Characterization of a Propionic Acid Producing Actinomycete, Actinomyces propionicus, Sp.nov.

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Abstract
An anaerobic actinomycete isolated from the lachrymal duct of a case of human lachrymal canaliculitis is described. Although the organism was described previously as Actinomyces israelii, more recent observations show it differs significantly from members of this genus in metabolism, physiology and cell-wall composition. The organism is similar to the Actinomyces in its production of true branching mycelial elements in vivo and in vitro, catalase negativity, pathogenicity for experimental animals and amino acid cell-wall composition. It is similar to the propionic acid bacteria in its fermentation of glucose to propionate, acetate and CO2 its morphological variation, formation of a dull orange colour, and the presence of diaminopimelic acid in its cell wall. Other characteristics such as the formation of DL-lactic acid, absence of a CO2 requirement either anaerobically or aerobically, inability to ferment glycerol or lactate and sugar and amino sugar composition of the cell wall also serve to differentiate this organism from other strains of Actinomyces and from Propionibacterium. In view of these observations the organism is reclassified and named A. propionicus, sp. nov. The possible phylo-genetic relation of A. propionicus to certain other branching filamentous organisms is discussed.