Petri dish - wikipedia Petri dish The bottom half of a glass Petri dish Petri dish at the Pacific Northwest National Laboratory A Petri dish ( sometimes spelled `` Petrie Dish '' and alternatively known as a Petri plate or cell - culture dish ), named after the German bacteriologist Julius Richard Petri, is a shallow cylindrical glass or plastic lidded dish that biologists use to culture cells -- such as bacteria -- or small mosses. Modern Petri dishes usually feature rings and / or slots on their lids and bases so that when stacked, they are less prone to sliding off one another. Multiple dishes can also be incorporated into one plastic container to create a `` multi-well plate ''. While glass Petri dishes may be reused after sterilization ( via an autoclave at 121 ° C for about 15 - 20 minutes in the case of moist heat sterlization or one hour 's dry - heating in a hot - air oven at 160 ° C, for example ), plastic Petri dishes are often disposed of after experiments where cultures might contaminate each other. Contents 1 Microbiology 2 Other uses 3 Notes and references 4 External links Microbiology Further information : Agar plate A Petri dish with bacterial colonies on an agar - based growth medium Petri dishes are often used to make agar plates for microbiology studies. The dish is partially filled with warm liquid containing agar and a mixture of specific ingredients that may include nutrients, blood, salts, carbohydrates, dyes, indicators, amino acids or antibiotics. Once the agar cools and solidifies, the dish is ready to be inoculated ( `` plated '' ) with a microbe - laden sample. Virus or phage cultures require a two - stage inoculation : after the agar preparation, bacteria are grown in the dish to provide hosts for the viral inoculum. Petri plates are incubated upside - down to lessen the risk of contamination from airborne particles settling on them and to prevent the accumulation of any water condensation that may otherwise disturb or compromise a culture. 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. A special type of petri dishes are Replicate Organism Detection And Counting often also referred to as rodac plates or contact plates. Those are petri dishes in which the medium protrudes ( raised agar level ) the edges of the dish to make it easier to take samples on hard objects. The plates are also divided in squares to make counting of CFUs easier. They are often used to monitor how clean certain areas ( e.g. in kitchens ) are. Other uses See also : Microbial art Petri dishes are also used for eukaryotic cell culture in a liquid medium or on solid agar. They are used in immunodiffusion studies when partially filled with agar or agarose gel. Empty Petri dishes may be used to observe plant germination, the behavior of very small animals or for other day - to - day laboratory practices such as drying fluids in an oven and carrying or storing samples. Their transparency and flat profile also mean they are commonly used as temporary receptacles for viewing samples, especially liquids, under a low - power microscope. Notes and references Jump up ^ Petri dish in the American Heritage Dictionary. Jump up ^ Petri, R.J. ( 1887 ) `` Eine kleine Modification des Koch'schen Plattenverfahrens '' ( A small modification of Koch 's plate method ), Centralblatt für Bakteriologie und Parasitenkunde, 1 : 279 -- 280. Jump up ^ Mosby 's Dental Dictionary ( 2nd ed. ). Elsevier. 2008. Retrieved 2010 - 02 - 11. Jump up ^ Reski, Ralf ( 1998 ). `` Development, genetics and molecular biology of mosses '' ( PDF ). Botanica Acta. 111 : 1 -- 15. doi : 10.1111 / j. 1438 - 8677.1998. tb00670. x. Jump up ^ Gilbert, P.M. ( 2010 ). `` Substrate elasticity regulates skeletal muscle stem cell self - renewal in culture ''. Science. 329 ( 5995 ) : 1078 -- 1081. doi : 10.1126 / science. 1191035. PMC 2929271. PMID 20647425. Jump up ^ Chowdhury, F. ( 2010 ). `` Soft substrates promote homogeneous self - renewal of embryonic stem cells via downregulating cell - matrix tractions ''. PLoS ONE. 5 ( 12 ) : e15655. doi : 10.1371 / journal. pone. 0015655. PMC 3001487. PMID 21179449. Jump up ^ Lemmen, Sebastian W. ; Häfner, Helga ; Zolldann, Dirk ; Amedick, Günter ; Lutticken, Rüdolf ( 2001 ). `` Comparison of two sampling methods for the detection of Gram - positive and Gram - negative bacteria in the environment : Moistened swabs versus Rodac plates ''. International Journal of Hygiene and Environmental Health. 203 ( 3 ) : 245. doi : 10.1078 / S1438 - 4639 ( 04 ) 70035 - 8. PMID 11279821. Jump up ^ ( 1 ) `` Immunodiffusion ''. ScienceDirect. Elsevier B.V. Archived from the original on 2017 - 05 - 19. Retrieved 2017 - 05 - 19. ( 2 ) `` Photograph of double immunodiffusion in a Petri dish '' ( photograph ). Retrieved 2017 - 05 - 15. ( 3 ) `` Photograph of radial immunodiffusion in a Petri dish '' ( photograph ). Edvotek, Inc. 2017. Retrieved 2017 - 05 - 15. External links Wikimedia Commons has media related to Petri dishes. Laboratory equipment General Heaters Dryers Alcohol burner Bunsen burner Desiccator Heating mantle Hot plate Lab oven Kiln Meker -- Fisher burner Striker Teclu burner Water bath Vacuum dry box Mixers Shakers Chemostat Homogenizer Liquid whistle Magnetic stirrer Mortar and pestle Shaker Sonicator Static mixer Stirring rod Vortex mixer Wash bottle Stands Clamps Holders Beaker clamp Clamp holder Tripod Burette clamp Extension clamp Flask clamp Funnel support Iron ring Pinch clamp Retort stand Screw clamp Test tube holder Test tube rack Wire gauze Lab drying rack Containers Storage Agar plate Cryogenic storage dewar Incubator Laminar flow cabinet Microtiter plate Petri dish Picotiter plate Refrigerator Weighing boat Weighing dish Other items Aspirator Autoclave Balance brush Cork borer Crucible Filter paper File Forceps Centrifuge Microscope Pipeclay triangle Spectrophotometer Splint Stopper Scoopula Spatula Test tube brush Wire brush Inoculation needle Inoculation loop Glassware Apparatus Dean -- Stark Soxhlet extractor Kipp 's Bottles Boston round Pycnometer Condensers Cold finger Liebig Dishes Evaporating Petri Watch glass Flasks Büchner Vacuum ( Dewar ) Erlenmeyer Fernbach Fleaker Florence Retort Round - bottom Schlenk Volumetric Funnels Büchner Hirsch Dropping Separatory Measuring devices Burette Conical measure Cuvette Eudiometer Graduated cylinder Ostwald viscometer Pipette Pipette ( dropper ) Tubes Boiling Drying Cragie Ignition Nuclear magnetic resonance ( NMR ) Test Thiele Thistle Other items Beaker Gas syringe Vial Analytical chemistry Compositional AutoAnalyzer CHN analyzer Colorimeter Inductively coupled plasma ( ICP ) device Gas chromatograph ( GC ) Liquid Chromatograph ( LC ) Mass spectrometer ( MS ) pH indicator pH meter Microscopy Scanning electron microscope ( SEM ) Transmission electron microscope ( TEM ) Thermochemistry Calorimeter differential scanning Melting - point apparatus Thermometer Thermogravimetric analyzer ( TGA ) Other items Analytical balance Colony counter Spiral plater Nuclear magnetic resonance ( NMR ) instrument Plate reader Electronics Ammeter Current source Function generator Galvanostat Multimeter Network analyzer Oscilloscope Pulse generator Potentiostat Spectrum analyzer Time - domain reflectometer Voltage source Voltmeter Safety Personal protective equipment ( PPE ) Lab coat Face shield Respirator Rubber apron Safety shower Eye and hand Acid - resistant gloves Eyewash station Glove box Medical gloves Nitrile gloves Safety glasses Safety goggles Other items Acid ( solvent ) cabinet Biosafety cabinet Fire blanket Fire extinguisher Fume hood Instruments used in medical laboratories Retrieved from `` https://en.wikipedia.org/w/index.php?title=Petri_dish&oldid=862551260 '' Categories : Laboratory glassware Microbiology equipment German inventions 1887 in science 1887 in Germany Talk Contents About Wikipedia Asturianu Български Bosanski Català Čeština Dansk Deutsch Eesti Ελληνικά Español Esperanto Euskara فارسی Français Galego 한국어 Hrvatski Bahasa Indonesia Italiano עברית Қазақша Lëtzebuergesch Magyar Монгол Nederlands 日本 語 Norsk Norsk nynorsk Polski Português Română Русский සිංහල Simple English Slovenčina Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska Tagalog ไทย Türkçe Українська Tiếng Việt 中文 38 more Edit links This page was last edited on 5 October 2018, at 03 : 43 ( UTC ). About Wikipedia

Question: why do inoculated plates need to be incubated in the inverted position
Answer: to lessen the risk of contamination from airborne particles settling on them