What is the first thing you think of when I say bacteria? Probably the nasty Vibrio Cholerae or Streptococcus pyogenes. But do you ever think about the Escherichia coli that helps you digest the food you eat? Or the Akkermansia muciniphila that is tied to healthy metabolism in most people? It is not a stretch to say that microbes (especially bacteria and archaea) are responsible for the standard of living we have.
For reference, I will generalize all microbes as simply "bacteria" from now on.
If you think that you are ever safe from bacteria, you should think again. No amount of washing or sanitizing will take these friendly creatures from you (that being said, please continue to wash your hands). Bacteria could be considered the most successful organisms ever to exist. According to fossil records, bacteria have existed the longest of any life form on earth, and it is likely that they will exist until the end of time. To put it in perspective, if the history of earth were scaled to fit in a typical calendar year, you would be reading this on December 31st just before the stroke of midnight. Thankfully, fireworks were invented 9 seconds ago (thanks to Ed Yong for that joke, and the inspiration for this post). Dinosaurs ruled the earth until the evening of the 26th of December when their existence was rudely ended by a rouge asteroid. Multi-cellular organisms have shown up by the beginning of October, just in time to figure out what they are dressing up as for Halloween. But bacteria, the simple single-cellular organisms we know and love have been around since March. If you were to make a pie chart that graphed the percentage of time a specific type of life has existed on earth, Bacteria would practically be the only thing you could distinguish. They have figured out this whole life thing, and have it down to a science (ha. Biology pun).
The Bacterial Epoch
The first thing that Bacteria ever did for you was make earth habitable. It is small, I know, but has anyone ever thanked them for it? Early earth would be acutely toxic according to our standards. Think something like Venus. Unbearably hot, toxic gasses occupy upwards of 90% of the atmosphere, and sunlight is a thing of dreams. The very earliest bacteria were what we would call anaerobes. They don't use oxygen for metabolism. In fact, they hated oxygen. They were disgusted by it. It literally made them sick. They thought so little of Oxygen gas that they expelled it as a waste product. They much preferred the methane and sulfide gasses present. Much to their dismay, their reckless use of these toxic gasses and mindless expulsion of oxygen led to a decrease in atmospheric toxicity and made it more difficult for them to survive. This was the bacterial epoch's equivalent of today's climate change problem. This change in atmospheric conditions is pretty incredible to think about. There were enough of these microscopic organisms to completely renovate earth's entire atmosphere. This atmospheric shift led to the evolution of facultative aerobic bacteria who could not only metabolize using the toxic gasses, but utilized the abundance of oxygen. Then came rise to aerobic bacteria who only used oxygen, and were poisoned by the toxic gasses in much the same way anaerobes are poisoned by oxygen.
The atmospheric oxygen that we have today is held in balance by a variety of living organisms. Since many use CO2 or other things for metabolism, and expel oxygen, it makes up for the oxygen that us animals use on a daily basis. An atmosphere of oxygen helped earth's biological diversity explode, and gave rise to multicellular life, which requires oxygen for metabolism. Everything we associate with the word "nature" is in existence because of bacteria.
Bacteria in Our Lives Today
Bacteria are ubiquitous. There are more microbial species on earth than there are stars in the galaxy. Many of these live in extreme environments, or in the dirt below our feet. But a vast majority of them live on and within us. An estimate suggests that for every human cell, there are roughly ten bacterial cells. This ratio is not proven, however it is a good guess, and provides the correct frame of mind for thinking about our microbial partners.
Some of you may look at this picture and get a sudden urge to take a shower, but when I look at it, I see a world of wonder. I am filled with wonder because there is so much diversity to be found on just this one individual's hand. What can we learn from our microbial partners? We can learn much about the strength needed to survive. We can learn many things about living in harmony with those that surround us. In reality, we can learn a lot about ourselves.
Bacteria that make up our microbiome (the collection of bacteria contained on and in us) are with us our entire lives, and biologists are discovering more every day about how they influence our day to day actions.
In our digestive tract, we have a zoo full of species, each fulfilling their own unique purpose. A genus that I mentioned earlier, Akkermansia, seems to be responsible for a lean body composition. In recent studies, the introduction of this bacteria resulted in weight loss. The balance between two dominant phyla, Bacteroidetes and Firmicutes, showed a dramatic correlation to body composition. By more fully recognizing these bacteria's role, and recognizing their potential, we step closer to a healthier world.
Our microbiome is bestowed upon us at birth by our mothers, fathers, siblings, and the things we eat. It is possible to alter the composition of our microbiome, and research is spending a lot of time testing the effects that certain compositions of bacteria have on health. For victims of certain diseases, like Clostridium difficile, the use of microbial transplant therapy has around a 90% success rate while the use of antibiotic treatment hovers only around 30% successful. These two papers (1 and 2) show a strong correlation between bacteria and the event of chronic disease. I think that is incredible. Chronic diseases have always thought to be incurable, and so we have only ever really treated symptoms. Yet, we may be able to use antibiotics and rid the individual of the sickness for good. I hope that one day, altering microbial composition may be the go-to treatment for physicians around the world for preventing and treating disease.
Our ecosystem is teeming with wonderful bacteria that provide and help us in many more ways than I have mentioned. So the next time you get the chance, thank them.
"We see individuals, working their way through life as a bunch of cells in a single body, driven by a single brain, and operating with a single genome. This is pleasant fiction. In fact, we are legion, each and every one of us. Always a 'we' and never a 'me.'" -Ed Yong, I Contain Multitudes (I really recommend this book. Ed presents the material in such a fun way that is easily understood regardless of your background. Check it out!)