Wednesday, 6 March 2013

Petri Dish



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 and antibiotics. After the agar cools and solidifies, the dish is ready to receive a microbe laden sample in a process known as inoculation or "plating." For virus or phage cultures, a two-step inoculation is needed: bacteria are grown first to provide hosts for the viral inoculum. 

Petri plates are incubated upside down to lessen the risk of contamination from settling airborne particles and to prevent water condensation from accumulating and disturbing the cultured microbes. Scientists have long been growing cells in natural and synthetic matrix environments to elicit phenotypes that are not expressed on conventionally rigid substrates. Unfortunately, growing cells either on or within soft matrices can be an expensive, labor intensive, and impractical undertaking.

Friday, 11 May 2012

Magnoliaceae


Unlike most angiosperms, whose flower parts are in rings, the Magnoliaceae have their stamens and pistils in spirals on a conical receptacle. This arrangement is found in some fossil plants and is believed to be a basal or early condition for angiosperms. The flowers also have parts not distinctly differentiated into sepals and petals, while angiosperms that evolved later tend to have distinctly differentiated sepals and petals. The poorly differentiated perianth parts that occupy both positions are known as tepals.

The family has approximately 219 species in 7 genera, although some classification systems include all of subfamily Magnoioideae in genus Magnolia. The family ranges across eastern North America, Mexico and Central America, the West Indies, tropical South America, southern and eastern India, Sri Lanka, Indochina, Malesia, China, Japan, and Korea.

Wednesday, 21 September 2011

Petri dish


A Petri dish (or Petri plate or cell culture dish) is a shallow glass or plastic cylindrical lidded dish that biologists use to culture cells  or small moss plants. It was named after German bacteriologist Julius Richard Petri, who invented it when working as an assistant to Robert Koch. Glass Petri dishes can be reused by sterilization (for example, in an autoclave or by dry heating in a hot air oven at 160°C for one hour). For experiments where cross-contamination from one experiment to the next can become a problem, plastic Petri dishes are often used as disposables.

Modern Petri dishes often have rings on the lids and bases, which allow them to be stacked so that they do not slide off one another. Multiple dishes can also be incorporated into one plastic container to create what is called a "multi-well plate".