Bacteria are the huddled masses of the microbial world, performing tasks that
include everything from causing disease to fixing nitrogen in the soil. The
estimated number of bacteria on Earth is five million trillion trillion --
that's a five with 30 zeroes after it. When
people think of bacteria, they likely first consider the nasty ones that cause
disease, but the bacteria inside all animals combined -- including humans --
makes up less than one percent of the total amount. By far the greatest numbers
are in the subsurface, soil and oceans.
bacterial swabs from various places in the school
To inoculate a
petri dish with a bacterial culture
what kind of environmental conditions influence bacterial growth
dish, pencil, incubator, hot water bath, nutrient agar, thermometer
(Part A): Petri Dish Preparation
Set up a hot
water bath at 95oC.
Loosen the caps
and place nutrient agar bottle in hot water bath until agar liquefies. (Agar
melts above 95oC and remains liquid until cooled to about 45oC.)
bottles and allow the agar to cool to about 50-55oC.
the cover of the petri dish and pour about 15-20ml of liquid to cover 2/3 of
the plate surface.
Lower the lid of
the dish and gently swirl the plate to spread the media over all the bottom