There’s a lot of hate in the world today. As a social activist, I’d like to do my part to try to reduce some of the baseless negative judgments that are often thrown about so carelessly. Two groups in particular, which I would like to focus on for the remainder of this article, have received a lot of bad press lately. These are, of course, viruses and bacteria, or the prokaryotes.
Ubiquitous media reports on the H1N1 flu virus, Methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli, make it difficult to appreciate not just the remarkable characteristics of each bacterium and virus, but also their significant contributions to human life.
Not only do these tiny creatures directly benefit human health in countless ways, but they are also incredibly impressive from an evolutionary point of view.
According to eminent scientist and essayist Stephen Jay Gould, the Devonian period was not the “age of fish,” the Mesozoic was not the “age of reptiles,” and this is not the “age of mammals.” According to Gould, not only are we currently living in the “age of bacteria,” but the bacterial epoch has extended back 3.5 billion years, beginning with the origin of life on earth.
Ever since they appeared on the scene during the Archaen period, bacteria have thrived on earth. There are currently five nonillion (that’s a five with 30 zeros after it) bacteria on the planet, whose survival we depend on for number of reasons.
Nitrogen, the most abundant element in our atmosphere, is essential for the survival of living organisms, yet exists as N2 in air, which is unusable to many of the living things on our planet. Luckily for us, bacteria engage in a process called “nitrogen fixation,” which breaks down the molecule into ammonium and nitrate ions — a form our bodies can then use to synthesize the basic building blocks of life (such as DNA, and proteins.)
Other helpful bacteria exist in much closer proximity to us. In fact, our bodies contain more bacterial cells than human cells — 10 times more, to be exact. Most of these bacterial colonies live in our digestive tracts, and are not just beneficial to us, but are actually crucial to our survival — aiding in digestion, boosting immunity, removing toxins and preventing harmful bacterial species from infecting us.
While smelly and disgusting, the human gut is not the strangest choice of living environment for bacteria, not by a long shot. “Extremophiles” are a group of bacteria and bacteria-like organisms which are named for their propensity to seek out and thrive in environments that are too extreme and deadly for other organisms. These thrill-seekers have been found living 2.8 km below the Earth’s surface beside thermal vents on the ocean floor in environments of extreme acidity and salinity, where temperatures can reach 120 C.
The vast number and diversity of bacteria on earth attests to their impressive survival abilities. They have withstood six major mass-extinction events, live in incredibly diverse environments, and boast a wide variety of different species. Scientists believe that these little guys are here to stay, regardless of any type of environmental destruction humans could possibly inflict upon the earth (even a nuclear blast would not be enough to eradicate all of the Earth’s bacteria.)
What is it that makes bacteria so great at thriving in almost any environment they find themselves in (giving them a significant survival advantage over us)?
The answer to this turns out to be very similar to what gives viruses a similar advantage.
Only 1/100th the size of a single bacteria, viruses consist of little more than some genetic material wrapped in protein. These seemingly unimpressive entities, like bacteria, are ingenious survivors and provide important benefits to humankind.
Richard Spalding, a microbiologist at the University of Manitoba, has a lot of respect for viruses, despite the fact that his work primarily focuses on bacteria. He points out that wherever there is life, there are viruses, meaning, ironically, that even the most extreme bacteria can be susceptible to infection by dormant viruses nearby. “Bacterial viruses are called ‘phages,’” Spalding says, “and yes, E. coli can catch a ‘cold’ and so can Thermus thermophilus, which grows above 80 C.”
The fact that viruses can attack bacteria means that they can potentially be used to treat harmful bacterial infections (“phage therapy”). In fact, Spalding points out that “phage therapy was used with some success in the Soviet Union as a replacement for antibiotics against pathogenic enteric [gut] bacteria.”
Viruses, unlike bacteria, depend on a host in order to replicate themselves and can remain dormant for extremely long periods of time laying in wait for a suitable host to come along.
The inability of viruses to replicate without a host is why they are generally considered to be non-living, though there is some controversy around this. Paradoxically, there are several strains of bacteria (including Chlamydia trachomatis, the bacterium which causes the STI chlamydia), which depend on a host for survival as well, yet they are considered to be alive.
Despite their typical status as non-living entities, viruses definitely seem to be winning the battle for “survival of the fittest.” They attack every form of living being, are incredibly prolific, and are found in a multitude of locations all over the earth.
The incredible evolutionary advantages that both bacteria and viruses show in nearly every environment can be mostly attributed to two factors: fast reproduction and horizontal gene transfer. Both of these kinds of organisms reproduce extremely quickly (E. coli can replicate once every 20 minutes under ideal conditions,) which increases the probability that a beneficial random mutation will occur in a population. Once a beneficial gene arises, it spreads quickly, not just through the organism’s descendants (“vertical transfer”), but it can also be transferred directly to other members of the population through the transfer of small chromosome-like structures called “plasmids” and even by phages. This “horizontal transfer” allows viruses and bacteria to share genetic information with their counterparts directly and immediately, allowing adaptive traits to spread incredibly quickly throughout a population. This adaptive ability is what allows bacteria to thrive in extreme conditions, and viruses to live off of bacteria in extreme environments. It also accounts for some of the nastier outcomes of viruses and bacteria, such as the development of antibiotic resistant strains of bacteria, such as Mycobacterium tuberculosis, as well as the new H1N1 virus that has recently jumped the species barrier to humans.
Despite some of their negative activities, it is awe-inspiring to consider that these tiny and brainless micro-organisms (on whom we depend for our own survival) seem to be a lot better at surviving in this world than we are. It’s also slightly humbling to consider that, unlike the thinking organisms of this planet, they probably have no motivation or will to live, yet they are better at it than anything else we know of, thanks to their extreme adaptability and underlying simplicity.
Hats off to you, prokaryotes. We concede the evolutionary race.