Here’s how your vegetable salad may be getting poisoned, reveals IISc-UAS study

Bengaluru:

A study published by researchers at the Indian Institute of Science (IISc) and University of Agricultural Sciences (UAS) has claimed that increasing incidence of vegetable salads causing food poisoning may be due to infectious bacteria sneaking into plant roots.

“In recent years, contamination of salad vegetables by e.coli and salmonella bacteria — the most common causes of food poisoning — have led to largescale recalls. Although most salmonella outbreaks are linked to contamination from post-harvest handling and transportation, this infectious bacterium can also enter the plant from contaminated soil,” researchers said in a statement.

But how exactly does it enter from the soil? In their study, the researchers said unlike other disease-causing bacteria that enter the root, fruit or leaf by producing enzymes to break down the plant’s cell wall, salmonella sneaks in through a tiny gapcreatedwhen a lateral root branches out from the plant’s primary root.

“This is the first time we have shown how different salmonella are from other plant pathogens based on their ability to colonise roots,” said Kapudeep Karmakar, a PhD student, department of microbiology and cell biology, IISc, and first author of the paper published in BMC Plant Biology.

Karmakar andhiscolleagues studied how different types of bacteria, including salmonella, colonise the roots of tomato plants. While other bacteria were spread across the root, salmonella bacteria clustered almost exclusively around areas where lateral roots emerge.

“When a lateral root pierces open the wall of the primary root to spread across the soil, it leaves behind a tiny opening. Using fluorescent tagging and imaging, the researchers figured out that salmonella bacteria were using this gap to enter the plant.”

Researchers also noticed that under the same conditions, a plant with a more lateral roots harboured a greater concentration of salmonella than one with fewer lateral roots. Similarly, when plants were artificially induced to produce more lateral roots, the salmonella concentration increased.