Yarus, Michael Jeffrey (1966) Bacteriophage [phi chi]-174: Its sensitivity to ultraviolet light and growth in starved and irradiated cells. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-09232002-152158
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Part I Ultraviolet action spectra for inactivation of [phi chi]-174 virus, its infective single-stranded DNA (SS), and an infective, intracellular and presumably double-stranded DNA (RF) have been determined. The biological activity of the irradiated DNA was measured using bacterial protoplasts.
The inactivation cross-section of the RF is nearly an order of magnitude less at all wavelengths than that of either the free single-stranded DNA or the intact virus, which have very similar cross-sections. Besides the difference in magnitude, the action spectrum of RF, when compared to that of SS [phi chi] DNA shows several differences in band shape.
The similarity of the free SS and virus sensitivities to radiation in the range 240-302 [megamicrons] suggests that energy of these wavelengths which is effective in inactivation of the virus is that absorbed by the nucleic acid. Below 240 [megamicrons] the DNA is less sensitive than the virus; UV inactivation as a consequence of energy absorbed by the virus protein is a likely explanation of the higher viral sensitivity.
The quantum yield for inactivation of the single-stranded DNA is a function of wavelength in the range of wavelengths used, 225-302 [megamicrons]. This may be understood as a result of the variable fraction of absorbed energy localized in pyrimidines. This dependence of quantum yield on wavelength is altered in the case of the whole virus, presumably because of the important role of the protein at low wavelengths. The quantum yield of SS [phi chi] DNA increases slightly with salt concentration, reflecting the existence of some process which is enhanced on contraction of the polymer and the resulting stronger interactions between bases.
The ability of [phi chi] bacteriophage-infected cells to release progeny after UV irradiation has been examined using both a host possessing host cell reactivation (E. coli C(subscript)N) and one lacking it (E. coli C(subscript s). The UV sensitivity of both free [phi chi] DNA extracted from infected cells and DNA irradiated in situ in the infected cell, as judged by their infectivity to bacterial protoplasts, is sufficient to account for the intrinsic sensitivity of the host-phage complex.
The burst of a starved bacterium infected with several (phi chi]-174 bacteriophage is usually found to contain descendants of only one of the parents; less often, two phage may multiply. Unstarved cells, in contrast, can support the growth of at least four phage. The unproductive phage seem to convert their parental single-stranded DNA into intracellular, double-stranded RF. These results are interpreted to mean that some factor required by [phi chi] for the production of progeny is limited in starved cells.
Evidence is presented that starved, UV-irradiated E. coli C which has lost its capacity to support [phi chi] bacteriophage reproduction, has also become unsuitable for the synthesis of infective RF, though the incoming single stranded viral DNA is able to undergo the transition to an RF whose behavior on neutral density gradient analysis is the same as normal RF. Very alkaline conditions appear to activate the inactive RF, releasing infective parental single strands as well as making infective those RF whose strands do not separate.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||16 September 1965|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||24 Sep 2002|
|Last Modified:||26 Dec 2012 03:02|
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