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Chapter 31 : Natural Competence and Transformation in Campylobacter
Category: Bacterial Pathogenesis
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Over 40 naturally competent bacterial species are known, and that number continues to grow. Almost all competent bacteria studied to date use components of the type II secretion/type IV pilus biogenesis family of proteins for transformation, with slight differences between the transformation machinery in each system. The two known exceptions are Helicobacter pylori, which requires components of a type IV secretion/conjugation system for transformation, and Campylobacter jejuni, in which some strains use both type II-like and type IV-like secretion systems. Three different mechanisms may contribute to generating genetic diversity. The first is local sequence change such as nucleotide substitutions or small insertions or deletions of one or a few nucleotides. Another mechanism is DNA rearrangement, where related sequences in the genome undergo recombination to create novel fusion genes, and duplicate or delete DNA segments. Finally, diversity can be generated by horizontal acquisition of DNA through mechanisms such as natural transformation, conjugation, and transduction. Given the natural competence of most Campylobacter species, antibiotic resistance is probably spread in part through transformation. Several species of Campylobacter are naturally competent for transformation, including C. jejuni and C. coli. The candidate gene approach identified recombinase RecA as having a function in transformation. recA mutants were unable to be transformed to streptomycin resistance in three C. jejuni strains tested, 81-176, VC83, and 81-116. Modification of C. jejuni proteins by addition of an N-linked glycan is due to the activity of a number of genes found in the pgl locus.
Conserved locus encoding cts type II secretion system genes from several strains of C. jejuni. See text for details.
Conserved proteins associated with transformation in naturally competent bacteria