Exposure to C. pneumoniae is widespread due to effective aerosol transmission and outbreaks have been reported in humans [18-21], horses [22], frogs [23] and koalas [13]. However, the original source of infection remains undetermined. Myers et al. [24] recently published the full 1.24 Mbp genome sequence of the C. pneumoniae koala LPCoLN isolate, the first analysis of a C. pneumoniae genome from a non-human host species. This study revealed that the five C. pneumoniae genomes were highly similar in genomic organisation and gene order, although some notable differences were observed [24]. In contrast to the highly conserved human-derived isolates, a relatively high number of single nucleotide polymorphisms, SNPs (6213) differentiated koala LPCoLN from human AR39 [24]. In the proposed phylogeny (based on SNPs from 111 highly conserved genes), which encompassed all five C. pneumoniae genomes and five sequenced animal chlamydial genomes (C. pecorum E58, C. muridarum Nigg, C. caviae GPIC, C. psittaci 6BC and C. abortus s26/3), koala LPCoLN was basal to the C. pneumoniae human isolates (larger genome and many full-length genes relative to human isolates).