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Do microbes ever feel fear?
Or concern?
Or trepidation?
While they can’t of course tell us, they probably don’t–
at least not in ways that we could understand.
But we can tell that they definitely experience stress.
Now, that stress is not terribly similar to what we experience when tax season rolls around
or a traffic jam makes you late for an important meeting.
The microbial world is mercifully free of such troubles.
But at its core, what microbes experience is stress nonetheless -
the recognition of, and response to, less-than-ideal circumstances.
And when you think about it, of course the microcosmos, can be a very stressful place -
from shifts in food availability, to sudden temperature swings, to changes in pH that
can begin picking apart a microbe molecule by molecule.
All in all, there’s a lot going on that can get in the way of microbes
living their best lives.
So maybe it is no surprise that, naturally, stressed microbes are everywhere.
Like a bear going into hibernation through a frigid winter, this tardigrade, also known
as a water bear, has seemingly given up trying to face the stresses of the world.
Instead, it is lying motionless in a state of reduced metabolic activity, almost as if
it is simply waiting for all of its problems to disappear.
It has formed a durable and protective cyst, and it will stay in there until more favorable
conditions arise.
And it can stay encysted like this for months, to be woken up by a change in seasons, perhaps.
Microbes from all domains of life have evolved similar abilities to outlast those trying times.
And they do this by entering extended periods of reduced metabolic activity, or dormancy.
Because, while microbes can be found everywhere you point your microscope, that doesn't mean
they can thrive just anywhere.
Each species has its own preferences when it comes to habitat, its own comfort zone
that is specific to its biology and way of life.
Holophyra ciliates, for example, prefer non-acidic habitats that have plenty of dissolved oxygen.
If these ciliates find themselves in a more stressful acidic environment, they, too, form
cysts and sit tight, waiting for the world to change.
If they’re lucky, that change might arrive in the form of heavy rains that increase the
pH of those puddles and pools that their cysts lie dormant in.
Sensing a more hospitable habitat, they re-awaken, face the day, and go about their ciliate business.
Now cysts are not the only way members of the microcosmos can enter the liminal boundary
between life and death, though.
These bacteria have found another way to cope.
The brighter pockets at their tips are the first stages of their last resort to stress.
Maybe it’s a lack of nutrients in the sample, maybe the pH levels don't suit them.
Whatever it is that’s left them distressed, their coping mechanism is unfolding.
They’re each building a cellular bunker, a spore, which we can see forming here.
Their DNA and essential cellular machinery will be almost completely dehydrated and tightly
packaged inside the spore’s thick envelope.
Eventually, the spore will abandon the cell altogether, jettisoning like an escape pod
as the mother cell undergoes a self-destruct sequence.
In their spore form, with their metabolism at minimum possible levels, they can last
for decades or even centuries, protected from the harshest of conditions, biding their time.
But until then, they are part of the ecosystem’s microbial seed bank -
the repository of dormant microorganisms too stressed out by local conditions to fully
live their lives, but also too stubborn to die.
Seed banks are a big deal in the microscosmos.
They allow species to enter cold storage when times are tough.
In that seed bank, species have tapped out of the stressful game of life or death.
They’ve found a temporary third option.
And when they awaken, whole microbial ecosystems can simply pick back up where they left off.
You can wake up a seedbank yourself and watch it happen at home.
All you need is some food and, of course, a microscope.
If you soak the vegetables and herbs destined for your next meal in water overnight and
check the water under your microscope the next day, you are pretty much guaranteed
to spot some colpodids swimming around.
You have just enticed them out of the seed bank –
by providing them with a welcomingly wet habitat, you triggered them to ‘excyst’.
Not to exist, ‘ex-cyst’.
Colpodid ciliates can be found in soils around the world and they will often hitch a ride
on the surfaces of your food.
Now, do not lose any sleep over the idea that you are exposed to and are ingesting dormant
microbes throughout your day.
That is just part and parcel of life on this planet I promise, like you consume them just
breathing- it's just one of many of the bridges between us and the microcosmos.
Encysted colpodids are not dangerous, they’re just sleepy stowaways, making the trip from
the soil, to the surface of a tomato, and then, into your mouth.
James, our master of microscopes, often tries a few different tricks to coax stressed out
microbes back into excystence.
And using different chemical cues, he can activate the dormant cysts and spores
of different organisms.
If he wants to awaken the seedbanks of microbes that have a particular love of sulfur, for
example, he might add the yolk of a cooked egg to the sample.
For others, the wake up call comes in the form of fertilizer, which provides nitrogen
and phosphorus.
This stage that we’re looking down at right now can host an endless combination of casts
performing an endless number of plays, it all comes down to direction.
It seems wherever you look in the microcosmos, microbes enduring stressful conditions can
be found, suspended in a twilight zone between life and death, each species sitting, waiting,
holding out hope for their own version of paradise to appear.
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
And thank you again to our amazing supporters over at Patreon.com/JourneytoMicro.
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I am so happy to have been able to be a part of the creation of this show and thank you
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Thank you so much.
If you want to see more from our master of microscopes, James Weiss, you can check out
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