PROPIONIC ACID-PRODUCING STRAINS PREVIOUSLY DESIGNATED AS CORYNEBACTERIUM-XEROSIS, CORYNEBACTERIUM-MINUTISSIMUM, CORYNEBACTERIUM-STRIATUM, AND CDC GROUP-I2 AND GROUP F2 CORYNEFORMS BELONG TO THE SPECIES CORYNEBACTERIUM-AMYCOLATUM

Propionic acid-producing Corynebacterium strains that lacked mycolic a cids and were formerly identified as Corynebacterium minutissimum, Cor ynebacterium xerosis, Corynebacterium striatum, and CDC group I-2 and F-2 strains were studied to determine their relatedness to Corynebacte rium amycolatum, A total of 60 strains were used for phenotypic charac terization studies, and 26 of these strains were used for genetic stud ies, DNA-DNA hybridization experiments performed at 65 degrees C revea led that the levels of relatedness between the propionic acid-producin g strains and the type strain of C. amycolatum were more than 70% and that the Delta T-m, values ranged from 0 to 5 degrees C (Delta T-m is the difference between the denaturation temperature of a homoduplex an d the denaturation temperature of a heteroduplex); these values are co nsistent with inclusion of these strains in the species C. amycolatum, Currently used conventional tests, such as urease, nitrate reduction, and sugar fermentation tests, were not suitable for accurate identifi cation of C. amycolatum, Phenotypic differentiation of this species fr om related taxa should be based on the following characteristics in ad dition to propionic acid production: lipid requirement, Tween esterase activity, tyrosine clearing, alkaline phosphatase activity, alpha-glu cosidase activity, and beta-glucuronidase activity.