- Volume 72, Issue 1, 1972

SUMMARY: The toxicity of n-alkanes, n-alk-1-enes, n-alkan-1-ols and n-alkyl-1-bromides towards Candida tropicalis, Candida 107 and Saccharomyces carlsbergensis is related to their solubilities in an aqueous medium. n-Alkanes of chain-length longer than C9, n-alkenes longer than C12, n-alkyl bromides longer than C10 and n-alkanols longer than C14 generally do not inhibit growth and respiration. Toxicity may be reduced or relieved if oxidation by the yeasts can occur or if a non-toxic aliphatic compound is also added. Relief of inhibition is not dependent upon the oxidation of the non-toxic compound. It is also produced when the biologically inert hydrocarbon, pristane, is added. These effects are attributed to the reduction of the solubility of the toxic compound by the added compound in accordance with Raoult’s and Henry’s Laws. If the solubility of the toxic material is decreased below a critical level, growth on it as sole carbon source may occur with either of the two species of Candida. These results imply that small amounts of potentially deleterious compounds need not affect the growth of micro-organisms on petroleum hydrocarbons.

SUMMARY: Valine did not inhibit the production of diacetyl from pyruvate by extracts of Saccharomyces cerevisiae that contained coenzyme A (CoA) and the co-factors necessary for forming acetyl-CoA. However, it did inhibit the production of diacetyl from glucose by a growing culture, though Ca-pantothenate, a precursor of CoA, was supplied. α-Ketoisovaleric acid enhanced the production of diacetyl from pyruvate and acetyl-CoA by extracts if mercaptoethylamine was present. Results indicate that α-ketoisovaleric acid has two roles in the synthesis of diacetyl by S. cerevisiae, a synthesis that generally requires an acidic environment, and that each is inhibited by excess valine. In addition to serving as an intermediate in the synthesis of acetyl-CoA, α-ketoisovaleric acid, which was not formed from valine by transamination at pH below 6·0, enhanced the activity of diacetyl synthetase.

SUMMARY: Microelectrophoresis has shown surface lipid to be present on conidia of Alternaria tenuis, Botrytis fabae and Neurospora crassa and on sporangiospores of Rhizopus stolonifer. Surface lipid is absent from conidia of Erysiphe cichoracearum, E. graminis, Nectria galligena, Penicillium expansum and Verticillium albo-atrum and sporangiospores of Mucor rouxii. The compositions of the fatty acid and hydrocarbon fractions of the surface and wall lipids from the same organisms are different. The fatty acids are mainly straight-chain and even carbon-numbered. Palmitic and stearic acids predominate. Polyunsaturated acids were absent. Surface hydrocarbons consist almost entirely of n-alkanes but wall fractions are more complex. An equal distribution of odd and even carbon-numbered alkanes occurs in both the surface and wall lipid fractions.

SUMMARY: Spore coat of Bacillus subtilis ATCC6051 was fractionated as described by Kondo & Foster (1967). X-ray diffraction, infrared spectra, amino acid analyses and N-terminal amino acid studies showed that most of the fractions resembled each other in physical and chemical structure and constituents. Electron micrographs of sections and shadowed replicas of the coat fractions at various stages showed that the inner part of the coat disappeared during treatment; no drastic morphological change was observed throughout the fractionation.

The amounts of cystine in the coat and the coat fractions were less than in keratins. This result and solubilizing experiments suggested that the spore coat does not chemically resemble keratins.

SUMMARY: Thin-walled sporangia of an African strain of Coelomomyces indicus dehisced in exposed drops of water in 1 to 2 days. Good aeration was necessary. During dehiscence granules in the sporangial contents became redistributed and a lateral bulge arose on the sporangial wall. A split opened at the crest of the bulge, and the sporangial contents cleaved into planonts. A vesicle emerged from the split, expanded, filled with planonts from within the sporangium, burst, and finally dissolved. The wall of the sporangium was initially two-layered, but a third amorphous layer continuous with the vesicle developed internally during dehiscence. Dividing nuclei were seen in the early stages of dehiscence. The nuclear membrane persisted during division and intranuclear spindle microtubules arose near differentiated pockets in the nuclear envelope adjoining the apparently unpaired centrioles. Shortly before cleavage, groups of lipid droplets in the sporangium became associated with each nucleus together with an apparently single elongated centriole. After cleavage, flagella were well developed, but the ribosomes were still dispersed throughout the cytoplasm of the planonts. They then became sequestered into large membrane-bounded nuclear caps. A single large mitochondrion was present in each planont, possibly arising by coalescence of several smaller ones. A lipid body adjoined each mitochondrion. The cytoplasm of each unliberated planont contained numerous cytoplasmic vesicles and a single crystalline body. An abnormal ‘9 + 1’ flagellum was seen.

SUMMARY: Small numbers of several bacterial species were rapidly and specifically detected with the 125I-labelled antibody method described previously. Multibacterial species detection was achieved in one operation with 125I-labelled mixtures of type-specific anti-bacterial globulins but the level and variability of the blank value increased, and sensitivity decreased, with the number of globulin components in the mixture. An indirect radio-assay that involved successive treatments of bacteria with unlabelled rabbit anti-bacterial serum and 125I-labelled immunopurified goat anti-rabbit globulin was less sensitive and reproducible than the direct radio-assay. A modified assay, developed to detect and determine bacteria filtered on to a membrane filter, allowed the detection of small numbers of bacteria in large volumes of aqueous sample.

The feasibility of rapidly and specifically detecting small numbers of virus particles with 125I-labelled anti-viral globulin was investigated with bacteriophage T7 as a model particle. Methods for the rapid separation of phage-125I-labelled globulin complex were developed and a minimum of about 5–105 total phage particles was detected.

A mutant of Mycobacterium smegmatis required 3 to 4 μg salicylate, or certain other phenolic acids/ml to restore optimal growth. Iron-deficient growth did not increase the requirement for salicylate. Salicylate, but nota salicylate-substitute was incorporated solely into mycobactin S. Mycobactin S was absorbed by growing bacteria but it did not substitute or spare the requirement for salicylate. Another mutant has been produced which required about 0·2 μg desferrimycobactin S/ml to restore growth under iron-deficient conditions. Salicylate, citrate, cobactin S with mycobactic acid S or Tween 80 did not substitute for mycobactin, but iron at 2 or more μg/ml permitted growth without mycobactin. Under these growth conditions the mycobactin requirement would be minute and some synthesis or carry-over during inoculation cannot be eliminated as a source of mycobactin. Salicylate and mycobactin were thus both required for growth.

SUMMARY: Column-separated, clean trypanosomes were subjected to nitrogen cavitation and ultracentrifugation (90 min, 99000 g); the supernatant contained most of the immunogens but a few remained in the well washed residue. Column chromatography yielded a strongly immunogenic protein fraction (SAF1), small doses (0·035 mg protein/dose ⨯ 4) of which protected mice against a maximum challenge of 5 ⨯ 104 of the homologous variant organisms for a minimum of 17 weeks. No heterologous (variant or strain) protection was obtained with SAF1 either with increased doses or by homologous challenge followed by heterologous challenge 3 weeks later. Disc electrophoresis of SAF1 showed four anodic components intermediate in mobility between α-macroglobulin and transferrin of normal rat serum. Analytical ultracentrifugation indicated a substantial proportion of 6·5S protein together with 3·0S and 1-1·5S proteins. A smaller soluble antigen fraction (SAF8) consisted of 2·0S protein but preliminary experiment has not shown it to be immunogenic. Infected rat plasma separated after 6 h was as effective as SAF1 in protecting mice against homologous challenge whereas rapidly separated infected rat plasma gave only slight protection. Two identical precipitinogens were detected in infected rat plasma and SAF1 by immunodiffusion. Three additional precipitinogens were present in SAF1 and one other in the infected rat plasma. Antisera raised against various trypanosome fractions, including SAF1, agglutinated the homologous trypanosomes but to a lesser extent than antisera to living trypanosomes.

Incubation of trypanosomes in either SAF1, or infected rat serum or plasma decreased their infectivity which was not altered by 8 h of incubation in normal rat plasma.

SUMMARY: Highest levels of β-galactosidase specific activity found after protracted growth of Klebsiella aerogenes (syn. Aerobacter aerogenes) in lactose-limited chemostat culture were only developed with cultures previously conditioned to lactose in batch culture. The hyperactivities were not induced further by methyl thiogalactoside (MTG) and depended on dilution rate, being maximal at D = 0·25 h-1. They were associated with increased substrate transport and utilization and, apart from a transient disturbance, were not affected by addition of glucose, galactose or glucose-6-phosphate to the lactose-limiting medium. Maltose addition produced a greater transient effect than the substances above, while citrate, β±-methyl glucoside and 2-deoxy-glucose were inactive. Before hyperactivity developed, adding glucose led to a rapid decline and adding MTG led to a rapid increase in β-galactosidase activity. Methyl thiogalactoside exerted an inhibiting action at only the final stage, the bacterial yield being decreased, and its continued presence enabled glucose-adapted organisms to utilize glucose and lactose simultaneously. The lactose was utilized in two stages. β±-Galactosidase hyperactivity occurred after protracted growth in melibiose-limited conditions, but β-glucosidase hyperactivity did not develop in cellobiose-limited medium.

SUMMARY: Mycelium of Neocosmospora vasinfecta harvested in mid-logarithmic phase absorbs Zn2+ from dilute solutions in the absence of growth. Zn2+ uptake involves two phases: a rapidly established phase 1 believed to represent adsorption to negatively charged groups in the hyphal surface-membrane and a slowly established phase 2 which represents transport into the cytoplasm. Phase 1 is not influenced by low temperature, NaN3 or anaerobiosis applied for short periods, conforms to the Langmuir adsorption equation and is reduced in the presence of various other divalent cations. Phase 2 is strongly inhibited by low temperature, NaN3 and anaerobiosis and exhibits carrier-type kinetics with an apparent K m for Zn2+ of 0·2 mM. Mn2+ competitively inhibits phase 2 zinc uptake: Mg2+ acts as a ‘mixed-type’ inhibitor. Electron microscopy of unstained material indicates that part at least of phase 2 Zn is deposited in the cytoplasm and nucleus. A model for the metabolic uptake of Zn2+ involving phase 1 binding as a requisite preliminary process is suggested.