52
EDWARD C. CANTINO AND JAMES S. LOVETT
number of spores per cell) depending upon the composition and
concentration of the medium and other environmental factors (Cantino
and Hyatt, 1953a). In any case, the spores liberated from the parent
cell, now submerged, will swim about and distribute themselves at
random in the liquid; thus, a population—albeit a very light one—of
swimming spores is formed.
These motile spores can then be transferred to a second plate of
medium, whereon they germinate and give rise to a population of
second-generation plants. If allowed to do so, these cells will discharge
in situ as before. The degree of synchrony involved is inherently rather
good; on YpSs medium, for example, over 80% of the population will
liberate spores within an hour's time (Cantino and Hyatt, 1953a). If,
however, plates are flooded once again just before the time of normal
discharge, a very heavy population of spores can be obtained. These, in
turn, are used to start new cultures, with a considerable increase in the
size of the ensuing population of third-generation cells. In this fashion,
successive spore populations can be formed, and in numbers which
approach astronomical proportions; the final density of the cellsuspension depends only upon the wishes and the ingenuity of the
investigator (as limited, of course, by the number of Petri plates that his
laboratory can accomodate). The spore-suspension finally selected for
starting liquid cultures should be passed through filter paper to remove
plants or germlings that might have been dislodged from the flooded
agar surface ; they are trapped and held effectively while motile spores
pass through unhindered. The final density of the spore suspension can
be roughly estimated turbidimetrically, and much more accurately by
viable spore counts on plates.
It is important to note that the
e
age' of the swimming spores can be
controlled precisely and at will. For example, if only those spores are
selected which have been discharged from cells within, let us say, a
10 minute period, then the 'degree of synchrony' of the spore-suspension
is defined in no uncertain terms—all swimming spores in the population
are no more than 10 minutes old.
Finally, spore-suspensions of suitable age and density can be introduced into liquid media for growing vigorously-aerated, submerged,
single-generation cultures of several million to a billion cells (McCurdy
and Cantino, 1960; Goldstein and Cantino, 1962; Lovett and Cantino,
1960b). Under these conditions, spores give rise to individual germlings
which, in their state of constant agitation, develop exponentially in
exceedingly uniform fashion and then differentiate synchronously into
either OC or RS cells, depending upon the medium previously selected.
Thus, in contrast to bacteria for example, where visible estimation of
the degree of synchrony of a culture may have to be followed solely by
EDWARD C. CANTINO AND JAMES S. LOVETT
number of spores per cell) depending upon the composition and
concentration of the medium and other environmental factors (Cantino
and Hyatt, 1953a). In any case, the spores liberated from the parent
cell, now submerged, will swim about and distribute themselves at
random in the liquid; thus, a population—albeit a very light one—of
swimming spores is formed.
These motile spores can then be transferred to a second plate of
medium, whereon they germinate and give rise to a population of
second-generation plants. If allowed to do so, these cells will discharge
in situ as before. The degree of synchrony involved is inherently rather
good; on YpSs medium, for example, over 80% of the population will
liberate spores within an hour's time (Cantino and Hyatt, 1953a). If,
however, plates are flooded once again just before the time of normal
discharge, a very heavy population of spores can be obtained. These, in
turn, are used to start new cultures, with a considerable increase in the
size of the ensuing population of third-generation cells. In this fashion,
successive spore populations can be formed, and in numbers which
approach astronomical proportions; the final density of the cellsuspension depends only upon the wishes and the ingenuity of the
investigator (as limited, of course, by the number of Petri plates that his
laboratory can accomodate). The spore-suspension finally selected for
starting liquid cultures should be passed through filter paper to remove
plants or germlings that might have been dislodged from the flooded
agar surface ; they are trapped and held effectively while motile spores
pass through unhindered. The final density of the spore suspension can
be roughly estimated turbidimetrically, and much more accurately by
viable spore counts on plates.
It is important to note that the
e
age' of the swimming spores can be
controlled precisely and at will. For example, if only those spores are
selected which have been discharged from cells within, let us say, a
10 minute period, then the 'degree of synchrony' of the spore-suspension
is defined in no uncertain terms—all swimming spores in the population
are no more than 10 minutes old.
Finally, spore-suspensions of suitable age and density can be introduced into liquid media for growing vigorously-aerated, submerged,
single-generation cultures of several million to a billion cells (McCurdy
and Cantino, 1960; Goldstein and Cantino, 1962; Lovett and Cantino,
1960b). Under these conditions, spores give rise to individual germlings
which, in their state of constant agitation, develop exponentially in
exceedingly uniform fashion and then differentiate synchronously into
either OC or RS cells, depending upon the medium previously selected.
Thus, in contrast to bacteria for example, where visible estimation of
the degree of synchrony of a culture may have to be followed solely by