CELLS alive!


Video: Bacteria Divide and Multiply



connection Connections connection

Binary Fission in E. coli

In this video, see how two E. coli, given a suitable environment for growth, divide and form a colony of hundreds of bacteria in about three hours. Then visit the CELLS alive! Bacteria BioCam to follow a colony of bacteria in "real time".

Bacteria are all around us. Given good growing conditions, a bacterium grows slightly in size or length, a new cell wall grows through the center forming two daughter cells, each with the same genetic material as the parent cell. If the environment is optimum, the two daughter cells may divide into four in 20 minutes. Oh my! 1, 2, 4, 8, 16, 32, 64... Then why isn't the earth covered with bacteria?

The primary reason may be that conditions are rarely optimum. Scientists who study bacteria try to create the optimum environment in the lab: culture medium with the necessary energy source, nutrients, pH, and temperature, in which bacteria grow predictably.

Bacterial Growth CurveLAG PHASE: Growth is slow at first, while the "bugs" acclimate to the food and nutrients in their new habitat.

LOG PHASE: Once the metabolic machinery is running, they start multiplying exponentially, doubling in number every few minutes.

STATIONARY PHASE: As more and more bugs are competing for dwindling food and nutrients, booming growth stops and the number of bacteria stabilizes.

DEATH PHASE: Toxic waste products build up, food is depleted and the bugs begin to die.


Bacterial Infection and Fever

Laboratory growth of bacteria  does not tell you how they will multiply in the body. Not only do invading bacteria need to be where there is nutrient to support growth and strategies for tolerating the immune system, but also they require an optimum temperature.  There is debate concerning the value of low grade fever to stem the growth of pathogens.

Some Keywords:

exponential growth, binary fission, asexual reproduction, population dynamics, lag phase, log phase, stationary phase, death phase