I recently learned about the concept of biofilms from a lecture given by Dr. Stephen Olmstead. According to Dr. Olmstead, a biofilm is a community of microorganisms, usually bacteria and yeast, that produce a physical environment within their host. This collection of microbes secretes a polysaccharide matrix to create an exclusive environment in which to proliferate. This matrix provides considerable advantages to the microbes over independent dwelling. It offers protection from “predators” like the host’s immune cells, allows for improved attachment to interface surfaces, and minimizes vulnerable surface areas that would otherwise be susceptible to toxins from antibiotic agents or other competing microbes.
 
Biofilms offer more than just protection; they have infrastructure. Each biofilm is traversed by a network of micro channels analogous to the microfilaments that form the cytoskeleton of eukaryotic cells. Why would microbes need channels? To communicate! What is amazing about biofilms is that they are comprised of symbiotic organisms from different species and even different kingdoms. Bacteria and fungi, who normally compete for resources, form an alliance to increase their ability to survive. They are able to detect changes in cytokines that alert them to opportune times of host vulnerability when reproduction would be most successful. This ability to perceive the environment is used with something called quorum sensing, a form of communication that allows for coordinated “group decisions.” They even differentiate to some degree. Different members of the community actually take on different roles like protection, attachment, reproduction, and resources collection. Microbes even exhibit altruistic behaviour by sacrificing themselves for the good of the collective. From an evolutionary standpoint these biofilms are functioning in ways not unlike a multi-cellular organism.
 
While Dr. Olmstead’s discussion was mostly focused on clinical implication of these biofilms, what amazed me was the undeniable similitude of these micro-communities to our human macro-communities. While the concept of the microcosm within the macrocosm is a theoretical concept with which most people are familiar, this was the first time (since maybe my introduction to cellular biology) that I had really seen such a clear and concrete example. These microbes that live in side us, are 10 times greater in number than the cells that comprise our bodies. They are all striving to live and reproduce, by adapting to their ecosystem and forming symbiotic relationships with other members of their bionetwork. As with any environment, there are diverse factions competing for the same resources. Some of these groups, like our resident microflora, thrive because they confer a benefit to their host – a win-win situation. Others are parasitic; they survive by harming the host - consuming resources and poisoning the environment to make it more suitable to their own needs.
 
We are the earth on which these microbes live, reproduce, and die. Our actions modify the environment in which they live and, in turn, determine which are fit to survive and which are not. Not surprisingly, healthy choices, such as a high fiber diet, favor the fitness of symbiotic flora - a win-win situation. While unhealthy choices shift the balance toward opportunistic invaders. If then, we are members of the flora of this planet, how are we relating to our host? Do we confer benefits on the earth? Do we protect her from pathogenic organisms that seek to exploit her for their own proliferation? Or, instead, do we colonize her ports, flood her veins with toxins, fill her airways with phlegm, and raise her temperature? Our ultimate survival as a species depends on the relationship we have with our host. Are we honoured guests or unwelcome pests?