The first transformation method for the thermo-acidophilic archaeon Thermoplasma acidophilum

• A novel transformation method for T. acidophilum was developed.
• Culturing the cells on Gelrite-based solid medium was improved.
• Novobiocin resistant clones were obtained and selected.
• No plasmid maintenance was detected.
• Variants of the NovRgyrB gene recombined into the chromosomal gyrB gene.

A transformation method yielding up to 104 transformants per μg circular DNA was developed for Thermoplasma acidophilum. The method is based on a natural DNA uptake process in which T. acidophilum cells keep their integrity and turn competent at pH 3.5 and 58 °C. Shuttle vector maintenance could not be detected, since the used NovR gyraseB gene integrated into its chromosomal counterpart by homologous recombination.