Leaving Italy

Why are bacteria important?

This week I will follow up with my MRes time in York (UK) (have a look here if you missed my last post) and, after presenting to you the medical problem behind my research, today I would use this post to talk about bacteria. Indeed, bacteria are very important for the humankind and they are not necessarily always dangerous. Instead, they actually are very important for our wellbeing, the food we eat, some drugs we use and, in my case, for my research.

Therefore, let’s start from the beginning and for this week I will talk about the importance of bacteria for the humankind.

Bacteria are single-celled microorganisms that can exist either as independent (free-living) organisms or as parasites (dependent on another organism for life). The first one that was actually able to see bacteria was a Dutch merchant named Leeuwenhoek (1632-1723). He was using lenses to check the quality of the fabrics he was selling and, after a trip to London where he bought some new and powerful lenses, he was able to build one of the first microscopes. Using his microscope, he casually discovered bacteria, that he described in his observations as strange being with a round shape.

However, bacteria have been used unconsciously for thousands of years. Many different foods are prepared with bacteria. Their action modifies the raw material and it transforms the food in new products with different chemical-physical, sensorial and nutritional characteristics. Indeed, these foods have a greater shelf-life and, sometimes, a higher degree of safety of use. We have to thank bacteria for cheese, yogurt, bread, wine and many more other products.

The first one researching on these bacterial-food processes was Luis Pasteur (1822-1895), a French chemistry and microbiologist considered the father of Microbiology, that studied fermentation and demonstrated the essential role played by microorganisms in these processes. He also discovered that the production of undesired substances in alcoholic beverages, such as lactic acid or acetic acid, is due to the presence of bacteria. Indeed, sometimes the presence of bacteria can accelerate the food decomposition, and this can be dangerous for humans: Pasteur conceived a method that kills the harmful bacteria in food, without altering its sensorial and nutritional characteristics. Today, sauces, creams, canned food and beer are produced using pasteurisation.

Nevertheless, not all bacteria are useful: some of them causes disease that (especially in the past) were able to create plagues, such as the black death or cholera. It is thanks to Alexander Fleming (1881-1955) that we are actually able to treat these diseases and his (fortuitous) discover of penicillin (have a look here if you missed my post about this very important discovery).

These days bacteria are used in the production of many pharmacological substances: some of them are used to produce antibiotics and vitamins, some others are used to test the efficacy of antibiotics or the presence of substances in foods or pharmaceutical preparations.

Last but not least, bacteria are used in biomedical research: indeed, it is possible to introduce pieces of DNA in the bacterium’s genome, thus giving instruction to the bacterial cell to produce proteins that they do not normally synthesise. Exploiting this methodology, it is possible to obtain proteins that are used to cure diseases. Today, substances that were extracted from natural resources, usually available in limited quantities, are now obtained in a low cost-high efficiency manner. Among these substances, we find interferon for viral infections (to stimulate the immune system to attack the virus), the growth hormone and the insulin hormone for diabetic people (have a look below for a schematic of the insulin production in bacteria).

Schematic of insulin production bacteria. The human insulin gene is inserted into a bacterial plasmid (a vector that the bacteria usually use to transfer useful genes, as antibiotic resistance genes). Once the bacterium takes up the plasmid, it starts to produce the human insulin hormon, that can then be extracted and purified for pharmacological use. Modified from ib.bioninja.com.au

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