Changes

*Variation can occur either by mutations in their DNA, or by ''lateral gene transfer'':

*Variation can occur either by mutations in their DNA, or by ''lateral gene transfer'':

**Transformation- small, naked pieces of DNA are directly transferred between bacteria, e.g. ''S pneumoniae''

**Transformation- small, naked pieces of DNA are directly transferred between bacteria, e.g. ''S pneumoniae''

**Transduction- viruses known as bacteriophages transfer the DNA, many genes encoding toxins are transferred this way[[Image:Conjugative plasmids.png|thumb|right|100px|Conjugative plasmids- copyright Magnus Manske]]

**Transduction- viruses known as bacteriophages transfer the DNA, many genes encoding toxins are transferred this way[[Image:Conjugative plasmids.png|thumb|right|100px|Conjugative plasmids (Magnus Manske 2006, WikiMedia Commons)]]

**Conjugation- DNA is transferred in the form of plasmids, genes encoding antibiotic resistance are typically transferred this way.  

**Conjugation- DNA is transferred in the form of plasmids, genes encoding antibiotic resistance are typically transferred this way.