by David Pride and
- inside and out -
is covered in microorganisms:
bacteria, viruses, fungi and
many other microscopic life forms.
Scientists have only recently begun to quantify the microbiome (or microbiota), and discovered it is inhabited by at least 38 trillion bacteria (Revised Estimates for the Number of Human and Bacteria Cells in the Body).
More intriguing, perhaps, is that bacteria are not the most abundant microbes that live in and on our bodies.
That award goes to viruses...
of multiple bacteriophages
attached to a bacterial cell wall.
Dr. Graham Beards
But these viruses are not the dangerous ones you commonly hear about, like those that cause the flu or the common cold, or more sinister infections like Ebola or dengue.
Many of these viruses infect the bacteria that live inside you and are known as bacteriophages, or phages for short.
The human body is a
breeding ground for phages, and despite their abundance, we have
very little insight into what all they or any of the other viruses
in the body are doing.
One might rightly assume that if viruses are the most abundant microbes in the body, they would be the target of the majority of human microbiome studies. But that assumption would be horribly wrong.
The study of the human virome lags so far behind the study of bacteria that we are only just now uncovering some of their most basic features.
This lag is due to it
having taken scientists much longer to recognize the presence of a
human virome, and a lack of standardized and sophisticated tools to
decipher what's actually in your virome.
The 411 on the virome
Why? Because phages kill bacteria. They take over the bacteria's machinery and force them to make more phages rather than make more bacteria.
When they are done, they burst out of the bacterium, destroying it. Finally, phages sit on our body surfaces just waiting to cross paths with vulnerable bacteria.
They are basically bacteria stalkers...
A virus called a bacteriophage infects bacteria
and inserts its genetic material into the cell.
The bacterium ‘reads' the genetic instructions
and manufactures more viruses
which destroy the bacterium
when they exit the cell.
Guido4, CC BY
It's clear that there's a war being fought on our body surfaces every minute of every day, and we haven't a clue who's winning or what the consequences of this war might be.
Viruses may inhabit all surfaces both inside and outside of the body. Everywhere researchers have looked in the human body, viruses have been found.
...and so on.
To put it simply, when it comes to where viruses live in the human body, figuring out where they don't live is a far better question than asking where they do.
Viruses are contagious. But we often don't think about bacterial viruses as being easily shared. Researchers have shown that just living with someone will lead to rapid sharing of the viruses in your body.
If we don't know what the consequences are of the constant battle between bacteria and viruses in our body, then it gets exponentially more complicated considering the battle between your bacteria and their viruses that are then shared with everyone including your spouse, your roommate, and even your dog...
Viruses keeping us healthy?
Viruses destroy the bacterium
when they burst out of the cell.
Here, the clear circles reveal
where the bacteriophage
have killed the bacteria.
Ultimately, we need to know what all these viruses in the human body are doing, and figure out whether we can take advantage of our virome to promote our health.
But it's probably not clear at this point why anyone would believe that our virome may be helpful.
It may seem counterintuitive, but harming our bacteria can be harmful to our health.
For example, when our healthy bacterial communities are disturbed by antibiotic use, other microbial bad guys, also called pathogens, take advantage of the opportunity to invade our body and make us sick. Thus, in a number of human conditions, our healthy bacteria play important roles in preventing pathogen intrusion.
Here's where viruses come in. They've already figured out how to kill bacteria. It's all they live for.
So the race is on to find those viruses in our viromes that have already figured out how to protect us from the bad guys, while leaving the good bacteria intact.
Indeed, there are recent anecdotal examples utilizing phages successfully to treat life-threatening infections from bacteria resistant to most if not all available antibiotics - a treatment known as phage therapy.
Unfortunately, these treatments are and will continue to be hampered by inadequate information on how phages behave in the human body and the unforeseen consequences their introduction may have on the human host. Thus, phage therapy remains heavily regulated.
At the current pace of research, it may be many years before phages are used routinely as anti-infective treatments.
But make no mistake about it: