Microenvironments

The small physical zone surrounding a microbe or a microbial community forms its microenvironment.

It is characterized by distinct physicochemical properties such as oxygen levels, pH, temperature, light intensity, and nutrient concentration.

The microenvironment can vary greatly within a small area. For instance, oxygen may be abundant on the surface of a soil particle but absent just a few millimeters inside.

As a result, aerobic microbes may occupy the outer, oxygen-rich zone, while anaerobic microbes inhabit the inner, anoxic regions.

The microenvironment can also undergo temporal changes.

For example, in the microenvironment of an aquatic microbial community, oxygen levels increase during the day due to photosynthesis and drop at night when respiration dominates.

As a result, aerobic microbes become more active during the day.

Over time, such temporal changes can reshape the spatial structure of microbial communities.

Aerobic and photosynthetic microbes colonize the upper layers, while others settle in deeper regions.