Abstract
Bacterial uptake of DNA through type IV filaments is an essential component of natural competence in numerous gram-positive and gram-negative species. Recent advances in the field have broadened our understanding of the structures used to take up extracellular DNA. Here, we review seminal experiments in the literature describing DNA binding by type IV pili, competence pili and the flp pili of Micrococcus luteus; collectively referred to here as type IV filaments. We compare the current state of the field on mechanisms of DNA uptake for these three appendage systems and describe the current mechanistic understanding of both DNA-binding and DNA-uptake by these versatile molecular machines.
Highlights
The explosion of genomic data available from high-throughput sequencing and the rising burden of antimicrobial resistance in pathogenic bacterial species have generated a great deal of interest in horizontal gene transfer, the process by which genetic material is transmitted from one species to another
Flp/tad-like pilus of Micrococcus luteus are united by their use of several homologous proteins; (i) pilin proteins which contain an N-terminal transmembrane-like helix and can be extracted from the inner/plasma membrane and assembled into extracellular helical fibers, (ii) AAA+ ATPase proteins (Frickey and Lupas, 2004; Iyer et al, 2004) responsible for extension and/or retraction of the filament by the transfer of pilin subunits from the inner/plasma membrane to the pilus and (iii) an integral membrane protein of the inner/plasma membrane which is essential for pilus biogenesis
In Pseudomonas stutzeri, deletion of pilU resulted in a 90% reduction in natural transformation (Graupner et al, 2001) while the equivalent mutation had no effect on transformation in Vibrio cholerae (Seitz and Blokesch, 2013)
Summary
Bacterial uptake of DNA through type IV filaments is an essential component of natural competence in numerous gram-positive and gram-negative species. Recent advances in the field have broadened our understanding of the structures used to take up extracellular DNA. We review seminal experiments in the literature describing DNA binding by type IV pili, competence pili and the flp pili of Micrococcus luteus; collectively referred to here as type IV filaments. We compare the current state of the field on mechanisms of DNA uptake for these three appendage systems and describe the current mechanistic understanding of both DNA-binding and DNA-uptake by these versatile molecular machines. Reviewed by: Chew Chieng Yeo, Sultan Zainal Abidin University, Malaysia Arijit Dutta, Yale University, United States. Specialty section: This article was submitted to Molecular Recognition, a section of the journal Frontiers in Molecular Biosciences
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