. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. R. J. REDFIELD 405 Animals Fungi Plants Rhodophytes Alveolates (Ciliates, Dinoflagellates) Kinetoplastids (Trypanosomes, Euglena) Percolozoans (Naegleria) Parabasalans (Hypermastigotes, Trichomonads) Metamonads (Diplomonads, Oxymonads?) Figure 1. A very simplified eukaryote phylogeny. showing only the major groups relevant to this their contagious-transfer functions. The third gene transfer process, DNA uptake by naturally competent bacteria, has no infectious-transfer component, and has been thought to exist fo
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. R. J. REDFIELD 405 Animals Fungi Plants Rhodophytes Alveolates (Ciliates, Dinoflagellates) Kinetoplastids (Trypanosomes, Euglena) Percolozoans (Naegleria) Parabasalans (Hypermastigotes, Trichomonads) Metamonads (Diplomonads, Oxymonads?) Figure 1. A very simplified eukaryote phylogeny. showing only the major groups relevant to this their contagious-transfer functions. The third gene transfer process, DNA uptake by naturally competent bacteria, has no infectious-transfer component, and has been thought to exist for genetic exchange or possibly for DNA repair (6). However, our analysis of the regulation of competence suggests that DNA is taken up primarily as a nutrient. DNA damage does not induce competence in Haemophilus infln- en~ae or Bacillus subrilis. contrary to predictions of the DNA-repair hypothesis (7). Furthermore, induction of com- petence in H. influenzae is controlled by adenylate cyclase and a fructose-specific phosphotransferase system, which together provide signals connecting shortages of preferred catabolites to induction of operons allowing use of alterna- tive energy resources (8). Theoretical work also shows that competence is unlikely to provide significant recombination benefits, for two reasons. First, the available DNA will carry an excess of deleterious mutations, and second, it may carry alleles that preclude competence, especially if the compe- tence cell has recently arisen in a population of noncompe- tent cells (9, 10). Physical recombination: Although the many "rec" genes were identified in Escherichia coli because they are required for efficient recombination, analysis of their mechanisms and regulation shows that they evolved not for recombina- tion with incoming DNA but for their roles in DNA repli- cation and repair. For example, an excellent discussion of the primary function of RecA in DNA repair is given by Cox (11), and the importance o
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
