Anaerobic spirochaetes of the genus Brachyspira have long been known as important gut pathogens
of pigs, but increasingly they are recognised as causing disease in birds and other animal species,
including human beings. The genome sequence of the major swine pathogen Brachyspira
hyodysenteriae was recently published, and this revealed extensive genome optimisation that leads
to adaptation to the complex environment of the colon. The genome sequences of other
pathogenic and non-pathogenic Brachyspira species are becoming available, and this data will help
to reveal how these species have evolved and adapted to varied lifestyles in the large intestines of
different species, and why some but not others can induce colitis and diarrhoea.