Decarboxylation of Substituted Cinnamic Acids by Enterobacteria: the Influence on Beer Flavour

Many species within the Enterobacteriaceae decarboxylate the substituted cinnamic acids p -coumaric acid and ferulic acid. The enzyme responsible is principally associated with the 'free-living' genera, Klebsiella, Enterobacter and Hafnia and is absent from Proteus mirabilis, Escherichia coli, Serratia and Salmonella spp. Some strains of Hafnia protea , a common bacterial contaminant of brewers' yeast display decarboxylase activity towards hydroxycin-namic acids. These H. protea strains (members of taxonomic group 1) produce higher concentrations of steam-volatile phenolic compounds when grown in wort than strains lacking the decarboxylase. The addition of ferulic acid or p -coumaric acid to wort prior to the growth of H. protea group 1 strains increases the concentration of steam-volatile phenolic compounds thus implicating this route as a source of phenolic off-flavours in beer.     

Tree‐mediated interactions between the jack pine budworm and a mountain pine beetle fungal associate

1. Coniferous trees deploy a combination of constitutive (pre‐existing) and induced (post‐invasion), structural and biochemical defences against invaders. Induced responses can also alter host suitability for other organisms sharing the same host, which may result in indirect, plant‐mediated interactions between different species of attacking organisms. 2. Current range and host expansion of the mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB) from lodgepole pine‐dominated forests to the jack pine‐dominated boreal forests provides a unique opportunity to investigate whether the colonisation of jack pine (Pinus banksiana Lamb.) by MPB will be affected by induced responses of jack pine to a native herbaceous insect species: the jack pine budworm (Choristoneura pinus pinus Freeman; JPBW). 3. We simulated MPB attacks with one of its fungal associates, Grosmannia clavigera Robinson‐Jeffrey & Davidson, and tested induction of either herbivory by JPBW or inoculation with the fungus followed by a challenge treatment with the other organism on jack pine seedlings and measured and compared monoterpene responses in needles. 4. There was clear evidence of an increase in jack pine resistance to G. clavigera with previous herbivory, indicated by smaller lesions in response to fungal inoculations. In contrast, although needle monoterpenes greatly increased after G. clavigera inoculation and continued to increase during the herbivory challenge, JPBW growth was not affected, but JPBW increased the feeding rate to possibly compensate for altered host quality. 5. Jack pine responses varied greatly and depended on whether seedlings were treated with single or multiple organisms, and their order of damage.     

Control of potato gangrene by thiabendazole in relation to time of harvest after haulm destruction and site of production

The efficiency of thiabendazole in controlling gangrene on potato tubers harvested on different dates was assessed over two years in Scotland (East Craigs) and England (Rothamsted). At East Craigs the incidence of gangrene on wounded and cold-stored tubers was greater than on those tubers kept at ambient store temperatures and graded in January, but the assessments were correlated. The incidence of gangrene increased with delay in harvest after haulm destruction although the pattern differed with year and site. Dipping tubers in thiabendazole or sodium hypochlorite almost eliminated gangrene on all harvest dates at Rothamsted but at East Craigs the incidence of gangrene on dipped tubers was much greater and tended to increase the longer the interval between haulm destruction and harvest. Furthermore, dipping tubers in thiabendazole was much more effective than spraying even though the fungicide residues were twice as large with the latter treatment. All 43 isolates of Phoma foveata collected in Scotland were sensitive to thiabendazole in agar plate tests. The results are discussed in relation to disease development at each of the sites.     

The Structure and Composition of the Stalk of the Ciliated Protozoan Sorogena stoianovitchae1

Sorogena stoianovitchae is an unusual ciliated protozoan with a life cycle characterized by the aggregation of individual trophic cells to form a multicellular sorogen that rises from the liquid culture medium surface by the secretion of a stalk. The noncellular stalk is a tapered, longitudinally furrowed structure composed of a fibrillar matrix that is initially hydrated, but with time dehydrates, the stalk becoming thin and brittle. This dehydration is of importance from the earliest stages of stalk formation since it results in the formation of the outer sheath-like region of the stalk that appears to provide much of the support of the stalk. Cytochemical tests of the stalk for polysaccharides (including acidic mucopolysaccharides) and proteins are positive. Proteolytic enzymes degrade the stalk. Lectins specific for glucose and N-acetyl-D-glucosamine bind to the stalk. Gas chromatography analysis detected the presence of fucose, glucose, glucosamine, and arabinose, as well as a variety of amino acids, predominantly glycine. The cytochemical and biochemical tests, the ultrastructural data, and the behavior of the stalk material suggest that the staik is composed of a matrix of complex protein-polysaccharide molecules.