living organisms that are sensitive to air temperatures outside of a narrow range, e.g. virus vaccine that does not replicate at deep body temperature, but does replicate in the respiratory tract.
temperature-sensitive (ts) mutants
strains of viruses or other microorganisms that are able to grow at certain low temperatures, say 90°F (32°C), which is referred to as the permissive temperature, but are unable to grow at higher temperatures, say 102°F (39°C), which is referred to as the nonpermissive temperature. Such conditionally lethal mutants have been much used in the genetic analysis, i.e. gene mapping, of microorganisms. At the nonpermissive temperature the protein product of a particular gene is unstable and hence nonfunctional, whereas the protein function is normal at the permissive temperature. These mutants have also been selected for use in vaccines because of their growth requirements for lower temperatures and lower pathogenicity, e.g. ts strains of bovine herpesvirus 1 which, when administered intranasally, grow on nasal mucosa but do not cause systemic illness.
proteins that are functional at higher temperatures, but not at others. See temperature-sensitive mutants (above).