An alternative mevalonate-independent pathway for isoprenoid biosynthesis has been recently discovered in eubacteria (including Escherichia coli) and plant plastids, although it is not fully elucidated yet. In this work, E. coli cells were engineered to utilize exogenously provided mevalonate and used to demonstrate by a genetic approach that branching of the endogenous pathway results in separate synthesis of the isoprenoid building units isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). In addition, the IPP isomerase encoded by the idi gene was shown to be functional in vivo and to represent the only possibility for interconverting IPP and DMAPP in this bacterium.z 2000 Federation of European Biochemical Societies.

Caparratriene (1), a new sesquiterpene hydrocarbon with significant growth inhibitory activity (IC50 = 3.0 +/- 0.5 x 10(-6) M) against CEM leukemia cells, was isolated from the oil of Ocotea caparrapi (Nates) Dugand. The structure of 1, determined by spectroscopic techniques, corresponded to (E,E)-3,7,11-trimethyl-2,4,10-dodecatriene (C15H26).

The aim of this study was to use the natural dietary markers (stable isotopes and fatty acids) during grow‐out in a biofloc system and for the egg production of Farfantepenaeus brasiliensis shrimp. Egg production was compared for two broodstock origins: biofloc and a wild origin. To delineate the relative contribution to shrimp muscle and eggs, IsoSource software was used. The most important source that contributed to grow‐out shrimp was biofloc ≥250 μm. According to the principal component analysis (PCA) applied to the fatty acid profile of food sources, the first component explains 84.4% of the variability, and the most important source of fatty acids for this component was biofloc ≥250 μm. The most important fresh food sources that contributed to egg production were Artemia biomass, polychaetes and semi‐moist feed for both broodstock origins. According to a PCA analysis of the fatty acid profiles, the most important fresh foods were polychaetes and semi‐moist feed. In conclusion, both isotopic signature and fatty acid profile of the food sources can be used successfully to determine the integration of carbon in the diets of shrimp.

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