Industrial Microbiology

De novo biosynthesis of vanillin in fission yeast ( Schizosaccharomyces pombe ) and baker's yeast ( Saccharomyces cerevisiae) Hansen, E. H. et al. Appl. Environ. Microbiol. 13 Mar 2009 (doi:10.1128/AEM.02681-08)

Most vanillin, the compound in vanilla that gives it its flavour, is produced from petrochemicals or wood pulp lignins. Hansen and colleagues have now produced strains of Saccharomyces cerevisiae and Schizosaccharomyces pombe that can produce vanillin. They first searched for strains that did not convert vanillin to vanillyl alcohol. They then added genes from the dung mould Podospora pauciseta, a bacterium of the Nocardia genus, and humans, which allowed the yeast strains to produce vanillin (an additional gene from Corynebacterium glutamicum was added to S. cerevisiae to activate the Nocardia enzyme). At 45–65 mg per litre, vanillin production was at a sufficient level to scale up for large-scale industrial production. These de novo pathways for vanillin synthesis in yeast represent the first examples of one-cell microbial generation of these valuable compounds from glucose.

Parasitology

Influence of ecto-nucleoside triphosphate diphosphohydrolase activity on Trypanosoma cruzi infectivity and virulence. Santos, R. F. et al. PLoS Negl. Trop. Dis. 3, e387 (2009)

ATP is an important signalling molecule in the host response to pathogens. Many pathogens, including the eukaryotic parasite Trypanosoma cruzi, produce an ecto-nucleoside triphosphate diphosphohydrolase (ecto-NTPDase) that decreases extracellular ATP levels in the human host, thereby decreasing the immune response. Santos and colleagues now show that this enzyme plays an important part in T. cruzi infections. Three inhibitors of ecto-NTPDase each decreased T. cruzi infectivity. However, recombinant T. cruzi NTPDase 1 could be inhibited by only one of the three inhibitors, indicating that T. cruzi produces additional ecto-NTPDase enzymes. Ecto-NTPDase could therefore be an important new target for drugs against T. cruzi.

Bacterial physiology

RNase E autoregulates its synthesis in Escherichia coli by binding directly to a stem-loop in the rne 5′ untranslated region Schuck, A., Diwa, A., Belasco, J. G. et al. Mol. Microbiol. 6 Mar 2009 (doi: 10.1111/j.1365-2958.2009.06662.x)

RNase E plays an important part in the breakdown of mRNA and the maturation of tRNA and rRNA in bacteria, as it cuts RNA into single-stranded regions that are AU-rich. Because alterations in the concentration of the enzyme have detrimental effects on the cell, enzyme production is tightly regulated, in part through processing of the RNase E mRNA by RNase E itself. Schuck and colleagues show that the enzyme binds to the conserved hp2 stem loop in RNase E mRNA, yet cleaves that stem loop poorly. The authors speculate that this binding facilitates RNase E cleavage of the mRNA at other sites. Their findings help to clarify the mechanism by which hp2 mediates feedback regulation of RNase E levels.