- Volume 116, Issue 1, 1980

[14C]Methylamine was transported into mycelial cells of Stemphylium botryosum by a specific and energy-dependent transport system having an optimum at pH 6·0, a Km of 12·5 μ m and a V max of 4·1 μmol (g dry wt)−1 min−1; uptake occurred against a concentration gradient. NH4 + competitively inhibited methylamine transport with higher affinity towards the latter system. Sucrose and nitrate were required during transport for maximal activity. Highest transport activity developed in nitrate-grown mycelium. Nitrogen starvation decreased the activity by approximately 60%. Preloading of mycelium with glutamine, asparagine or ammonia almost completely prevented methylamine uptake. Transport activity was inversely proportional to the intracellular concentration of the l-amides. It is postulated that ammonia uptake might be regulated by l-amides rather than by ammonia.

In Pseudomonas C, a facultative methylotrophic bacterium, methanol is assimilated via the 2-keto-3-deoxy-6-phosphogluconate (KDPG) variant of the ribulose monophosphate (RMP) pathway of formaldehyde fixation. The oxidation of methanol to CO2 is accomplished by the direct oxidation pathway (which involves formic acid as an oxidation intermediate), via a cyclic oxidation pathway (glucose monophosphate shunt) and by other decarboxylation reactions. The distribution pattern of methanol carbon among the assimilation and the different oxidation pathways was studied by measuring the distribution between CO2 and cell constituents of 14C-labelled compounds after their injection into a culture growing on methanol in a chemostat. From these measurements, it was calculated that 25% of the methanol consumed by the cells was oxidized through formate to CO2, while the remainder was diverted into the hexulosephosphate synthase reaction from which 55% was assimilated through the KDPG reaction and 17% was oxidized to CO2 via a cyclic oxidation pathway and other decarboxylation reactions. The remaining 7% from the methanol carbon was re-incorporated as CO2, into cell material through carboxylation reactions.

The bacterium Pseudomonas C was grown in a chemostat on methanol as sole source of carbon and energy. At a dilution rate of 0·1 h−1, other methanol-utilizing bacteria (Pseudomonas 1 and Pseudomonas 135), when added separately at a steady state, became dominant in the fermenter and Pseudomonas C was excluded. At a dilution rate of 0·3 h−1, however, Pseudomonas C dominated and the other bacteria were excluded. When various bacteria unable to utilize methanol were added to the chemostat during a steady state growth of Pseudomonas C, they remained in the fermenter independent of the dilution rate, but as a very low percentage of the total population (about 1%). When pathogenic bacteria (Staphylococcus aureus and Salmonella typhimurium), which are unable to utilize methanol as a sole carbon source, were added separately to a pure culture of Pseudomonas C in a chemostat, they too remained in the fermenter independent of the dilution rate. However, they constituted less than 1% of the population in the culture broth but a high percentage of the population on the fermenter wall. When added to a mixture of Pseudomonas C and bacteria unable to utilize methanol, the pathogenic bacteria could not be found in the fermenter after a few medium changes.

The results suggest that operation of a continuous culture of Pseudomonas C at high dilution rates serves to prevent contamination with other methylotrophs that may have lower yields. A mixture of Pseudomonas C and heterotrophs from soil is relatively resistant to invasion by pathogens.

A new haemolysin from Staphylococcus aureus produced opaque zones of haemolysis on horse blood agar but did not lyse equine erythrocytes suspended in phosphate-buffered saline. The haemolysin was not neutralized by normal rabbit serum and was distinct from α, β- and δ-haemolysins as well as human leucocidin. Partially purified preparations produced erythema when injected intradermally into rabbit skin.

Although β-galactosidase activity could be induced in Escherichia coli K12 during uridine starvation, material which cross-reacted with antiserum against β-galactosidase could be detected. The synthesis of enzymically inactive proteins during uridine starvation appeared to be due to errors in transcription.

The addition of nickel ions restored urease activity in vivo and ability to grow on urea in a mutant strain of Aspergillus nidulans otherwise unable to utilize urea. This strain carries a mutation in the ureD locus, one of four loci involved in urea utilization. No other urease-deficient strains tested responded to the presence of nickelions.

The analogous characteristics of the ureD mutant and the nitrate reductase and xanthine dehydrogenase associated cnxE mutants in Aspergillus nidulans are discussed. It is postulated that the ureD locus is in some way involved in the production or incorporation of a nickel cofactor essential for urease activity.

A high-resolution screening procedure for the selection of mutants was developed based on the ability of some strains of Mycobacterium smegmatis to produce pigment in the light. Out of 23000 colonies investigated, 17 auxotrophic mutants were isolated. Specific growth factor requirements for the mutants and the proportion of revertants were determined.

A Halobacterium species isolated from solar evaporation ponds and sodium sesquicarbonate deposits at Lake Magadi, Kenya, differs from known species of Halobacterium in its GC content, in being obligately alkalophilic with a pH optimum between 9·0 and 10·0, and in having a Mg2+ requirement of between 0·1 and 2·0 mm for optimum growth.

Gas-liquid chromatography (g.l.c.) was investigated as a potential tool in the classification and identification of Corynebacterium strains isolated from human skin, on the basis of the g.l.c. profile of the trimethylsilyl derivatives of their mycolic acid methyl esters. The g.l.c. patterns of five skin corynebacteria were compared with those of reference strains Corynebacterium diphtheriae PW8 and Corynebacterium xerosis NCTC 9755 and NCTC 7929. Further compositional information was obtained by gas-liquid chromatography/mass spectrometry (g.l.c./m.s.) of mycolates from C. diphtheriae PW8 and two of the skin isolates. In addition to identifying and examining the individual mycolate species and comparing the differences in mycolate profile between skin corynebacteria and between reference strains, a limited assessment was made of the possibility of distinguishing between organisms at both strain and species levels on the basis of mycolic acid composition as revealed by g.l.c. fingerprinting.

A new Gram-negative, non-sporulating, rod-shaped, anaerobic bacterium capable of fermenting cellulose and starch was isolated from the rumens of sheep fed supplemented maize stover diets. The organism fermented few carbohydrates, showing a preference for polysaccharides. The main acid products of carbohydrate fermentation were butyrate and formate. Acetate was utilized.