Editing Petri dish (section)

== Uses ==
[[File:Agar plate with colonies.jpg|thumb|A Petri dish with [[bacteria]]l colonies on an [[agar]]-based [[growth medium]]]]
[[File:Physcomitrella_growing_on_agar_plates.jpg|thumb|Axenic [[cell culture]] of the plant ''[[Physcomitrella patens]]'' on an [[agar]]plate in a Petri dish]]

Petri dishes are widely used in biology to [[microbiological culture|cultivate]] microorganisms such as [[bacterium|bacteria]], [[yeast]]s, and [[Mold (fungus)|mold]]s.  It is most suited for organisms that thrive on a solid or semisolid surface. The [[growth medium|culture medium]] is often an [[agar plate]], a layer a few mm thick of [[agar]] or [[agarose]] [[hydrogel|gel]] containing whatever nutrients the organism requires (such as [[blood]], [[salt (chemistry)|salts]], [[carbohydrate]]s, [[amino acid]]s) and other desired ingredients (such as [[staining|dyes]], [[chemical indicator|indicators]], and [[medicinal drug]]s). The agar and other ingredients are dissolved in warm water and poured into the dish and left to cool down.  Once the medium solidifies, a sample of the organism is [[Inoculation|inoculated]] ("plated"). The dishes are then left undisturbed for hours or days while the organism grows, possibly in an [[Incubator (culture)|incubator]].  They are usually covered, or placed upside-down, to lessen the risk of contamination from airborne [[spore]]s. [[Virus]] or [[phage]] cultures require that a population of bacteria be grown in the dish first, which then becomes the culture medium for the viral inoculum.

While Petri dishes are widespread in microbiological research, smaller dishes tend to be used for large-scale studies in which growing cells in Petri dishes can be relatively expensive and labor-intensive.<ref>{{cite journal|author=Gilbert, P.M. |title=Substrate elasticity regulates skeletal muscle stem cell self-renewal in culture|doi=10.1126/science.1191035 |journal=Science|volume= 329 |issue=5995|year=2010|pages=1078–81 |pmid=20647425 |pmc=2929271|bibcode=2010Sci...329.1078G}}</ref><ref>{{cite journal|author=Chowdhury, F.|title= Soft substrates promote homogeneous self-renewal of embryonic stem cells via downregulating cell-matrix tractions|journal=PLOS ONE |volume=5|issue= 12|pages= e15655 |year=2010|doi= 10.1371/journal.pone.0015655|pmid=21179449|pmc=3001487
|bibcode= 2010PLoSO...515655C|doi-access= free}}</ref>

Petri dishes can be used to visualize the location of contamination on surfaces, such as kitchen counters and utensils,<ref>{{cite journal|doi=10.1078/S1438-4639(04)70035-8|pmid=11279821|title=Comparison of two sampling methods for the detection of Gram-positive and Gram-negative bacteria in the environment: Moistened swabs versus Rodac plates|journal=International Journal of Hygiene and Environmental Health|volume=203|issue=3|pages=245–48|year=2001|last1=Lemmen|first1=Sebastian W.|last2=Häfner|first2=Helga|last3=Zolldann|first3=Dirk|last4=Amedick|first4=Günter|last5=Lutticken|first5=Rüdolf}}</ref> clothing, food preparation equipment, or animal and human skin.<ref>Kasia Galazka (2015): "[https://www.buzzfeednews.com/article/kasiagalazka/petri-handprint Here's A Gorgeous Petri Dish Handprint Of An 8-Year-Old After He Played Outside]". BuzzFeed.News online article, June 9, 2015.  Accessed on 2019-10-25.</ref><ref>Sonja Bäumel (2009): "[http://www.sonjabaeumel.at/work/bacteria/oversized-petri-dish Oversized petri dish]". Culture of microorganisms from the artist's skin pressed onto a body-size culture plate, photographed over the span of 44 days. Part of her ''(In)visible membrane'' project. Wageningen, Germany. Accessed on 2019-10-25.</ref> For this application, the Petri dishes may be filled so that the culture medium protrudes slightly above the edges of the dish to make it easier to take samples on hard objects.  Shallow Petri dishes prepared in this way are called [[RODAC plate|Replicate Organism Detection And Counting (RODAC) plates]] and are available commercially.<ref name=sutt2007>Scott Sutton (2007): "Microbial Surface Monitoring", p. 78. Chapter 5 of Anne Marie Dixon (ed.), ''Environmental Monitoring for Cleanrooms and Controlled Environments''. {{isbn|978-1420014853}}</ref><ref name=dane2016>Géraldine Daneau, Elie Nduwamahoro, Kristina Fissette, Patrick Rüdelsheim, Dick van Soolingen, Bouke C. de Jong, Leen Rigouts (2016): "Use of RODAC plates to measure containment of Mycobacterium tuberculosis in a Class IIB biosafety cabinet during routine operations." ''International Journal of Mycobacteriology'', volume 5, issue 2, pp. 148–54. {{doi|10.1016/j.ijmyco.2016.01.003}}</ref>

Petri dishes are also used for [[cell culture|cell cultivation]] of isolated cells from [[Eukaryote|eukaryotic]] organisms, such as in [[immunodiffusion]] studies, on solid agar or in a liquid medium.

Petri dishes may be used to observe the early stages of plant [[germination]], and to grow plants asexually from isolated cells.

Petri dishes may be convenient enclosures to study the behavior of insects and other small animals.

Due to their large open surface, Petri dishes are effective containers to evaporate [[solvent]]s and dry out [[precipitate]]s, either at room temperature or in [[oven]]s and [[desiccator]]s.

Petri dishes also make convenient temporary storage for samples, especially liquid, granular, or powdered ones, and small objects such as insects or seeds.  Their transparency and flat profile allows the contents to be inspected with the naked eye, [[magnifying glass]], or low-power microscope without removing the lid.