- Sometimes you come across a paper
that really helps you understand the whole collective state
of our knowledge on a given subject.
I recently came across a paper like that.
It was all about probiotics in relation to coral.
How do microbes affect the corals that they live on and in?
How do they get there in the first place?
Are corals just born preceded with all of those microbes?
Or can we maybe manipulate the microorganisms
to make our corals more healthy, grow faster, be stronger?
Maybe put a bit of probiotic solution
into a shipping bag
to protect the coral from temperature stress.
Hey, guys and girls, I'm ReefMan.
And this time we are gonna talk about a paper
that was just published.
It's titled "Coral Probiotics: Premise, Promise, Prospects."
It was published in the Annual Review of Animal Bioscience
and like always,
you can find a link to the paper itself down there
in the description below.
In this case,
I would strongly encourage you to read the actual paper.
It's an amazing overview of the science as we know it
behind probiotics for coral,
it's got a great set of sources as well.
The authors might be familiar to us as well.
Raquel Peixoto is the lead author
and we've covered her papers before on probiotics.
Michael Sweet is another name you might know of,
he was involved with the paper on captive bred corals
that I covered on this channel a while back.
The authors of this paper are from all over the world,
it's really an amazing group of authors,
all the way from Brazil to Saudi Arabia,
to the United Kingdom to Australia,
the whole world is involved in this research.
So how do microorganisms actually affect coral?
We're not just talking about bacteria here,
viruses, even the symbiotic dinoflagellates
that provide our coral with food, qualify.
Symbiodinium, those are the dinoflagellates
that provide about 90% of the energy needs of our coral.
This is why we need such strong lights over our tank,
'cause they're photosynthetic.
These guys live in the tissue of our coral
and photosynthesize, just like a plant,
giving a lot of the resulting chemical energy
back to the coral that houses them.
But it's not just Symbiodinium.
There are a whole world of other bacteria
on and in our coral.
There are viruses too.
Viruses that infect the coral
and also viruses that infect the bacteria
living with the coral.
Some of those bacteria cause disease.
Although we actually only know of about 28 coral diseases
and of those 28, we only know what causes them in six cases.
Obviously, there's a lot more to learn here
but as you can imagine,
it's not easy to sample
or even find sick corals in the wild a lot of the time.
Both coral cells and symbiodinium lack the ability
to produce vitamin B12,
yet it's a critical thing that's important for life
and used for things like amino acids in our cells.
In fact, the bacteria that live in the coral's gut
is now thought to produce
not only vitamin B12 that the coral needs,
but also biotin which is also called vitamin H,
thiamine, vitamin B1 and even riboflavin or vitamin B.
So those microbes are providing a whole wealth
of different vitamins
that the coral would otherwise just totally lack
and not survive.
The paper included this amazing image
that I'm showing you, the different micro organisms
and how they can impact our coral.
The coral houses all these different things,
but they can help with nutrient cycling
as the bacteria and archaea do,
they can provide organic carbon like the symbiodiniceae,
they can control infectious diseases like viruses do
and they can even make
and contribute antibiotics back to the coral,
like we found some fungi doing.
It really is an amazing microscopic ecosystem,
a microbiome right there in our tanks
in the coral right in front of her eyes.
I will not look at coral the same way again,
after reading this paper.
What are beneficial microorganisms for corals?
After all, we're interested in building this microbiome
to help us combat chemical contamination disease
and even the warming caused by climate change.
We found microbes that can do all of that.
Microbes that live naturally on corals
but which we can culture in our labs or facilities
and re-introduce when we wanna solve a problem
that we're seeing effect the coral.
We've already proven that this works in amphibians, bees,
even in bats and of course, coral.
So we know the science is solid.
It works on the same principle
behind you eating some probiotic yogurt
when you're having to digestive issues, we know it works.
The coral probiotic hypothesis was created
to explain observations that coral health varied
with changes in the composition of its microbial community.
That hypothesis states
that alterations in that mix of microbes
can help coral adapt to changing environmental conditions.
Some corals are more receptive
to us modifying their microbiome than others
but it does seem to work at some level in nearly all corals
that we've tried it on.
The term beneficial microorganisms for coral was coined
to describe those specific species of microorganisms,
which exhibit those beneficial effects on corals.
By adding certain strains of bacteria, fungi,
or even viruses to a coral,
we can help it survive oil spills,
increased ocean temperatures,
or even infection with bacteria
that might otherwise kill it.
It's an interesting idea.
One of the things that kills a lot of coral in transit
when we're just trading or selling frags in the hobby
is the lack of temperature control.
If we could add the probiotic dinoflagellate
durusdinium trenchii to the water maybe a day
or two before sending it out, we would inoculate the coral
and that would then give it some protection
against those temperature extremes.
And then hopefully, we could reduce the number of frags
that die in transit in the hobby.
Similarly, we could do the same on wild reefs
to help limit the impact of temperature related bleaching.
Microbes can also influence coral calcification
and the rate they grow.
Some of those microbes actually live in the skeleton itself
where they associate with a certain kind of fungus
that helps skeletal cells live longer.
This particular fungus is really interesting.
It does have an impact on the growth of coral skeleton
but we think that it might actually be having that impact
to offset damage that's caused by the fungal infection.
Scientists are currently looking at this,
if we could maybe limit the damage
but keep the impact it has on those skeletal cells
and the growth,
it could be a great way
to just improve the overall growth of stony coral
in both the ocean and our reef tanks.
Some microbes even break down skeleton
when the coral is bleached and stressed,
when the microbes are not protected from the sun
as much by the pigments
that would otherwise be in the coral.
This provides the coral with an energy source
even when it's completely bleached
literally eating its own skeleton
as a last ditch effort to stay alive
when the coral is severely stressed.
Those microbes in particular are called endoliths
and we usually think of them growing
amongst the microscopic little pores in rocks,
even deep in the earth.
But I guess a coral skeleton
really isn't that far off from a rock if you think about it,
and they grow in the skeleton as well.
The microbiome of corals
can protect against toxic compounds, even oil spills.
Some of the compounds that they create
combat the buildup of reactive oxygen species
which would otherwise damage the DNA,
the genetic material inside the cells.
Now, maybe like you,
I had never heard of a reactive oxygen species before,
but it's really simple,
it's just a group of chemicals
that are formed in cells when oxygen is used.
If too much of those buildup,
they damage the genetic material in the cell,
causing the cell to die or maybe become cancerous, bad news.
As temperatures increase,
corals produce more and more reactive oxygen species,
those chemicals.
So it is important for our corals
to have some way to produce antioxidants to combat them.
The bacteria living in their tissues, you guessed it,
they produce a large percentage of those antioxidants.
We have actually manually tested that
by adding those antioxidants
to coral that's suffering from bleaching due to heat stress.
Through those experiments, we've proven
that antioxidants do help corals survive bleaching.
So perhaps we can see the corals tissue with those microbes,
knowing that they would continue
to produce those protected compounds
and that would provide
a long lasting level of protection against bleaching
and ocean warming or stress in our fish tanks.
The microbes that live in coral
also contain a lot of carcinoids,
compounds that act a bit like sunscreen,
they block UV radiation, things like that.
Symbiodinium produces a lot of dimethylsulfonipopionate
or DMSP, which also helps to control
the reactive oxygen species,
produced by cellular respiration.
Exposing a coral to copper
actually significantly reduces the amount of that DMSP,
which is available,
and that might be
why we can never use copper medications with coral.
We would just suffocate them, reduce that chemical.
Another interesting thing that microorganisms do
is control the growth of other microorganisms.
As you know, some bacteria
and viruses are gonna make you sick,
they make coral sick too.
And so this pathogen control
can be an immense help to the coral.
Some microorganisms, those fungi, produce antibiotics
that prevent others from getting established.
Other bacteria actually change the pH of coral mucus
making it less hospitable to invading organisms.
This could be something that could be very useful
for our reef tanks in addition to the wild reefs.
When coral dies in our tanks,
it's rarely because of physical trauma, physical damage.
I strongly believe that most of the time,
when we experience RTN or STN, it's not just magic,
what we're actually seeing is the result of an infection,
moving through the tissue of our coral.
Being able to inoculate our tanks in coral
with a bacterial strain
that might help prevent that could be huge.
In fact, viruses can infect bacteria just as easily as us
and some viruses are being used to infect
and kill pathogenic coral bacteria in labs today.
So we might be able to use viruses in our battle as well
against coral disease in our tanks.
I ran across another interesting thing I hadn't heard of,
quorum sensing, I'd never heard of that before.
It's a way that bacteria and even some insects
can communicate using chemical signals between each other.
And then that allows them to trigger a change
when their density gets high enough.
Think of it as if you were a king in a medieval castle,
and you wanted to invade a nearby castle.
You'd build up your army over time, train them up,
and once you had enough members in your army,
you'd change their behavior.
Instead of just training in your castle,
they'd invade nearby castle.
It turns out that some bacteria do the same thing.
Some bacteria is benign until enough of it grows,
until that colony becomes dense enough
then it triggers a change
and it causes damage to the coral and it bleaches.
So you guys too, bacteria can help here too.
Some types of bacteria actually break down
and block those chemical signals, which are produced,
which tell other nearby bacteria how dense the colony is.
If we can block those signals, quorum sensing can't happen,
and the bad bacteria never globalizes
and the coral is protected.
So where do those microorganisms come from
in the first place?
It's clear that there's numerous ways
that microorganisms can help our coral,
and hopefully soon in our tanks
we'll be able to maybe apply a paste or something over STN
which will help slow it down or even treat it.
But in the wild, where do those organisms originate?
How do corals get them in the first place?
Well, there's a few ways.
Broadcast spawning corals like Acropora
seem to get them from the water.
As you know, ocean water, even our reef tank water,
is a soup of bacteria
and Acropora collect this in their mucus as they grow
and that's why each colony has a unique microbiome
based largely on where it grew up.
The bacteria is just picked up
while the Acropora larva are floating through the water
and that bacteria and biofilms that it creates
even helps those larva settle out of the water
and get a strong hold on the rock
where they're going to grow.
There are also brooding corals like (indistinct) though,
corals that brute like that,
and don't broadcast their larva into the water,
transmit their microbiome
directly from the parent to the offspring.
As the baby corals are developing,
they're exposed directly to their parent's microbiome
and to a large extent,
they'll have the same microbiome as they grow up.
Okay, so if bacteria can be so helpful to our coral,
how can we get the bacteria to our corals?
This is actually a problem
that's much harder in the ocean than in reef tanks.
The current and waves
quickly wash away any fluid you might spread around a coral.
That means we need to immobilize it somehow.
And various natural and synthetic gels
are being investigated to help keep the microbes
in close contact with the target coral.
In an aquarium, it would be really pretty easy
to inoculate the entire tank
but you can't do the same in the ocean.
There are some inventive ways to solve this,
maybe using weighted plastic drapes to limit water movement
around a coral or using gels like I mentioned,
or even packaging up the probiotics inside something else,
something the coral would eat like a rotifer.
As long as the coral is willing to eat the rotifer,
you've got the probiotics in the coral
where they won't be easily washed away.
Using a living organism like this
to distribute the probiotics is also something
that would work well in our tanks
but it's probably not gonna really happen
on the hobbyist level
due to the difficulty in raising those live foods,
not many of you have rotifer cultures at home,
not to mention you also have to culture the probiotics
and get them inside those rotifers somehow.
So this paper, really, believe me,
it's super interesting, and you should check it out.
It's very much worth checking out
and it goes into way more detail
than I ever could in his video.
And I think you'll agree, it's probably long enough already.
As you can tell, I'm super excited for the coral
or for the future of coral probiotics.
They hold so much promise
and solve so many problems for the world's reefs
and by extension for our reef tanks.
Thanks for watching.
Let me know down below what you thought
and if you enjoyed the video,
then give it a thumbs up.
Otherwise, stay safe, have a great day.
I'll see you next time. Bye.