According to The Chronie, the way bacteria multiplies varies between different species and genus of bacteria. E.coli multiplies every 20 minutes, while Mycobacterium tuberculosis multiplies every 24 hours. Bacteria require the right conditions in order to multiply.
Bacteria multiplies in a relatively straightforward way. A single cell of bacterium grows until the stage that the cell can split into two separate cells of bacteria. The split bacteria is known as progeny bacteria. When the bacterium splits, the process is called binary fission. The length of time taken for this split is called generation length. The circumstances for this growth include the right environment and a supply of the right nutrients.