<unk>  are obligately anaerobic non-sporeforming Gram-negative bacilli. Since the first reports in the late nineteenth century, various names have been applied to these organisms, sometimes with the same name being applied to different species. More recently, not only have there been changes to the nomenclature, but also attempts to differentiate between species which are believed to be either pathogenic or commensal or both. Because of their asaccharolytic nature, and a general paucity of positive results in routine biochemical tests, laboratory identification of the<unk>  has been difficult. However, the application of novel molecular biological techniques to taxonomy has established a number of new species, together with the subspeciation of Fusobacterium necrophorum and F. nucleatum, and provided new methods for identification. The involvement of<unk>  in a wide spectrum of human infections causing tissue necrosis and septicaemia has long been recognised, and, more recently, their importance in intra-amniotic infections, premature labour and tropical ulcers has been reported. Since the first reports of<unk>  in the late nineteenth century, the variety of species names has led to some confusion within the genera Fusobacterium and Leptotrichia. However, newer methods of investigation have led to a better understanding of the taxonomy, with the description of several new species of<unk> . Among the new species described are F. ulcerans from tropical ulcers, and several species from the oral cavity. Subspeciation of the important species F. necrophorum and F. nucleatum has also been possible. It is probable that the taxonomy of the<unk>  may be further developed in the future.
Fusobacteriota
Lactobacillus
Actinobacillus
Legionellales
Clostridium
Streptococcus
Caulobacter
Fusobacterium