thiotrichales thiotrichales the thiotrichales are an order of pseudomonadota, including thiomargarita magnifica, the largest known bacterium. thiotrichales thiomargarita namibiensis scientific classification domain: bacteria phylum: pseudomonadota class: gammaproteobacteria order: thiotrichalesgarrity et al. 2005 families fastidiosibacteraceae francisellaceae piscirickettsiaceae thiofilaceae thiolinaceae thiotrichaceae they also include certain pathogens, such as francisella tularensis which causes tularemia (rabbit fever).