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Reproduction: Bacteria

Asexual Reproduction

Asexual reproduction in bacteria is very simple. The cell increases in size. A double wall develops across the midline of the enlarged cell. The cell separates into two cells at the midline wall. Each cell is then able to function as a separate entity. The process of multiplication can be quite rapid. The bacterium E. coli may double in number every 20 minutes in ideal conditions. If you plot the graph of population over time, you get an exponential increase.

 View animation of asexual reproduction in bacteria (160 Kb).

 View movie of E. coli reproduction (532 Kb).

Sexual reproduction

Sex in bacteria differs somewhat from what we consider sex in eukaryotes. It involves the plasmid, which has several important characteristics:

  1. A plasmid is a loop of DNA. Plasmids can multiply autonomously within the cell. Thus we may find from zero to many of one or more plasmids in each cell.
  2. Many plasmids can insert into the DNA of the nucleus, and detach from it. In doing so, the plasmid may leave part of the plasmid DNA behind, and take some of the nuclear DNA with it.
  3. plasmids can transfer from cell to cell. The cells need not be of the same bacterial 'species'.

Reference: Ochman et al (2000) Lateral gene transfer and the nature of bacterial innovation. Nature 405: 299-304.

 View animation of sexual reproduction in bacteria (14 Kb).

 Question 2