotobacter agile group as a unit did oxidize succinate with a shorter lag period (not greater than 30 min.) than strains of the A. vinelandii group (not less than 50 min.). A similar response to malate was noted, but in contrast most strains of A. vinelandii oxidized α-ketoglutarate after a shorter lag than did strains of A. agile. Citrate oxidation was variable among strains; all organisms but A. vinelandii O were apparently inhibited by the chelation of magnesium (and possibly calcium) by citrate. The physiological and oxidative responses of freshly isolated strains did not differ markedly from those of laboratory cultures of the same species.

SUMMARY: The labyrinthula isolates of Watson will grow over a wide range of pH values in a medium of which the inorganic constituents reflect their marine origin. All are obligately marine, though the less exacting requirements of L. macro-cystis var. atlantica suggest an estuarine habitat. Although only L. minttta var. atlantica requires an amino acid (l-leucine) as a growth factor, no isolate grew well on substrates other than amino acids. All require thiamine. Organic requirements may be obtained from host plants.

SUMMARY: Further investigation of the specificity of the steroid growth factor requirement of Labyrinthula vitellina var. pacifica has provided a detailed description of the structural requirements for activity. Active compounds include sterols and products of their autoxidation; the activity of the sterols is not, however, due to autoxidation during the assay period. The data obtained circumscribe the characteristics of the essential metabolite represented by this requirement but do not identify it.

SUMMARY: Cells of Saccharomyces carlsbergensis and S. cerevisiae were fixed with osmic acid, embedded in plastic, sectioned at one-twentieth of a micron, and then observed in the electron microscope. The pictures obtained gave confirmation of the double membrane nature of the yeast cell wall reported by earlier workers such as Northcote & Home (1952) , and gave some indication of the presence of additional very thin membranes in the cell wall. It was suggested that the two cell wall membranes might be the two osmotic barriers observed to be present in the yeast cell wall by Conway & Downey (1950) . No structure was seen which could be identified as the cytoplasmic membrane.

SUMMARY:Two species of naphthalene-utilizing bacteria from soil were able to metabolize 1-chloro- and 1-bronionaphthalene. From cultures in which 1-chloro-naphthalene was the sole source of organic carbon, d-8-chloro-1:2-dihydro-1:2-di-hydroxynaphthalene and 3-chlorosalicylic acid were isolated. 3-Bromosalicylic acid was isolated from cultures with 1-bromonaphthalene and evidence of the formation of a ‘diol’ compound obtained. The course of the metabolic pathways is discussed.

SUMMARY:By the selective action of certain bacteriophages on cultures of susceptible streptococci it is possible to alter or enhance certain of their characteristics. The extractable M antigen may be greatly increased; non-mucoid strains may become completely mucoid with or without the increase in M antigen. Some phage-selected cultures have shown a marked increase in mouse virulence and some an ability to survive in normal human blood not possessed by the parent strain.

SUMMARY:Cultures of Strigomonas oncopelti multiplied more rapidly and a higher peak population was reached when glucose was added to the peptone medium. The rate of glucose consumption varied during the growth cycle; the maximum rate recorded was 90 μg./106 organisms 24 hr. The breakdown of glucose resulted in the production of acetic, succinic, probably lactic, and an unidentified non-volatile acid.

SUMMARY :In developing a technique for the freeze-drying of lactobacilli particular attention was paid to the percentage survival rate; this was estimated by viable counts immediately after drying and after storage of the dried cultures. The main factor influencing survival rate was the suspending medium, the best results being obtained in horse serum with 8 % added glucose. Forty-four cultures, fourteen freshly isolated, representative of a comprehensive collection of 452 lactobacilli (see Briggs, 1953 a ) were freeze-dried in this vehicle using the apparatus and technique described. The majority of the survival rates were over 50 % immediately after drying, and over 25 % after 6 months storage; all but two of the freshly isolated strains dried well. Some of the dried cultures were tested again after a storage period of about 2 years and then showed satisfactory percentage survivals.

SUMMARY:A comparison of physiological and serological characters of 41 strains of lactobacilli before freeze-drying and after freeze-drying and storage for 6 months showed that freeze-drying did not materially alter these characters.

SUMMARY: A new species of Spirillum has been isolated from grass cuttings. Main characters: vacuoles and volutin granules; motile by lophotrichous or amphitrichous flagella; no spores; Gram-negative; good growth in 0·5% Evans peptone; no growth in meat extract or grass infusion; inhibited by 0·5% (w/v) sodium chloride; catalase-negative; microaerophilic; good growth at 4°: optimum temperature 28°. The species has been designated Spirillum mancuniense.

SUMMARY: Proteolytic bacteria were isolated from the rumen of three sheep receiving an adequate protein diet. Using selective anaerobic conditions to suppress the majority of bacteria which were not capable of utilizing casein, proteolytic representatives of several bacterial genera were found. All of these may have been derived from the environment or food of the sheep. The most frequent organism was Bacillus licheniformis which existed in the vegetative form in the rumen, although present mostly in the form of spores in the hay fed to the animal.

SUMMARY: The free amino acid composition of the 75% ethanol extracts of a strain of Sarcina lutea varied considerably depending on the composition of the growth medium. Differences in hydroxyproline content were particularly significant. The amino acid composition of the ethanol-extracted cell residues remained constant.