Two glass or plastic disks: that is the definition of one of the simplest, most sophisticated and basic tools in microbiology. Also known as the Petri dish, this tool has revolutionized the way scientists study microorganisms, allowing their crop and theirs observation under controlled conditions.
Its basic design, consisting of a base and a slightly larger lid that fits without closing tightly, has proven more than effective in minimizing contamination and providing an ideal environment for the growth of bacteria, mold and other microorganisms.
JULIUS RICHARD PETRI: THE GENIUS BEHIND
The origin of the Petri dish dates back to the end of the 19th century, at a time when microbiology was beginning to rank among the basic disciplines and its protagonist was a German microbiologist and physician, Julius Richard Petri.
Petri was born in 1852, received his doctorate at the Charité Clinic in Berlin, and soon after joined the team of Robert Koch, a prestigious bacteriologist who obtained Nobel Prize in Physiology and Medicine in 1905 for the discovery of the tuberculosis bacillus. Koch used a bell jar to grow bacteria, but this method had major problems pollution and air exposure.
To deal with these problems, Petri came up with an innovative solution: a round glass box with a lid slightly larger than the base, which allowed for the creation of a controlled environment for the cultivation of microorganisms. But it is interesting that the idea of a growing box was not a completely new idea: Emanuel Klein, a Croatian researcher, described a similar board in 1885 in his book “Microorganisms“. Klein suggested using a shallow, covered dish, similar to a petri dish. Further in 1886 Percy Frankland in an article published in a magazine Proceedings of the Royal Societyalso mentioned a comparable design.
Despite these precedents, it was Petri’s version that was accepted in the scientific field due to its simplicity and effectiveness. The Petri dish thus allowed scientists to isolate and observe microbial colonies under controlled conditions, making it easier study of infectious diseases and contributes significantly to it advances in microbiology and medicine. The simplicity of the Petri dish design made it an essential tool in laboratories around the world and ushered in a new era in microbiological research.
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Portrait of Julius Richard Petri
MICROSCOPIC WORLDS
But how does a petri dish achieve this efficiency? For the growth of microorganisms, a suitable culture medium is placed on the base, such as agar nutritious, providing essential nutrients and physical support for cell growth. Once the medium is inoculated with a sample of the desired microorganism, the plate is covered with a lid and placed in incubator ensure suitable environmental conditions such as temperature and humidity. A very strange fact is that during incubation it is common for the petri dish to remain reversei.e. with the cap at the bottom and the base at the top. This arrangement prevents the condensation of water vapor produced by microbial metabolism from falling on the culture medium and diluting the colonies formed, allowing the microorganisms to remain attached.
In addition, the petri dish also allows direct observation and microbial colony analysis no need to lift the lidwhich minimizes the risk of external contamination. Colonies can be examined visually to evaluate their morphology, size, and color, and can also be handled for further testing such as antibiotic susceptibility testing or genetic studies. In addition, this device not only facilitates the visualization of isolated colonies, but also allows separation and cultivation of different species from a mixed sample, something essential for clinical diagnosis and research.
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Different cultures in petri dishes
TUBERCULOSIS, CHOLERA AND DIPHTHERIA
Since its invention, the Petri dish has had a major impact on science and medicine. In the field of microbiology, this tool was a breakthrough: methods of culturing bacteria and fungi were available before its introduction. basic and it usually resulted sample contaminationbut the ability to grow microorganisms in a solid, controlled medium allowed scientists to isolate specific bacteria, observe their properties, and study their behavior in detail. This was decisive for identify the pathogens responsible diseases such as tuberculosis, diphtheria and cholera, opening the door to the development of effective vaccines and treatments.
In medicine, the Petri dish has become an essential tool for diagnosis of bacterial infectionswhich facilitates the identification of pathogens and the evaluation of their susceptibility to different antibiotics.
Additionally, the petri dish has played a key role in disease research and expanded its impact on the field molecular biology and geneticswhere it made it possible to identify the genes responsible for virulence and resistance to antibiotics.
All in all, the Petri dish has been essential to advances in genetic engineering, biotechnology, and the production of drugs such as antibiotics and vaccines that have transformed modern medicine and underscored its importance more than a century after its creation.
