54
EDWARD C. CANTINO AND JAMES S. LOVETT
1. Exponential Growth Along the OG Path
Conditions for growing synchronized, single-generation cultures of OC
cells were worked out some time ago (McCurdy and Cantino, 1960);
recently, the method was improved significantly (Goldstein and Cantino,
1962). With this kind of culture, a good deal of definitive information
has been obtained, on a per-cell basis, about OC plants growing exponentially; precise data on oxygen uptake, synthesis and alteration of
enzyme activities, total volume and mass, nucleic acids, soluble protein,
internal pools of polysaccharide, etc. We do not propose to simply
retabulate these data here ; the reader is referred to the original reports
for this information. We should like to emphasize, instead, the potential
importance and utility of this system as a tool for investigations of
biological phenomena and, in particular, the biochemical bases for the
early stages of morphogenesis in B. emersonii.
The genesis of multicellular organization is, without question, one of
the main problems of biology, and the pseudoplasmodial mould
Dictyostelium
discoideum (Raper, 1935) has been exploited intensively
by many workers and with notable success (Bonner, 1959; Sussman,
1958; Sussman and Sussman, 1961, etc.) for studies of this phenomenon.
But one could also state with justifiable conviction that the genesis of
multinucleate organization is another topic, of some broad significance,
which is worthy of attention. And, for studies of the ontogeny of a single
coenocytic cell or organism, Blastocladiella emersonii provides a model
system. If one of the usual purposes of a synchronized culture is to infer
the order of events during the normal doubling cycle of a micro-organism
(Campbell, 1957), then another would be to do the same for a cycle
which involves not a doubling, nor quadrupling, but a many-fold
reduplication. With B. emersonii, this can be done, directly and conveniently ; within a single generation time, half a billion cells or more
simultaneously go through their act.
During exponential growth in darkness, the weight of both the OC
cell and one of its ingredients, a soluble polysaccharide, increases
exponentially (Goldstein and Cantino, 1962); in the period between
30% and 60% of the cell's generation-time, for example, these rates are
almost identical (Fig. 4). On the other hand, the exponential rate of
synthesis of the soluble-protein pool per cell is only 78% of these values.
Clearly, differential exponential rates of synthesis occur during exponential growth of this unicellular—albeit multinucleate—micro-organism;
even during exponential growth, the composition of its cell does not
remain constant (compare discussion by Herbert, 1961, on the composition of bacterial cells).
Other evidence points to the same conclusion. If it is assumed, for the
EDWARD C. CANTINO AND JAMES S. LOVETT
1. Exponential Growth Along the OG Path
Conditions for growing synchronized, single-generation cultures of OC
cells were worked out some time ago (McCurdy and Cantino, 1960);
recently, the method was improved significantly (Goldstein and Cantino,
1962). With this kind of culture, a good deal of definitive information
has been obtained, on a per-cell basis, about OC plants growing exponentially; precise data on oxygen uptake, synthesis and alteration of
enzyme activities, total volume and mass, nucleic acids, soluble protein,
internal pools of polysaccharide, etc. We do not propose to simply
retabulate these data here ; the reader is referred to the original reports
for this information. We should like to emphasize, instead, the potential
importance and utility of this system as a tool for investigations of
biological phenomena and, in particular, the biochemical bases for the
early stages of morphogenesis in B. emersonii.
The genesis of multicellular organization is, without question, one of
the main problems of biology, and the pseudoplasmodial mould
Dictyostelium
discoideum (Raper, 1935) has been exploited intensively
by many workers and with notable success (Bonner, 1959; Sussman,
1958; Sussman and Sussman, 1961, etc.) for studies of this phenomenon.
But one could also state with justifiable conviction that the genesis of
multinucleate organization is another topic, of some broad significance,
which is worthy of attention. And, for studies of the ontogeny of a single
coenocytic cell or organism, Blastocladiella emersonii provides a model
system. If one of the usual purposes of a synchronized culture is to infer
the order of events during the normal doubling cycle of a micro-organism
(Campbell, 1957), then another would be to do the same for a cycle
which involves not a doubling, nor quadrupling, but a many-fold
reduplication. With B. emersonii, this can be done, directly and conveniently ; within a single generation time, half a billion cells or more
simultaneously go through their act.
During exponential growth in darkness, the weight of both the OC
cell and one of its ingredients, a soluble polysaccharide, increases
exponentially (Goldstein and Cantino, 1962); in the period between
30% and 60% of the cell's generation-time, for example, these rates are
almost identical (Fig. 4). On the other hand, the exponential rate of
synthesis of the soluble-protein pool per cell is only 78% of these values.
Clearly, differential exponential rates of synthesis occur during exponential growth of this unicellular—albeit multinucleate—micro-organism;
even during exponential growth, the composition of its cell does not
remain constant (compare discussion by Herbert, 1961, on the composition of bacterial cells).
Other evidence points to the same conclusion. If it is assumed, for the