can cause illness. In a bacterial parasitic relationship, the bacteria benefit and the other
organism is harmed. Harmful bacteria will be discussed later in the lesson.
Reproduction in Bacteria
Bacteriareproduceasexuallythroughbinary fission.Duringbinaryfissionthechromosome
copies itself (replicates), forming two genetically identical copies, then the cell enlarges and
divides into two new daughter cells. The two daughter cells are identical to the parent cell
(Figure8.7).
Binary fission can happen very rapidly. Some species of bacteria have been shown to double
their populations in less than ten minutes! (Figure8.8)
Figure8.7: Bacteria cells reproduce bybinary fission, resulting in twodaughtercells identical
to the parent cell. ( 11 )
Sexual reproduction does not occur in bacteria, but genetic recombination, the combining
andexchangeofDNA,doeshappeninbacteriathroughthreedifferentmethods: conjugation,
transformation, and transduction. Inconjugation,DNA passes through the sex pilus, a
hairlike extension on the surface of many bacteria, that temporarily joins two bacteria. In
transformation,bacteriapickuppiecesofDNAfromtheirenvironment. Intransduction,
bacteriophages, viruses that infect bacteria, carry DNA from one bacteria to another.
Helpful Bacteria
Bacteria are crucial in nature since they are commondecomposers,organisms that break
down dead materials and waste products. This decomposition of dead organisms is necessary
sothatthenutrientsintheirbodiescanberecycledbackintotheenvironment. Thisrecycling
of nutrients, such as nitrogen, is essential for living organisms; organisms cannot produce