Etude morphologique, physiologique et taxonomique de Bacillus azotoformans

Abstract

Seventeen strains of B. azotoformans were isolated by enrichment culture in peptone broth inoculated with pasteurized soil and then incubated under N2O at 32.degree. C. The bacterium is a gram-negative rod, motile with peritrichous flagella, which produces oval spores without exosporia in swollen sporangia. The cells have thick walls, mesosomes and persistent septa characteristic of gram-positive bacteria. The bacterium lacks fermentative activity, does not attack carbohydrates, has complex growth requirements, and will grow anaerobically only if one of the following electron acceptors is present: NO3-, NO2-, N2O, S4O6 .sbd. or fumarate. Nitrate, nitrite and nitrous oxide are denitrified with the production of N2. The microorganism is mesophilic, gives a positive oxidase reaction, synthesizes a type c cytochrome and does not hydrolyze gelatin, starch or Tween 80. Poly-.beta.-hydroxybutyric acid is synthesized when the bacterium is grown in a medium containing DL-3-hydroxybutyrate. The following enzymes are present: nitrate reductase A, respiratory nitrite reductase, tetrathionate and fumarate reductases, and L-glutamate dehydrogenase. The following enzymes are absent: thiosulfate reductase, urease, lecithinase, arginine dihydrolase, phenylalanine deaminase and catalase. For the 17 strains, the mean value of the G + C percent of the DNA is 39.8 .+-. 1.2. All the strains are highly similar.