Preventing Disease: Normal Human Flora

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  • 0:58 Human and Mutualistic Flora
  • 1:33 Gut Flora
  • 2:33 Opportunistic Pathogens
  • 3:33 Commensal Flora
  • 4:36 Other Types of Flora
  • 6:34 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
This lesson will give you a basic understanding of what human flora is. You'll learn about the different locations of flora, such as the gut, and what mutualistic, commensal, and opportunistic microbes are.

Your Microbial Friends

Some little kids have invisible friends when growing up. These friends provide them comfort, support, and so on. Regardless of whether or not you had these friends when growing up, you have them right now. I'm being serious, too. You have invisible friends that are silently helping you live a better life. And no, I'm not crazy. Without them, you'd be in a world of trouble.

These friends are alive. They are on you and they are in you. That sounds a bit scary, but it's true. Of course, 'invisibility' is a relative term. It's not like these friends are ghosts. They're actually tiny microbes, such as bacteria, that cannot be seen with the naked eye. This lesson will go into how these friends help protect you and where they are located.

Human and Mutualistic Flora

The microbes that reside on or within a human, some of which are beneficial to a person's survival, are known as human flora. Some of the microbes in human flora are mutualistic microorganisms, meaning they are organisms that derive a benefit from and provide a benefit to their host. Essentially, mutualistic bacteria are like your invisible best friend. You make them laugh and they make you laugh. They cook for you and you cook for them.

Gut Flora

In real life, one prime example of mutualistic flora is found in a collection of microbes living in your digestive tract, collectively referred to as gut flora. Here, mutualistic gut flora is provided with nutrients by way of the food you eat. Yeah, they basically siphon off a little bit of that food for themselves before your own body even gets a piece. They do this so they can survive and live off of something. They have to eat, too!

However, they provide you with more than one thing in return that is of benefit for you. For example, they help you digest your food and help to kill off flora that may be bad for you, meaning they essentially prevent certain diseases from occurring by killing off the bacteria in your gut that may cause such diseases.

Opportunistic Pathogens

The bad or potentially bad microbes found in human flora, gut or otherwise, are known as opportunistic pathogens. These are microbes, such as fungi and bacteria, that take advantage of a host's weakened immune system.

In the case of our mutualistic gut flora, they actually help to keep down the levels of some of the opportunistic pathogens through competition, meaning your best friends in your gut either directly kill these bad bacteria or fungi or they outcompete them for resources, such as food, causing the opportunistic bacteria to die in the process due to starvation.

In essence, you can liken this little, but important, process to your best friend withholding food from your enemy and giving it to you instead or your best friend going and just punching the lights out of your enemy in order to keep you safe and healthy.

Commensal Flora

Besides having friends and enemies inhabiting your body, you may also have commensal microbes in your flora as well. Commensal microbes are microbes that live in a non-harmful co-existence with their host. This basically means they don't benefit you like your friend or try to hurt you when you're down like your enemy; they are just there.

Working off of our example from before, if your enemy is trying to hurt you and your friend is trying to help you in a fight, then the commensal organisms are the bystanders that just stand there for the sheer enjoyment of watching a fight. They do nothing otherwise. They don't help you or hurt you.

In reality, commensal organisms may actually derive a benefit from you, such as a having place to live, but in the end, whatever benefit they derive from you doesn't affect you negatively, and therefore they are not considered to be pathogenic, or disease-causing, microorganisms in a healthy person.

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