Do microorganisms such as bacteria and yeast have a
definite life span and die after attaining a particular age? If yes give
life span of some bacterial species.
Well this is hard to say, because bacteria reproduce asexually; therefore
they split in half. Most bacteria have a very short generation time-from the
time they are "born" until they split again. So it is hard to keep track of
which bacteria are what age. You can keep a bacterial culture growing
indefinitely if you provide it with the nutrients and conditions it needs.
However, if the culture is growing in a closed environment, eventually their
own waste will build up, poisoning them, and nutrients will run out because
of the sheer numbers. They will eventually all die. Again this depends on
the generation time of the organisms. It would be very difficult to keep
track of one organism to see how long it lived if it was not able to divide
and it had enough food, etc. to just die of "old age".
This is an interesting question. Bacteria grow as
individual cells that divide themselves to produce
offspring. Thus, it is sometimes difficult to say what
is one cell, what is a dividing cell, and what is a
'baby cell'. I guess your question regards a single
cell, from division till it divides itself. Then their
age can vary from a few hours to a few days. After that
the cell either divides and has become two new
individuals, or it degenerates and dies. An exception
are bacteria that can build spores. These are
fastidious 'mini-cells' that form when the conditions
do not favor growth. They have a very low metabolism
(compare this to hibernation) but they can come back
to life if the conditions improve. Spores can remain
viable for long periods, months to years. Some
bacterial species, like Bacillus anthracis (causing
Anthrax) can build spores that survive tens of years.
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Update: June 2012