Ch.4 — The Pharmaceutical Industry • 75 
Antibiotics 
Antimicrobial agents for the treatment of in- 
fectious diseases ha\e been the largest selling 
prescription pharmaceuticals in the world for 
the past three decades. Most of these agents are 
antibiotics— antimicrobials naturally produced 
by micro-organisms rather than by chemical 
synthesis or by isolation from higher organisms. 
However, one major antibiotic, chlorampheni- 
col— originally produced by a micro-organism, 
is now synthesized by chemical methods. The 
field of antibiotics, in fact, pro\ ides most of the 
precedent for employing microbial fermenta- 
tion to produce useful medical substances. The 
L'nited States has been prominent in their 
development, production, and marketing, with 
the result that .American companies account for 
about half of the roughly S5 billion worth of an- 
timicrobial agents sold worldwide each year. 
7'he .American market share has been growing 
as new antibiotics are de\eloped and intro- 
duced e\erv year. 
For 30 years, high-yielding, antibiotic-pro- 
ducing micro-organisms ha\ e been identified by 
selection from among mutant strains. Initially, 
organisms producing new antibiotics are iso- 
lated by soil sampling and other broad screen- 
ing efforts. They are then cultured in the lab- 
oratory, and efforts are made to improx e their 
productivity. 
Antibiotics are complex, usually nonprotein, 
substances, which are generally the end prod- 
ucts of a series of biological steps. U'hile knowl- 
edge of molecular details in metabolism has 
made some difference, not a single antibiotic 
has had its complete biosynthetic pathway eluci- 
dated. This is partly because there is no single 
gene that can be isolated to produce an antibi- 
otic. However, mutations can be induced within 
the original micro-organism so that the level of 
production can be increased. 
Other methods can also increase production, 
and possibly create new antibiotics. Microbial 
mating, for example, which leads to natural 
recombination, has been widely investigated as 
a way of developing vigorous, high-yielding an- 
tibiotic producers. However, its use has been 
limited by the mating incompatibility of many 
industi'ially important higher fungi, the pres- 
ence of chromosomal aberrations in micro-orga- 
nisms improved by mutation, and a number of 
other problems. Furthermore, natural recom- 
bination is most ad\ antageous when strains of 
extremely diverse origins are mated; the pro- 
prietary secrets protecting commercial strains 
usually j)revent the sort of divergent "competi- 
tor” strains most likely to produce vigorous 
hybrids from being brought together. 
The technique of pi'otoplast or cell fusion 
provides a convenient method for establishing a 
recombinant system in strains, species, and 
genera that lack an efficient natural means for 
mating. For example, as many as four strains of 
the antibiotic-producing bacterium Streptomy- 
ces have been fused together in a single step to 
yield recombinants that inherit genes from four 
parents. The technique is applicable to nearly 
all antibiotic producers. It will help combine the 
benefits developed in divergent lines by muta- 
tion and selection. 
In addition, researchers have compared the 
quality of an antibiotic-producing fungus, Ceph- 
alosporium acremonium, produced by mating to 
one produced by protoplast fusion. (See Tech. 
Note 15, p. 82.) They concluded that protoplast 
fusion was far superior for that purpose. What 
is more, protoplast fusion can give rise to hun- 
dreds of recombinants— including one isolate 
that consistently produced the antibiotic ceph- 
alosporin C in 40 percent greater yield than the 
best producer among its parents— without los- 
ing that parent strain’s rare capacity to use in- 
organic sulfate, rather than expensive methio- 
nine, as a source of sulfur. It also acquired the 
rapid growth and sporulation characteristics of 
its less-productive parent. Thus, desirable at- 
tributes from different parents were combined 
in an important industrial organism that had 
proved resistant to conventional crossing. 
Even more significant are the possibilities for 
preparation by protoplast fusion between dif- 
ferent species or genera of hybrid strains, 
which could have unique biosynthetic capaci- 
ties. One group is reported to have isolated a 
novel antibiotic, clearly not produced by either 
parent, in an organism created through fusion 
of actinomycete protoplasts. (See Tech. Note 16, 
