- Volume 71, Issue 3, 1972

Summary: Carbon catabolism was studied during the synchronous development of conidiophores of Aspergillus niger. The activities of key enzymes of the Embden-Meyerhof-Parnas (EMP) and pentose phosphate (PP) pathways were measured and studies of 14CO2 production from [1-14C]- and [6-14C]glucose were made. The enzyme activities together with the radiorespirometric studies showed that both the EMP and PP pathways were present and operative at all stages of conidiophore development but that the relative activities of the pathways differed. The highest activity of the EMP pathway occurred during the initial period of vegetative growth before any signs of morphological change. High EMP activity and high 6-C/1-C ratios were obtained in a medium which did not support conidiophore initiation but allowed vegetative growth to occur. In contrast, high activity of the PP pathway and very low 6-C/1-C ratios accompanied each stage of conidiophore development. The results suggest that the PP pathway predominates during conidiophore development of this fungus.

Summary: Zoospores of an estuarine fungus isolated from Bryopsis plumosa and tentatively identified as a species of Phlyctochytrium were positively phototactic. Electron microscopy revealed a complex of organelles consisting of a relatively electron opaque, membrane-bounded sac, a lipid droplet and a highly ordered array of membranous tubular units which may have been involved in photoreception. The ribosomes of the zoospores were aggregated into a nuclear cap and separated from the rest of the cytoplasm by mitochondria, the nucleus, membranous sheets and membrane-bounded vesicles. There was a vestigial kinetosome nearly parallel to the functional kinetosome. A Golgi-like body was associated with the nucleus.

Summary: Mutants blocked in different stages of flagellar development were isolated and examined by light and electron microscopy. Flagellum-less mutants had normal basal bodies but lacked the flagellar shaft and showed abnormalities in the transitional region. Stumpy mutants had very short flagellar shafts in which electrondense material, sometimes arranged in sheet-like arrays, accumulated in the space between the outer tubules and the distended flagellar membrane. Short-flagellum mutants also showed abnormalities in the flagellar shaft; abnormally spaced radial spokes were seen in negatively stained frayed flagella of one of these mutants. The flagellum lengths andflagellar regeneration characteristics of two long-flagellum mutants with defective length control were determined; length was highly variable with some abnormally long flagella, and regeneration was slow and asynchronous.

Summary: Escherichia colistrains B Hill(FIL+) and B/r(FIL-), when grown on minimal medium containing glycerol, ceased respiration for several hours after ultraviolet (u.v.) irradiation at 520 ergs/mm2. Treatment of cells with 5-fluorouracil (FU) had two effects on viability: (i) pre-irradiation treatment enhanced survival of E. coliB Hill(+) but not that of B/r(FIL-) when survival was measured immediately after irradiation; (ii) pre- or postirradiation treatment of either strain resulted in a large and rapid increase in viability over the first hour of postirradiation incubation. Postirradiation treatment with pantoyl lactone (PL) resulted in a moderate increase in viability, but maintenance of growth and respiration was favoured only by FU. Postirradiation treatment with FU and PL together produced kinetics of respiration, growth and viability intermediate between those observed when the drugs were used separately. Irradiated B Hill organisms, which usually form filaments after u.v. irradiation, only did so in glycerol medium when FU was present. If FU was then replaced by PL, the filaments broke up and viability increased. Viability of B Hill was always higher when irradiated bacteria were plated on agar containing PL than without PL. Thus the increased viability caused by PL and FU when present singly during postirradiation incubation occurred by different means: PL by stimulation of division, and FU by maintenance of respiration.

Chloramphenicol acetyl transferase (CAT) was purified from Escherichia coli K12 carrying R1 and 222 and from E. coli K12 recA (R1 Cm8 7/R100-99 TcRCmS). The third enzyme has a lower affinity for chloramphenicol and greater heat lability than those specified by R1 and 222, compatible with the enzyme's resulting from interallelic complementation. CAT has a molecular weight of 80000, with subunits of 20000. Material cross reacting with anti-222 CAT serum was detected in CmS mutant cell sonicates.

Summary: Out of nine strains of Bacillus megaterium from culture collections, only five grew in a minimal medium that contained glucose and ammonium sulphate as principal nutrients. One strain required biotin, while three other strains required two or more amino acids for growth. A freshly isolated strain of B. megaterium required three amino acids for growth.

Three strains of Bacillus cereus from a culture collection each required two or more amino acids for growth. From two of these strains, substrains independent of amino acids were developed by serial transfers. Ability to grow in a minimal medium is therefore not so valuable as a distinction between B. megaterium and B. cereus as previously had been supposed.

Summary: The influence of oxygen on growth and cytochrome synthesis was investigated in four species of Propionibacterium. After anaerobic growth all species contained cytochrome b, cytochrome a or a 1, cytochrome a 2 and a carbon monoxide-binding pigment. Cytochrome b functions in an electron transport system from lactate to fumarate since the lactate-fumarate dismutation reaction, unlike lactate oxidation via methylene blue, was strongly inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO). No species grew on agar plates under aerobic conditions but all grew in aerated media, though at different rates and with diminished synthesis of all cytochromes. In Propionibacterium freudenreichii and P. shermanii, which grew slower under aerobic conditions than P. rubrum and P. pentosaceum, cytochrome synthesis was more repressed by oxygen. Large amounts of pyruvate accumulated under aerobic conditions whereas acetate, propionate and succinate were not formed. The bacteria are therefore dependent on oxidative phosphorylation for energy under aerobic conditions. For P. freudenreichii an Y 0 value (g dry wt bacteria/g-atom oxygen taken up) of 15 was measured, suggesting a P/O value of 1 to 2. Absence of cytochrome synthesis resulting in the loss of oxidative phosphorylation may explain the absence of aerobic growth on agar plates.

Summary: Of 21 amino acids tested, only L- and D-threonine, L-phenylalanine, L-histidine, L-tyrosine and L-homoserine inhibited exponential growth of Methylococcus capsulatus at 1.0 mM. Inhibition by L-threonine was relieved by L-methionine, L-homoserine, L-alanine and L-valine, but not by L-lysine, 2, 6-diaminopimelic acid or L-arginine. 14C-labelled methane, L-aspartate, L-threonine, L-homoserine, L-glutamic acid, L-phenylalanine and L-tryptophan were all assimilated. The results suggested that the branched pathway for threonine, isoleucine, methionine and lysine synthesis from aspartate is functional. An explanation of threonine-inhibition in terms of an interference with end-product regulation of this pathway is proposed.

A lethal reaction followed fusion between plasmodia of two strains (15 and 29) of the Myxomycete Physarum polycephalum on a solid medium. Dead areas were seen about 5 h after fusion and increased in size rapidly. Strain 29 was often wholly destroyed but strain 15 commonly survived and subsequently reinvaded the dead areas. Large plasmodia of 29 were destroyed by fusion with small plasmodia of 15, but large plasmodia of 15 survived fusion with small plasmodia of 29. The lethal reaction did not normally occur under conditions of suboptimal nutrition, but disappearance of strain 29 still took place. It is suggested that protoplasm of strain 15 can eliminate nuclei of strain 29, but that strain 29 has little or no ability to tolerate or eliminatenuclei of strain 15.

Summary: A new species of Eubacterium has been isolated from the rumen and caecum of fistulated goats. This species, Eubacterium fissicatena, degraded the ribityl chain of riboflavin hydroxyethylflavin.