Construction and characterisation of a BAC library made from field specimens of the onchocerciasis vector Simulium squamosum (Diptera: Simuliidae)

A Bacterial Artificial Chromosome (BAC) library was made from wild-caught Simulium squamosum, which is an important vector of human onchocerciasis. The library is composed of 12,288 BACs, with an average insert size of 128 kb, and is expected to contain ~ 1.54 GB of cloned DNA. Random BAC-end sequencing generated over 95 kb of DNA sequence data from which putative S. squamosum gene sequences and novel repetitive DNA families were identified, including DNA transposons, retrotransposons and simple sequence repeats (SSRs). The sequence survey also provided evidence of DNA of microbial origin, and dissection of sample blackflies indicated that some of those used to prepare the library were likely to be parasitized by the mermithid Isomermis lairdi. Hybridisations with a set of three independent blackfly single-copy genes and two Wolbachia genes suggest that the library provides around 13-fold coverage of the S. squamosum genome and about 12-fold coverage of its Wolbachia endosymbiont.