Characterization of intragenic recombination in a hyperthermophilic archaeon via conjugational DNA exchange

Sulfolobus acidocaldarius is so far the only hyperthermophilic archaeon in which genetic recombination can be assayed by conjugation and simple select ions. Crosses among spontanteous pyr mutants were able to resolve closely s paced chromosomal mutations, identify deletions and rearrangements, and map mutations to a given deletion interval. Frameshift mutations in pyrE exert ed polar effects that depressed orotidine-5'-monophosphate decarboxylase ac tivity (encoded by pyrF), whereas base pair substitutions and an 18-bp dele tion had no effect.