Assembly and annotation of Pneumocystis jirovecii from the human lung microbiome

Pneumocystis jirovecii is a fungus that causes Pneumocystis pneumonia in immunosuppressed patients and has been closely associated with AIDS since the beginning of the AIDS epidemic. Because in vitro cultivation of P. jirovecii is not possible, progress has been hindered in our understanding of its life cycle, mode of transmission, metabolic function, and genome. Limited amounts of P. jirovecii can be obtained from infected patients, but the occurrence of bacteria, other fungi, and human cells in clinical samples presents new challenges for whole-genome sequencing and downstream bioinformatic analysis. In a recent article, Cissé et al. used cell immunoprecipitation enrichment together with whole-genome amplification to generate sufficient quantities of DNA for Roche 454 and Illumina sequencing [O. H. Cissé, M. Pagni, and P. M. Hauser, mBio 4(1):e00428-12, 2012, doi:10.1128/mBio.00428-12]. In addition, a bioinformatic pipeline was devised to sort and assemble lung microbiome reads, thereby generating an 8.1-Mb P. jirovecii genome comprised of 356 contigs with an N50 (median length of all contigs) of 41.6 kb. Knowledge of this genome will open new avenues of research, including the identification of nutritional requirements for in vitro cultivation as well as the identification of new and novel drug and vaccine targets.