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Chapter 28 : Three Histories of Competence and Transformation
This chapter talks about competence and transformation in their bacterial senses (competence to take up DNA, genetic transformation by recombination with this DNA) and also about the skills and sudden changes at the heart of a research career. Thus, one of the three histories is the author's own—how he came to work on DNA uptake, why he thinks it is so important. Another is the history of research into competence and transformation--what has been learned and where it has led. The third is the evolutionary history of the phenomena themselves--when and how the ability to actively take up DNA evolved, how often it leads to genetic transformation, and what this has contributed to bacterial evolution. The author knew from introductory biology that the first evidence DNA carried genetic information was the ability of Streptococcus pneumoniae to change its genes by taking up DNA from its surroundings. Since then a number of bacteria had been shown to take up fragments of chromosomal DNA and recombine them into their chromosomes, although only a few (the gram-positive S. pneumoniae and Bacillus subtilis and the gram-negative Haemophilus influenzae) had been studied in any detail. The author's tests, using agents that produced single-strand or double-strand damage, showed that DNA damage did not induce competence in either H. influenzae or B. subtilis. Proponents of the transformation function for competence argue that the sequence bias of the uptake machinery is an adaptation for transformation.