1966

Bruce Ames uses auxotrophic strains of Salmonella typhimurium to screen for mutagens and potential carcinogens. The test is based on a determination of whether exposure to a particular chemical alters the mutation rate of the microorganism. There is a high correlation between mutagenicity and carcinogenicity in the "Ames test".

Smith, D. E., and B. N. Ames. 1966. Phosphoribosyladenosine monophosphate, an intermediate in histadine biosynthesis. J. Biol. Chem. 240: 3056-3063.

Jon Beckwith and Ethan Signer transpose the lac region of E. coli into another microorganism to demonstrate genetic control. The implication of this work is the realization that chromosomes could be redesigned and genes moved.

Beckwith, H. R.[sic] and E. T. Signer. 1966. Transposition of the lac region of E. coli. I. Inversion of the lac operon and transduction of the lacoperan by (phi)80. J. Mol. Biol. 19: 254. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.414 [pdf]

William Kirby and Alfred Bauer establish standards for antibiotic susceptibility testing based on a single disc diffusion procedure that distinguishes susceptible strains of bacteria from their resistant variants. This method permits clinical laboratories to provide physicians with accurate, reproducible, and reliable information with which to chose antimicrobials.

Bauer, A. W., W. M. M. Kirby, J. C. Sherris, and M. Turck. 1966. Antibiotic susceptibility testing by a standardized single disk method. Am. J. Clin. Path. 45: 493-496. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.40 [pdf]

Walter Gilbert and Mark Ptashne isolate the repressor regulatory molecules postulated by Jacob and Monod. Gilbert isolates the lac repressor protein and Ptashne purifies the lamda repressor from bacteriophage. The repressor protein recognizes a specific site on the genome and binds to the site preventing transmission of DNA into RNA. Repressors are a key element of regulatory pathways and affect reaction by genes to environmental signals.

Gilbert, W. and B. Muller-Hill. 1966. Isolation of the lac repressor. Proc. natl. Acad. Sci. USA 56: 1891-1898.

Ptashne, M. 1967. Isolation of the phage repressor. Proc. Natl. Acad. Sci. USA 57: 306-313.

J. Woodland Hastings shows that Vibrio fischeri, a luminous species of bacterium, produces a diffusible compound, termed an autioinducer, which accumulates in the medium during growth. This phenomenon allows the bacterium to sense its elevated density. The concept is analogous to the production of pheromones in higher organisms.

Quorum Sensing in Gram Negative Bacteria, ASM News 63, 1997. p.371 [pdf]

Hastings, J. W., and Q. H. Gibson. 1967. The role of oxygen in the photoexcited luminescence of bacterial luciferose [Photobacterium fischeri] J. Biol. Chem. 242: 720-726.

Waclaw Szybalski and William Summers use the bacteriophage T7 to show that only one DNA strand acts as a template for RNA synthesis. They use the technique of DNA-RNA hybridization to anneal the newly synthesized RNA to a parent DNA strand.

Summers, W. C. and W. Szybalski. 1967. Y-Irradiation of deoxyribonucleic acid in dilute solutions: I. A sensitive method for detection of single-strand breaks of polydisperse DNA samples (bacteriophage, Sarcina lutea, Escherichia coli, Bacillus subtilis, Crytophaga johnsoni). J. Mol. Biol. 26: 107-123.

Summers, W. C. and W. Szybalski. 1967. Gamma-irradiation of deoxyribonucleic acid in dilute solutions: II. Molecular mechanisms responsible for inactivation of phage, its transfecting DNA, and bacterial transforming activity. J. Mol. Biol. 26: 227-235.

Theodor O. Diener discovers viroids, plant viruses that do not have a protein capsid. The infectious agent is a low molecular weight RNA that contains no protein capsid. Among the plants that are affected are potatoes, coconuts, and tomatos.

Diener, T. O. 1967. Potato spindle-tuber virus; a plant virus with properties of free nucleic acid. Science 158: 378-381.

Thomas Brock identifies the thermophile bacterium Thermus aquaticus from which heat stable DNA polymerase is later isolated and used in the polymerase chain reaction. Brock became interested in microbial mats during a trip to Yellowstone. It was believed at the time that the upper limit for bacterial growth was 73 degrees centigrade. Brock isolated a pink material that was growing at 85 degrees centigrade. Later the bacterium was cultured and ultraviolet irradiation was used to prove growth was taking place. Isolation and culture of this organism later leads to the discovery of the domain Archea.

Early Days in Yellowstone Microbiology, ASM News 64, 1998. p.137 [pdf]

Brock, T. D. 1967. Micro-organisms adapted to high temperatures. Nature 214; 882-885.

Brock, T.D. 1967. Life at high temperatures. Science 158:1012-19. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.214 [pdf]

R. John Collier describes the mechanism by which diphtheria toxin inhibits protein synthesis in a cell-free system from recticulocytes. This is the first definition at the molecular level of the function of a bacterial protein virulence factor.

Collier, R. J. 1967. Effect of diphtheria toxin on protein synthesis: Inactivation of one of the transfer factors. J. Mol. Biol. 25: 83-89. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.146 [pdf]

Werner Arber shows that bacterial cells contain highly specific enzymes that add methyl groups to adenosine and cytosine at recognition sites. Methylation is a defensive mechanism of the cell preventing hydrolysis of the parent DNA by nucleases in the cell. These nucleases protect against the introduction of foreign DNA. With Nathans and Smith, Arber is awarded the Nobel Prize in Medicine or Physiology in 1978

1978 Nobel Prize

Arber, W. and U. Kehnlein. 1967. Mutational loss of B-specific restriction of the bacteriophage fd. Path. Micro. 30: 946-952.

Marvin Bryant, the Wolins, and Ralph Wolfe show that anaerobic bacteria can effect interspecies transfer of H2. One strain oxidizes ethanol to acetate and the other reduces carbon dioxide to methane. This provides an explanation for the interactions of anaerobes during the fermentation of complex organic compounds.

M.P. Bryant, E.A. Wolin, M.J. Wolin, and R.S. Wolfe. 1967. Methanobacillus omelianskii, a symbiotic association of two species of bacteria. Archiv. Fur Mikrobiologie 59:20-31. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.224 [pdf]

Lynn Margulis proposes that endosymbiosis has led to the generation of mitochondria and chloroplasts from bacterial progenitors.

Margulis, L. 1968. Evolutionary criteria in Thallophytes: A radical alternative. Science 161: 1020-1022.

Charles Helmstetter and Stephen Cooper, using the "baby machine" establish the rules for replication in the Escherichia coli cell cycle.

Cooper, S. and C. Helmstetter. 1968. Chromosome replication and the division cycle of Escherichia coli B/r. J. Mol. Biol. 31: 519-540

From the Woods Hole Marine Station summer research program came the discovery by Levin and Bang that the lysate of the amebocytes from the hemolymph of the horseshoe crab, Limulus polyphermus clots in the presence of the lipopolysaccharides in the cell walls of gram-negative bacteria. This finding lead to the development of an in vitro assay for the pyrogens that contaminated injectable products that replaced the rabbit pyrogen test.

Levin, J., and F. B. Bang. "Clottable Proetin in Limulus: Its Localization and Kinetics of its Coagulation by Endotoxin." Thrombosis et Diathesis Haemorrhagica 19:186

Bacterial Endotoxin Test:

Julius Adler describes chemoreceptors in bacteria, a discovery demonstrating that bacteria can sense and process environmental information. His method involved inserting a tube of chemicals into a solution of bacteria and then counting the number of bacteria that swam to the chemical.

Adler, J. 1969. Chemoreceptors in bacteria. Science 166: 1588-1597. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.428 [pdf]

Don Brenner and colleagues establish a more reliable basis for the classification of clinical isolates among members of the Enterobacteriaceae. They use nucleic acid reassociation in which denatured DNA labelled DNA fragments of one organism are reacted under annealing conditions with DNA of another organism. Studies on many species have proven the value of DNA-DNA hybridization to define a species.

Brenner, D.J., G.R. Fanning, K.E. Johnson, R.V. Citrella, and S. Falkow.1969. Polynucleotide sequence relationships among members of the Enteriobactiaceae. J. Bacteriol. 98:637-50. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.46 [pdf]

Hamilton Smith and Kent W. Wilcox describe the action of restriction enzymes, which are a bacterial defense mechanism, but which quickly become tools for sizing DNA. They report the isolation of an enzyme capable of cleaving a double strand T7 DNA but not native DNA from the source organism, Haemophilus influenzae, or denatured DNA. They conclude that the enzyme has the ability to recognize specific DNA sequences. With Nathans and Arber, Smith is awarded the Nobel Prize in Medicine or Physiology in 1978

1978 Nobel Prize

Smith, H. O. and K. W. Wilcox. 1970. A restriction enzyme from Haemophilus influenzae: I. Purification and general properties. J. Mol. Biol. 51: 379-391. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.164 [pdf]

Howard Temin and David Baltimore independently discover reverse transcriptase in RNA viruses. The enzyme, reverse transcriptase, uses single stranded RNA as a template to synthesize a single stranded DNA complement . The latter then acts as a template for a complementary DNA chain consistent with general replication mechanisms. This process establishes a pathway for genetic information flow from RNA to DNA. Temin postulated that certain viruses possess an enzyme in their viral coat that facilitates the duplication of viral genes into the DNA of a cell. He called this gene a proviral gene and speculated that the genetic information was conveyed from RNA to DNA by the enzyme of the gene. With Dulbecco, Baltimore and Temin are awarded the Nobel Prize in Medicine or Physiology in 1975

1975 Nobel Prize

Baltimore, D. 1970. Viral RNA-dependent DNA polymerase. Nature 226: 1209-1211. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.518 [pdf]

Temin, H. M. and S. Mizutani. 1970. RNA-dependent DNA polymerase in virions of Rous carcinoma virus. Nature 226: 1211-1213. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.522 [pdf]

Joan Mertz and Ronald W. Davis establish that the R1 restriction endonuclease from Escherichia coli cuts DNA at a specific site four to six nucleotides long. The DNA sequence that is cut is complementary to other DNA cut by the same enzyme. This opens the way for cloning.

Mertz, J. E. and R. W. Davis. 1972. Cleavage of DNA by R1 restriction endonuclease generates cohesive ends. Proc. Natl. Acad. Sci USA 69: 3370-3374.

Paul Berg constructs a recombinant DNA molecule from viral and bacterial DNA. . With Gilbert and Sanger, Berg is awarded the Noble Prize in Chemistry in 1980

1980 Nobel Prize

Jackson, D. A., R. H. Symons, and P. Berg. 1972. Biochemical method for inserting new genetic infromationinto DNA of simian virus 40: Circular SV 40 DNA molecules containing lamda phage genes and the galactose operon of Escherichia coli. Proc. Natl. Acad. Sci. 69: 2904-2909. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.528 [pdf]

Stanley Cohen, Annie Chang, Robert Helling, and Herbert Boyer show that if DNA is broken into fragments and combined with plasmid DNA, such recombinant DNA molecules will reproduce if inserted into bacterial cells. They show that plasmids act as vectors for maintaining cloned genes. Boyer was researching restriction enzymes to determine whether they could cut the DNA at certain points. Cohen was isolating plasmids from E. coli. Cohen and Boyer met at a conference in Hawaii and shared their information.The discovery is a major breakthrough for genetic engineering, allowing for such advances as gene cloning and the modification of genes. The discovery also raised fears about accidental production of organisms with unexpected disease potential.

Cohen, S. N., A. C. Y. Chang, H. W. Boyer, and R. B. Helling. 1973. Construction of biologically functional bacterial plasmids in vitro. Proc. Natl. Acad. Sci. USA 70: 3240-3244. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.178 [pdf]

I'll Have the Chopped Liver Please, or How I Learned To Love the Clone, ASM News 67,2001. p.555 [pdf]

Daniel Nathans, George Khoury, Malcolm Martin use restriction enzymes to cleave SV40 DNA into specific segments and then construct a complete physical map of the virus.

Adler, S. P., and D. Nathans. 1973. Studies of SV40 DNA: V. Conversion of circular to linear SV40 DNA by restriction endonuclease from Escherichia coli B. Biochim. Biophys. Acta. 299: 177-188.

Khoury, G., M.A. Martin, T.N. Lee, K.J. Dana, and D. Nathans. 1973. A map of simian virus 40 transcription sites expressed in productively infected cells. J. Mol. Biol. 78:377-89. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.536 [pdf]

George Laver and Robert Webster demonstrate that the genomes of influenza virus strains responsible for pandemics possess genome fragments acquired by genome segment reassortment from influenza strains circulating in animals.

Laver, G. and R.G. Webster. 1973. Studies on the origin of pandemic influenza. III. Evidence implicating duck and equine influenza as possible progenitors of the Hong Kong strain of human influenza, Virology. 51:391-93

Peter Doherty and Rolf Zinkernagl show that the cellular immune system requires that lymphocytes recognize both the virus invader and major histocompatibility antigens in order to kill virus-infected cells. This establishes the principle of simultaneous recognition, of both self and non-self molecules, as the basis of the specificity of the cellular immune system. Doherty and Zinkernagl are awarded the Nobel Prize in Medicine or Physiology in 1996

1996 Nobel Prize

Zinkernagel, R. M. and P. C. Doherty. 1973. Cytotoxic thymus-derived lymphocytes in cerebrospinal fluid of mice with lymphocytic choriomeningitis. J. Exp. Med. 138: 1266-1269.

Viral Studies Illuminate the Nature of Immunity, ASM News 65, 1999, p.340

Paul Berg, David Baltimore, Herbert Boyer, Stanley Cohen, Ronald Davis, David Hogness, Richard Roblin, James Watson, Sherman Weissman, and Norton Zinder publish a letter in "Nature, Science, and the Proceedings of the National Academy of Sciences". They recommend that scientists defer from creating microorganisms with novel genes for drug resistance and toxin production, and also defer inserting cancer causing genes from viruses into bacterial host cells. They also suggest that the Federal government set guidelines for the conduct of research and that scientists themselves organize a conference to discuss these issues.

This appeared in the letters to Science from Paul Berg et al as: Potential biohazards of recombinant DNA. Science 185: 303.

Ralph Wolfe and Charles Taylor describe a novel coenzyme from a methanogen. This is the first of five new coenzymes, two of which are also widely distributed among the procaryotes.

C.D. Taylor and R.S. Wolfe. 1974. Structure and methylation of coenzyme M (HSCH2CH2SO3). J. Biol. Chem. 249:4879-85. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.256 [pdf]

David Hogness and Michael Grunstein develop colony hybridization, a technique to transfer bacterial colonies to filters, lyse, and fix the DNA. Labeled probes of single stranded DNA, complementary to the fixed DNA, can be applied to determine the identity of the unknown bacterium.

Kreigstein, H. J. and D. S. Hogness. 1974. Mechanism of DNA replication in Drosophila chromosomes: Structure and replication forks and evidence for bidirectionality. Proc. Natl. Acad. Sci. USA 71: 131-139.

Jeff Schell and Marc Van Montagu discover that a circular strand of DNA (a plasmid) carried by A. tumefaciens transforms plant cells into tumor cells.

Van Larabeke, N., Engler, G., Holsters, M., Elcacker, SVD, Zaenen, I., Schilperoort, R.A., and Schell, J. 1974. Large plasmid in Agrobacterium tumefaciens essential for crown gall-inducing ability. Nature 252:169

The Asilomar Conference is convened to discuss possible problems associated with gene cloning. A one-year moratorium, as well as guidelines for cloning research and for genetic engineering, is suggested.

This is described in 1975 as: Genetics: Conference sets strict controls to replace moratorium. Science 187: 931-934.

Kyung (June) Kwon-Chung describes sexual reproduction in the fungus, Cryptococcus neoformans.

Kwon-Chung, K. J. 1975. Filobasidiella, the perfect state of Cryptococcus neoformans. Mycologia 57: 1197-12

C.M. Wei and Bernard Moss, and Aaron Shatkin and colleagues show that messenger RNA contains a specific nucleotide cap at its 5-prime end that affects correct processing during translation.

C.M. Wei and B. Moss. 1975. Methylated nucleotides block the 5'-terminus of vaccinia virus mRNA. Proc. Nat'l. Acad. Sci. 72:318-22. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.550 [pdf]

Y. Furuichi, M. Morgan, S. Muthukrishnan, and A. Shatkin. 1975. Reovirus messsenger RNA contains a methylated blocked 5'-terminal strucure: m7G(5')ppp(5')GmpCp. Proc. Nat'l. Acad. Sci. 72:362-67. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.556 [pdf]

Georg Kohler and Cesar Milstein physically fuse mouse lymphocytes with neoplastic mouse plasma cells to yield hybridomas that can produce specific antibodies and can survive indefinitely in tissue culture. This approach offers a limitless supply of monoclonal antibodies. Monoclonal antibodies permit the generation of diagnostic tests that are highly specific and also function as probes to study cell function. With Jerne, Kohler and Milstein are awarded the Nobel Prize in Medicine or Physiology in 1984

1984 Nobel Prize

Kohler, G. and C. Milstein. 1975. Continuous cultures of fused cells secreting antibody of predefined specificity. Nature 256: 495-497.

Thomas Cech and Sidney Altman independently show that RNA can serve directly as a catalyst of hydrolytic reaction. Altman investigated RNase P from Escherichia coli and Cech studied the rRNA gene from Tetrahymena thermophilia. They each determined that an RNA component could be separated from protein while retaining catalytic activity. Cech and Altman are awarded the Nobel Prize in Chemistry in 1989

1989 Nobel Prize

Altman, S. 1975. Biosynthesis of transfer RNA in Escherichia coli. Cell 4: 21-30.

Cech, T. and M. L. Pardue. 1976. Electron microscopy of DNA crosslinked with trimethylpsorlen: Test of the secondary nature of eukaryotic inverted repeat sequences. Proc. Natl. Acad. Sci. USA 73: 2644-2648.

J. Michael Bishop and Harold Varmus identify oncogenes from the Rous sarcoma virus that can also be found in the cells of normal animals, including humans. Proto-oncogenes appear to be essential for normal development but can become cancer genes when cellular regulators are damaged or modified. Bishop and Varmus are awarded the Nobel Prize in Medicine or Physiology in 1989

1989 Nobel Prize

Stehelin, D., R. V. Guntaka, H. E. Varmus, and J. Michael Bishop. 1976. Purification of DNA complementary to nucleotide sequences required for neoplastic transformation of fibroblasts by avian sarcoma viruses. J. Mol. Biol. 101: 349-365.

Stehelin,D. H.E. Varmus, J.M. Bishop, and P. Vogt. 1976. DNA related to the transforming gene(s) of avian sarcoma virus is present in normal avian DNA. Nature 260:170-73. In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.562 [pdf]

The National Institutes of Health issues guidelines for the conduct of NIH supported research using recombinant DNA technology. The guidelines define physical and biological containment levels for research.

Recombinant DNA Research Guidelines, 41 Fed. Reg. 27902, 1976.

William Trager and Jim Jensen succeed in cultivating the human malaria parasite Plasmodium falciparum, which allowed its study, in the laboratory, for the first time.

Trager, W., Jensen, J. B. 1976. Human malaria parasites in continuous culture. Science 193: 673-5