Transduction of bacteriophage Mu by bacteriophage T1.

Phage T1 transduces phage Mu PFU from Mu-lysogenic donor cells to sensitive recipient cells. The efficiency of transduction depends on the chromosomal location of the Mu prophage. T1, therefore, appears to package different regions of the bacterial chromosome with different efficiencies. Although T1 transduces bacterial markers with different efficiencies, there is no direct correlation between the efficiency of transduction of a bacterial marker and the efficiency of transduction of Mu PFU from donor cells with the Mu prophage located in that marker.     

Transduction of bacteriophage lambda by bacteriophage T1.

When bacteriophage T1 was grown on bacteriophage lambda-lysogenic cells, phenotypically mixed particles were formed which had the serum sensitivity, host range, and density of T1 but which gave rise to lambda phage. T1 packaged lambda genomes more efficiently both when the length of the prophage was less than that of wild-type lambda and when the host cell was polylysogenic. Expression of the red genes of lambda or the recE system of Escherichia coli during T1 growth enhanced pickup of lambda by T1, whereas packaging was reduced in recB cells. If donors were singly lysogenic, the expression of transduced lambda genomes as a PFU required lambda-specified excisive recombination, whereas lambda genomes transduced from polylysogens required only lambda- or E. coli-specified general recombination to give a productive infection.     

Bending of synthetic bacteriophage 434 operators by bacteriophage 434 proteins.

The extent of DNA bending induced by 434 repressor, its amino terminal DNA binding domain (R1-69), and 434 Cro was studied by gel shift assay. The results show that 434 repressor and R1-69 bend DNA to the same extent. 434 Cro-induced DNA bends are similar to those seen with the 434 repressor proteins. On approximately 265 base pair fragments, the cyclic AMP receptor protein of Escherichia coli (CRP) produces larger mobility shifts than does 434 repressor. This indicates that the 434 proteins bend DNA to a much smaller extent than does CRP. The effects of central operator sequence on intrinsic and 434 protein-induced DNA bending was also examined by gel shift assay. Two 434 operators having different central sequences and affinities for 434 proteins display no static bending. The amount of gel shift induced by 434 repressor on these operators is identical, showing that the 434 repressor bends operators with different central sequences to the same extent. Hence, mutations in the central region of the operator do not influence the bent structure of the unbound or bound operator.     

Control of bacteriophage lambda CII activity by bacteriophage and host functions

We have studied the regulation of the lambda cII gene in vivo using cloned lambda fragments. Lambda N protein stimulated cII expression. Surprisingly, although very high cII protein levels were detected by gel electrophoresis, little cII protein activity, measured as stimulation of the lambda pI and pE promoters, was observed. The half-life of cII protein depended critically on its initial level. At low concentrations its half-life was as short as 1.5 min, whereas at high cII protein levels, it could be as long as 22 min. The Escherichia coli mutant ER437 directs lambda towards lysogeny; cII protein was more stable in this strain than in the wild type. On the other hand, although cyclic AMP is required for efficient lysogeny, it did not appear to influence the synthesis, stability, or activity of cII protein.     

Bordetella pertussis bacteriophage

For the first time Bordetella pertussis bacteriophage was isolated, and its presence was confirmed by electron microscopy and by agar layer titration. The lysogenic strains were activated by their treatment with mitomycin C in a dose of 4.5 mg/ml. The phage system of the Bordetella genus, heretofore unknown, has been revealed: Bordetella pertussis phage lyzed all the tested strains of Bordetella parapertussis (25 strains) and could be passaged in these strains. The phage formed turbid and transparent negative colonies 0.1 mm and 0.15 mm in size. The phage titer (e. g., in strain No. 3865) was 1 X 10(10). The lysogenic variants of Bordetella pertussis, capable of spontaneous release of the phage, were obtained. These variants were characterized by changes in some of their phenotypical properties, e.g., the increased content of certain toxic substances and increased virulence.     

On bacteriophage anti-Flexner

Summary 1. The Flexner strain KB ofFlu from 1921 has given rise to two strains: the Flexner strain 38 which has grown SR and the Flexner strain 39 which has grown R. The Flexner strain 39 is at this moment a spontaneously agglutinating, lyso-sensitive strain, while the Flexner strain 38 apparently has kept up its original properties and is inagglutinable and lyso-resistant. Both strains belong to the type X ofAndrewes andInman. The Flexner strain 38, however, appears to agglutinate very specifically with an X serum. This strain can also be lysed by a special group of Flexner phage and not by others.2. The Flexner strain 38, however, is probably no variation of the strain KB ofFlu.3. The results ofBurnet andMcKie as to the correlation between antigenic structure of the Flexner strains and their sensitiveness to some groups of bacteriophage anti-Flexner could be confirmed in a high measure.