mtDNA sequences from dust environmental samples
Amplifications of target mtDNA sequences prior to pyrosequencing were performed with specific primer sets. PCR products originating from the amplification of multiple samples were pooled  and purified with QIAquick PCR Purification Kit (QIAGEN) by following the recommendations of the supplier. Next, the amplicons of the three different mtDNA target regions were pooled together and purified with the Agencourt AMPure XP procedure (Beckman Coulter) by following the recommendations of the supplier. Quantification of the pooled amplicons was performed with a Nanodrop fluorometer ND 3300 (Thermo Scientific). Libraries were prepared starting from 100 ng of purified PCR products using Rapid Library Preparation Method (Series GS FLX+; Roche 454 sequencing), starting from step 3.2: Fragment End Repair (thus avoiding the step 3.1, DNA Fragmentation by Nebulization). Single libraries were tagged with univocal MIDs. Emulsion PCR and 454 sequencing were carried out according to the manufacturer’s instructions on the Roche 454 FLX Titanium platform. Library sequencing was carried out using a Roche 454 GS Junior System.