Please explain in detail. Why can\'t Salmonella be infected by lambda phage? Why can\'t salmonella be successfully transfected using lambda DNA? Solution Lambda phage is a bacteriophage or bacteria virus which is known to infect bacteria especially Escherichia coli hence, sometimes also called as coliphage.This virus is used in recombinat DNA technology for transferring special genes or you can say that as a vector. To infect a bacterium a virus needs to: 1) interact first with the cell surface receptors which are different in different species thus, making coliphage entry difficult inside the Salmonella species. 2) Multiplication of virus genome inside the bacteria is another factor for a virus to cause infection in a bacterium. To multiply inside bacteria, phage join its nucleic acid with host\'s nucleic acid, this stage of infection is called prophage. To attach its nucleic acid a phage must recognise an attachment site called att site in host\'s genome which varies among different genera. At this stage genetic exchange takes place hence, it is difficult too transfect Salmonella with a coliphage. However, Phage P22 can transfect Salmonella because the bacterium has specific att sites for P22. Also, Transduction i.e. transfer of nucleic acid by a bacteriophage to bacteria was first discovered in P22 infecting Salmonella. Salmonella species can be made competitive( susceptible to genetic exchange by transfection) for coliphage by altering its genomic structure using recombinant DNA tools..

1. Please explain in detail. Why can't Salmonella be infected by lambda phage? Why can't
salmonella be successfully transfected using lambda DNA?
Solution
Lambda phage is a bacteriophage or bacteria virus which is known to infect bacteria especially
Escherichia coli hence, sometimes also called as coliphage.This virus is used in recombinat DNA
technology for transferring special genes or you can say that as a vector. To infect a bacterium a
virus needs to:
1) interact first with the cell surface receptors which are different in different species thus,
making coliphage entry difficult inside the Salmonella species.
2) Multiplication of virus genome inside the bacteria is another factor for a virus to cause
infection in a bacterium. To multiply inside bacteria, phage join its nucleic acid with host's
nucleic acid, this stage of infection is called prophage. To attach its nucleic acid a phage must
recognise an attachment site called att site in host's genome which varies among different
genera. At this stage genetic exchange takes place hence, it is difficult too transfect Salmonella
with a coliphage.
However, Phage P22 can transfect Salmonella because the bacterium has specific att sites for
P22. Also, Transduction i.e. transfer of nucleic acid by a bacteriophage to bacteria was first
discovered in P22 infecting Salmonella. Salmonella species can be made competitive(
susceptible to genetic exchange by transfection) for coliphage by altering its genomic structure
using recombinant DNA tools.