Yeasts are better known as Man’s Oldest Industrial Microorganisms. History shows that our relationship with this Fungi-form is quite ancient. It is believed that “Man” starting using yeast way before inventing written text! Ancient Egyptian hieroglyphics mention the use of yeast to produce alcohol and bread. This is over 5000 years ago. Back in the day, “Fermentation” was a mysterious magical phenomenon that left everyone in awe. Well, it is still is quite magical!
From what we know, most of the alcohol and bread was being fermented by natural microbial contaminants. These would get into the grains and fruits during the milling and juice extraction phase. These microbial florae would have included wild yeast cultures and lactic acid bacteria. That is usually found associated with cultivated grains and fruits.
Leaven when referred to in the Bible, is described as a soft, dough-like medium. A small portion of this dough was kept aside and used along with the next batch of bread dough. They were, in fact, keeping aside the culture of bacteria to kick start the fermentation in the next batch of growing medium. It was a practice amongst bakers to get hold of the yeast needed to leaven their bread from the brewers. This is how bakers contributed to the selection of these industrial microorganisms. This happened over thousands, if not millions of rounds of making bread dough!
Bakers continued this practice almost ritualistically, without really knowing what was going on. All that was until the invention of the microscope. It was only in the 1860’s that yeast was identified by Louis Pasteur. And for the first time identified as a living organism. A living organism that played a role in alcoholic fermentation and dough leavening. It was only beyond this discovery people started to realise that it is possible to isolate pure strains from wild culture. This pretty much set the stage for the commercial production of the baker’s yeast at the turn of the 20th century.
So, What are Yeasts?
Yeasts are single-celled fungi. They have played a significant role in not just the food and beverage department but also the health sector. Some of this yeast is responsible for the worst fungal infections humans suffer from.
Yeast is different from other Fungi in the aspect that most Fungi grow thread-like structures called hyphae. Though not every yeast species sticks this man-made distinction, most of them do. Sometimes there are fungi that alternate between hyphal and yeast phase to add to the perplexity of trying to classify them. Quite simply these fungi have been referred to as Dimorphic. Dimorphic literally translates to “having two forms”. These shapeshifting dimorphs are pretty important to us. That is because they are the root cause for several diseases humans suffer from.
Yeasts pretty much thrive in areas which contain simple sugars and soluble nutrients. Anything rich in sugars and amino acids aka the protein building blocks is their hangout spot. This is most commonly found on surfaces of leaves, fruits, roots and various types of food left exposed or uncovered. If you have paid attention closely to foods that start rotting, they always start rotting from the surface before moving inwards. Now you know why!
Some of the most common dimorphic fungi include:
- Common baker’s yeast: Saccharomyces cerevisiae
- Cryptococcus (yup! That’s how clueless we were when we named them). Specifically, Cryptococcus neoformans, a well-known pathogen to humans.
- Candida albicans which can wreak havoc in those who have a weak immune system.
The Baker’s Yeast is one of the nicer yeast species compared to the others. This budding yeast has been part of the bread-making process ever since bread has been made. It is this yeast that plays a role in the dough rising as it ferments. Very similar forms of yeast are used in the production of beers, wines and various other alcoholic beverages across the world. A recent study has shown that this yeast has great potential to be used in preventive medicine.
One species of this yeast is most deadly. Referred to as Cryptococcus neoformans. This pathogen is known to affect people with a compromised immune system. The condition is referred to as Cryptococcosis. About 7-8% of people who are suffering from AIDS in the US suffer from this particular condition.
Cryptococcus loves growing on “weathered” bird poop. Yup! One more reason to avoid those duck from those flying splatter bombers. This yeast at first affects the lungs causing a mild infection which soon escalates to persistent pneumonia. People were randomly tested across Britain, Australia and US for skin reactions to this yeast. And it was found that many people were unknowingly exposed to the fungus, but have not faced any negative effects. There are only a small number of people who are susceptible to this infection and where the effects are fatal.
For a long time, it was thought that these yeast cells entered the body through the nostrils. But lately, researchers have found that these fungi release tiny 3-micrometre spores. That is almost equal to 1/40th the thickness of a single strand of hair! And these tiny spores get into the system and start off the infections in the air sacs of the lungs.
This particular yeast multiplies most actively when the temperature is 37-degree Celsius. Yes! That exactly coincides with the normal human body temperature. It thrives in the mucous membranes of humans and other warm-blooded animals. More often than not, it causes little to no damage. And it can be extracted from the saliva of more than 50% of the people on the face of the earth.
It is only in some cases that this yeast becomes pathogenic. Once triggered into this mode starts invading the mucous membranes in the mouth, intestinal tracts and vagina. This often causes a lot of irritation and the body starts to shed the tissue. This sudden burst of activity and growth is set in motion by various environmental, health factors. It has been noticed that when the resident bacteria are not strong enough, these Candida take charge. And once they have a chance to do so, they multiply themselves to no end.
One of the most common examples of a Candida caused condition is a disease referred to as “Thrush”. The symptoms are usually white specks on the tongue and the back of the throat. It resembles the speckling on the bird’s chest, and hence the name. It is commonly seen in newborn babies and those suffering from AIDS or prolonged course of antibacterial drugs. It is a classic case of an opportunistic pathogen that needs to be kept in check with help from our healthy bacterial flora.
All in all, Yeasts have been playing a role in our lives for the better or the worse for ages. The more we are aware of these Yeasts, the easier it will be for us to harvest all the benefits and avoid all ailments caused by them.
Disclaimer: The above article is sponsored by Thyrve, the world’s first Gut Health Program that incorporates microbiome testing and personalized probiotics to ensure a healthier gut, happier life, and a brighter future.