My Times Today.Contamination of salad vegetables by E.coli and Salmonella bacteria are the most common causes of food poisoning. Although most Salmonella outbreaks are linked to contamination during handling and transportation of the vegetables, there are also cases where the infectious bacteria had entered the plant when it was still in the farmland.How does it enter the plant? So far, the mechanism was not known. A new study by researchers at the Indian Institute of Science and the University of Agricultural Sciences, Bengaluru, has solved the mystery.They have found that 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 gap created when a lateral root branches out from the plant’s primary root.The researchers were studying how different types of bacteria colonize the roots of tomato plants. While other bacteria were spread across the root, Salmonella 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. They figured out that it was entering through the gap with the help of fluorescent tagging and imaging.