Porin-deficient mutant

[Layd33foxx]

Some bacteria become resistant to tetracycline because they don't make porins. Why can a porin-deficient mutant be detected by its inability to grow on a medium containing a single carbon source such as succinic acid?

[AstraSequi]

What is the function of a porin?

Knowing that, what sort of experiment might you design to see whether or not the porin is present? A system where the cell dies if the porin is not present (that is, the cell can't execute the porin's function) is usually very convenient.

[Layd33foxx]

Porins are channels control the transport of substances in and out of the cell, imparting the membrane its property of semipermeabililty.

[Layd33foxx]

Bacteria can develop resistance to the antibiotic by mutating the gene that encodes the porin – the antibiotic is then excluded from passing through the outer membrane

[AstraSequi]

Now suppose that the porin actually transports more than one substance - say, it can act on succinic acid as well as tetracycline. How might you figure out whether the porin is working or not?