Orthologs of the MACPF were identified in several chlamydial species. The first biological characterisation of the C. trachomatis MACPF by Taylor et al. [50] has revealed that the MACPF (CT153) might be activated by proteolytic processing and may play a role in the acquisition or modification of host-derived lipids. By contrast, studies of the MACPF in other organisms, including that of Toxoplasma spp. have shown that ablation of the MACPF (termed TgPLP1) resulted in a reduction in virulence (in mice), whereby TgPLP1 deficient parasites were unable to exit normally and were entrapped within host cells, due to the inability to permeabilise the parasitophorous vacuole membrane [51]. If the chlamydial MACPF was to play a similar role in egression or virulence, then why have several species failed to retain this gene? Non-lytic family members have also been identified in other organisms including Astrotactin involved in neural migration in mammals [52], a Drosophila torso-like protein involved in embryonic development [53] and Plu-MACPF of Photorhabdus luminescens which binds to the surface of insect cells [54]. Further investigation of this gene should provide more insight into its role in Chlamydiaceae.