Observing microbial communities

Microscopic organisms such as bacteria and fungi live together in neighborhoods known as microbial consortia. Some of these neighborhoods naturally exist in soils, food, water, and even the human gut and skin. Others are engineered together in order to degrade pollutants or to produce or convert chemicals.

Scientists examine microbial consortia to understand and dissect the complex interactions that occur between the tiny organisms in order to explain their observable behavior and design new, beneficial consortia. Researchers have always assumed that microbial interactions take place through release of select chemicals into their environmental milieu or the culture medium. Other cells could uptake those chemicals, but the exchange was always thought to occur without exchanging cellular material between the different cells in the consortium.

"But there is growing evidence that different cells may exchange material en masse," said Eleftherios "Terry" Papoutsakis, Unidel Eugene du Pont Chair Professor in the College of Engineering's Department of Chemical and Biomolecular Engineering. "We need tools to examine such possibilities."

This type of unexpected exchange of cellular material in groups, or "en masse," alters the behavior of the individual members of the consortium and may result in the development of new synthetic capabilities and metabolic activities as well as in energy savings. Such alterations can be used for many practical applications to benefit sustainability and the environment.

University of Delaware researchers have developed a new technique to observe how cell populations interact in these synthetic (human-made) microbial communities. The researchers published their findings in the journal, mSystems. The findings highlight a new method to get clues into microorganisms' behavior and their population dynamics. The bacterial cultures examined may also serve as a tool to help fight climate change.

A new diagnostic tool

A few years ago, UD researchers were growing two species of bacteria together when they noticed the cells doing something unusual.

"The cells would come together at their poles and then exchange a lot of material originating from inside of the cytoplasm," said John Hill, a fourth-year doctoral candidate in the UD Department of Chemical and Biomolecular Engineering.

Cytoplasm is a thick liquid inside cells that contains all the genetic information and cellular machinery that allows the cells to live and replicate. Hill said the bacteria cells coming together and exchanging this material was unusual because the cells eventually gave rise to hybrid cells - cells containing an amalgam of both organisms' cytoplasmic material, which hasn't been seen before.