“Bacterial” Genetics I Chromosome; If It Is a Fictitious Unit, It Must Be Referred to a Definite Location in a Chromosome

Home , Joshua Lederberg, Salvador Luria, Selman Waksman

“Influential ideas are always simple. Since natural phenomena need not be simple, we master them, if at all, by formulating simple ideas and exploring their limitations.”

Al Hershey

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“What are the genes? What is the nature of the elements of heredity that Mendel postulated as purely theoretical units? … Frankly, these are questions with which the working geneticist has not much concern himself… If the gene is a material unit, it is a piece of a “Bacterial” genetics I chromosome; if it is a fictitious unit, it must be referred to a definite location in a chromosome. … Therefore, it makes no difference in the actual work in genetics which point of view is taken.” T.H. Morgan The Relation of Genetics to Physiology and Medicine Nobel Lecture, June 4, 1934

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1 DNA ! RNA ! protein

central dogma of molecular biology

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Today even the layman thinks of resistant bacteria as originating from mutation … but when Luria and Delbrück first got together, conventional bacteriologists were by no means clear that microorganisms could be tought about genetically… Many believed that resistance was some kind of adaptation induced, in a few of the bacteria in a culture, by the exposure to the antibacterial agent.

Max Delbrück (1906 -1981) & Salvador Luria (1912 - 1991), Cold Spring Harbor Laboratory, Long Island NY, Summer 1941 Judson p. 55 MCB 140 11/3/05 9 MCB 140 11/3/05 10

The idea smacks of the pre- Mendelian, pre-Darwinian Let’s all do science in Nevada notion of the inheritance of acquired characteristics; One Saturday evening … Luria went to Luria damned bacteriology a faculty dance… There, watching the fluctuating returns obtained by as the “last stronghold of colleagues gambling on a slot Lamarckism.” machine, he thought of the experiment that would distinguish between resistance induced in bacteria and resistance resulting from previous spontaneous mutation upon which selection acts.

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2 What Luria perceived was that previous spontaneous mutation would pay out jackpots of resistant bacteria that would fluctuate much more widely in size than those paid out by induction. He tried the first experiment on the following morning and wrote off to Delbrueck; Delbrueck promptly replied that Luria really ought to go to church …

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S. Luria, M. Delbrück (1943) What Luria actually did Mutations of bacteria from virus sensitivity to virus resistance. Genetics 28: 491-511. Sample set A: Sample set B: “If the production of resistance began only at the 1. Inoculate bacteria 1. Take an aliquot of moment of exposure to phage, then it wouldn’t into individual bacteria, and start a matter whether the bacteria came from many cultures (1 culture (which will individual cultures or one bulk culture. … When bacterium per therefore not be Luria performed the experiment, though, the culture). clonal). twenty separate cultures showed much wider 2. Let it grow up to a 2. Let them grow up to fluctuations from the average number of resistant large number. a large number colonies, indicating that a few of the individual tubes contained resistant bacteria from near the Expose both to phage, and count, how many phage- beginning of the overnight growth period.” resistant colonies per culture are found. Ask, if there is a Judson p. 56 difference between these two sample sets. MCB 140 11/3/05 15 MCB 140 11/3/05 16

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3 Remember Prof. Amacher’s lecture #8?

George Beadle (left) and Edward Tatum (right) receiving their Nobel Prizes

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7.20

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Joshua Lederberg “Conjugation” in bacteria

Take strain of E. coli that is auxotrophic for two distinct nutrients (thiamine and leucine). Take different strain of E. coli that is also auxotrophic for two distinct nutrients, but different ones (biotine and cysteine). Mix the two. Ask, if ANY NOVEL PHENOTYPES APPEAR.

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4 J. Lederberg, E. Tatum (1946) Novel genotypes in mixed cultures of biochemical mutants of bacteria. Cold Spring Harbor Symp. Quant. Biol. 11: 113-114.

Paramecium

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B.H. and A.H. William Hayes

In the pre-Hayes period, mating in bacteria was envisioned as a conventional sex process, perhaps modified by aspects of “relative sexuality,” but nevertheless a standard haploid/diploid/meiosis mechanism. After Hayes, it was known that bacteria were not just small cells, but constituted a completely different kind of cell … The terms prokaryote and eukaryote were not introduced until 1962.

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Selman Waksman Hayes expt: Take strain A, which is streptomycin-resistant, and auxotrophic for biotin and methionine. Take strain B, which is streptomycin-sensitive, and auxotrophic for threonine and leucine. Mix the two on a minimal- medium plate containing streptomycin. Wait and see.

streptomycin

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5 Rich husband, poor wife “'I discussed these results with Denny Mitchison and I think it was he who first suggested that one is not the same as poor husband, rich wife of the parents, A, might be acting as a gene Cross #1: donor and the other, B, as a recipient'. Strain A (StrR, -,B -)M × Strain B (StrS, -,L -)T It was from this experiment that the concept of Result: streptomycin completely inhibits prototroph asymmetry in bacterial sexuality arose. Parent B formation (i.e., appearance of B+,M+,L+,T+ was the recipient or 'female', the continued bacteria) if added before conjugation is viability of which was essential for the whole complete. process of recombination and segregation, while Cross #2: the A donor or 'male' cell was dispensable once Strain A (StrS, -,B -)M × Strain B (StrR, -,L -)T genetic transfer had been effected.” Result: streptomycin has no effect whatsoever. W. Hayes (1952) Recombination in Bact. coli K 12; You can add it all you want, at any time, and unidirectional transfer of genetic material. Nature prototrophs will still form!! 169: 118.

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14.12

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6 E. Wollman, F. Jacob (1955) Sur le mecanisme du transfert de materiel genetique au cours de la recombinaison chez E. coli K12. CR Academie Sciences 240: 2449.

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Cours de Physiologie et de génétique bactériennes, 1957 Illustration humoristique des cours par une série de dessins de F. Lavallé Légendes de Georges Cohen The life cycle of a temperate phage http://www.pasteur.fr/infosci/archives/mon/im_laval.html

Interruption de la pénétration de l'ADN mâle dans le cytoplasme de la bactérie femelle à l'aide d'un warring blender (simple mixer ménager). 14.12 MCB 140 11/3/05 41 MCB 140 11/3/05 42

7 J. Bacteriol. 64(4): 557–569 (1952) Three other aspects of phage biology with long-term impact 1. Transduction (phage carrying additional genetic information from cell to cell) → oncoretroviruses 2. Lysogeny (phage resident in bacterial genome) → latent viruses in eukaryotic genomes 3. Recombination between phage → the fine structure of a gene

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Annual budget: $3,780.00

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