Bacteria to the rescue?! Beyond the human vision of gargantuan stars and structures exists a unique world populated by organisms much smaller than the smallest human cell. They represent a novel domain of life, tracing a unique evolutionary heritage that pre-dates any living history ever recorded on the planet. Bacteria, as small as 0.2 microns,1 are often brought to public attention in the case of disease and despair linked to an outbreak of monumental proportions. Before we look into how bacteria can potentially help humans reverse some of the environmental damage we have inflicted on our planet, let’s take a look at the context in which humans have placed bacteria in history.
Bacteria in Human History
Yersinia pestisiThe black death of 1348 stemmed from the bacterium Yersinia Pestis, and on its own was responsible for the 25 to 50 percent reduction in the European population.2 In spite of this catastrophic example and contrary to the negative press, less than 1% of bacteria are disease-causing in humans.3 In fact, without bacteria, life would be virtually impossible one earth. Apart from being one of the first organisms on the planet,4 specialized bacteria such as cyanobacteria5 made the process of photosynthesis possible from which every living organism derives its nitrogen in the atmosphere could never be fixed6 and biologically important macromolecules such as proteins would never become available for animals to use. As a result, our survival and development as a species is almost completely derived from the actions of bacteria in the environment.
How can such a small organism that can occasionally cause diarrhea in human beings be the gateway to complex life on earth? The evolutionary timescale of bacteria including both domain Archae—a type of bacterial organism—and Bacteria places the genesis of these class of organisms at the very beginning of life on earth.7 As a result, the expanded niche of bacteria in the environment has enabled this organism to become a harbinger of unique biochemical activity in an almost witchcraft-like fashion. Hence, the existence of sulfur metabolizing8 bacteria that create energy out of what seems to be nothing. Such a functional ability is analogous to a human being that is able to generate food by simply breathing. Unfortunately, this is far from the truth.
One can say that bacteria are protectors of the environment, and indeed the shapers of the global warming potential than carbon dioxide.11 It is fair to say that we have been creating much waste through noxious anthropogenic activity that is poisoning the environment, and slowly undoing what our microscopic ancestors have created for us over evolutionary time.
With a growing need for remediation technologies, the options have been fairly limited in implementing a practical and cost effective method to address environmental concerns. Is there a way to make use of our ancient allies of the environment to combat the ills of industrialization? Indeed, there is such a wide variety of unique functional bacteria with unique biochemical properties that one might be bound to find some organism capable of reducing methane or plastic in the environment. More so, the wonders of genetic engineering have made it possible to harness the capabilities of one bacterium in another bacterium, or even a completely different type of organism. Advancements in molecular biology have given birth to innovative means of environmental remediation that range from massive oil clean ups to the containment of radioactive contamination. Here is an overview of some of the incredible work bacteria are being employed to do to save our environment.
1. Oil Spill Clean Ups
The Deep Water Horizon oil spill takes the prize for the most disastrous spill over of oil in human history, estimated to have dumped 200 million gallons of crude oil into the Gulf of Mexico.12 Having destroyed 400 miles of Louisiana coastline, a barrage of in situ oil burns and mass dispersal of detergents could be arguably further destroying the gulf coast, but fortunately an amazing bacterium known as Alcanivorax borkumensis13 that has evolved molecular mechanisms to not only persist in oily environments but successfully propagate in them as well. The bacterium is fairly robust, with good resistance to high salt conditions in the ocean and highly UV tolerant thanks to special resistance and repair genes that enable it to propagate on ocean surfaces. Most important is the bacterium’s ability to degrade long chain alkanes in crude oil using special hydroxylation enzymes that allow it to metabolize oils for food. One of the cardinal rules of life on earth is that living organisms must have some source of carbon, whether it be through photosynthesizing carbon dioxide or consuming photosynthesizing crops. Incredibly, Alcanivorax uses oils to derive its own form of carbon. Furthermore, the organism dramatically multiplies within oil slicks to further degrade oil dispersed on the water surface. As a match almost made in heaven, Alcanivorax’s safe and practical implementation has made the gulf clean up more effective and environmentally safer without the excessive use of potentially harsh detergents.
2. Solid Waste Clean Up and Electricity
If one remembers their first trip to a financial advisor, the inevitable discussion of strategies and risks would usually create a conundrum for many thinking long and hard for a rewarding financial plan. But what if you can bake the cake and eat it too, or in other words minimize risk and maximize profit? Most economists would tell you that this is an impossible guarantee, but thankfully the world of microbiology works quite differently. An amazing new application for a little known bacterium known as Shewanella Oneidensis14 is being investigated as a possible source of both waste remediation and electric generation. The bacterium makes use of specialized nanowires15 that are believed to not only digest PCBs (polychlorinated biphenyls—a family of man-made chemicals banned in the United States in 1979)16 and organic solvents, but also generate electricity following the metabolism of waste. The bacterium is a deep sea organism, typically living in oxygen deprived environments and is furthermore being investigated in its role as a heavy metal reducing agent for bioremediation. As a result, Shewanella Oneidensis potentially represents the killing of three birds with one stone should future efforts reveal a practical mechanism of implementing its use in sewage plants or toxic waste sites—a tremendous feat for any living organism!
3. Plastic Degradation
ivThe unchecked use of plastic bags and plastic products has undoubtedly taken a toll on both marine and terrestrial environments housing animal species that inevitably find their way into the death grip of non-biodegradable plastics. Images of chocking ducks and strewn garbage are certainly eye opening, but plastic is still being used on a very large scale with only a few countries implementing strong recycling and legal initiatives that successfully curb rampant plastic usage. Until recycling and monitoring fall in full swing, there is fortunately an intermediate solution to the accumulation of plastic in the environment. Rather than one particular species, a range of bacteria are capable of decomposing plastic, namely the genus Vibrio17 that surprisingly is also the parent group to the infamous cholera causing organism Vibrio Cholerae. Electron micrographs have revealed Vibrio species as well as other bacteria living within pockets of plastic gradually degrading them into a more digested form. This ability perhaps explains the gradual disappearance of plastics in ocean water or landfills. The degradation, however, is not well understood, and it is unknown whether these break down products may in fact be harmful or bio-accumulate in marine and terrestrial organisms. Their discovery, however, does offer a unique opportunity to address the issue of plastic contamination in the environment.
4. Acid Rain Runoff Remediation
Sulfur oxides, especially sulfuric acid, is a major environmental contaminant responsible for stunting forest growth, damaging soils and even acid rain , or even run off from mining operations.19 Amazingly, two species of bacteria have been identified near mining areas that are capable of metabolically reducing sulfuric acid, thereby rendering it less toxic while the bacterium uses the pollutant as an energy source. Acidithiobacillus ferrooxidans and Acidiphilium spp are two bacteria that operate mutually to form pods that convert sulfur into numerous more benign forms.20 The numerous metabolic mechanisms of converting sulfur into energy are still relatively unknown, but it is believed that these synergistic bacteria can be used together to minimize the effects of acid rain within an area or purify mining waste.
5. Radioactive Contamination
vAmazingly, the specialized nano-wire structure described earlier in bacteria may actually be utilized to contain radioactive residues of uranium21 or plutonium. Geobacter, a bacterium found naturally in soil, is now known to chemically reduce uranium in an electroplating-like mechanism, rendering radioactive soluble forms of uranium salts as insoluble. As a result, the bacterium prevents radioactive and soluble nuclear residues from dissolving into ground water supplies. While the bacterium cannot possibly neutralize the radiation itself, the bacterium may significantly limit the systemic spread of radiation into water supplies and food crop. Incredibly, the same genus has also been investigated for producing electricity within muddy environments.22 Just as in the case of Shewanella, the Geobacter could be a multipurpose group for environmental remediation along with numerous other soil bacteria that are being discovered for their unique metabolic roles. While there are many issues with nuclear power , bacteria could at least provide a means for curtailing one of the negative aspects of this form of energy production.
Last Word on Bacteria
From containing radioactive residues to generating sewage electricity, the role of bacteria in bioremediation is gradually being realized as a safe, practical and cost effective mechanism of curbing environmental damage stemming from large scale human activity. At the current pace of the technology, it is plausible that these incredible little creatures will be used in the field in the near future, but simultaneously it is difficult to measure the net impact given the increasing global industrialization that threatens our planet’s sustainability. While addressing the fall out of environmental damage is a positive step forward, global strategy of prevention through cooperation and outreach is a leap forward that would surpass the need for excessive bioremediation. As newer and more interesting bacterial species are discovered, perhaps a limitless treasure trove of possibility is to be discovered from the small and humble bacteria of the Earth.
