Which type of mutation can be expressed through the example given in the passage?

A mutation in the Escherichia coli bacteria might not be expressed under permissive conditions such as low temperature but could be expressed under restrictive conditions such as high temperature.

Conditional mutation is a mutation that has wild type or less severe phenotype under certain permissive environmental conditions and a mutant phenotype under certain restrictive conditions. For example a temperature sensitive mutation can cause cell death at high temperature (restrictive condition) but might have no deleterious consequences at a lower temperature (permissive condition).