National Centre for Biological Sciences (NCBS), Azim Premji University in Bengaluru and Princeton University, USA, have identified a worm-farming-bacteria as a new model system to help understand the spread of epidemics in a population.

Researchers have now shown that worms feeding on bacteria can also carry these bacteria with them as they move. The discovery of the agricultural worm is a serendipitous. It was a realisation that dawned on two researchers over a breakfast table conversation. Sravanti Uppaluri affiliated to the Azim Premji University had noticed that a petri dish with a patch of bacteria and worms that fed on the bacteria had developed more bacterial colonies away from the original patch.

To confirm that worms did transport bacteria from one place to another, the researchers placed worms, known as Caenorhabditis elegans or C. elegans, on a small patch of fluorescent bacteria in a dish and observed them. Over several days, worm trails all over the dish were seen to literally glow with new colonies of luminous bacteria, said Shashi Thutupalli affiliated to NCBS.

“We knew that the bacteria were non-motile, that is, they could not move. There were new bacterial colonies away from the original patch of bacteria,” says Uppaluri.

“This is an extremely cool experimental set-up. The parallels between C. elegans farming bacteria and macro-ecological systems are clear. There is a prey which is the bacteria and a predator which is C. elegans that engages in complex foraging behaviour,” stated George Constable, a co-author who worked on modelling the worm-farming bacteria system.

“At the same time the system remains experimentally tractable. A lot is known about the neurobiology and individual foraging behaviour of C. elegans and on top of that the whole experiment takes place within a petri dish!” he added.

The results of these investigations have been published as a paper in the Proceedings of the National academy of Sciences (PNAS). Thutupalli, Uppaluri and their collaborators from Princeton University propose that the worm-farming-bacteria as a unique table-top experimental system.

Using this system, one can study a vast array of complex natural phenomena like the evolution of foraging systems, population dynamics and the movement of an infection through a host population. For example, the dynamics of the bacterial spread across the dish were uncannily like an epidemic advancing via infectious transmission, said Thutupalli who added that the model of bacterial spread based on these experiments resembled that of a rabies epidemic in Switzerland in the late 1970s.

“We are excited about the theoretical avenues that this research opens, especially because this model system will allow investigations to be grounded into experimental work,” says Corina Tarnita, another co-author who works on mathematical modelling of complex biological phenomena.

“It’s exciting to see that this research has seeded a whole new set of interesting questions and research directions, said Clifford Brangwynne from Princeton.