Department of Microbiology, B103 Chemical and Life Science Laboratory, University of Illinois, 601 S. Goodwin Ave., Urbana, IL 61801, USA.
We report here the first use of directed mutagenesis in Methanosarcina acetivorans C2A. The method employs homologous recombination-mediated gene replacement and was used to construct a variety of proline auxotrophs with mutations in the proABC locus. Each mutation was also complemented in trans with autonomously replicating Methanosarcina-Escherichia plasmid shuttle vectors.