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T F Anderson

Publications and source records attributed to T F Anderson.

At least 55 records · Page 3Linked to original sources
PubMed1974

Jack Schultz.

Explore the source record for details and available documents.

Genetics↗
PubMed1972

Effect of Zn2+ on bacterial conjugation: inhibition of mating pair formation.

Zn(2+) at 10(-3)m has been found to block the formation of mating pairs between Hfr and F(-) strains of Escherichia coli as observed both by light microscopy and by Coulter counter measurements. Kinetic studies show that Zn(2+) reduces the fertility of the male and that its effect disappears within 2 min after Zn(2+) has been removed from the medium. Short treatments of female cells with Zn(2+) have no detectable effect on their ability to form mating pairs. Later steps in the mating process such as mobilization of the male chromosome, transfer of the chromosome to the female, or its integration into the female chromosome seem not to be affected by 10(-3)m Zn(2+).

Chromosomes, Bacterial↗
PubMed1970

Role of pili in bacterial conjugation.

We describe techniques for isolating individual pairs of mating Escherichia coli and observing them under the light microscope. Some pairs achieved close cell-to-cell contact, whereas others remained loosely connected by invisible connections which may be F pili. After 30 min of mating, the pairs were separated and allowed to grow into clones. That many exconjugants derived from "loose"-mating pairs produced recombinants suggests that F pili are involved in the transfer of genetic material. The frequency of formation of recombinants from "close"-mating pairs, however, was significantly higher than that from loose-mating pairs, indicating that a close cell-to-cell contact facilitates chromosome transfer. Death rates of exconjugants from close pairs were also higher than those from loose pairs. Hfr x F(-) matings produced higher death rates than F(+) x F(-) matings. Male cells were found capable of transferring genetic markers to two F(-) cells simultaneously. We conclude that F pili play at least three roles in mating: (i) they initiate contacts between mating pairs; (ii) they facilitate the transfer of genetic material; and (iii) they draw mating cells into a close contact which increases the fertility of the union.

Chromosomes, Bacterial↗
PubMed1970

Morphological variants of coliphage P1.

Lysates of P1 from all hosts tested contained at least three morphological variants with respect to head size. These were termed "big" (P1B), "small" (P1S), and "minute" (P1M). Since successive clonings of plaques isolated on many different hosts failed to change the proportions of the variants, we concluded that the production of variants was a function of the P1 genome rather than that of the host. In the electron microscope, the heads appeared to be icosadeltahedra, having face-to-face head diameters of 86 +/- 2 nm, 65 +/- 2 nm, and 47 +/- 2 nm. Assuming the head capsids to be composed of the same protein subunits, these diameters were compatible with T = 16, 9, and 4 with a lattice constant (intercapsomere distance) of 12 to 13 nm. The tails of all variants were morphologically indistinguishable. Each consisted of a hollow tail tube surrounded by a contractile sheath attached to the head by means of a "head-neck connector" which could be a specialized vertex capsomere. In CsCl gradients, a number of bands were observed. One band contained the majority of P1B particles and 99% of the plaque-forming units. Two other bands contained P1S particles whose densities suggested a content of about 40 and 60% of the complete P1B genome. The less dense of these two bands also contained defective P1B particles with a calculated content of only 60% of the complete genome. The P1S particles tested injected their deoxyribonucleic acid (DNA) into host cells and killed them. Genetic markers contained in this band could be rescued by infectious P1B particles, confirming the evidence of Ikeda and Tomizawa that this fraction contains P1 DNA.

Agar↗
PubMed1969

Effect of host cell wall material on the adsorbability of cofactor-requiring T4.

The adsorbability of T4 on host cells was determined as a function of time after their liberation from infected cells. Freshly liberated (nascent) particles are readily adsorbed but lose their adsorbability with a half-time of about 2 days at 5 C, but only about 20 min at 37 C. They can be made adsorbable again with an alpha-amino acid cofactor like l-tryptophan, and this state of adsorbability can be stabilized by cell wall material from Escherichia coli. Such stabilized particles lose their adsorbability at a rate similar to that at which nascent particles lose theirs. Most freshly liberated particles are observed by means of electron microscopy to have "debris" attached to their baseplates and to have most of their six, long tail fibers free, whereas "old" particles that have lost their adsorbability appear relatively "clean" with most of their tail fibers wrapped around their sheaths. Nascent particles have densities that are lower than those of old particles. The material responsible for nascent adsorbability seems to be a fragment of the host's cell wall, for nascent adsorbability is destroyed by lysozyme. Furthermore, nascent T4 particles liberated from host cells with radioactively labeled walls carry the label in density gradients but lose it as they lose adsorbability. In addition, only a small proportion of particles liberated from infected spheroplasts are nascently adsorbable, whereas most particles liberated from intact cells are adsorbable.

Adsorption↗