The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in Escherichia coli / phage systems V. A comparison of the inactivation of phages T 2, T 7 and two strains of T 4 by alkylating agents

1959 ◽  
Vol 151 (942) ◽  
pp. 148-155 ◽  
Keyword(s):  
Deoxyribonucleic Acid ◽  
Osmotic Shock ◽  
Alkylating Agents ◽  
Acid Synthesis ◽  
Acid Moiety ◽  
Rate Of Penetration ◽  
Injection Process ◽  
Deoxyribonucleic Acid Synthesis ◽  
And Function ◽  
Escherichia Coli Phage

The sensitivity of phage T 7 to epoxides and freshly prepared solutions of di(2-chloroethyl) methylamine ( HN 2) was identical with that of T 2. T 7, however, proved considerably the more sensitive to ethylenimine and to aged solutions of HN 2. It was considered that this was due to the cationic nature of these latter agents affecting the rate of penetration into the phage heads, and that the susceptibility of T 2 and resistance of T 7 to osmotic shock was a parallel phenomenon. Confirmation was afforded by the fact that a strain of T 4 sensitive to osmotic shock behaved like T 2, and a resistant strain of T 4 like T 7. These results, together with others previously reported, are believed to offer very strong evidence that inactivation of bacteriophage by alkylating agents derives from reaction with the deoxyribonucleic acid moiety, probably leading to a failure of the injection process.

The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in Escherichia coli phage systems - II. Properties of coliphage T 2 treated with di(2-chloroethyl)methylamine

1959 ◽  
Vol 150 (941) ◽  
pp. 486-496 ◽  
Keyword(s):  
Deoxyribonucleic Acid ◽  
Acid Synthesis ◽  
Small Degree ◽  
Host Cells ◽  
Acid Moiety ◽  
Deoxyribonucleic Acid Synthesis ◽  
Protein Membrane ◽  
X Irradiation ◽  
And Function ◽  
Escherichia Coli Phage

An examination of the properties of T 2 coliphage, after treatment with the nitrogen mustard di(2-chloroethyl)methylamine, revealed a remarkable similarity to those of T 2 after X-irradiation. In particular, the phage remained capable of adsorption to the host cells and of combining with specific antibody, whilst showing a progressive loss of ability to kill the host cells with increasing dose. Further, a small degree of multiplicity and cross-reactivation was manifested, commensurate with that shown by phage X-irradiated in vitro . It is considered that these facts are consistent with the view that loss of plaque-forming ability is largely due to a failure of injection of the deoxyribonucleic acid moiety of the virus into the host cells following adsorption, an explanation already put forward by other workers in respect of X-rayed phage. This failure could arise by internal cross-linking of the DNA by the chloroethylamine, or of the DNA with the protein membrane. The experimental evidence supports the former proposal. The term 'radiomimetic' used in respect of di(2-chloroethyl)methylamine in the general title of this series is thus justifiable so far as phage inactivation is concerned.

The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in Escherichia coli / phage systems - III. Mutation of T 2 bacteriophage as a consequence of alkylation in vitro : the uniqueness of ethylation

1959 ◽  
Vol 150 (941) ◽  
pp. 497-508 ◽  
Keyword(s):  
Escherichia Coli ◽  
Burst Size ◽  
Alkylating Agents ◽  
Direct Consequence ◽  
Acid Synthesis ◽  
Deoxyribonucleic Acid Synthesis ◽  
Methane Sulphonate ◽  
Average Burst Size ◽  
And Function

Of a comprehensive set of alkylating agents tested, only two, namely, ethyl methane sulphonate and diethyl sulphate, have been found so to interact with T 2 bacteriophage that cells of Escherichia coli , infected with phage treated extracellularly, manifest a considerably increased likelihood of yielding mutated phage. Since this increase can occur where the infective titre of the phage and the latent period and average burst size of the infected bacteria remain unchanged, it is considered that the increased mutation rate is a direct consequence of the chemical treatment, although the alkylation itself does not constitute the mutation. A study of the manner of inactivation of the phage by these agents has not revealed any characteristic difference between ethylation and other alkylations which could be held to account for its apparent uniqueness.

The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in Escherichia colil /phage systems VI. The action of di(2-chloroethyl)methylamine ( HN 2) on bacteriophage T 2 during the intracellular growth cycle

1964 ◽  
Vol 159 (975) ◽  
pp. 348-365 ◽  
Keyword(s):  
Deoxyribonucleic Acid ◽  
Acid Synthesis ◽  
Growth Cycle ◽  
Chemical Substance ◽  
Wild Type ◽  
Intracellular Growth ◽  
Deoxyribonucleic Acid Synthesis ◽  
Geometrical Form ◽  
And Function ◽  
High Degree

The work reported herein constitutes essentially a repetition of the well-known Luria-Latarjet experiment (Luria & Latarjet 1947; Latarjet 1948) employing the radiomimetic nitrogen mustard di(2-chloroethyl)methylamine, commonly known as HN 2, in place of radiations. A more complicated experimental design than that employed by those authors had to be elaborated to overcome the problem of accurate dosimetry when using a chemical substance. The procedures adopted and the results afforded using, variously, bacteriophage T 2 r + (wild-type) and an r mutant thereof together with Escherichia coli strains B and B / r are reported. Five main conclusions are drawn: (1) immediately after infection of the cell the phage material offers a more resistant target to HN 2 than does the extracellular phage; (2) the first 2 or 3 min after infection see a small increase in sensitivity; (3) a striking increase in resistance occurs around the 8th min together with a change in form of the survival curves to a ‘multi-hit’ type; (4) thereafter, though the curves remain ‘multi-hit’ a second increase in sensitivity is manifested; (5) there is a component of the infected cell population which shows a high degree of resistance at all times. (1) and (2) are attributed to changes in the geometrical form of the phage deoxyribonucleic acid ( DNA ) consequent upon its extrusion into the cell from the phage head; it is also considered that the early transient increase in sensitivity might be associated with the formation of a DNA-RNA complex; (3) is attributed to DNA replication which is known to occur at this time, thus providing a multiplicity of target, though it is not known if multiplicity reactivation takes place; (4) is thought likely to be the consequence of the condensation of phage DNA into discrete units having the same geometry as that of the fully formed phage. No explanation is currently offered for the occurrence of highly resistant complexes.

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