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Volume 3, Number 4—December 1997
THEME ISSUE
Foodborne

Special Issue

Infectious Disease as an Evolutionary Paradigm

Joshua Lederberg
Author affiliation: Sackler Foundation Scholar, Rockefeller University, New York, New York, USA

Main Article

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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