Petri dish

A Petri dish is a shallow transparent lidded dish that biologists use to culture cells, such as bacteria, fungi or small mosses. It is the most common type of culture plate; the container is named after the German bacteriologist Julius Richard Petri. Penicillin, the first antibiotic, was discovered in 1929 when Alexander Fleming noticed that mold that had contaminated a bacterial culture in a Petri dish had killed the bacteria all around it; the Petri dish is one of the most common items in biology laboratories, has entered popular culture. The term is written in lower case in non-technical literature; the universal character set Unicode has a Petri dish emoji "", with code point U+1F9EB. Petri dishes are cylindrical with diameters ranging from 30 to 200 mm, a height to diameter ratio ranging from 1:10 to 1:4. Squarish versions are available. Petri dishes were traditionally made of glass. Plastic dishes disposable, are now common too. Petri dishes are covered with a shallow transparent lid, resembling a slighly wider version of the dish itself.

The lids of glass dishes are loose-fitting. Plastic dishes may have close-fitting covers. Alternatively, some glass or plastic dishes versions may have small holes around the rim, or ribs on the underside of the cover, to allow for ventilation of the air space over the culture and avoid water condensation that may be a problem that needs some attention; some Petri dishes plastic ones feature rings and/or slots on their lids and bases so that they are less prone to sliding off one another when stacked. Small Petri dishes may have a protruding base that can be secured on a microscope stage for direct examination Petri dishes may have grids printed on the bottom to help measuring the density of cultures. A multiwell plate is a single transparent container with an array of flat-bottomed cavities, each being a small Petri dish, it makes it possible to inoculate and grow dozens or hundreds of independent cultures of dozens of samples at the same time. Besides being much cheaper and convenient than separate dishes, the multiwell plate is more amenable to automated handling and inspection.

Petri dishes are used in biology to cultivate microorganisms such as bacteria and molds. It is most suited for organisms that thrive on a semisolid surface; the culture medium is an agar plate, a layer a few mm thick of agar or agarose gel containing whatever nutrients the organism requires and other desired ingredients. 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 inoculated; the dishes are left undisturbed for hours or days while the organism grows in an incubator. They are covered, or placed upside-down, to lessen the risk of contamination from airborne spores. Virus or phage cultures require that a population of bacteria be grown in the dish first, which 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 expensive and labor-intensive.

Petri dishes can be used to visualize the location of contamination on surfaces, such as kitchen counters and utensils, food preparation equipment, or animal and human skin For this application, the Petri dishes may be filled so that the culture medium protrudes 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 Replicate Organism Detection And Counting plates and are available commercially. Petri dishes are used for cell cultivation of isolated cells from eukaryotic organisms, such as in immunodiffusion studies, on solid agar or in a liquid medium. In the latter, the cells grow as a layer attached to the bottom surface of the dish, below the culture medium. Petri dishes may be used to observe the early stages of plant germination, to grow plants asexually from isolated cells. Petri dishes may be convenient enclosures to study the behavior of other small animals. Due to their large open surface, Petri dishes are effective containers to evaporate solvents and dry out precipitates, either at room temperature or in ovens and desiccators.

Petri dishes make convenient temporary storage for samples liquid, granular, or powdered ones, 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; the Petri dish is one of a small number of laboratory equipment items whose name entered popular culture. It is used metaphorically, e. g. for a contained community, being studied as if they were microorganisms in a biology experiment, or an environment where original ideas and enterprises may flourish. Microbial art Cell spreader Inoculation loop Roux culture bottle


Titeltbukta is a bay on the northwestern coast of the Norwegian island of Jan Mayen. The name originates from the establishment of ten "tents", in reality wood and brick structures, as a basic whaling station; this was set up in 1624 by Dutch whalers to lodge the men. The Dutch called it Zuidbaai, in contrast to the other on the island, to the north at Engelskbukta). Hacquebord, Lawrens.. The Jan Mayen Whaling Industry, its Exploitation of the Greenland Right Whale and its Impact on the Marine Ecosystem. In: S. Skreslet, Jan Mayen in Scientific Focus. Amsterdam, Kluwer Academic Publishers. 229-238. Norwegian Polar Institute Place Names of Svalbard Database

Calothamnus villosus

Calothamnus villosus known as woolly net-bush or silky net-bush, is a plant in the myrtle family, Myrtaceae and is endemic to the south-west of Western Australia. It is a tall shrub forming thickets, it has cylindrical leaves and blood red flowers for many months of the year. It is superficially similar to Calothamnus quadrifidus but can be distinguished from that species by its flowers which have five stamen claws compared to the four of C. quadrifidus. Calothamnus villosus is an evergreen shrub sometimes growing to a height of 2 metres; the leaves are arranged alternately and needle-like. The flowers are blood red and arranged in bottlebrush-like clusters about 30 millimetres long on one side of the stem, the new growth of the previous year, they have 5 sepals. There are 5 petals and 5 claw-like bundles of stamens which are at least 30 millimetres long. Flowering occurs from March to December and is followed by fruits which are smooth, woody spherical capsules with two prominently thickened lobes at the top.

Calothamnus villosus was first formally described in 1812 by Robert Brown in William Aiton's Hortus Kewensis. The specific epithet is a Latin word meaning "hairy". Calothamnus villosus occurs from Albany to Esperance in the Esperance Plains and Mallee biogeographic regions, it is most common in the Cape Le Grand National Park and in the Mount Burdett Nature Reserve. It grows in thickets on sand, gravel or over granite. Christoper Brickell: RHS A-Z Encyclopedia of Garden Plants. Third edition. Dorling Kindersley, London 2003, ISBN 0-7513-3738-2