Borrelia afzelli is part of the spirochete phylum.
Borrelia is a genus of bacteria of the spirochete phylum . Borrelia afzelii is a species of Borrelia a bacterium that can infect various species of vertebrates and invertebrates . Borrelia lusitaniae is a bacterium of the spirochete class of the genus Borrelia , which has a diderm ( double-membrane ) envelope .