● Van Bruggen JJA,Zwart KB,Hermans JGF,Van Hove EM,Stumm CK,Vogels GD (1986). Isolation and characterization of Methanoplanus endosymbiosus sp. nov., an endosymbiont of the marine sapropelic ciliate Metopus contortus Quennerstedt. Arch. Microbiol. 144, 367-374.