04
EDWARD C. CANTINO AND JAMES S. LOVETT
that we also conveniently avoided mentioning a variety of pitfalls which
will have to be considered in any careful evaluation of the biology of
B. emersonii ; and we have not raised certain questions, which have been
asked in connection with studies of other micro-organisms, and which
must be asked—sooner or later—of
Blastocladiella.
For example, in the light of recent work on the developmental biochemistry of Dictyostelium
(Wright, 1960), it will be necessary to ask:
which, if any, of our measurements of enzymatic activities may have
been in error because of in vitro inactivation of enzymes before assays
were performed. It seems unlikely that any extensive error arose from
lack of substrate protection or non-specific inhibitions (Cantino,
unpublished data). Nonetheless, it will behove all of us interested in the
application of biochemical techniques to studies of morphological
differentiation to be aware of the possible susceptibility of pertinent
enzyme systems to in vitro inactivations of the sort described by Wright,
of inhibitions by naturally-occurring substances (Stickland, 1961), etc.
These, and many other pitfalls, have got to be avoided; the trouble is,
new and better pitfalls are being uncovered by the enzymologist and the
biochemist at an exponential rate—much more rapidly than one can
hope to do experiments to eliminate them.
But aside from dull, defensive manoeuvres for avoiding or outdistancing such pitfalls, as essential as this is, there are challenges and
hurdles, at least equally deserving of attention and certainly far more
exciting and appealing, which must be overcome and which the
venturesome biologist cannot resist.
Precisely how, for example, does bicarbonate initiate the many
changes which occur during the exponential growth of a
Blastocladiella
cell—not only the events described earlier, but all the other things as
well? Assuming that one main locus is, indeed, the region of the two
successive decarboxylations in the tricarboxylic acid cycle as has been
supposed, is it simply a mass action effect that is at first involved,
thereby causing a short-lived accumulation of some ketoglutarate
and/or succinate? On the other hand, are alternative and/or additional
loci proximal to this decarboxylation chain also implicated ; for example,
a C0 2 inhibition of the succinic dehydrogenase system (more specifically,
the succinic-cytochrome c reductase) as reported by Bendall et al. (1960 ;
see also Wright et al., 1960, regarding the inhibitory effect of C0 2 upon
the maintenance of adenosine triphosphate levels, presumably related
to this same effect). Incubation of Blastocladiella
with bicarbonate
(Cantino, 1956)—albeit, in this case, with mixed non-growing OC cells
of various ages—does in fact bring about an increase in the internal
soluble pool of ketoglutarate. Whether or not succinate also piles up
under these particular conditions is not yet known ; but, it is a fact that
EDWARD C. CANTINO AND JAMES S. LOVETT
that we also conveniently avoided mentioning a variety of pitfalls which
will have to be considered in any careful evaluation of the biology of
B. emersonii ; and we have not raised certain questions, which have been
asked in connection with studies of other micro-organisms, and which
must be asked—sooner or later—of
Blastocladiella.
For example, in the light of recent work on the developmental biochemistry of Dictyostelium
(Wright, 1960), it will be necessary to ask:
which, if any, of our measurements of enzymatic activities may have
been in error because of in vitro inactivation of enzymes before assays
were performed. It seems unlikely that any extensive error arose from
lack of substrate protection or non-specific inhibitions (Cantino,
unpublished data). Nonetheless, it will behove all of us interested in the
application of biochemical techniques to studies of morphological
differentiation to be aware of the possible susceptibility of pertinent
enzyme systems to in vitro inactivations of the sort described by Wright,
of inhibitions by naturally-occurring substances (Stickland, 1961), etc.
These, and many other pitfalls, have got to be avoided; the trouble is,
new and better pitfalls are being uncovered by the enzymologist and the
biochemist at an exponential rate—much more rapidly than one can
hope to do experiments to eliminate them.
But aside from dull, defensive manoeuvres for avoiding or outdistancing such pitfalls, as essential as this is, there are challenges and
hurdles, at least equally deserving of attention and certainly far more
exciting and appealing, which must be overcome and which the
venturesome biologist cannot resist.
Precisely how, for example, does bicarbonate initiate the many
changes which occur during the exponential growth of a
Blastocladiella
cell—not only the events described earlier, but all the other things as
well? Assuming that one main locus is, indeed, the region of the two
successive decarboxylations in the tricarboxylic acid cycle as has been
supposed, is it simply a mass action effect that is at first involved,
thereby causing a short-lived accumulation of some ketoglutarate
and/or succinate? On the other hand, are alternative and/or additional
loci proximal to this decarboxylation chain also implicated ; for example,
a C0 2 inhibition of the succinic dehydrogenase system (more specifically,
the succinic-cytochrome c reductase) as reported by Bendall et al. (1960 ;
see also Wright et al., 1960, regarding the inhibitory effect of C0 2 upon
the maintenance of adenosine triphosphate levels, presumably related
to this same effect). Incubation of Blastocladiella
with bicarbonate
(Cantino, 1956)—albeit, in this case, with mixed non-growing OC cells
of various ages—does in fact bring about an increase in the internal
soluble pool of ketoglutarate. Whether or not succinate also piles up
under these particular conditions is not yet known ; but, it is a fact that