Petri dishes are inverted during incubation to prevent condensation from falling into the microbes, thereby contaminating samples. Condensation in Petri dishes causes bacterial samples to spread and potentially mix with each other. Warm incubators tend to attract more condensation, so the dishes are inverted. Inversion allows water to drip down onto the lid, away from the agar, rather than onto bacteria.Know More
Inversion also prevents contamination of other bacteria in the samples, in case Petri dishes were not thoroughly cleaned or other microbes happened to contaminate samples. Petri dishes can be stored up to three months in cold storage before use in an incubator.
Inverted Petri dishes also minimize the evaporation of water used to grow the samples sealed in the containers. Dishes are sealed with tape so that lids do not fall off when the inversion occurs, and the tape can be written on for labeling purposes. The apparatus can also be stacked for easy storage in an incubator.
Petri dishes were invented in 1887 by German physician Julius Petri. He improved upon the design of his mentor, Dr. Robert Koch, by inventing a small plate that has a slightly larger plate that fits over it to create smaller samples for bacterial growth. The plate allowed samples in growth media to be more easily observed under a microscope without cross-contamination from other samples. Previously, glass plates were kept under a bell jar.Learn more about Biology
A Petri dish is a shallow dish that is used to culture microorganisms. By mixing different ingredients, such as blood, salts, amino acids or bacteria, together with an agar (or medium), scientists are able to observe reactions and watch microorganisms grow and develop.Full Answer >
Petri oil is probably a mishearing of tea tree oil, a substance derived from the leaves of the Australian tea tree. Tea tree oil is used topically as an antifungal and antibacterial treatment for various infections, according to WebMD. It is not related to tea and shouldn't be ingested.Full Answer >
Skin cells work by forming a protective layer on the body to shield it from microbes, protect it from the elements and allow the nervous system to detect sensations such hot and cold. Together, the cells of the skin combine to amass an amount of 20 square feet. There are three basic layers of the skin, including the epidermis, the dermis and the hypodermis.Full Answer >
According to NASA, 7 billion years ago, Mars may have been an excellent place for microbes to live, but currently it cannot support life because the air is too thin and is comprised mainly of carbon dioxide. After drilling into the rocks on Mars, scientists discovered the key ingredients of life, including sulfur, nitrogen, hydrogen, oxygen and carbon.Full Answer >