E. coli phages

Pol I and pol III holoenzyme are both essential for E. coli replication. The need for two polymerases seems to be characteristic of all cellular organisms but not all viruses, e.g., E. coli. Phage T4 synthesizes its own DNA polymerase, which is capable of carrying out all functions necessary for synthesizing phage DNA. 

The E. coli phage T5 promoter, together with two lac operator, sequences is derived from the pQE30 plasmid belonging to the pDS family of plasmids [3, 4]. 

DAG 652 and 178, but also their ribofuranosides were capable of inhibiting nucleic add synthesis. iV- -D-ribofuranosides and other glycosides of unsubstituted IbPs and IcPs, as well as their halo and nitro derivatives act similarly but less efficiently. For example, 3- -D-ribofuranosyl-IbP inhibits the reproduction of Ranikhet disease virus and shows to some extent an anticancer activity. However, the aglycone of IbP also shows definite activity towards E. coli phage. But 3- -D-ribofuranosyl-IcP does not possess any activity (63IJC30). 6-Bromo-IbP, its 2-methyl derivative, as well as... 

Cohen et al. (IS) discovered that fluorodeoxyuridylate (but not fluoro-uridylate) is a potent inhibitor of the phage-induced thymidylate synthetase in E. coll and is competitive with deoxyuridylate. Since this discovery, inhibition of the synthetase from other sources has been studied (see review, reference 8). The inhibition by fluorodeoxyuridylate of the E. coli phage synthetase, or that from chick embryo or Ehrlich ascites cells, is competitive with respect to deoxyuridylate when all of the reaction components are added together. However, noncompetitive kinetics and a stoichiometric binding of the inhibitory nucleotide are obtained with the chick enzyme, if it is first incubated with fluorodeoxymidylate and 5,10-methylene H4-folate. Evidently the eofactor must be present for fluorodeoxyuridylate to bind in the noncompetitive manner (7). Similarly, it has been found that the bacterial enzyme can be virtually titrated with the inhibitor, if enzyme and inhibitor are preincubated prior to assay of the reaction. The Ehrlich cell enzyme differs in that fluorodeoxyuridylate is competitive with deoxyuridylate, in spite of preincubation with the enzyme. 

Of the many varieties of bacteriophage, only phage X and filamentous M13 have been confirmed as major cloning vectors in E. coli. Phage X has a 48.5 kb DNA molecule which has been sequenced and mapped so that the positions and functions of its genes are known. Related genes, e.g. those... 

In principle, the in vitro synthesis of phage enzymes in an E, coli system can be applied to both, E. coli and non-E. coli phage. Enzyme synthesis was observed using DNAs from various B. subtilis phage (j)29 lysozyme (in col-... 

One system among the E. coli phages remains to be discussed in this context Lambda. Lambda DNA is a poor template for E, coli RNA polymerase (Schweiger et al., 1969 Gesteland and Kahn, 1972) which may be due to the need for transcriptional control proteins. These are peculiar to the lambda system and have only recently been investigated by a direct method such as the in vitro enzyme synthesis. 

The renaturation rate of DNA is an excellent indicator of the sequence complexity of DNA. For example, bacteriophage T4 DNA contains about 2 X 10 nucleotide pairs, whereas Escherichia coli DNA possesses 4.64 X 10 . E. coli DNA is considerably more complex in that it encodes more information. Expressed another way, for any given amount of DNA (in grams), the sequences represented in an E. coli sample are more heterogeneous, that is, more dissimilar from one another, than those in an equal weight of phage T4 DNA. Therefore, it will take the E. coli DNA strands longer to find their complementary partners and reanneal. This situation can be analyzed quantitatively. 

The phage lambda (X) ofE. coll is the temperate phage that has been most extensively studied. When any particular strain oiE. coli, say K12, is infected with A, the cells surviving the infection are designated E. coli K 12(A) to indicate that they are carrying the /1-prophage. 

Baert, L., Uyttendaele, M., Van Coillie, E., and Debevere, J. (2008a). The reduction of murine norovirus 1, B. fragilis HSP40 infecting phage B40-8 and E. coli after a mild thermal pasteurization process of raspberry puree. Food Microbiol. 25, 871-874. 

Figure 4.5. Integrative and excisive X phage recombination pathways. Integration is catalyzed by the X Int protein in a reaction that also requires the E. coli IHF protein. Recombination occurs within a common core sequence of 15 base pairs. The excision reaction requires the X Xis protein in addition to Int and IHF.

A majority of the work done in our laboratory has been conducted on E. coli and B. anthracis using MS2 and gamma-phage, respectively. Amplification results have been obtained from several other host bacteria and bacteriophages. Table 14.1 summarizes the materials studied. In all cases studied, no two bacteriophages contained the same proteins. 

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