Lima Bean Bacteria
For my biology class we did a lab
that had to do withb DNA. To find the DNA we used lima bean bacteria.
Now we are trying to find what bacteria is in lima beans. If you could
help me out I would be
Martha, can you explain the experiment in more detail?
Plants contain DNA as well, so how are you sure you
isolated DNA from bacteria and not from the plant?
What part of the plant did you use, or was it the bean
itself? Did the bacteria come from the inside or
outside of the lima bean? I need more information to
answer your question.
Lima Bean Bacteria Suspension:
We place 1-2 handfuls of dry lima beans in a
large jar and fill halfway
to the top with distilled water. Then, covered and
sat in a warn room for
2-3 days. After the 2-3 days we took one mL of the
juice it produced and
mixed it with different detergents.
To find more about this experiment you can go to
The lab at this web sight is very similar to the lab
we performed. I hope
this will help you in finding the bacteria in lima
beans. Thank You Again,
I understand your experiment better now. Let's follow
the life of those Lima beans step by step. When they
were inside their pod, they were sterile. When they
came out, they no longer were, they must have been
covered by bacteria present in the air, on the soil,
on our hands, etc.
You took these beans and put them in sterile water
with sugar. Then you left it grow. The bacteria
present on those beans must have loved it and started
to multiply. But, unless you made all precautions to
keep the inside of the bowl sterile (tight, sterile
lids, etc.) those bacteria that fly over will have
landed in your soup and started growing there as well.
So I think what you were culturing will have been a
mixture of soil bacteria, skin bacteria, and the odd
one flying by. I am afraid I can't tell you which of
these will have multiplied best, for the ones that
were there in highest numbers will have resulted in
the most DNA.
In real-life lab work (if you like these science
classes you may want to become a microbiologist) we
want to be sure that we work with one type of bacteria
only. This is what we would do to investigate this:
From the sugar water after it had grown, we would take
0.1 ml and spread this on a sterile agar plate. We
would also dilute the solution one to 10 and 1 to 100
with sterile water and plate out 0.1 ml of tose
dilutions on two more agar plates. These would be
incubated at 37 C untill we see bacterial colonies.
From the size, shape and color of the colonies you can
see if they are only one type, or if there are several
types. If there are too many colonies present to
judge, you use the plate from the dilutions that grows
less colonies. Then we would take one pure, single
colony, and spread this out over a fresh agar plate.
Now we can be sure that all bacteria that grow there
mst be the same. We would isolate DNA from the
bacteria that grow on that final plate.
Maybe you can suggest to your teacher to do the first
part of the experiment to see how many different kinds
of bacteria were growing from your bean soup.
Good luck in science!
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Update: June 2012