Naturally competent organisms are capable of DNA uptake directly from the environment through the process of transformation. Despite the importance of transformation to microbial evolution, DNA uptake remains poorly characterized outside of the bacterial domain. Here, we identify the pilus as a necessary component of the transformation machinery in archaea. We describe two naturally competent organisms, Methanococcus maripaludis and Methanoculleus thermophilus. In M. maripaludis, replicative vectors were transferred with an average efficiency of 2.4×103 transformants μg-1 DNA. In M. thermophilus, integrative vectors were transferred with an average efficiency of 2.7×103 transformants μg-1 DNA. Additionally, natural transformation of M. thermophilus could be used to introduce chromosomal mutations. To our knowledge, this is the first demonstration of a method to introduce targeted mutations in a member of the order Methanomicrobiales. For both organisms, mutants lacking structural components of the type IV-like pilus filament were defective for DNA uptake, demonstrating the importance of pili for natural transformation. Interestingly, competence could be induced in a noncompetent strain of M. maripaludis by expressing pilin genes from a replicative vector. These results expand the known natural competence pili to include examples from the archaeal domain and highlight the importance of pili for DNA uptake in diverse microbial organisms.
Bibliographical noteFunding Information:
Experiments on M. maripaludis were sponsored by the Army Research Office and were accomplished under grant number W911NF-19-1-0024. Experiments on M. thermophilus were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under grant number DE-SC0019148. D.R.F. was supported by the National Science Foundation Graduate Research Fellowship Program under grant number CON-75851.
© 2020 American Society for Microbiology.
- Methanococcus maripaludis
- natural competence
- type IV-like pili