Microorganisms in/on everyday objects and a diffusion antibiogram Creative Commons, Attribution alone (BY)
Authors: Jožef Stefan Institute
This content is provided in languages:

A microbial culture includes microorganisms that grow in or on a culture medium. A microbial culture may be mixed or pure. A pure culture contains only one type of microorganism and the characteristics (e.g. antibiotic production, inducing diseases) of that culture are also the characteristics of that type of microorganism. The characteristics of a mixed culture, however, cannot be attributed to only one type of bacteria. Microorganisms in a mixed culture may also affect one another, thus facilitating or hindering each other’s growth. The offspring of a single bacteria or cell that grew and reproduced on a solid culture medium is called a colony, i.e. a mass of cells visible to the naked eye. Microbiology examines the activity of mixed cultures, such as those usually found in nature, while a pure culture is prepared when an individual type is to be examined.

The cultivation of microorganisms provides the basis for studying them. The growth of microorganisms implies the growth of cells and an increased number of cells. It is necessary to provide the nutrients, energy source and suitable physico-chemical conditions for growth, and everything mentioned must imitate the natural environment to maximum possible degree. Every microorganism has optimal, minimum and maximum growth temperatures. Culture media are solutions of nutrients for the development of microorganisms under laboratory conditions, while the structure of a medium and its pH is adjusted to the needs of the microorganism being developed. Every medium may be prepared as a liquid, solid or semi-solid medium with respect to the amount of agar added to the culture medium. Agar causes the medium to solidify. For inoculation, i.e. the addition of microorganisms in/on a culture medium, an inoculation loop is used, also in combination with a swab or pipette.

Diffusion antibiogram is a simple way to establish bacterial resistance to antibiotics. Antibiotics are applied to an infected agar plate. An area emerges around the place of application where the bacteria did not grow; it is called the zone of inhibition. The diameter of the zone of inhibition is measured with a ruler. The agent with the largest zone of inhibition is the most effective in the destruction of that type of bacteria.

Workforce in Chemistry

Chemistry is everywhere in our daily life and there are many jobs chemistry graduates do. Around 540,000 students study chemistry, physics, astronomy, and earth science in the EU. Chemistry graduates work as analysts, healthcare scientists, clinical chemists, forensic scientists, nanotechnologists, pharmacologists and toxicologists among others. Jobs for chemists, other scientists and engineers grew by 7% in the past five years. Jobs for technicians in the field grew by 2%. Overall, they account for 7% of all jobs in the EU. As of 2016, around 15 million European science and engineering workers are employed. They work in a variety of sectors, many of which related with chemical industry, such as agrochemicals, metallurgical, petrochemicals, pharmaceuticals, and plastics and polymers. Many also work in professional services, utilities, and in the education systems. In the next years, jobs for chemistry scientists, other researchers and engineers will increase by 13%, and jobs for science and engineering technicians will increase by 2%.