- Volume 110, Issue 1, 1979

Summary: The phosphorus content of phosphate-limited Saccharomyces cerevisiae was only 71% of that of non-limited yeast. Walls prepared from phosphate-limited cells contained slightly less phosphorus than control walls. No evidence was obtained for the presence in these walls of uronic acid or succinyl residues. The carbohydrate content of walls of phosphate-limited yeast was less than that of non-limited walls, and this was reflected in a decreased glucan content. There was only a slight decrease in glucosamine content while the protein content increased. The major change in the lipid composition of phosphate-limited yeast was a decrease in both sterol esters and triacylglycerols. There was a decrease in total lipid content, but increased production of phosphatidylethanolamine and phosphatidylcholine. The phosphatidylserine content was decreased. These results suggest that there are fewer intracellular low-density vesicles in phosphate-limited yeast.

Summary: Enzyme preparations active against crystalline cellulose, marble-milled filter paper, carboxymethyicellulose (CM-cellulose), hemicellulose and xylan were obtained from cultures of Ruminococcus flavefaciens. These preparations also contained swelling factor, pectin methylesterase, pectin lyase and low levels of aryl β-glucosidase and aryl β-xylosidase. CM-cellulase and xylanase activities were present in a high molecular weight complex, but substrate competition studies showed that different active sites were probably responsible for each activity. Analysis of products and viscosity changes during enzymic hydrolysis of CM-cellulose and xylan indicated that the most active enzymes were of the exo-1, 4-β-glycosidase type. A variety of reducing sugars were released from cell walls of Lolium perenne (perennial ryegrass) by enzyme preparations.

Summary: As the first stage in investigating the genetic basis of natural variation in Escherichia coli, the gene(s) conferring the ability to use sucrose as a carbon and energy source (given the symbol sac +) was transferred from a wild strain to k12, which does not use sucrose. The sac + region was transferred by two different methods. On both occasions it took a chromosomal location at minute 50·5 on the linkage map, between aroC and supN, in the region of the dsd genes, which confer the ability to use d-serine as a carbon and energy source. When the sac + region was present in the k12 chromosome the bacteria were unable to use d-serine as a carbon and energy source. In F'sac +/dsd + diploids, the dsd + genes were similarly not expressed. Strain k12(sac +) bacteria were sensitive to inhibition by d-serine; they mutated to d-serine resistance with much greater frequency than did a dsd mutant of k12. Such bacteria also mutated frequently to use raffinose. Strain k12(sac +) bacteria did not utilize sucrose when they carried a mutation affecting the phosphotransferase system.

Summary: Pseudomonas cepacia strains of plant and clinical origin were compared with the type strains of P. cepacia, P. kingii and P. multivorans. Conventional biochemical tests and antibiotic sensitivity patterns supported the previous proposals of synonymy between P. cepacia, P. kingii and P. multivorans. However, bacteriocin production patterns, onion maceration tests and hydrolysis of low pH pectate agar clearly differentiated strains of clinical and plant origin into two distinct groups; these tests may therefore be helpful in epidemiological studies. In contrast, plant and clinical strains were of equal lethality to mice. Agarose gel electrophoresis indicated the presence of one or more plasmids (molecular weights 9 × 106 to 120 × 106) in 15 out of 16 strains of both types examined.

Summary: A phytotoxic extract of Pseudomonas morsprunorum (cherry isolate c28) was shown to contain phytotoxic protein associated with bacteriophage-specific lipopolysaccharide. This and similar extracts from two other pathogenic pseudomonads produced a silvery effect when infiltrated at 100 μg ml−1 (14·4 mu;g protein ml−1) into leaves of some plant species. The effect was similar to that caused by Stereum purpureum infection in cherry. In contrast to the fungal toxin, the bacterial extracts were not translocated in treated plants. Wax-embedded sections of cherry leaves silvered either by the fungus or by bacterial extracts showed optically active cells when stained with toluidine blue. Different plant species differentiated between extracts of different pseudomonads by their reaction to treatment. The hypersensitive response of tobacco to heterologous pathogenic bacteria was suppressed by prior treatment with extracts of cherry-type and saprophytic bacteria. Similar phytotoxic material isolated from culture filtrates of the cherry isolate produced the silvery effect in bean leaves when infiltrated at 10 μg ml−1 (5 μg protein ml−1). The silvering agents (molecular weight in excess of 25 × 106 by gel filtration) were dissociated into smaller units by electrophoresis in sodium dodecyl sulphate-polyacrylamide gel. The activities described were destroyed by protein-inactivating treatments.

Summary: Glucose repressed the synthesis of 1,3-β-glucanase in Neurospora crassa. The production of enzyme during growth in glucose-supplemented medium was negligible, but if deprived of carbon source the fungus actively synthesized high levels of enzyme when growth ceased. Similar results were obtained for 1,6-β-glucanase but less enzyme was produced. A different pattern of production of these enzymes was found in Trichoderma viride and Saccharomyces cerevisiae. The enzymes were produced in glucose-supplemented medium with increasing specific activity during growth. Resting cells deprived of glucose either failed to produce β-glucanases or produced them in smaller quantities.

Summary: A bacterium capable of utilizing the selective herbicide 2,2-dichloropropionate (Dalapon) as sole source of carbon and energy was isolated from soil and tentatively identified as a fast-growing species of Rhizobium. 2-Chloropropionate also supported good growth of the organism but 3-chloropropionate, monochloroacetate and dichloroacetate were not utilized. Bacteria grown in the presence of either 2,2-dichloropropionate or 2-chloropropionate oxidized these compounds and a variety of non-chlorinated substrates but not monochloroacetate.

Cell-free extracts of 2,2-dichloropropionate-grown bacteria converted 2,2-dichloropropionate into pyruvate with the concomitant release of two chloride ions for each molecule of pyruvate formed, indicating the presence of dehalogenase activity. Dichloroacetate and 2-chloropropionate were also inducers and substrates for the dehalogenase. Monochloroacetate was a substrate for the dehalogenase but did not serve as an inducer whereas 3-chloropropionate was a non-substrate inducer.

Summary: Exochelins are a group of extracellular iron chelators produced by mycobacteria. Iron uptake by washed suspensions of iron-deficiently grown Mycobacterium smegmatis from 55Fe(III)-exochelin fractions (at about 1 μm) was greatest from the fractions containing the compounds that naturally predominate in culture filtrates. Uptake from the major fraction, as well as from combined exochelins, had a K m of about 6 μm and was unaffected by the presence of a large excess of desferriexochelin; it was inhibited by more than 90% by electron transport inhibitors, uncouplers of oxidative phosphorylation, thiol reagents and by anaero-biosis and low temperature. Uptake of iron from 55Fe-salicylate, which is mediated by myco-bactin, was insensitive to these inhibitors and a 10-fold excess of ferric salicylate did not inhibit 55Fe-exochelin uptake. Thus mycobactin is probably not involved in the transport of iron from ferriexochelin at physiological concentrations. The rate of uptake of iron from 55Fe-exochelin into iron-sufficiently grown cells, which contain less than 0·05% of the concentration of mycobactin found in iron-deficiently grown cells, was only slightly lower than the rate of uptake into iron-deficiently grown cells.

Uptake of ferri[3H]exochelin, which could only be carried out at high and probably non-physiological concentrations (about 60 μm), was also extremely sensitive to metabolic inhibitors suggesting that the whole complex was being transported. At these high external concentrations of ferriexochelin a second, non-saturable, inhibitor-insensitive iron uptake process occurred. This process was inhibited in iron-deficiently grown cells by ferric salicylate and may therefore involve mycobactin. A similar but not identical second system which was not sensitive to ferric salicylate was found in iron-sufficiently grown cells; this might indicate yet another pathway of iron uptake from ferriexochelin.