The most commonly detected microorganisms in the transcriptome libraries comprised intestinal and skin-dwelling bacteria and soil and freshwater bacteria. Ruminococcus, which is part of the commensal intestinal microbial community of ungulates, was detected in all seven libraries ( Fig. 1A and Table S3 ). Other bacteria found in at least three of the seven data sets were Propionibacterium, a commensal bacterium of skin and the gastrointestinal tract, and the environmental soil or water inhabitants Magnetospirillum, Streptomyces and Pseudomonas. Members of the latter genus are able to colonize a wide range of niches and are also potential pathogens. Other animal and human pathogenic genera detected in at least three different libraries were Burkholderia, Streptococcus, Flavobacteria, and members of the Enterobacteriaceae (Escherichia, Providencia).