TRANSFER AND EXPRESSION OF DEGRADATIVE AND ANTIBIOTIC-RESISTANCE PLASMIDS IN ACIDOPHILIC BACTERIA

The genetic accessibility of selected acidophilic bacteria was investi gated to evaluate their applicability to degrading pollutants in acidi c environments. The IncP1 antibiotic resistance plasmids RP4 and pVK10 1 and the phenol degradation-encoding plasmid pPGH11 were transferred from neutrophilic bacteria into the extreme acidophilic eubacterium Ac idiphilium cryptum at frequencies of 1.8 x 10(-2) to 9.8 x 10(-4) tran sconjugants per recipient cell. The IncQ antibiotic resistance plasmid pSUP106 was mobilizable to A. cryptum by triparental matings at a fre quency of 10(-5) transconjugants per recipient cell. In the transconju gants, antibiotic resistances and the ability to degrade phenol were e xpressed. A. cryptum AC6 (pPGH11) grew with 2.5 mM phenol at a doublin g time of 12 h and a yield of 0.52 g (dry cell weight) per g of phenol . A. cryptum harbored five native plasmids of 255 to 6.3 kb in size. P lasmids RP4 and pVK101 were transferred from Escherichia coli into Aci dobacterium capsulatum at frequencies of 10(-3) and 2.3 X 10(-4) and t o the facultative autotroph Thiobacillus acidophilus at frequencies of 1.1 x 10(-5) and 2.9 x 10(-6) transconjugants per recipient cell, res pectively. Plasmid pPGH11 could not be transferred into the latter str ains. T. acidophilus wild type contained six so far cryptic plasmids o f 220 to 5 kb.