The Living Dormant: MicroZombies

There’s life.  There’s death.  And there is dormancy. Somewhere in between a zombie and a hibernating bear, dormant microorganisms potentially have a profound impact on the natural environment.

A recent study in Nature Reviews: Microbiology examines the cellular mechanisms that allow these microbes to exist in a dormant state.  The study also explores the impact these dormant microbes can have on larger ecosystems, including the ground, the oceans, and humans.

Study author Jay Lennon, Michigan State University assistant professor of microbiology and molecular genetics, explained:  ”Only a tiny fraction is metabolically active at any given time. How would our environment be altered, in terms of carbon emissions, nutrient cycling and greenhouse gases such as nitrous oxide, by dramatic increases or decreases in the dormancy of microbes?”

“Dormancy” has properties of low metabolic activity, and it is considered a reversible state. Organisms sometimes enter into this state in response to freezing temperatures or lack of food. These organisms do not follow a linear growth pattern, and dormancy could occur at any time.

Lennon added: “However, it does take a certain level of commitment, a certain energy investment to make it happen. Just as people don’t run out and winterize their homes if it gets cool in August, microbes want to be sure that truly hard times have set in before shifting into a dormant phase.”

Lennon and his co-author, Stuart Jones at the University of Notre Dame contend that 90 percent of microorganisms in the ground are usually dormant and only half of bacterial species are active, creating an enormously large “seed bank” that could have profound implications.  According to Lennon: ”The idea of a microbial seed bank is a rather novel concept, but from our research we found that dormancy and seed banks are prevalent in most ecosystems. What’s fascinating is that there’s only a small fraction that are active, which means there’s a large reservoir that could potentially be activated at any given time.”

Among other things, the authors contend that dormancy may explain the sudden outbreak of diseases, triggered by environmental changes.  Lennon noted:  ”One-third of world’s population carries dormant tuberculosis microbes. Obviously, you can live a long time with the dormant cell in your body, but it’s important to understand what can trigger its reanimation or what maintains its dormancy.”