Losing our mutualists is like losing a limb
Mutualists very likely either enhance, replace, or provide functions. We lose obligate mutualists at our peril because not having them means not having the function they provide and that loss should predictably be followed by disease. If obligate bacteria support our health and physiological functions, loss of those bacteria cannot be good. It should also be very difficult to do this because the 100% elimination of any bacteria is almost impossible.
When we experience disease after damage to the microbiome, it is more likely is that the healthy microbe populations have crashed to low numbers and are struggling to recover. If the colon environment is damaged or disturbed and becomes dominated by bacteria that cause pathogenic conditions, those conditions may well prevent the obligate and beneficial bacteria from re-establishing. Any such situation would also involve the reduction of a great many facultative bacteria.
Deciphering the exact consequences of such losses in terms of any subsequent diseases is very difficult. The disease could result from the loss of the function provide by the obligate species, but could be from or compounded by the loss of the diversity and stability provided by the facultative species.
In the modern era (i.e., the one dominated by modern medicine), the loss of obligate bacteria may be one of the root causes of a number of new, curious, and difficult to understand diseases. We have to appreciate that an obligate mutualist bacterium, by definition, provides a benefit to its partner species and the loss of that mutualist is accompanied by a loss of a necessary function.
For us to fully appreciate that relationship, we must also appreciate the complexity of the relationship and this is where certain aspects of modern medicine may have reached their limits. The mutualism is an evolutionary process and that means it is capable of changing and, in fact, may be capable of a range of expression. That is, the expression can be low, medium, or high, depending on the situation.
Medical interventions are technological and geared toward the replacement of known and simple functions, and are predicated on a single level of expression. That is, a bioactive chemical (medicine) is designed to provide a missing function in a very linear fashion. However, the focus is on replacing the exact function, which is to say the function as it is understood by medical science.
The medicine cannot replace the range of benefits that have been lost nor can it operate as a replacement for a complex interaction. A therapeutic medicine replaces something that we, as humans, have identified as a lost function, but we typically lack a complete understanding of the disease associated with that loss of function. Importantly, if we have lost a biological interaction provided by a biological entity, such as a bacterium, and replaced it with a technological solution, we may be interfering with the ability of the human body to re-establish the original mutualism or its associated (and unknown) benefits. That is, the artificial medicine may act to prevent the restoration of the natural process. Whether or not this is always the case, the goal of medicine is typically curative and not restorative.
It is also worth remembering that medicines are rarely tailored to the patient in any real sense. This is a characteristic of the one-size-fits-all approach of technology and medicine. I can only wear a shoe of a certain size, but in truth my feet change shape over the course of a day and my shoes cannot adjust in response. And I tend to buy certain brands of shoes because of the differences in comfort and fit, but other people are comfortable buying those brands that I find uncomfortable.
As mentioned before, anti-inflammatory or anti-histamine medicines may eliminate or reduce discomfort, but they do not address the underlying issue or issues that caused the discomfort, nor do they account for body size, personal medical history, family history, genetics, and so on. In that sense, nearly all drugs are “generic” in that they address a specific ailment in a general way and without any specificity for each of us as individuals.
In stark contrast, an obligate mutualist, such as a species of bacteria inhabiting our colon and living on the plant materials we consume, has a vested interest in maintaining the health of the colon environment. Indeed, the very ability of humans to consume the range of plant foods that we do is a testament to the workings of the microbiome on our behalf.
Although it is a bit of a “which came first, the chicken or the egg?” problem, we eat to feed the microbiome and the microbiome protects our ability to keep eating, and that is the essence of a mutualistic relationship. More importantly, as our environment changes (for example, from summer to winter), the microbiome is capable of shifting too. If we experience a shift in our physiological functions over the seasons, perhaps due to temperature, activity levels, and the food we eat, the microbiome will shift with us.
It does not do this with any sense of intention, but because we are shifting the food supply flowing through the colon and the bacterial ecosystem there is shifting in abundance as a response. We should predict that this response is moderated by the feedback from the host in terms of host health. That is, a healthy shift in bacterial diversity and abundance should be reflected in the maintenance of the host’s health.
The importance of this relationship with regard to modern medicine is that medicines cannot shift in response to changes in host physiology. Medicine is inert in that respect while bacteria are dynamic. If the microbiome is acting as a mutualistic barometer, the changes in the host are matched by changes in the microbial diversity and abundance as changes occur in the external environment and in terms of host physiology.
This is fundamentally what biological systems do: feedback from the environment stimulates changes that maintain homeostasis and ultimately maintain the stability and health of the system.