- The effects of various physical parameters on the binding, uptake,
and catabolism of glucose in the marine psychrophilic bacterium,
Vibrio marinus, were studied. It was shown that shortly after
the cell was exposed to labeled glucose, the radioactive label became
rapidly associated with the cell fraction. It was also shown that much
of this activity was readily removed when the cells were exposed to
an acidic environment. Since this release was not associated with
leakage and the release was practically instantaneous, it appeared
that this loss was related to the removal of loosely bound glucose.
In order to reduce the chance of error in measuring substrate uptake,
this loosely bound glucose was routinely removed by acidification
prior to cell activity assay.
The requirements for specific ions in the uptake of glucose
were studied. It was found that Na⁺, Li⁺, and Mg⁺⁺ would permit
uptake but that K⁺, Rb⁺, and NH₄⁺ would not. Of the various different
salts of Na⁺ studied, all permitted glucose uptake. This was the
same pattern that was seen when the effects of specific ions on cell
growth were studied.
The salinity limits of growth were defined, and their relationship
to patterns of glucose uptake and respiration was observed.
It was shown that there were no significant pattern shifts associated
with the maximum growth salinity but that there were significant
changes associated with the region of minimum growth salinity.
When the effects of altering salinity on the uptake and respiration
of specifically labeled glucose were studied, several patterns of
potential, significance were observed. The total uptake of glucose,
as measured by the first, second, third and sixth carbon activities,
showed that all portions of the molecule were used for energy and
cell material at 0,15 M NaCl but at higher salinities, part of the
molecule was released by the cells in some form other than CO₂.
Three basic patterns associated with the first and sixth carbons
were observed as the salinity was increased from 0.0 M to 1.0 M
NaCl. In the 0.0 M to 0.15 M range, the amount of CO₂ released
from both carbons increased at approximately the same rate. In the
0.15 M to 0.30 M range, there was a decrease in the CO₂ associated
with both of these carbons and a concomitant increase in the amount
of cell activity associated with both of these carbons. As the salinity was increased above this point, the CO₂ associated with the sixth
carbon remained relatively constant while that associated with the
first carbon increased markedly. This shift in the C₆/C₁ ratio was
shown to be relatively unaffected by changes in temperature over a