Characterization of a bacterioruberin-producing Haloarchaea isolated from the marshlands of the Odiel river in the southwest of Spain.

In this work, we describe the isolation, identification, pigment characterization, and optimization of the culture conditions for a haloarchaea strain isolated from salt evaporation ponds in the Odiel river, at Southwest of Spain. The haloarchaea belongs to the genus Halorobrum, as deduced from the analysis of its 16S rRNA encoding gene and has been designated as Halorubrum sp. SH1.

Efficiency of different heterologous promoters in the unicellular microalga Chlamydomonas reinhardtii.

Despite the biotechnological interest of microalgae, no robust and stable methods for genetic transformation of most microalgal strains exist. The scanty and disperse data about the efficiency of heterologous promoters in microalgae and the use of different transformation methods, DNA quantities and reporter genes in the existing studies makes very difficult a real comparison of their efficiency. Using Chlamydomonas reinhardtii as a host, we have evaluated the efficiency of the heterologous promoters of cauliflower mosaic virus 35S (CaMV 35S) and Agrobacterium nopaline synthase (NOS) genes.

Promoter trapping in microalgae using the antibiotic paromomycin as selective agent.

The lack of highly active endogenous promoters to drive the expression of transgenes is one of the main drawbacks to achieving efficient transformation of many microalgal species. Using the model chlorophyte Chlamydomonas reinhardtii and the paromomycin resistance APHVIII gene from Streptomyces rimosus as a marker, we have demonstrated that random insertion of the promoterless marker gene and subsequent isolation of the most robust transformants allows for the identification of novel strong promoter sequences in microalgae. Digestion of the genomic DNA with an enzyme that has a unique restriction site inside the marker gene and a high number of target sites in the genome of the microalga, followed by inverse PCR, allows for easy determination of the genomic region, which precedes the APHVIII marker gene.