R. Kayne Last Modified Date: August 24, 2020

It may be startling, but according to the Howard Hughes Medical Institute (HHMI) of Maryland, we each house two to five pounds (1.0 to 2.26 kilograms) of live bacteria inside our bodies. These microorganisms come in good and bad varieties, or more to the point, can be helpful or harmful. While the vast amount of attention is given to the bad kinds because of their potential for creating illness, humans share a necessary symbiotic relationship with many types of helpful bacteria. Some are crucial to our very survival.

The highest concentration of bacteria in the human body can be found in the intestines.

HHMI reports that the largest concentration of bacteria in the human body is found in the intestines. Species numbering in the thousands create trillions of silent passengers functioning en masse. The relationship between the different strains of bacteria and the human body is a dynamic one, constantly adjusting to changing conditions.

Yogurt with probiotics, a helpful type of bacteria.

Probiotics, or the study of treatment through helpful bacteria, is gaining more attention as infections increase from overuse of antibiotics. One familiar example of probiotics is the promotion of yogurt containing live bacterial cultures for easing diarrhea associated with antibiotics. The probiotics in this case are of the lactobacilli strain. Though it is clear through research that probiotics can have a positive effect, as a treatment regimen, their effectiveness is less than sufficient to replace antibiotics, given our current state of knowledge. However, the medical community believes a replacement is exactly what’s needed.

Bacteria in a petri dish.

One of the problems with treatment through probiotics is that bacteria within us are not well understood. For example, a dormant or neutral bacterium might become harmful if triggered by conditions that cause it to multiply or change. Bacteria can interact with human cells, causing cell receptors to “grow extensions” that they can stick to. Complicating matters, scientists report that at least 50% of these strains cannot be grown in a lab because of the difficulty in creating a suitable environment that simulates the human gut.

Some bacteria can become resistant to antibiotics over time.