leptobacterium leptobacterium leptobacterium is a gram-negative, obligately aerobic and non-motile genus of bacteria from the family of flavobacteriaceae with one known species (leptobacterium flavescens). leptobacterium scientific classification domain: bacteria phylum: bacteroidota class: flavobacteria order: flavobacteriales family: flavobacteriaceae genus: leptobacteriummitra et al. 2009 type species leptobacterium flavescens species l. flavescens