How bacteria "talk" - Bonnie Bassler
Summary
TLDRThis script delves into the fascinating world of bacteria, the most ancient life forms on Earth. It reveals that we are more bacterial than human, with 10 times more bacterial cells than human ones. These microorganisms play a crucial role in our health, aiding digestion, immune system education, and vitamin production. The talk explores how bacteria communicate through chemical signals, a process known as quorum sensing, which coordinates group behaviors. This communication is key to their social behaviors, including pathogenic attacks. The speaker discusses the potential of disrupting these chemical conversations to develop new antibiotics, offering a promising approach to combat antibiotic resistance.
Takeaways
- 🌿 Bacteria are the most ancient living organisms on Earth, existing for billions of years.
- 🔬 Bacteria are single-celled and microscopic, with a limited number of genes due to having only one piece of DNA.
- 🌱 Bacteria reproduce by consuming nutrients, growing, and dividing, a process that's fundamental to their survival.
- 🤝 Humans have a symbiotic relationship with bacteria, hosting 10 times more bacterial cells than human cells.
- 🧬 Humans possess around 30,000 genes, but the bacterial genes associated with us are about a hundred times more, suggesting we are largely bacterial.
- 🛡️ Bacteria provide essential services like forming a protective barrier, aiding digestion, producing vitamins, and educating our immune system.
- 🌌 Some bacteria can cause severe illnesses if they enter the human body inappropriately.
- 🗣️ Bacteria communicate with each other using chemical signals, a process known as quorum sensing, which coordinates group behaviors.
- 🐙 The bioluminescent bacterium Vibrio fischeri demonstrates how bacteria can synchronize behaviors based on population density.
- 🔬 Scientists have discovered that bacteria use both species-specific and universal communication systems to interact with each other.
- 💊 New approaches to antibiotics target bacterial communication systems, potentially offering a solution to antibiotic resistance.
Q & A
What is the significance of bacteria being single-celled organisms with a single piece of DNA?
-Bacteria being single-celled with a single piece of DNA means they have a limited number of genes to encode their traits, which affects their complexity and the functions they can perform.
How do bacteria reproduce and what is the process called?
-Bacteria reproduce by consuming nutrients, growing to twice their size, and then dividing into two cells through a process known as binary fission.
What is the ratio of human cells to bacterial cells in the human body, according to the script?
-There are about 10 times more bacterial cells than human cells in or on the human body.
How do bacteria interact with the human body, and what roles do they play?
-Bacteria interact with the human body by forming an invisible body armor that protects against environmental insults, aiding in digestion, producing vitamins, and educating the immune system to keep harmful microbes out.
What is the concept of 'Quorum sensing' in bacteria, as mentioned in the script?
-Quorum sensing is a communication method used by bacteria where they release and detect specific molecules to coordinate group behaviors based on population density.
How does the bacterium Vibrio fischeri demonstrate quorum sensing?
-Vibrio fischeri demonstrates quorum sensing by producing bioluminescence only when a certain cell density is reached, indicating they are communicating and acting collectively.
What is the symbiotic relationship between Vibrio fischeri and the Hawaiian bobtail squid?
-Vibrio fischeri lives in the light organ of the Hawaiian bobtail squid, providing light for the squid to counter-illuminate itself and avoid predators, while the squid provides a safe environment and nutrients for the bacteria.
How do bacteria 'talk' to each other, as described in the script?
-Bacteria 'talk' to each other by secreting small molecules that act as chemical signals, which are detected by other bacteria to coordinate behaviors such as bioluminescence or virulence.
What are the potential applications of understanding quorum sensing in bacteria?
-Understanding quorum sensing can lead to the development of new antibiotics that target bacterial communication, potentially reducing the ability of bacteria to launch coordinated virulence attacks and thus overcoming antibiotic resistance.
How do bacteria distinguish between their own species and others?
-Bacteria use a combination of species-specific and generic chemical signaling molecules to distinguish between their own species and others, allowing for both intra- and inter-species communication.
What is the potential of anti-quorum sensing molecules as a new class of antibiotics?
-Anti-quorum sensing molecules have the potential to disrupt bacterial communication, preventing coordinated virulence and offering a new strategy in combating antibiotic resistance.
Outlines
🌿 The Ubiquity and Importance of Bacteria
The script begins by introducing bacteria as the oldest living organisms on Earth, existing for billions of years. These single-celled microscopic organisms have a unique characteristic of possessing only one piece of DNA, which limits their genetic information. Bacteria sustain themselves by consuming nutrients from their surroundings, growing, and dividing through a simple process. The speaker humorously points out that humans, despite considering themselves as distinct entities, are vastly outnumbered by bacterial cells, which are both internal and external. These bacteria play crucial roles in human health, providing a protective barrier, aiding in digestion, vitamin production, and immune system education. The narrative also touches on the duality of bacteria's impact, highlighting both their beneficial and harmful potentials, and posing a question about how such tiny organisms can exert significant influence given their size and solitary lifestyle.
🐙 The Symbiotic Relationship of Vibrio fischeri and the Hawaiian Bobtail Squid
This section delves into the fascinating symbiosis between Vibrio fischeri, a bioluminescent bacterium, and the Hawaiian bobtail squid. The speaker explains how the bacteria, which emit light when present in high concentrations, reside within the squid's light organ. The squid uses the bacteria's light for counter-illumination, a defense mechanism that prevents it from casting a shadow and becoming prey. The bacteria's light production is regulated by a quorum sensing mechanism, where they communicate chemically and synchronize their light emission based on population density. The speaker then discusses the molecular biology behind this phenomenon, revealing that Vibrio fischeri produces a specific molecule that triggers light production when a critical cell density is reached. This mechanism is not unique to this bacterium but is a widespread communication strategy among bacteria, known as quorum sensing, which allows them to coordinate group behaviors.
🔬 Bacterial Communication and Its Implications for Medicine
The speaker explores the concept of bacteria as multilingual communicators, capable of both intra- and inter-species communication using chemical signals. This ability allows bacteria to take a census of their population and their environment, which is crucial for their social behaviors. The script then transitions into the potential medical applications of understanding bacterial communication. By disrupting these chemical conversations, it may be possible to create new antibiotics that do not kill bacteria but rather incapacitate their ability to communicate and coordinate virulent attacks. This approach could offer a solution to the growing problem of antibiotic resistance. The speaker also mentions the development of pro-quorum sensing molecules aimed at enhancing the beneficial bacteria that coexist with humans, potentially leading to improved health outcomes.
🌐 The Broader Impact of Bacterial Studies on Human Health and Scientific Discovery
In the final paragraph, the speaker reflects on the broader implications of studying bacteria for understanding multicellularity and human health. They suggest that bacteria, with their ancient existence on Earth, may have laid the groundwork for multicellular organization, and by studying these simple organisms, we can gain insights applicable to complex human systems. The speaker also emphasizes the practical applications of this research, with the development of anti-quorum sensing molecules as a new therapeutic approach. Additionally, they celebrate the contributions of young scientists to the field, highlighting the importance of nurturing the next generation of scientific talent.
Mindmap
Keywords
💡Bacteria
💡Genetic Code
💡Quorum Sensing
💡Bioluminescence
💡Vibrio fischeri
💡Symbiosis
💡Virulence
💡Anti-Quorum Sensing Molecules
💡Multicellular Organization
💡Chemical Language
Highlights
Bacteria are the oldest living organisms on Earth, with a history of billions of years.
Bacteria are single-celled organisms with a single piece of DNA, making them genetically simple.
Bacteria reproduce by consuming nutrients, growing, and dividing.
There are 10 times more bacterial cells in and on the human body than human cells.
Bacteria play a crucial role in human health, including digestion and immune system education.
Bacteria can communicate with each other using chemical signals, a process known as quorum sensing.
Vibrio fischeri, a bioluminescent bacterium, demonstrates collective behavior through quorum sensing.
Bacteria use a chemical language to coordinate group behaviors like virulence.
Bacteria have species-specific and universal communication systems for intra- and inter-species interaction.
The discovery of bacterial communication molecules has led to the development of new antibiotics.
Anti-quorum sensing molecules can prevent bacteria from launching virulence attacks.
Bacteria may have invented multicellular organization principles that are reflected in human biology.
Pro-quorum sensing molecules are being developed to enhance the beneficial bacteria in our bodies.
The study of bacteria can provide insights into human diseases and behaviors.
Bacteria can distinguish self from others using specific chemical signals.
The research presented was conducted by a team of young scientists at Princeton University.
Transcripts
[Music]
[Music]
bacteria are the oldest living organisms
on the earth they've been here for
billions of years and what they are are
single cell microscopic organisms so
they're one cell and they have the
special property that they only have one
piece of DNA so they have very few genes
and genetic information to encode all of
the traits that they carry out and the
way bacteria make a living is that they
consume nutrients from the environment
they grow to twice their size they cut
themselves down in the middle and one
cell becomes two and so on and so on so
they just grow and divide and grow and
divide so kind of boring life except
that what I would argue is that you have
an amazing interaction with these
Critters I know you guys think of
yourself as humans and this is sort of
how I think of you and so this man is
supposed to represent a generic human
being and all of the circles in that man
are all of the cells that make up your
body so there's about a trillion human
cells that make each one of us who we
are and able to do all the things that
we do but you have 10 trillion bacterial
cells in you or on you at any moment in
your life so 10 times more bacterial
cells than human cells on a human being
and so of course it's the DNA that
counts so here's all the ATS G's and C's
that make up your genetic code and give
you all your Charming characteristics so
so you have about 30,000 genes well it
turns out you have a hundred times more
bacterial genes playing a role in you or
on you all of your life and so at the
best you're 10% human you're more likely
about 1% human depending on which of
these metrics you like so I know you
think of yourself as human beings but I
think of you as 90 or
99%
bacterial and these bacteria are not
passive Riders these are incredibly
important they Keep Us Alive they cover
Us in an invisible body armor that keeps
environmental insults out so that we
stay healthy they digest our food they
make our vitamins they actually educate
your immune system to keep bad microbes
out so they do all these amazing things
that help us and keep and are vital for
keeping us alive and they never get any
press for that but they get a lot of
press because they do a lot of terrible
things as well so there's all kinds of
bacteria on the earth that have no
business being in you or on you at any
time and if they are they make you
incredibly sick and so the question for
my lab is whether you want to think
about all the good things that bacteria
do or all the bad things that bacteria
do the question we had is how could they
do anything at all I mean they're
incredibly small you have to have a
microscope to see one they live this
sing sort of boring life where they grow
and divide and they've always been to
considered to be these asocial reclusive
organisms and so it seemed to us that
they're just too small to have an impact
on the environment if they simply act as
individuals and so we wanted to think if
there couldn't be a different way the
bacteria live and the clue to this came
from another Marine bacterium and it's a
bacterium called vibrio fisheri and so
what you're looking at on this slide is
just a person from my lab holding a
flask of a liquid culture of a bacterium
a harmless beautiful bacterium that
comes from the ocean named Vio ferai and
this bacterium has the special property
that it makes light so it makes
bioluminescence like fireflies make
light so we're not doing anything to the
cells here we just took the picture by
turning the lights off in the room and
this is what we see and what was
actually interesting to us was not that
the bacteria made light but when the
bacteria made light what we noticed is
when the bacteria were alone so when
they were in dilute suspension they made
no light but when they grew to a certain
cell number all the bacteria turned on
light simultaneously and so the question
that we had is how can bacteria these
primitive organisms tell the difference
from times when they're alone and times
when they're in a community and then all
do something together and what we
figured out is that the way that they do
that is that they talk to each other and
they talk with a chemical language so
this is now supposed to be my bacterial
cell when it's alone it doesn't make any
light but what it does do is to make and
secrete small molecules that you can
think of like hormones and these are the
red triangles and when the bacteria is
alone the molecules just float away and
so no light but when the bacteria grow
and double and they're all participating
in making these molecules the molecule
the extracellular amount of that
molecule increases in proportion to cell
number and when the molecule hits a
certain amount that tells the bacteria
how many neighbors they are they
recognize that molecule and all of the
bacteria turn on light in synchrony and
so that's how bioluminescence Works
they're talking with these chemical
words and the reason that vibrio fisher
is doing that comes from the biology so
again another plug for the animals in
the ocean Vio fish frry lives in this
squid what you're looking at is the
Hawaiian bobtail squid and it's been
turned on its back and what I hope you
can see are these two glowing loes and
these house the vibal feriz cells they
live in there at high cell number that
molecule is there and they're making
light and the reason the squid is
willing to put up with these Shenanigans
is because it wants that light and so
the way that this symbiosis works is
that this little squid lives just off
the coast of Hawaii so just in sort of
shallow kneee water and the squid is
nocturnal so during the day it buries
itself in the sand and sleeps but then
at night it has to come out to hunt and
so on bright nights when there's lots of
Starlight or Moonlight that light can
penetrate the depth of the water the
squid lives in since it's just in those
couple feet of water and what the squid
has developed is a shutter that can open
and close over this specialized light
organ housing the bacteria and then it
has detectors on its back so it can
sense how much Starlight or Moonlight is
hitting its back and it opens and closes
the shutter so the amount of light
coming out of the bottom which is made
by the bacterium exactly matches how
much light hits the Squid's back so the
squid doesn't make a Shadow so it
actually uses the light from the
bacteria to counter illuminate itself in
an anti-predation device and so it so
predators can't see its shadow calculate
its trajectory and eat it and so this is
like the stealth bomber of the
ocean but then if you think about it
this squid has this terrible problem
because it's got this D ing thick
culture of bacteria and it can't sustain
that and so what happens is every
morning when the sun comes up the Squid
goes back to sleep it buries itself in
the sand and it's got a pump that's
attached to its circadian rhythm and
when the sun comes up it pumps out like
95% of the bacteria and so now the
bacteria are dilute that little hormone
molecule is gone so they're not making
light but of course the squid doesn't
care it's asleep in the sand and as the
day goes by the bacteria double they
release the molecule and then light
comes on at night exactly when the squid
wants it and so first we figured out how
and this bacterium does this but then we
brought the tools of molecular biology
to this to figure out really what's the
mechanism and what we found so this is
now supposed to be again my bacterial
cell is that vibrio fishery has a
protein that's the red box it's an
enzyme that makes that little hormone
molecule the red triangle and then as
the cells grow they're all releasing
that molecule into the environment so
there's lots of molecule there and the
bacteria also have a receptor on their
cell surface that fits like a lock and
key with that molecule these are just
like The receptors on the surfaces of
your cells and so when the molecule
increases to a certain amount which says
something about the number of cells it
locks down into that receptor and
information comes into the cells that
tells the cells to turn on this
Collective behavior of making light and
why this is interesting is because in
the past decade we have found that this
is not just some anomaly of this
ridiculous glow-in-the-dark bacterium
that lives in the ocean all B have
systems like this so now what we
understand is that all bacteria can talk
to each other they make Chemical words
they recognize those words and they turn
on group behaviors that are only
successful when all of the cells
participate in unison and so now we have
a fancy name for this we call it Quorum
sensing they vote with these chemical
votes the vote gets counted and then
everybody responds to the vote and
what's important for today's talk is
that we know that there are hundreds of
behaviors that bacteria carry out in
these Collective
Fashions but the one that's probably the
most important to you is virulence so
it's not like a couple bacteria get in
you and then they start secreting some
toxins you're enormous that would have
no effect on you you're huge but what
they do we Now understand is they get in
you they wait they start growing they
count themselves with these little
molecules and they recognize when they
have the right cell number that if all
of the bacteria launch their virulence
attack together they're going to be
successful at overcoming an enormous
host so bacteria always control
pathogenicity with chorum sensing and so
that's how it works we also then went to
look at what are these molecules so
these were the red triangles on my
slides before and so this is the vibal
fisheri molecule this is the word that
it talks with and then we started to
look at other bacteria and these are
just a smattering of the molecules that
we've discovered and what I hope you can
see is that the molecules are related so
the leftand part of the molecule is
identical in every single species of
bacteria but but the right hand part of
the molecule is a little bit different
in every single species and what that
does is to confer Exquisite species
specificities to these languages so each
molecule fits into its partner receptor
and no other so these are private secret
conversations these conversations are
for intas species communication each
bacteria uses a particular molecule
that's it Lang its language that allows
it to count its own
siblings and so once we got that far we
thought we were starting to understand
that bacteria have these social
behaviors but we started what we were
really thinking about is that most of
the time bacteria don't live by
themselves they live in incredible
mixtures with hundreds or thousands of
other species of bacteria and that's
depicted on this slide this is your skin
so this is just a picture a micrograph
of your skin anywhere on your body it
looks pretty much like this and what I
hope you can see is that there's all
kinds of bacteria there and so we
started to think if this really is about
Communication in bacteria and it's about
counting your neighbors it's not enough
to be able to only talk within your
species there has to be a way to take a
census of the rest of the bacteria in
the population so we went back to
molecular biology and started studying
different bacteria and what we found now
is that in fact bacteria are
multilingual so they all have a species
specific system they have a molecule
that says me but then running in
parallel to that is a second system that
we've discovered that's generic so they
have a second enzyme that makes a second
signal and it has its own receptor and
this molecule is the trade language of
bacteria it's used by all different
bacteria and it's the language of inter
species communication and so what
happens is that bacteria are able to
count how many of me and how many of you
and they take that information inside
and they decide what tasks to carry out
depending on who's in the minority and
who's in the majority of Any Given
population and so then again we turn to
chemistry
and we figured out what this generic
molecule is so that was the pink ovals
on my last slide this is it it's a very
small five carbon molecule and what the
important thing is that we learned is
that every bacterium has exactly the
same enzyme and makes exactly the same
molecule so they're all using this
molecule for interspecies communication
so this is the bacterial espiranto
and so once we got that far we've
started to learn that bacteria can talk
to each other with this chemical
language but what we started think is
that maybe there's something practical
that we can do here as well so I've told
you that bacteria do have all these
social behaviors that they communicate
um with these molecules and of course
I've also told you that one of the
important things they do is to initiate
pathogenicity using corm sensing so we
thought what if we made these bacteria
so they can't talk or they can't hear
couldn't these be new kinds of
antibiotics and of course you've just
heard and you already know that we're
running out of antibiotics bacteria are
incredibly multi- drug resistant right
now and that's because all of the
antibiotics that we use kill bacteria so
they either pop the bacterial membrane
they make the bacterium so it can't
replicate its DNA we kill bacteria with
traditional antibiotics and that selects
for resistant mutants and so now of
course we have this Global problem in
infectious diseases so we thought well
what if we could sort of do Behavior
modifications just make these bacteria
so they can't talk they can't count and
they don't know to launch virulence and
so that's exactly what we've done and
we've sort of taken two strategies the
first one is we've targeted the intras
species communication system so we've
made molecules that look kind of like
the real molecules which you saw but
they're a little bit different and so
they lock into those receptors and they
Jam recognition of the real thing and so
by targeting the red system what we are
able to do is to make species specific
or disease specific anticor sensing
molecules we've also done the same thing
with the pink system we've taken that
Universal molecule and and turned it
around a little bit so that we've made
antagonists of the inter species
communication system and these the hope
is that these will be used as
broadspectrum antibiotics that work
against all bacteria and so to finish
I'll just show you the strategy and this
one I'm just using the inters species
molecule but the logic is exactly the
same so what you know is that when that
bacterium gets into the animal in this
case a mouse it doesn't initiate
virulence right away it gets in it
starts growing it starts secreting its
corn sensing molecules it recognizes
when it has enough bacteria that now
they're going to launch their attack and
the animal dies and so what we've been
able to do is to give these virulent
infections but we give them in
conjunction with our anti-m sensing
molecules so these are molecules that
look kind of like the real thing but
they're a little bit different which
I've depicted on this slide and what we
now know is that if we treat the animal
with a pathogenic bacterium a multi-drug
resistant pathogenic bacterium in the
same time we give our anti-m sensing MO
molecule in fact the animal lives and so
we think that this is the next
generation of antibiotics and it's going
to get us around at least initially this
big problem of resistance so what I hope
you think is that bacteria can talk to
each other they use chemicals as their
words they have an incredibly
complicated chemical lexicon that we're
just now starting to learn about and of
course what that allows bacteria to do
is to be multicellular right and so in
the spirit of Ted they are doing things
together because it makes a difference
right so what happens is that bacteria
have these Collective behaviors and they
can carry out tasks that they could
never accomplish if they simply acted as
individuals and and what I would hope
that I could further argue to you is
that this is the invention of
multicellularity bacteria have been on
the year uh on the earth for billions of
years humans couple hundred thousands so
we think bacteria made the rules for how
multicellular um organization works and
and we think by studying bacteria we're
going to be able to have insight about
multicellularity in the human body so we
know that the principles and the rules
if we can figure them out in these sort
of primitive organisms the hope is that
they will be applied to other human
diseases and human behaviors as
well I hope that what you've learned is
that bacteria can distinguish self from
others so by using these two molecules
they can say me and they can say you and
again of course that's what we do both
as mole in in a molecular way and then
also in an outward way but I think about
the molecular stuff this is exactly what
happens in your body it's not like your
heart cells and your kidney cells get
all mixed up every day and that's
because there's all of this chemistry
going on these molecules that say who
each of these groups of cells is and
what their tasks should be and so again
we think that bacteria invented that and
then you've just evolved a few more
bells and whistles but all of the ideas
are in these simple systems that we can
study and then the final thing is again
just to reiterate that there's this
practical part and so we've made these
anti form sensing molecules that are
being developed as new kinds of
Therapeutics but then to finish with a
plug for all the good and miraculous
bacteria that live on the earth we've
also made proor sensing molecules so
we've targeted those systems to make the
molecules work better and so remember
you have these 10 times or more
bacterial cells in you or on you keeping
you healthy what we're also trying to do
is to beef up the conversation of the
bacteria that live as mutualists with
you in the hopes of making you more
healthy making those conversations
better so bacteria can do things that we
want them to do by in better than they
would be on their own and then finally I
want to just show you this is my gang at
Princeton New Jersey everything I told
you about was discovered by someone in
that picture and I hope when you learn
things like about how the natural world
works I just want to say that whenever
you read something in the newspaper you
get to hear some talk about something
ridiculous in the natural world it was
done by a child so science is done by
that demographic they all of those
people are between 20 and 30 years old
and they are the engine that drives
scientific discovery in this country and
it's a really lucky demographic to work
with I keep getting older and older and
they're always the same age and it's
just an a crazy delightful job and I
want to thank you for inviting me here
it's a big treat for me to get to come
to this
conference thanks
than
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