Bacteria and their "Social" Relations

This is the age of humans; today, with the aid of technological development on all fronts, the human race alone sits at the top of the food chain, directly or indirectly controlling every aspect of the planet, from the landscape to the climate. For better or for worse, we consider ourselves to be rulers of the world we live in, though many, who worry about humanity's impact on the environment and what we may or may not leave for future generations, lament this fact. Despite the assumed power of our species, a closer look will show you that this is in fact not the age of man. To the contrary, we live in what is and always has been the age of bacteria.

Firstly, we are vastly outnumbered. According to recent estimates, the number of bacteria on earth is nearing thirty-one digits. This means that if each bacteria was represented by a penny, stacking them would produce a pile more than a billion times the length of our Milky Way galaxy. We usually think of bacteria as harmful towards humans, as they cause many fatal diseases, but the truth is that they are not only beneficial, but necessary for human life on earth. Bacteria aid the human body in digesting essential nutrients, and maintain homeostasis within living things as well as ecological balance within nature. Scientists have used bacteria to create some of the most advanced medicines, and studied them to produce theories of adaptation and evolution. While there are millions of types of bacteria, most behave relatively the same way, with just a few important exceptions.

Biologists have recently discovered a new strain of bacteria called Myxococcus xanthus. This organism is unique among others of its type because the single cells that comprise the bacteria are capable of working together to accomplish incredible things. Known colloquially as a swarm bacteria, the cells of this organism form themselves into complex three-dimensional structures, collaborating amongst themselves to find food and move about in their environment. Although we usually think of bacteria as being microscopic, these arrangements of hundreds of thousands of cells are often large enough to be seen by the naked eye.

So why haven't these “social” interactions between bacteria been observed before? Oleg Igoshin, an assistant professor of bioengineering at Rice University, explained that studies on bacteria are usually done in isolated test tubes, and samples are chosen based on which ones behave a certain way in which environment, rather than in their natural habitats. Myxococcus behaves completely differently in different situations, and generally does not exhibit its unique characteristics in standard laboratory conditions. Therefore, scientists have usually disregarded the species as uninteresting.

The Myxococcus is a predatory bacteria; in order to gather the microbes it uses as nutrients, the bacteria form swarm clusters that secrete enzymes to kill other microbes when prey is abundant. In this case, the swarming behavior is actually critical, because individual Myxococcus cells are unable to secrete enough enzymes to kill their prey. And so, the swarm acts as a kind of hunting party, helping in taking out the prey and sharing in the rewards. When food is not readily abundant, the cells arrange themselves into clusters called “fruiting bodies.” These clusters of roughly 100,000 cells each can form in just a few hours; during the formation process, the cells comprising the whole undergo a series of changes to their shape and the way they produce proteins. These changes allow them to break down food far more slowly, and allow them to survive without new prey for up to several years.

What is most remarkable about Myxococcus, however, is its capacity for rapid evolution. When the bacteria's swarming ability was first discovered, German biologists Gregory J. Velicer and Yuen-tsu N. Yu performed some tests by isolating the gene that enables the swarming behavior and removing it from a sample of Myxococcus. The bacteria were then left to sit on a plate with other bacteria so that they would have plenty of food. After just a few weeks, the scientists observed that swarms were forming once again, which suggests that the Myxococcus cells had re-developed the gene that had been removed at the beginning of the experiment.

Upon further investigation, however, it was observed that the bacteria contained an entirely new gene that enabled the swarming behavior yet bore little resemblance to the original gene. In wild-type Myxococcus xanthus, cells use pilli--extensions of their cellular membranes that form a bridge between different cells--to transfer DNA necessary for swarming. Using these new genes, they form the swarm and pass along the gene to more cells on the exterior. After this gene was removed and the populations were left alone, a new gene developed. This gene caused increased production of an extracellular matrix that binds cells together.

Further intriguing was the fact that this gene, when expressed, caused harm to individual cells because it diverted energy from metabolism and other important functions. The sole purpose of the new swarming mechanism was to benefit the group of cells contained in the swarm. This proved that not only that swarming together was beneficial to the point of necessity, but also that bacteria can readily evolve new ways to achieve this mechanism.

Because of their fast rates of reproduction and high availability, scientists often use bacteria to experiment with adaptation and evolution. Changes in populations of bacteria are both much more rapid and easily observable than changes in populations of other organisms, making bacteria the perfect lab subject. This unprecedented rapid development of genes for social interaction is unique among bacteria, and could lead to a whole new field of research in medicine or elsewhere. This strain of bacteria does not have any harmful effects on humans, and could prove instrumental in developing a new form of antibiotic or pesticide.

This unprecedented rapid development of genes for social interaction is unique among bacteria, and could lead to a whole new field of research in medicine or elsewhere.

New discoveries are made in science each and every day, but only rarely is something unearthed that could alter the course of science entirely. Although this new type of bacteria could merely be an interesting and unique organism, it could also prove to be one of these rare gems of scientific information. It could bridge a gap between single-celled organisms and more complex life, possibly hinting at future discoveries to be made.

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