Each of the following statements concerning bacterial spores is correct EXCEPT
A.
They are formed only by gram-positive bacteria
B.
They can be killed when being heated to 121.3 ℃ for 15 ~ 20 minutes
C.
They contain much less water than bacterial vegetative cells (细菌繁殖体)
D.
Their survival ability is based on their enhanced metablic activity
E.
They are formed under adverse environ- mental conditions such as the absence of a carbon source