Around the age when my interest in boys
went from beating them at monkey bar
tag to stealing smooches behind the high
school, my mum had the sex talk with
me.
We talked about consent, respect, not
getting pregnant and very importantly: “do
not get a sexually transmitted disease.”
No glove, no love.
This was, of course, very good advice. It’s
thought by the World Health Organization
that worldwide, more than one million
people a day acquire a sexually
transmitted disease (STD). Some of these
infections will affect your fertility, others
cause even more worrying health issues.
There are many reasons to prevent these
unwanted travellers from taking up
residence in our body.
The nasty rep of STDs or STIs (sexually
transmitted infections) could be why very
little consideration is given to the idea
that some of the microbes hitching a ride
between individuals on the sexual fluids
highway, might be beneficial. What if, in
protecting ourselves from the bad bugs
we know about, we’re missing out on
microbes that could provide all sorts of
benefits?
A growing body of evidence suggests
there is good reason to have a closer
look.
It’s not news that microbes - such as
bacteria and viruses - are incredibly
important to our health. Within all of us
there is a mixture of both beneficial and
potentially disease-causing mini critters. If
the balance between the two is lost, it
can cause problems.
Our bodies have co-evolved with
microbes
For example, the Candida genus of yeast
is a naturally occurring microbe found in
the vagina. Its growth is kept in check by
another microbe, the Lactobacillus
bacteria. However, if something prevents
the bacteria from doing its job, the result
is an overgrowth of yeast, causing the
uncomfortable symptoms of a yeast
infection.
Full of bugs
Our bodies have co-evolved with
microbes. These bacteria, fungi and
viruses are on our skin, in our gut and
part of our genitalia. While it’s not
pleasant to think about bacteria running
rampant in our colons, it’s becoming ever
clearer that microbes play a key role in
our very make up.
The first step to understanding the role
microbes play is to identify them. Those
that come with sex are called sexually
transmitted microbes (STMs). Although
we don't yet know much about them,
there are some fascinating examples that
should motivate researchers to take a
closer look, says Chad Smith, an
evolutionary biologist from the University
of Texas, US.
Take the pea aphid. It’s a juice-sucking
insect that makes its way around the
globe syphoning the life from legumes.
Their success could in part be attributed
to beneficial STMs that pass between
them while mating. The effects are as
follows: resistance to parasitoids (that kill
or sterilise the host), better tolerance to
heat and an improved ability to survive on
plants that aren’t legumes, until they find
their next meal.
Not to be outdone, some mosquitoes
have sexually transmitted bacteria that
colonise their gut, testes and the surface
of developing eggs. It’s thought this
bacterial coating provides nutrition for the
larvae, allowing them to develop two to
four days faster than those without it.
Finally, in fungi, beneficial STMs have
also been found to increase their
tolerance to heat as well as helping their
host grow more quickly.
But what about humans? We now know
there is one persuasive example that an
STM may do some of us some good.
It's in the form of the GB virus C (GBC-
C) formerly known as hepatitis G virus
(HGV). It's a sexually transmitted
infection that on its own does not appear
to cause any major symptoms, though it
is often found with other disease-causing
viruses such as HIV.
It can reduce the chance of
mothers with HIV passing the
infection onto their children
A six-study review found that it was
associated with a 59% reduction in the
mortality rate of HIV patients. Scientists
think GBV-C does this by reducing HIV’s
ability to compromise our immune
system cells. It may also stimulate other
parts of the immune system to actively
fight the infection.
GBV-C can also be passed from mother
to child. This is good news as it can
reduce the chance of mothers with HIV
passing the infection onto their children.
More recently, GBV-C has also been
linked to reduced mortality in those
infected with the Ebola virus, somehow
reducing the impact of the virus on its
host. Understanding how could save lives.
Extraordinary discoveries such as this
should make us wonder what else we are
missing, says Betsy Foxman, of the
University of Michigan, US.
In the past we’ve characterised sexually
transmitted microbes as bad, she says.
The preventative measures we’ve taken to
protect against them may mean that we
now lack some that are potentially
beneficial.
There are likely a host of
beneficial organisms yet to be
identified
Foxman would like to see more work
done on the benefits of one pathogen
interfering with another. “What could our
body have on it that would keep it
healthier [for] longer?”
There may even be microbes that help
target other kinds of infections, Foxman
says. If there are, these could reduce our
dependence on medicines such as
antibiotics. They often kill a broad
spectrum of microbes in order to
eradicate the one that is problematic.
Of course, at times antibiotics are
necessary to save lives, but it would be
“nice to have something a little more
judicious and targeted”, Foxman adds.
We're not sure which beneficial STMs are
passing between people, but Foxman
suggests Lactobacillus , the bacteria found
in yogurt and naturally present in
humans, is one of them. There are likely
a host of other beneficial organisms yet
to be identified, she says.
Cost benefit
This all sounds like great news, right?
There could be a whole bunch of little
known STMs floating around that could
be beneficial to our health.
Microbes that cause sexual
diseases need to ensure they can
hop from human to human
There’s just one problem. If we get them
by having sex that leaves us open to
getting other harmful infections as well.
There may be other ways to acquire them
in the future. Once beneficial STMs are
identified, scientists working in public
health can hopefully develop safe ways to
inoculate people, or figure out how to
replicate their effects, without risking
unprotected sex.
Most sexually transmitted infections such
as chlamydia and gonorrhoea don’t tend
to kill their hosts. They are also often
asymptomatic. “They’re just trying to
make a living,” says Foxman.
There could even be certain STMs
that encourage humans to have
sex more often
Microbes that cause sexual diseases need
to ensure they can hop from human to
human. This transaction is more likely to
happen if the person hosting the
microbes appears healthy, she adds. “If
someone looks sick, from an evolutionary
standpoint, they’re a bad bet,” she says.
It could be that as humans evolved, well
before condoms existed, the risk of
getting an STD was, at times, outweighed
by acquiring an important microbe. It’s an
evolutionary cost-benefit analysis, says
Smith.
Those who carry beneficial STMs could
even be unknowingly signaling that they
do so, says the evolutionary biologist
Michael Lombardo. They might then be
favoured as mates.
It gets more complicated. It may not just
be the physiological benefits, such as
disease prevention or tolerance to heat,
that make certain STMs advantageous.
These microbes could also affect their
host's behavior in a good way.
That microbes can do so is a relatively
new and promising area of research. For
example, certain gut bacteria are thought
to affect the brains of young mice,
reducing their anxiety levels.
Individuals that mate with more
than one partner are more likely
to acquire a beneficial STM
Microbes may also modify the chemical
signals that animals produce, says Smith.
This was discovered in research on fruit
flies as they acquired bacteria from
different diets. The result? Fruit flies
preferred to mate with others that shared
those same microbial communities.
Getting around
These are examples of gut bacteria
altering behaviour and therefore mate
choice, but can sexually transmitted
microbes do the same?
There is little evidence for this so far,
says Smith, but it would make sense. If a
male has a beneficial microbe and it has
a positive affect on him, females that
choose to mate with him would acquire it
too, he adds.
“Individuals that mate with more than one
partner are more likely to acquire a
beneficial STM,” says Smith. If that’s the
case, it could be one of the reasons a
species might favour mating with more
than one partner.
In the common lizard, for example, the
females that mate with more than one
partner have been found to have more
diverse microbial communities than those
that don’t. Scientists who study them
speculate that this could mean a
difference in health between sexually
active females and asexual reproducers.
Lombardo believes that some female
birds that mate repeatedly with the same
partner, or with more than one partner,
may receive benefits from STMs by
acquiring viruses that kill harmful
bacteria, or by acquiring less virulent
strains of pathogens.
These could limit the impact of more
virulent strains. Beneficial microbes that
produce bacteria-killing chemicals could
also help fight existing infections. This is
one of many theories that attempts to
explain why birds have extramarital sex
outside their main partnership.
There could even be certain STMs that
encourage humans to have sex more
often, says Foxman.“What if it just felt
better to have sex when you had a
particular bug?
“That bug could increase mucus flow. It
could be as simple as that.”
Foxman says there are conditions in both
men and women that create chronic pain
feedback loops related to sexual activity,
yet their cause is unknown. To identify a
beneficial STM that would alleviate these
conditions could mean all the difference
to a person’s sex life. It’s worth looking
into, she says.
“We are sexual beings. Things that make
people feel better sexually, tend to make
them feel better overall.”
It appears that whether you’re an aphid,
bird, lizard or human, odds are that you
are never quite alone with a mate. There
are perhaps thousands of other
organisms waiting for the magic to
happen so that they can make their way
back and forth between you, and perhaps
out into the population.
We may know more of them soon. Smith
says that with the exciting and explosive
growth of interest and research into the
human microbiome, there are now “new
techniques to survey and quantify the
function of microbes that we didn’t have
ten years ago.”
In the mean time, stay tuned and play
safe.
went from beating them at monkey bar
tag to stealing smooches behind the high
school, my mum had the sex talk with
me.
We talked about consent, respect, not
getting pregnant and very importantly: “do
not get a sexually transmitted disease.”
No glove, no love.
This was, of course, very good advice. It’s
thought by the World Health Organization
that worldwide, more than one million
people a day acquire a sexually
transmitted disease (STD). Some of these
infections will affect your fertility, others
cause even more worrying health issues.
There are many reasons to prevent these
unwanted travellers from taking up
residence in our body.
The nasty rep of STDs or STIs (sexually
transmitted infections) could be why very
little consideration is given to the idea
that some of the microbes hitching a ride
between individuals on the sexual fluids
highway, might be beneficial. What if, in
protecting ourselves from the bad bugs
we know about, we’re missing out on
microbes that could provide all sorts of
benefits?
A growing body of evidence suggests
there is good reason to have a closer
look.
It’s not news that microbes - such as
bacteria and viruses - are incredibly
important to our health. Within all of us
there is a mixture of both beneficial and
potentially disease-causing mini critters. If
the balance between the two is lost, it
can cause problems.
Our bodies have co-evolved with
microbes
For example, the Candida genus of yeast
is a naturally occurring microbe found in
the vagina. Its growth is kept in check by
another microbe, the Lactobacillus
bacteria. However, if something prevents
the bacteria from doing its job, the result
is an overgrowth of yeast, causing the
uncomfortable symptoms of a yeast
infection.
Full of bugs
Our bodies have co-evolved with
microbes. These bacteria, fungi and
viruses are on our skin, in our gut and
part of our genitalia. While it’s not
pleasant to think about bacteria running
rampant in our colons, it’s becoming ever
clearer that microbes play a key role in
our very make up.
The first step to understanding the role
microbes play is to identify them. Those
that come with sex are called sexually
transmitted microbes (STMs). Although
we don't yet know much about them,
there are some fascinating examples that
should motivate researchers to take a
closer look, says Chad Smith, an
evolutionary biologist from the University
of Texas, US.
Take the pea aphid. It’s a juice-sucking
insect that makes its way around the
globe syphoning the life from legumes.
Their success could in part be attributed
to beneficial STMs that pass between
them while mating. The effects are as
follows: resistance to parasitoids (that kill
or sterilise the host), better tolerance to
heat and an improved ability to survive on
plants that aren’t legumes, until they find
their next meal.
Not to be outdone, some mosquitoes
have sexually transmitted bacteria that
colonise their gut, testes and the surface
of developing eggs. It’s thought this
bacterial coating provides nutrition for the
larvae, allowing them to develop two to
four days faster than those without it.
Finally, in fungi, beneficial STMs have
also been found to increase their
tolerance to heat as well as helping their
host grow more quickly.
But what about humans? We now know
there is one persuasive example that an
STM may do some of us some good.
It's in the form of the GB virus C (GBC-
C) formerly known as hepatitis G virus
(HGV). It's a sexually transmitted
infection that on its own does not appear
to cause any major symptoms, though it
is often found with other disease-causing
viruses such as HIV.
It can reduce the chance of
mothers with HIV passing the
infection onto their children
A six-study review found that it was
associated with a 59% reduction in the
mortality rate of HIV patients. Scientists
think GBV-C does this by reducing HIV’s
ability to compromise our immune
system cells. It may also stimulate other
parts of the immune system to actively
fight the infection.
GBV-C can also be passed from mother
to child. This is good news as it can
reduce the chance of mothers with HIV
passing the infection onto their children.
More recently, GBV-C has also been
linked to reduced mortality in those
infected with the Ebola virus, somehow
reducing the impact of the virus on its
host. Understanding how could save lives.
Extraordinary discoveries such as this
should make us wonder what else we are
missing, says Betsy Foxman, of the
University of Michigan, US.
In the past we’ve characterised sexually
transmitted microbes as bad, she says.
The preventative measures we’ve taken to
protect against them may mean that we
now lack some that are potentially
beneficial.
There are likely a host of
beneficial organisms yet to be
identified
Foxman would like to see more work
done on the benefits of one pathogen
interfering with another. “What could our
body have on it that would keep it
healthier [for] longer?”
There may even be microbes that help
target other kinds of infections, Foxman
says. If there are, these could reduce our
dependence on medicines such as
antibiotics. They often kill a broad
spectrum of microbes in order to
eradicate the one that is problematic.
Of course, at times antibiotics are
necessary to save lives, but it would be
“nice to have something a little more
judicious and targeted”, Foxman adds.
We're not sure which beneficial STMs are
passing between people, but Foxman
suggests Lactobacillus , the bacteria found
in yogurt and naturally present in
humans, is one of them. There are likely
a host of other beneficial organisms yet
to be identified, she says.
Cost benefit
This all sounds like great news, right?
There could be a whole bunch of little
known STMs floating around that could
be beneficial to our health.
Microbes that cause sexual
diseases need to ensure they can
hop from human to human
There’s just one problem. If we get them
by having sex that leaves us open to
getting other harmful infections as well.
There may be other ways to acquire them
in the future. Once beneficial STMs are
identified, scientists working in public
health can hopefully develop safe ways to
inoculate people, or figure out how to
replicate their effects, without risking
unprotected sex.
Most sexually transmitted infections such
as chlamydia and gonorrhoea don’t tend
to kill their hosts. They are also often
asymptomatic. “They’re just trying to
make a living,” says Foxman.
There could even be certain STMs
that encourage humans to have
sex more often
Microbes that cause sexual diseases need
to ensure they can hop from human to
human. This transaction is more likely to
happen if the person hosting the
microbes appears healthy, she adds. “If
someone looks sick, from an evolutionary
standpoint, they’re a bad bet,” she says.
It could be that as humans evolved, well
before condoms existed, the risk of
getting an STD was, at times, outweighed
by acquiring an important microbe. It’s an
evolutionary cost-benefit analysis, says
Smith.
Those who carry beneficial STMs could
even be unknowingly signaling that they
do so, says the evolutionary biologist
Michael Lombardo. They might then be
favoured as mates.
It gets more complicated. It may not just
be the physiological benefits, such as
disease prevention or tolerance to heat,
that make certain STMs advantageous.
These microbes could also affect their
host's behavior in a good way.
That microbes can do so is a relatively
new and promising area of research. For
example, certain gut bacteria are thought
to affect the brains of young mice,
reducing their anxiety levels.
Individuals that mate with more
than one partner are more likely
to acquire a beneficial STM
Microbes may also modify the chemical
signals that animals produce, says Smith.
This was discovered in research on fruit
flies as they acquired bacteria from
different diets. The result? Fruit flies
preferred to mate with others that shared
those same microbial communities.
Getting around
These are examples of gut bacteria
altering behaviour and therefore mate
choice, but can sexually transmitted
microbes do the same?
There is little evidence for this so far,
says Smith, but it would make sense. If a
male has a beneficial microbe and it has
a positive affect on him, females that
choose to mate with him would acquire it
too, he adds.
“Individuals that mate with more than one
partner are more likely to acquire a
beneficial STM,” says Smith. If that’s the
case, it could be one of the reasons a
species might favour mating with more
than one partner.
In the common lizard, for example, the
females that mate with more than one
partner have been found to have more
diverse microbial communities than those
that don’t. Scientists who study them
speculate that this could mean a
difference in health between sexually
active females and asexual reproducers.
Lombardo believes that some female
birds that mate repeatedly with the same
partner, or with more than one partner,
may receive benefits from STMs by
acquiring viruses that kill harmful
bacteria, or by acquiring less virulent
strains of pathogens.
These could limit the impact of more
virulent strains. Beneficial microbes that
produce bacteria-killing chemicals could
also help fight existing infections. This is
one of many theories that attempts to
explain why birds have extramarital sex
outside their main partnership.
There could even be certain STMs that
encourage humans to have sex more
often, says Foxman.“What if it just felt
better to have sex when you had a
particular bug?
“That bug could increase mucus flow. It
could be as simple as that.”
Foxman says there are conditions in both
men and women that create chronic pain
feedback loops related to sexual activity,
yet their cause is unknown. To identify a
beneficial STM that would alleviate these
conditions could mean all the difference
to a person’s sex life. It’s worth looking
into, she says.
“We are sexual beings. Things that make
people feel better sexually, tend to make
them feel better overall.”
It appears that whether you’re an aphid,
bird, lizard or human, odds are that you
are never quite alone with a mate. There
are perhaps thousands of other
organisms waiting for the magic to
happen so that they can make their way
back and forth between you, and perhaps
out into the population.
We may know more of them soon. Smith
says that with the exciting and explosive
growth of interest and research into the
human microbiome, there are now “new
techniques to survey and quantify the
function of microbes that we didn’t have
ten years ago.”
In the mean time, stay tuned and play
safe.
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