Comparison of physiological and biochemical characters of Actinomyces spp. with those of Lactobacillus bifidus.

Abstract

SUMMARY: Evidence is presented that under the conditions described 11 strains of Actinomyces spp., representing strains described as A. israelii, A. israelii-like or A. naeslundii, require carbon dioxide for anaerobic growth. Some of these strains, under these conditions, are obligate anaerobes to microaerophils, while others appear to be facultative anaerobes. Cultures which are capable of aerobic growth may or may not require carbon dioxide for such growth. Of three strains of Lactobacillus bifidus tested, all required carbon dioxide for anaerobic growth. One avian strain required carbon dioxide to give limited aerobic growth; the remaining strains did not grow significantly under aerobic conditions. Comparisons of several strains of Actinomyces spp. with L. bifidus indicated that of eleven sugars tested, the sugar of choice for growth of Actinomyces spp. was glucose or maltose, whereas lactose or maltose was preferred by strains of L. bifidus. All strains of each group of organisms were found to be catalase-negative; none liquefied gelatin; all eleven strains of Actinomyces spp. reduced nitrate to nitrite, but none of the bifid strains possessed this ability; production of acetylmethylcarbinol was variable in both groups. All strains of Actinomyces spp. tested formed L (+) lactic acid, although the results suggested that small amounts of D (-) lactic acid were also formed. Fermentation analyses indicated that strains of L. bifidus and Actinomyces spp. form the same products from glucose and carbon dioxide (lactic, acetic, formic and succinic acids). However, strains of Actinomyces spp. form predominantly lactic acid with small amounts of acetic, formic and succinic acids; whereas the strains of L. bifidus form approximately equal amounts of lactic and acetic acids (based on glucose fermented) with trace amounts of succinic and formic acids. Actinomyces strains fermented but 34-59% of the glucose supplied as compared to the strains of L. bifidus which used from 59 to 89% of the glucose (1% glucose medium).