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Carotenoid cleavage dioxygenases (CCDs) are a class of enzymes involved in the biosynthesis of a broad diversity of secondary metabolites known as apocarotenoids. In plants, CCDs are part of a genetic family with members which cleave specific double bonds of carotenoid molecules. CCDs are involved in the production of diverse and important metabolites such as vitamin A and abscisic acid (ABA). Bixa orellana L. is the main source of the natural pigment annatto or bixin, an apocarotenoid accumulated in large quantities in its seeds. Bixin biosynthesis has been studied and the involvement of a CCD has been confirmed in vitro. However, the CCD genes involved in the biosynthesis of the wide variety of apocarotenoids found in this plant have not been well documented. In this study, a new CCD1 gene member (BoCCD1) was identified and its expression was charaterized in different plant tissues of B. orellana plantlets and adult plants. The BoCCD1 sequence showed high homology with plant CCD1s involved mainly in the cleavage of carotenoids in several sites to generate multiple apocarotenoid products. Here, the expression profiles of the BoCCD1 gene were analysed and discussed in relation to total carotenoids and other important apocarotenoids such as bixin.

A new method is described for extraction of metagenomic DNA from soil and sediments which is based on DNA adsorption to silica without the use of phenol, ethanol precipitation or a cesium chloride gradient. High-quality DNA was obtained, and PCR inhibition was overcome by adding bovine serum albumin and adjusting magnesium concentration. By using PCR-DGGE with Firmicutes and lactic acid bacteria-specific primers the extracted metagenomic DNA was shown to contain a mixture of bacterial genomes. This method can be used for screening bacterial diversity in soil and sediment samples.

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Biofilms colonizing ancient limestone Mayan monuments in Uxmal (Yucatán, Mexico) were characterized for their microbial composition and differences using phospholipid fatty acid (PLFA) analysis and single-strand conformation polymorphism (SSCP) of polymerase chain reaction (PCR)-amplified genes of the rRNA small subunit. Biofilms 1–7, displaying different macroscopic characteristics, were drawn from interior and exterior limestone walls, which were characterized by different microenvironmental conditions. Inner surfaces that were exposed to low light intensity and higher water availability supported a higher biofilm biomass, probably indicating that these environmental conditions are more suitable for biofilm growth and development. Sequencing of SSCP profiles from the biofilms showed that bacteria affiliated with the phyla Proteobacteria, Bacteroidetes and Cyanobacteria colonized both internal and external surfaces, although certain Nevskia and Salinibacter were particularly associated with internal biofilms. In contrast, a particular biofilm community composed almost exclusively of Rubrobacter-related bacteria was found in only one exterior partially shaded sample (biofilm 3), characterized by high illumination and low water content. No specific organisms were detected in biofilm 7. The PLFA profiles suggested that cyanobacteria were the biomass-dominant group in most biofilms, except for biofilm 3 (exterior) where actinobacterial markers were detected in significant proportions. Interestingly, most of the detected sequences were related to halophylic bacteria, although the similarity of these clones to known sequences in databases was low (< 94%). This finding suggests that much bacterial novelty, probably of halophylic nature, remains to be identified in these biofilms. Our study suggests that water availability and light regime appear to be the main environmental determinants defining boundaries for biofilm formation, while substratum salinity appears to be an important abiotic factor that influences biofilm community structure in these specialized microbial habitats.