Editing Microorganism (section)

===Bacteria===
{{Main|Bacteria}}
[[File:Staphylococcus aureus 01.jpg|thumb|''[[Staphylococcus aureus]]'' bacteria magnified about 10,000×]]
Like archaea, bacteria are prokaryotic – unicellular, and having no cell nucleus or other membrane-bound organelle. Bacteria are microscopic, with a few extremely rare exceptions, such as ''[[Thiomargarita namibiensis]]''.<ref>{{Cite journal |last=Schulz |first=H. |last2=Jorgensen |first2=B. | title=Big bacteria | journal=Annu Rev Microbiol | volume=55 | pages=105–137 | year =2001 |pmid=11544351 | doi=10.1146/annurev.micro.55.1.105}}</ref> Bacteria function and reproduce as individual cells, but they can often aggregate in multicellular [[Colony (biology)#Microbial colony|colonies]].<ref>{{Cite journal |author-link=James A. Shapiro |last=Shapiro |first=J. A. |title=Thinking about bacterial populations as multicellular organisms |journal=Annu. Rev. Microbiol. |volume=52 |pages=81–104 |year=1998 |pmid=9891794 |doi=10.1146/annurev.micro.52.1.81 |url=http://www.sci.uidaho.edu/newton/math501/Sp05/Shapiro.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110717183759/http://www.sci.uidaho.edu/newton/math501/Sp05/Shapiro.pdf |archive-date=17 July 2011 }}</ref> Some species such as [[myxobacteria]] can aggregate into complex [[swarm]]ing structures, operating as multicellular groups as part of their [[Biological life cycle|life cycle]],<ref>{{cite journal | title=Myxobacteria: Moving, Killing, Feeding, and Surviving Together | journal=Frontiers in Microbiology| volume=7| page=781| pmid=27303375| pmc=4880591| year=2016| last1=Muñoz-Dorado| first1=J. | last2=Marcos-Torres| first2=F. J. | last3=García-Bravo | first3=E. | last4=Moraleda-Muñoz| first4=A. | last5=Pérez| first5=J. | doi=10.3389/fmicb.2016.00781| doi-access=free}}</ref> or form clusters in [[colony (biology)|bacterial colonies]] such as ''[[E. coli]]''.

Their [[genome]] is usually a [[circular bacterial chromosome]] – a single loop of [[DNA]], although they can also harbor small pieces of DNA called [[plasmid]]s. These plasmids can be transferred between cells through [[bacterial conjugation]]. Bacteria have an enclosing [[Bacterial cell structure#Cell wall|cell wall]], which provides strength and rigidity to their cells. They reproduce by [[binary fission]] or sometimes by [[budding]], but do not undergo [[Meiosis|meiotic]] [[sexual reproduction]]. However, many bacterial species can transfer DNA between individual cells by a [[horizontal gene transfer]] process referred to as natural [[Transformation (genetics)|transformation]].<ref>{{cite journal |last=Johnsbor |first=O. |last2=Eldholm |first2=V. |last3=Håvarstein |first3=L. S. |title=Natural genetic transformation: prevalence, mechanisms and function |journal=Res. Microbiol. |volume=158 |issue=10 |pages=767–778 |date=December 2007 |pmid=17997281 |doi=10.1016/j.resmic.2007.09.004 |doi-access=free }}</ref> Some species form extraordinarily resilient [[endospore|spores]], but for bacteria this is a mechanism for survival, not reproduction. Under optimal conditions bacteria can grow extremely rapidly and their numbers can double as quickly as every 20 minutes.<ref>{{Cite journal| last=Eagon |first=R. | title=Pseudomonas Natriegens, a Marine Bacterium With a Generation Time of Less Than 10 Minutes | journal=J Bacteriol | volume=83 | issue=4| pages=736–737 | year =1962 | pmid=13888946 | pmc=279347| doi=10.1128/JB.83.4.736-737.1962 }}</ref>