Biology Reference
In-Depth Information
TABLE 11.3
Effect of Divalent Metals on the T
m
of the Anionic
Phospholipid DPPG (16:0,16:0 Phosphatidylglycerol).
T
m
(
C)
Added cation
NaCl, 100 mM
42
Mg
2
þ
, 1 mM
50
Mg
2
þ
, 5 mM
53
Ca
2
þ
, 1 mM
57
Ca
2
þ
, 1 mM
67
The unmodified T
m
of DPPG is 42
C.
for poikilothermic organisms would therefore be to decrease their membrane anionic phos-
pholipid content or to sequester their major divalent metals.
Don Juan Pond
An extreme example of life adjusting to a very harsh environment is the Don Juan Pond in
the west end of the Wright Valley in Victoria Land, Antarctica
[53]
(
Figure 11.14
,
[54]
). Despite
its provocative name, the pond is actually named after the two helicopter pilots, Lt Don Roe
and Lt John Hickey, who discovered the pond in 1961. The Don Juan Pond is a small and very
shallow hypersaline lake that almost never freezes despite temperatures that fall below
50
C. When it was first discovered, the pond was about 300 m long, 100 m wide and about
1 foot deep. Since then, the pond has shrunk considerably. The Don Juan Pond is defined as
being hypersaline, as it is over 18 times more saline than the ocean and more than twice as
saline as the Dead Sea. The major salt components of the pond are CaCl
2
(3.7 M) and
NaCl (0.5 M). Don Juan Pond levels of NaCl have been reported to decrease the freezing point
FIGURE 11.14
The Don Juan Pond in Antarctica
[54]
.
