Volume 3, Number 4—December 1997
THEME ISSUE
Foodborne
Special Issue
Infectious Disease as an Evolutionary Paradigm
Table 3
Genetic evolution
| Microbes (bacteria, viruses, fungi, protozoa) | |
| Rapid and incessant | |
| Huge population sizes 1014+ and generation times in minutes vs. years | |
| Intraclonal process | |
| DNA replicationmay be error-pronein sea of mutagens sunlight; unshielded chemicals, incl. natural products | |
| RNA replicationintrinsically unedited, >10-3 swarm species | |
| Haploid: immediate manifestation, but partial recessives not accumulated contra multicopy plasmids | |
| Amplification | |
| Site-directed inversions and transpositions: | |
| phase variation | |
| ?? Other specifically evolved mechanisms: | |
| genome quadrant duplication; silencing | |
| Interclonal process | |
| Promiscuous recombinationnot all mechanisms are known | |
| Conjugationdozens of species | |
| Viral transduction and lysogenic integration: | |
| universal | |
| Classical: phage-borne toxins in C. diphtheriae | |
| Plasmid interchange (by any of above) and integration | |
| Toxins of B. anthracis | |
| Pasteur: heat attenuation: plasmid loss; chemically induced | |
| RNA viral reassortment; ?? and recombination? | |
| Transgressive—across all boundaries | |
| Artificial gene splicing | |
| Bacteria and viruses have picked up host genes (antigenic masking?) | |
| Interkingdom: P. tumefaciens and plants, E. coli and yeast | |
| Vegetable and mineral! oligonucleotides and yeast. | |
| Host-parasite coevolution | |
| Coadaptation to mutualism or accentuation of virulence? | |
| Jury is still out (May and Anderson). Many zoonotic convergences. | |
| Probably divergent phenomena, with short-term flareups and Pyrrhic victories, atop long-term trend to coadaptation. | |
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