4 Study of the Life Cycle of an Actinomycete

Introduction
The actinomycetes which represent a transition between
the bacteria and the fungi, compose a large proportion
of the soil flora, It was not until their capacity to
synthesize antibiotic substances was recognized that this
group of organisms attracted wide-spread attention,
Eowever, primarily only those factors which influence
antibiotic procuction have been investigated. Although
sexual mechanisms have been conclusively demonstrated in
several fungi and at least one bacterium, the actinomycetes
have not been subjected to definitive tests.

Background
A generalized life cycle of the genus Streptomyces is as
follows: uni- or multinucleate scores germinate by pro-~
duction of one to four hyphae. Growth continues until a
mature unicellular mycelium is constituted. Aerial hyphae
are then formed which differentiate into spores, beginning
at the apical end and proceeding toward the base. Fragments

of the vegetative myceliua is able to regenerate a mature

eolony.

Klieneberger-lobel (1947) reported that the aerial aynhae of

Streptomyces result from the fusion of two separate hyphae,

producing “zygotic spores", No recombination has, however,

 
been demostrated.

spores often germinate by formation of one to four vegative
hyphae. This phenomena might conceivably be the product of
a meiosis.,
Proposed Research Project
I. aA stuay of the life cycle of an actinomycete
bt. isolation of a member of the genus Streptomyces
a@. one with an optinal temperature of 37°C
would probably grow faster than one with

an optimal taémperature of 28

2. Determination of the minimal nutritional requirements
for completion of the life cycle

3. Production of nutritional and morphological :arked
strains by ultra-violet and X-ray irradiation

a. mechanism for screening biochemical mutants

1) use of antibiotics to kill prototrophs
followed by addition of supplement

2) stamp technique of Lederberg

4. Recombination tests

a. mix reciprocal biochemically marked stocks
and plate onto minimal agar

b. analysis of the prototronphs

1) heterokaryons yielding only parental
types

2) recombinants
a) genetic mechanisms
b) transformations, test cell-free

extracts end by the bundling
board.