CULTURAL AND PHYLOGENETIC ANALYSIS OF MIXED MICROBIAL-POPULATIONS FOUND IN NATURAL AND COMMERCIAL BIOLEACHING ENVIRONMENTS

A range of autotrophic and heterotrophic enrichment cultures were esta blished to determine the cultural bacterial diversity present in sampl es obtained from the acidic runoff of a chalcocite overburden heap and from laboratory-scale (1- to 4-liter) batch and continuous bioreactor s which were being used for the commercial assessment of the bioleacha bility of zinc sulfide ore concentrates. Strains identified as Thiobac illus ferrooxidans, Thiobacillus thiooxidans, ''Leptospirillum ferroox idans,'' and Acidiphilium cryptum were isolated from both the natural site and the batch bioreactor, but only ''L. ferrooxidans,'' a moderat ely thermophilic strain of T. thiooxidans, and a moderately thermophil ic iron-oxidizing bacterium could be recovered from the continuous bio reactor running under steady-state conditions. Sequence analysis of th e 16S rRNA genes of 33 representative strains revealed that all of the strains were closely related to strains which have been sequenced pre viously and also confirmed the phylogenetic diversity of bacteria pres ent in bioleaching environments.