5. ANTIBIOSIS AND ANTIBIOTICS
335
when suitable conditions do reappear. The capacity of synthesizing secondary metabolites, whether antibiotically active or not, would therefore
be a definite advantage for the producer, inasmuch as it would thus
continue to remove from its surroundings nutrient materials that would
otherwise be at the disposal of its competitors. Bu'Lock's interpretation
has the merit of explaining the role of antibiotics, as well as that of
chemically related inactive compounds, without necessarily postulating
an antimicrobial function of the former.
As pointed out above on several occasions, some classes of antibiotics
and related substances are rather characteristic of certain taxonomic
groups. However, one should be aware that such a situation may be more
apparent than real and mainly due to the fact that some kinds of microorganisms have been more thoroughly explored from that point of view
than others. Even in the present sketchy stage of our knowledge, there
are generally conspicuous exceptions to any statement of a correlation
between the production of a given antibiotic and the taxonomic position
of the producing organisms.
Further, within the larger taxonomic groups, the capacity to produce
a given antibiotic appears, generally, not as a property of species, but
rather of strains. It is also a property which is often easily lost by mutation. These remarks apply equally to antibiotic sensitivity.
However, in the present-day rather confused situation with respect to
the definition of most microbial species, at least in the case of bacteria
and fungi imperfecti, production of and sensitivity to antibiotics are
given very different weight as criteria of classification by different
authors. Also, the intensive search for antibiotic production in some
bacterial groups, the streptomycetes for instance, has led to the study of
a large number of individual isolates, with the result that any one of the
characters studied showed a continuous quantitative change throughout
the series of specimens examined. Such observation rather blurs the
concept itself of species.
The existence of some correlation between the ability to produce a
given antibiotic and sensitivity of the producers to a definite bacterial
virus was reported in a few instances. Waksman and co-workers (332)
thus described an actinophage specifically lysing streptomycin-producing
strains of Streptomyces griseus. Burkholder and collaborators (333) also
described a virus acting upon streptomycin-, but not on grisein- or on
viomycin-, producers. More recently, Kutzner (334) reported that
heptaene-producing streptomycetes are specifically sensitive to a same
actinophage. Welsch (335) described an actinophage, φ-17, which first
appeared to act specifically upon actinomycin-producing strains. But
further and more extensive studies, using several viruses, including some
335
when suitable conditions do reappear. The capacity of synthesizing secondary metabolites, whether antibiotically active or not, would therefore
be a definite advantage for the producer, inasmuch as it would thus
continue to remove from its surroundings nutrient materials that would
otherwise be at the disposal of its competitors. Bu'Lock's interpretation
has the merit of explaining the role of antibiotics, as well as that of
chemically related inactive compounds, without necessarily postulating
an antimicrobial function of the former.
As pointed out above on several occasions, some classes of antibiotics
and related substances are rather characteristic of certain taxonomic
groups. However, one should be aware that such a situation may be more
apparent than real and mainly due to the fact that some kinds of microorganisms have been more thoroughly explored from that point of view
than others. Even in the present sketchy stage of our knowledge, there
are generally conspicuous exceptions to any statement of a correlation
between the production of a given antibiotic and the taxonomic position
of the producing organisms.
Further, within the larger taxonomic groups, the capacity to produce
a given antibiotic appears, generally, not as a property of species, but
rather of strains. It is also a property which is often easily lost by mutation. These remarks apply equally to antibiotic sensitivity.
However, in the present-day rather confused situation with respect to
the definition of most microbial species, at least in the case of bacteria
and fungi imperfecti, production of and sensitivity to antibiotics are
given very different weight as criteria of classification by different
authors. Also, the intensive search for antibiotic production in some
bacterial groups, the streptomycetes for instance, has led to the study of
a large number of individual isolates, with the result that any one of the
characters studied showed a continuous quantitative change throughout
the series of specimens examined. Such observation rather blurs the
concept itself of species.
The existence of some correlation between the ability to produce a
given antibiotic and sensitivity of the producers to a definite bacterial
virus was reported in a few instances. Waksman and co-workers (332)
thus described an actinophage specifically lysing streptomycin-producing
strains of Streptomyces griseus. Burkholder and collaborators (333) also
described a virus acting upon streptomycin-, but not on grisein- or on
viomycin-, producers. More recently, Kutzner (334) reported that
heptaene-producing streptomycetes are specifically sensitive to a same
actinophage. Welsch (335) described an actinophage, φ-17, which first
appeared to act specifically upon actinomycin-producing strains. But
further and more extensive studies, using several viruses, including some