Propionibacterium freudenreichii facts for kids

Propionibacterium freudenreichii is a tiny bacterium that cannot move on its own. It's super important for making Emmental cheese, and also helps create other cheeses like Jarlsberg cheese, Leerdammer, and Maasdam cheese. You'll find a lot of this bacterium in Swiss-style cheeses.

These bacteria are often found in milk and dairy products. But sometimes, they can also be found in soil. P. freudenreichii has a circular piece of genetic material, like a tiny loop, that's about 2.5 million units long.

When Emmental cheese is made, P. freudenreichii eats something called lactate. It then turns the lactate into different things: acetate, propionate, and carbon dioxide. These new products give the cheese its yummy nutty and sweet flavors. The carbon dioxide gas is what creates the famous holes, or "eyes", in the cheese. Cheesemakers can change the size of these holes by controlling how acidic the cheese mix is, its temperature, and how long it ages.

It's amazing to think that about one billion living P. freudenreichii cells can be found in just one gram of Emmental cheese! Unlike most other bacteria used in dairy, this one mostly breaks down fats. Scientists are also looking into how eating P. freudenreichii might be good for us. They think it could help clean our digestive system. Some research even suggests it might help lower the risk of colon cancer. This helpful relationship is quite special for this type of bacterium, as many are just "passengers" in our bodies.

The growth of P. freudenreichii often depends on another bacterium called Lactobacillus helveticus. L. helveticus provides important building blocks called amino acids that P. freudenreichii needs to grow. When L. helveticus breaks down, it releases these amino acids and other small parts. Even without L. helveticus, some types of P. freudenreichii can still grow. However, some strains were seen to break down themselves if they didn't have certain amino acids like glutamine, lysine, or tyrosine. This self-breakdown of P. freudenreichii might also add to the special flavor of Emmental cheese. We don't fully understand yet what makes this bacterium break down on its own.

How This Bacterium Was Found

Propionibacterium freudenreichii was first found and studied in the late 1800s. Two scientists, E. von Freudenreich and S. Orla-Jensen, discovered it. They were studying how propionic acid was made in Emmental cheese. The group of bacteria it belongs to, Propionibacterium, is named after propionic acid, which this bacterium produces. The specific name, freudenreichii, honors E. von Freudenreich.

What the Bacterium Looks Like

These bacteria usually look like tiny rods. They can be different shapes and sizes, from very small to up to 20 micrometers long. Sometimes they can also look like tiny balls, or even have branches.

When they grow on a solid surface, they can form colonies that are smooth, rounded, or rough. In liquid, they might appear as small grains. Their colonies can be many colors, including red, pink, orange, yellow, gray, and white.

As mentioned, P. freudenreichii is a gram-positive bacterium and cannot move on its own. A special thing about this bacterium is that it makes a lot of propionic and acetic acids. It can also break down sugars and other compounds. It can even use lactate if other bacteria nearby are making it. This is like a teamwork process! It can also produce smaller amounts of other acids and carbon dioxide. Some types of these bacteria have special proteins on their surface. These proteins help start the cheese ripening process. Depending on the type, they can also have tiny hair-like parts called pili.

The genetic material of P. freudenreichii is organized in a circle. It has one main circular chromosome and no smaller extra pieces of DNA called plasmids.

Role in Cheesemaking

Propionibacterium freudenreichii is probably most famous for its important role in making cheeses. It's especially key for Swiss cheese.

Possible Health Benefits

Scientists are very interested in P. freudenreichii because it might be used as a probiotic. Probiotics are good bacteria that can help our bodies. P. freudenreichii makes a special compound that helps other good bacteria, called bifidobacteria, grow.

Recent studies show that proteins on the surface of P. freudenreichii can stick to human gut cells. This sticking allows the bacteria to do certain things, like helping to control how our gut cells release important signals called cytokines.

See also

In Spanish: Propionibacterium freudenreichii para niños