ACIDIMICROBIUM FERROOXIDANS GEN-NOV, SP-NOV - MIXED-CULTURE FERROUS IRON OXIDATION WITH SULFOBACILLUS SPECIES

A new species of ferrous-iron-oxidizing, moderately thermophilic, acid ophilic bacteria, Acidimicrobium ferrooxidans, has been described. Two isolates of the species differed only in the tendency of one, previou sly known as strain TH3, to grow in filaments. The chromosomal DNA bas e composition is between 67 and 69 mol% G + C. The capacity of this sp ecies to fix CO2 from air was greater than that of iron-oxidizing ther moacidophiles of the genus Sulfobacillus, which required an enhanced C O2 concentration for optimum autotrophic growth. Under air, ferrous ir on oxidation in mixed cultures of A. ferrooxidans with either Sulfobac illus thermosulfidooxidans or Sulfobacillus acidophilus was more exten sive than in pure cultures of these three strains, The greater part of ferrous iron oxidation in mixed cultures probably resulted from activ ity of the Sulfobacillus species, which possess a greater tolerance of ferric iron, and which presumably grew mixotrophically utilizing orga nic compounds from A. ferrooxidans.