5. ANTIBIOSIS AND ANTIBIOTICS
261
that would be deduced from the facts gathered to date is apt to be
rather misleading. However, it is permissible to stress a few important
well-established points: (a) a given organism may well produce more
than one antibiotic, either simultaneously or one at a time according to
the prevailing environmental conditions; (b) a given antibiotic may be
produced by different organisms, sometimes closely related but sometimes taxonomically very distant; (c) antibiotics belonging to a same
chemical type are sometimes highly characteristic of a definite taxonomic
group, but, in other cases, quite unrelated species produce very similar
or even identical compounds. A comparative study of the biochemical
steps involved in the biosynthesis of identical or related substances by
different organisms would be of great interest, but few relevant data are
as yet available.
A second point of interest is the comparison of the chemical structure
of different antibiotics or, more fundamental no doubt, of the metabolic
pathways leading to their biosynthesis. Such a study should obviously
include biochemically related metabolites having no antibiotic activity.
But this raises a fundamental difficulty, since such substances are possibly biosynthesized simultaneously with, or under suitable conditions
instead of, the antibiotic but remain unnoticed because our techniques
of detection are not fit to reveal their presence.
It is now well known, however, that many antibiotics occur as families of closely related compounds endowed with quantitatively, and
sometimes qualitatively, different antimicrobial properties, the group
often comprising also members devoid of biological activity.
The diversity of chemical structures found among antibiotics was
long a subject of bewilderment until the efforts of Chain (24), of Regna
(25), and of Abraham and Newton (26) succeeded in introducing order
into chaos. They have shown that a great number of antibiotics can be
related, in whole or in part, structurally or biogenetically, to the common
building blocks of living matter such as sugars, amino acids, fatty acids,
and heterocyclic compounds. Many of them have been related to important metabolites (27). Antibiotics have thus lost their somewhat
mysterious character; according to Bu'Lock (28), they should be classified, together with innumerable biologically inert substances, among the
secondary metabolites, these being defined as molecules characterized
by their restricted distribution and the fact that they have no obvious
function in general metabolism. Antibiotics thus appear as further examples of the extreme diversity of variations on a few fundamental themes
which has been recognized in biochemical structures and processes since
the pioneer work of Kluyver, founder of comparative biochemistry.
261
that would be deduced from the facts gathered to date is apt to be
rather misleading. However, it is permissible to stress a few important
well-established points: (a) a given organism may well produce more
than one antibiotic, either simultaneously or one at a time according to
the prevailing environmental conditions; (b) a given antibiotic may be
produced by different organisms, sometimes closely related but sometimes taxonomically very distant; (c) antibiotics belonging to a same
chemical type are sometimes highly characteristic of a definite taxonomic
group, but, in other cases, quite unrelated species produce very similar
or even identical compounds. A comparative study of the biochemical
steps involved in the biosynthesis of identical or related substances by
different organisms would be of great interest, but few relevant data are
as yet available.
A second point of interest is the comparison of the chemical structure
of different antibiotics or, more fundamental no doubt, of the metabolic
pathways leading to their biosynthesis. Such a study should obviously
include biochemically related metabolites having no antibiotic activity.
But this raises a fundamental difficulty, since such substances are possibly biosynthesized simultaneously with, or under suitable conditions
instead of, the antibiotic but remain unnoticed because our techniques
of detection are not fit to reveal their presence.
It is now well known, however, that many antibiotics occur as families of closely related compounds endowed with quantitatively, and
sometimes qualitatively, different antimicrobial properties, the group
often comprising also members devoid of biological activity.
The diversity of chemical structures found among antibiotics was
long a subject of bewilderment until the efforts of Chain (24), of Regna
(25), and of Abraham and Newton (26) succeeded in introducing order
into chaos. They have shown that a great number of antibiotics can be
related, in whole or in part, structurally or biogenetically, to the common
building blocks of living matter such as sugars, amino acids, fatty acids,
and heterocyclic compounds. Many of them have been related to important metabolites (27). Antibiotics have thus lost their somewhat
mysterious character; according to Bu'Lock (28), they should be classified, together with innumerable biologically inert substances, among the
secondary metabolites, these being defined as molecules characterized
by their restricted distribution and the fact that they have no obvious
function in general metabolism. Antibiotics thus appear as further examples of the extreme diversity of variations on a few fundamental themes
which has been recognized in biochemical structures and processes since
the pioneer work of Kluyver, founder of comparative biochemistry.