The human microbiome and what we do to it

Summary

This transcript explores the human microbiome, highlighting that we are largely composed of microbial cells and genes. Professor David Relman explains the symbiotic relationship between humans and microbes, which aid in digestion, nutrient recycling, and protection against harmful pathogens. The overuse of antibiotics, however, can disrupt this balance, leading to severe impacts on microbial communities and potential health consequences. The discussion also touches on the potential benefits of probiotics in restoring a healthy microbiome, emphasizing the need for a new perspective on our microbial partners.

Takeaways

• 🌐 The human body is composed of a tiny percentage of human cells and a large percentage of microbial cells, suggesting a symbiotic relationship.
• 🧬 We are more microbial than human when considering the number of unique genes, with humans comprising only about 1% of our genetic makeup.
• 🌿 The human microbiome, a collection of microbial communities, has co-evolved with us and plays a crucial role in our health.
• 🛡️ Microbes provide functions that our bodies can't execute alone, such as the digestion of complex plant polysaccharides.
• 💪 Our microbiome acts as an internal shield, protecting us from harmful pathogens through a process known as competitive exclusion or colonization resistance.
• 📍 Microbes reside in all areas of our body that interface with the external environment, with particularly high concentrations in the colon.
• 🔄 The gut microbiome aids in the recirculation of valuable nutrients and helps maintain healthy cholesterol levels.
• ⚠️ Antibiotic use can have severe and long-lasting impacts on the microbiome, potentially leading to a decline in microbial diversity.
• 🤒 Antibiotics can lead to infections like Clostridium difficile, causing significant illness and death, especially in those who are already sick or weakened.
• 💊 Probiotics are suggested as a potential solution to restore friendly bacteria, although evidence of their effectiveness is still emerging.
• 🤔 There is a possibility that antibiotic overuse and the subsequent damage to the microbiome could be linked to chronic diseases like heart disease and cancer, but more research is needed.

Q & A

What is the human microbiome?

The human microbiome is a collection of microbial communities that have co-evolved with humans and are now considered part of the human landscape, providing essential functions that the human body cannot execute on its own.

How significant is the microbial component in comparison to human cells and genes?

It is estimated that we are ten parts microbial cells to one part human, and when considering unique genes, the difference is a factor of a hundred, meaning we are only one percent human in terms of unique genes.

What role do microbes play in our digestive system?

Microbes in our digestive system assist in the digestion of complex polysaccharides from plants, which humans are deficient in processing, and help in recirculating valuable nutrients and keeping cholesterol levels down.

How does the microbiome protect us from harmful invaders?

The microbiome provides an internal shield of friendly microbes that compete with and crowd out harmful pathogens, a process known as competitive exclusion or colonization resistance.

Where are the highest concentrations of microbes found in the human body?

The highest concentrations of microbes are found in the colon, with significantly lower numbers in the mouth, at ten million per gram compared to a hundred thousand times as many per gram in the colon.

What are the negative impacts of antibiotics on the microbiome?

Antibiotics can decimate microbial communities, leading to a severe impact on the microbiome, which is more pronounced in people who are already sick and weakened.

How does the microbiome recover after antibiotic use in healthy individuals?

In healthy individuals, the microbiome tends to recover quite well after an occasional course of antibiotics, although the recovery process can be slower and less complete in those who are sick or weakened.

What is Clostridium difficile and why is it a concern?

Clostridium difficile is a germ that can cause severe infections, particularly in people who have been treated with antibiotics, leading to hundreds of thousands of deaths worldwide.

What is the current understanding of probiotics in relation to the microbiome?

The evidence on probiotics is still early, but it suggests there may be potential benefits in replenishing friendly bacteria in the microbiome after antibiotic use.

Is there a known link between microbiome damage and chronic diseases like heart disease and cancer?

The link between microbiome damage due to antibiotic overuse and chronic diseases such as heart disease and cancer is not yet established, as no specific studies have been conducted to explore this connection.

What is the new perspective on bacteria and their relationship with humans?

The new perspective emphasizes the importance of bacteria as a significant part of our being, with 99% of what we are being non-human, and calls for a shift from viewing bacteria solely as enemies to recognizing their essential role in human health.

Outlines

00:00

🌿 The Human Microbiome: Our Co-Evolved Companions

This paragraph delves into the concept of the human microbiome, emphasizing that a significant portion of our bodies is composed of microbial cells and genes, which are essential for our survival and health. Professor David Relman explains that we are predominantly microbial, with only a small percentage being 'human' in terms of unique genes. These microbes co-evolve with us, aiding in digestion, particularly of complex plant polysaccharides, and provide a protective shield against harmful pathogens through competitive exclusion and colonization resistance. The discussion also touches on the distribution of these microbes, highlighting their abundance in the colon compared to other areas like the mouth. The paragraph concludes with a cautionary note on the negative impacts of antibiotic use, which can decimate these beneficial microbial communities, and the potential long-term health consequences, including the risk of Clostridium difficile infections.

05:05

💊 Antibiotics and the Microbiome: A Double-Edged Sword

The second paragraph continues the discussion on the impact of antibiotics on the human microbiome. It outlines how, despite the undeniable benefits of antibiotics in treating infections, their overuse can lead to severe disruptions in the microbial balance. The script mentions an experiment where volunteers were given antibiotics, resulting in a significant reduction in microbial diversity. While healthy individuals may recover their microbiome after such interventions, those who are already sick or weakened might not, increasing their vulnerability to infections like Clostridium difficile. The paragraph also introduces the concept of probiotics as a potential solution to restore the balance of friendly bacteria, although the evidence for their effectiveness is still emerging. It concludes with a call for a paradigm shift in our approach to bacteria, recognizing their crucial role in our health and the need for a more nuanced understanding of their relationship with human health.

Keywords

💡Human Microbiome

The human microbiome refers to the collection of microorganisms that live in and on the human body, including bacteria, viruses, fungi, and other microbes. It plays a crucial role in health by aiding in digestion, immune system development, and protection against harmful pathogens. In the video, it's highlighted that the microbiome is an extension of self, providing functions that the human body cannot execute on its own, such as digesting complex plant polysaccharides.

💡Microbial Cells

Microbial cells are the individual units of microorganisms, such as bacteria, that make up the human microbiome. The video script suggests that we are 'ten parts microbe and one part human' when counting microbial cells, emphasizing the vast number of these cells in comparison to human cells.

💡Unique Genes

Unique genes are the distinct segments of DNA that determine specific traits in an organism. The video points out that humans are only one percent human in terms of unique genes, indicating the genetic diversity and importance of the microbiome in shaping our biology.

💡Co-evolution

Co-evolution is the process by which two or more species influence each other's evolution over time. In the context of the video, it describes how the human microbiome has evolved alongside humans, leading to a symbiotic relationship where both parties benefit.

💡Colonization Resistance

Colonization resistance, also known as competitive exclusion, is a phenomenon where the presence of one set of microorganisms inhibits the ability of other, potentially harmful, microorganisms to establish themselves. The video explains this as a protective mechanism provided by the microbiome, where 'good' microbes crowd out 'bad' ones.

💡Antibiotics

Antibiotics are medications used to treat bacterial infections. The video discusses the negative impact of antibiotics on the microbiome, as they can decimate microbial communities, leading to health issues such as the overgrowth of harmful bacteria like Clostridium difficile.

💡Clostridium difficile

Clostridium difficile is a bacterium that can cause severe diarrhea and more serious intestinal conditions associated with the use of antibiotics. The video mentions it as a significant cause of illness and death, particularly in people with weakened immune systems.

💡Probiotics

Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. The video suggests probiotics as a potential solution to restore the balance of the microbiome after antibiotic use, although the evidence for their effectiveness is still being explored.

💡Cholesterol

Cholesterol is a waxy substance that has important functions in the body, such as the production of hormones and the maintenance of cell membranes. The video implies that the microbiome assists in managing cholesterol levels, which is an important aspect of overall health.

💡Detoxification

Detoxification is the process by which harmful substances are made less toxic or are removed from the body. The video mentions that the microbiome helps in detoxifying poisons, highlighting another way in which it contributes to maintaining health.

💡Overuse of Antibiotics

The overuse of antibiotics refers to the unnecessary or excessive use of these medications, which can lead to antibiotic resistance and harm to the microbiome. The video discusses the need for a new approach to using antibiotics, considering their impact on the human microbiome.

Highlights

Only a tiny percentage of what humans are made of is actually human, with the rest being non-human bits essential for survival.

The human body is said to be ten parts microbe and one part human when counting microbial cells.

In terms of unique genes, humans are only one percent human, with the rest being microbial.

The human microbiome is a set of microbial communities that have co-evolved with humans, becoming an extension of self.

Microbes provide functions that humans don't have the means to execute, such as digesting complex plant polysaccharides.

Microbes in the human body help manage encounters with the environment and protect against harmful invaders.

The concept of competitive exclusion, or colonization resistance, explains how beneficial microbes prevent harmful ones from taking hold.

Microbes are present in all areas of the body that are exposed to the outside world, not just the bowel.

The number of microbes in the mouth is significantly less compared to the colon, with the latter having a hundred thousand times more per gram.

Microbes in the bowel help recirculate valuable nutrients and assist in keeping cholesterol levels down.

Antibiotics can have severe impacts on the microbiome, with many microbial communities being decimated.

The microbiome in healthy individuals can recover from antibiotic use, but this is not the case for those who are sick and weakened.

Antibiotic use can lead to infections with Clostridium difficile, causing a significant number of deaths worldwide.

Probiotics are suggested as a solution to restore friendly bacteria after antibiotic use, with early evidence suggesting potential benefits.

The long-term effects of antibiotic overuse on the microbiome, such as the potential for causing heart disease and cancer, are currently unknown.

There is a need for a new way of thinking about bacteria, recognizing their essential role in human health rather than just as enemies to be eliminated.

Transcripts

[Norman Swan]

Have you ever wondered what it means to be human? Well, it turns out that only a tiny

percentage of what you and I are made of is in fact human. And we need these non-human

bits to survive. But we're doing dreadful things to this hidden majority and it's damaging

our health in ways that we are only just discovering.

[Professor David Relman]

It is said that we are ten parts microbe and one part human. And that's counting microbial

cells as the unit. If we count unique genes then the difference is a factor of a hundred.

We are only one percent human in terms of unique genes.

[Norman Swan]

So you and I are mostly bacteria of some kind. We need each other to stay healthy, and there's

now a name for this part of ourselves.

[Professor David Relman]

The human microbiome is a set of microbial communities that have co-evolved with us,

and we with them, and have become part of the human landscape. It is an extension of

self. They provide to us untold functions that we don't have the means of executing.

We're born deficient in our ability to digest certain kinds of foodstuffs, for example the

complex polysaccharides of plants. We can't manage those very well. Our microbes provide

us the means of taking advantage They also help us manage lots of other encounters with

the environment.

[Norman Swan]

One of the things our microbiome does is give us an internal shield of friendly microbes

which protect us against invasion by some of the nasties out there. The good guys try

to crowd out the bad ones

[Professor David Relman]

It's competitive exclusion. Another term for it is colonisation resistance. So -- you know

-- they man the beachhead and make it hard for others to arrive and find space.

[Norman Swan]

So where are these microbes? Well, while most are in our bowel, they can in fact be anywhere

where we're exposed to the outside world.

[Professor David Relman]

So we have them in our mouth. In the mouth it's a measly ten million per gram, but it's

only measly because in the colon we're talking about a hundred thousand times as many per

gram.

[Norman Swan]

So the microbes in our bowel, for example, help us to recirculate valuable nutrients,

and in fact assist us to keep our cholesterol down. So we need them, and they need us. But

we do some terrible things to our microbiome. Like assault it with antibiotics.

[Professor David Relman]

Yeah, unfortunately for us -- and for them -- everything I'm going to tell you about

the untoward effects of antibiotics has to be balanced against the obvious important

benefits. But I think for too long we have felt as though you can't do much wrong with

an antibiotic. So if in doubt, pull it out. And that clearly is not a good position to be taking.

We've been asking volunteers to take an antibiotic even though they didn't really need it. We

do it for short periods of time. We watch them before, we watch them after, and we're

now doing second exposures a half year later, and the bottom line is, maybe not surprisingly,

far more members of the microbial communities of the human body experience a severe impact.

They're decimated. Many more than we thought.

[Norman Swan]

Now, in healthy people, who might only have an occasional course of antibiotics, the microbiome

seems to recover quite well. That's not so true in people who are sick and weakened.

As a side effect of antibiotics, they can become infected with a germ called Clostridium difficile,

which causes hundreds of thousands of deaths worldwide.

[Professor David Relman]

So, you're right. Colstridium difficile is the cause of large numbers of deaths, but

even larger numbers of illnesses, where there is a recovery, but after some cost.

[Norman Swan]

One solution that some people suggest for this devastation to our microbiome is probiotics;

substances which put back the friendly bacteria.

[Professor David Relman]

The evidence on probiotics is still early to interpret. But I would say it's suggestive;

that there is some potential benefit there.

[Norman Swan]

As I said before, these friendly bugs -- our microbiome -- does a lot more than protect

us against nasty infections. They keep our cholesterol down and detoxify poisons. So

the question is, if we damage our microbiome with antibiotic overuse, are we causing heart

disease and cancer?

[Professor David Relman]

The short answer is, we don't know. Because no-one has looked for this particular link

in the story. We simply don't know.

[Norman Swan]

So while in the past we've seen bacteria as the enemy, and got excited about how we can

kill off disease-causing germs with antibiotics, it's time for a new way of thinking. Remember,

we're talking about ninety-nine percent of what we are.