3 82
E. A. FREUNDT E?' AL.
basis for species classification by serving as a means of selecting those
phenotypic characteristics that may be particularly useful in identifying an
organism as belonging to a certain species (Johnson, 1973). As a matter of
fact, a very remarkable agreement has been found between the results of
hybridisation experiments and the present species classification that has
been based, throughout the years, on the combination of biological properties and serological data.
It is only logical, therefore, that the Subcommittee on the Taxonomy of
Mycoplasmatales (1972) should strongly recommend the inclusion of
cultural and biochemical as well as antigenic characters among the properties to be determined when a new species is being proposed. It follows that
the identification of an unknown strain as belonging to one or other of the
mycoplasma species already established must be based on similar criteria.
Since, as mentioned already, the mycoplasmas unfortunately possess
relatively few distinctive morphological, cultural and biochemical properties, the identification of an unknown strain depends ultimately on serology.
Although it is indisputable that high priority must be given to the use of
antigenic markers in identification there is still doubt as to which serological
methods are the most suitable.
I n the following Sections, the serological methods that are most frequently used in species classification and thereby also for the identification
of mycoplasmas will be mentioned. The theoretical basis of the methods
will be discussed only for those techniques that are specifically used in
mycoplasmology, whereas an attempt will be made to evaluate the specificity and sensitivity of each test.
Although specificity is, of course, a relative term, a specific test is
defined here as a test that will identify an organism as belonging to a
certain species without revealing a significant degree of cross-reaction with
representatives of any other species. Thereby, a working definition of the
species concept for mycoplasmas becomes a prerequisite for a further
meaningful discussion of what is to be understood by the specificity of a
test. On empirical grounds, a definition of the mycoplasma species may be
deduced from experience gained with the two tests that have proved most
useful and to which reference will be made frequently in subsequent
sections, i.e. the growth inhibition and metabolism inhibition tests. In
terms of the methods that are routinely used to identify an organism at
species level, a mycoplasma species may be defined as a group of strains
which are so closely related that antibody produced against one strain will
prevent replication and metabolism of all the other strains within that
group. The specificity of any other method has thus to be evaluated on the
basis of the extent of agreement it shows with the results obtained by the
growth and metabolism inhibition tests: a test is specific if it results in
E. A. FREUNDT E?' AL.
basis for species classification by serving as a means of selecting those
phenotypic characteristics that may be particularly useful in identifying an
organism as belonging to a certain species (Johnson, 1973). As a matter of
fact, a very remarkable agreement has been found between the results of
hybridisation experiments and the present species classification that has
been based, throughout the years, on the combination of biological properties and serological data.
It is only logical, therefore, that the Subcommittee on the Taxonomy of
Mycoplasmatales (1972) should strongly recommend the inclusion of
cultural and biochemical as well as antigenic characters among the properties to be determined when a new species is being proposed. It follows that
the identification of an unknown strain as belonging to one or other of the
mycoplasma species already established must be based on similar criteria.
Since, as mentioned already, the mycoplasmas unfortunately possess
relatively few distinctive morphological, cultural and biochemical properties, the identification of an unknown strain depends ultimately on serology.
Although it is indisputable that high priority must be given to the use of
antigenic markers in identification there is still doubt as to which serological
methods are the most suitable.
I n the following Sections, the serological methods that are most frequently used in species classification and thereby also for the identification
of mycoplasmas will be mentioned. The theoretical basis of the methods
will be discussed only for those techniques that are specifically used in
mycoplasmology, whereas an attempt will be made to evaluate the specificity and sensitivity of each test.
Although specificity is, of course, a relative term, a specific test is
defined here as a test that will identify an organism as belonging to a
certain species without revealing a significant degree of cross-reaction with
representatives of any other species. Thereby, a working definition of the
species concept for mycoplasmas becomes a prerequisite for a further
meaningful discussion of what is to be understood by the specificity of a
test. On empirical grounds, a definition of the mycoplasma species may be
deduced from experience gained with the two tests that have proved most
useful and to which reference will be made frequently in subsequent
sections, i.e. the growth inhibition and metabolism inhibition tests. In
terms of the methods that are routinely used to identify an organism at
species level, a mycoplasma species may be defined as a group of strains
which are so closely related that antibody produced against one strain will
prevent replication and metabolism of all the other strains within that
group. The specificity of any other method has thus to be evaluated on the
basis of the extent of agreement it shows with the results obtained by the
growth and metabolism inhibition tests: a test is specific if it results in