This video introduces the human microbiome from the perspective of the narrator and one of its occupants, Heidi Helicobacter (Helicobacter pylori). Heidi lives in …
> Hi!
I'm Heidi Helicobacter.
I'm down here in my human host college freshman
Kristen's stomach as a member of her microbiome.
What's a microbiome you ask?
Well, it is all the trillions of microbial
organisms
that live in and on Kristen,
and any other human for that matter.
I am a member of the Bacteria domain and I
live in the
stomach with a lot of my bacterial friends
and family.
Some live close by in the intestines and others
live as far away as Kristen's mouth,
respiratory system, skin, and reproductive
system.
Scientists have been studying the microbiome
and they have discovered a lot about
bacteria like me who comprise it.
More recently scientists have realized that
it's not just bacteria that live here.
It's also archaea, fungi, and protists.
There are even quite a few viruses that
inhabit the healthy microbiome.
Unseen by most, we make up quite an exotic
group!
There are so many of us living here,
at least as many of us as there are Kristen's
own cells,
if not more of us!
Let me introduce you to some of
the microbes who live here.
This is my friend Millie Methanosphaera,
a member of the Archaea domain.
> Hi I'm Millie Methanosphaera
and I'm an Archaea.
Like the Bacteria, my domain has been around
for
over 3 billion years and we are both prokaryotic.
That means our DNA is free in our cells.
No need to have it enclosed in a membrane
like those eukaryotes do.
We are very independent –
always made up of just one cell and we are
simple folk.
We don't have any of those specialized
organelles that eukaryotes have.
I, like many Archaea, am an extremophile.
Extremophiles live in some pretty radical
environments,
such as very high or low temperatures,
or where there is a lot of sulfur or salt.
Here in Kristen's gut I live where there is
almost no oxygen.
It is important to note that I may look similar
to most bacteria,
but inside I am significantly different.
> Thank you Millie.
And here are a few of my other friends,
Charles Chilomastix and Carla Candida.
> Hi I'm Charles and next to me is Carla.
It's nice to meet you.
We're happy to finally be noticed and talked
about.
Everyone is so focused on the bacteria
and they forget all about us.
We are eukaryotic which means our DNA is in
a
special place in our cells called the nucleus.
We also have a bunch of other specialized
organelles
that those prokaryotes just don't have.
I am a protist and Carla is a fungus.
Although we are both single-celled,
many eukaryotic organisms are multicellular.
Our host Kristen is a eukaryote as are all
humans.
Recently scientists have started paying more
attention to our role in the human microbiome.
> Lastly, I want you to meet Fatima Phage,
who is very
different from the other organisms we've already
met.
> Hi, I'm happy to be included in this menagerie
even though I'm really not even considered
a cell, and I'm so much smaller than the rest of you.
I'm a bacteriophage, which is a type of virus.
Because I can only reproduce inside a
living cell,
some scientists argue that I am not even really
alive.
Although the role of viruses as part of the
microbiome is still unclear,
scientists have realized that there are so
many viruses
found in a healthy human microbiome
that we get our own name.
Together I and all my virus buddies are called
the virome.
> We are definitely a diverse bunch.
It took awhile for scientists to realize exactly
how diverse
because so many microbes don't grow well in
the lab
so it has been difficult to determine just
how
many different types of us there are.
Now that there are new genetic techniques,
scientists can characterize us based on our
DNA.
> Hey Heidi, you forgot to introduce me.
I am a bacterium also and I want to talk about
myself.
> No, sorry Carmen, you are a pathogen and
if there
are too many of you people can get very sick.
That's one of the things the rest of us do
down here –
we take up space and resources so organisms
like you can't gain a foothold.
> We'll see Heidi, we'll see!!
Ha ha ha ha ha!
> Sorry about that distraction.
Now that I have spent so much time
introducing you to my friends,
let me tell you a little more about myself.
My particular species, Helicobacter pylori,
has been a
resident in the human stomach for thousands
of years.
We burrow right through the mucus layer to
find a
nice place to live and there is a lot for
us to eat.
We don't mind all the acid that is around
us and we
even secrete enzymes to neutralize some of
that acid
and make it a little more comfortable for
ourselves.
In 1982 two Australian scientists,
Robin Warren and Barry Marshall,
determined that it isn't stress and spicy
foods that
cause stomach ulcers but Helicobacter pylori!
Some people react badly to us and develop
sores in the lining of their stomachs.
Even worse, we can be associated with stomach
cancer.
After this discovery, people with ulcers started
taking
antibiotics to get rid of us and I had a lot
fewer
cousins, aunts, uncles, and other family members
around.
Worldwide we live in 70% of the population,
but only 30% of the people in the United States.
Less than 6% of children in the U.S. test
positive for H. pylori
and the incidence of ulcers has declined significantly.
Sounds great, doesn't it, at least from the
human perspective?
Of course things are not always how they first
appear and
all I can say is our relationship with humans
is complicated.
Once our world of the microbiome was discovered
and
scientists started analyzing exactly what
roles each of us played,
they realized something interesting.
My family may not be so bad after all!
Most people who do have us in their gut don't
end up
getting sick and those who don't have us may
wish they did.
Loss of our species from the microbial ecosystem
has been correlated with an increase in
gastroesophageal reflux disease (GERD),
a chronic disease that happens when stomach
acid backs up into your esophagus.
This is heartburn that just won't go away
and people who
have this are often nauseous and may vomit
frequently.
Loss of H. pylori is also correlated with
an increase
in the incidence of esophageal cancer.
When we're not around to tamp down on all
that acid,
bad things can happen.
Even more interesting, scientists have evidence
that
our absence may be contributing to obesity!
How in the world can the absence of a lowly
bacterial species contribute to obesity?
Well, it all has to do with a hormone called
ghrelin.
This is produced when your stomach
is empty and you are hungry.
Once you eat and your stomach is full, ghrelin
decreases,
you feel satisfied, and you stop eating.
Well apparently when Helicobacter pylori is
not present,
ghrelin can be produced even when the stomach
is full.
In that case the brain would not receive a
signal
to stop eating and someone would continue
to eat
even when not hungry.
Over time, weight gain would occur
and could progress to obesity.
Like I said, our relationship with our
human host is complicated.
Scientists have been working hard
to determine what microbial composition
makes up a healthy human microbiome.
Scientists no longer believe that there is
an ideal
set of specific microbes found in each human.
One thing that does seem clear, however,
is that although scientists may not understand
the specific role of each microbial species
in the microbiome,
diversity of species is critical.
There is likely a set of metabolic functions
we perform
but different microbes may perform these
functions in different individuals.
Some of these functions include breakdown
of carbohydrates,
synthesis of vitamin D, regulation of pH,
and education of the immune system so it functions
properly.
There are quite a few external factors that
can
change the makeup of the microbial population
such as diet, age, or antibiotic use.
It is important that we be resilient and
able to recover from change.
If we are not able to do that,
our human host can end up in dysbiosis,
or in other words a microbial imbalance.
> You know Heidi, our host Kristen takes a
lot of antibiotics.
Every time she gets one of those respiratory
infections
her doctor prescribes them.
Doesn't she realize that those drugs
don't just target the bad bacteria?
They target ALL bacteria!
Talk about being at risk for dysbiosis and
letting
microbes like Carmen Clostridium take over!
Well Millie, we'll just have to hope for the
best.
Do you know that quite a few important studies
to fully characterize our role in human health
and disease are ongoing?
The National Institute of Health coordinates
the
Human Microbiome project and anyone can go
to
their website for updates on research.
One day analyzing your microbiome may be just
another part of a routine physical
and manipulating it when you are ill may
be one more way to restore health!

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