‘Bacteria can infect plants at a very early stage’

Infectious bacterium can enter a plant from contaminated soil at a very early stage, a new study has found.

The study was carried out by the Indian Institute of Science (IISC) and the University of Agricultural Sciences (UAS), Bengaluru.

Of late, E. coli and Salmonella bacteria infections - the most common cause of food poisoning - have led to large scale recalls.

The study conducted by Kapudeep Karmakar, a PhD student in the department of microbiology and cell Biology, IISC found, ‘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’.

“There are several possible sources from where Salmonella can reach the soil, such as manure containing animal faeces or contaminated irrigation water. Various studies show that irrigation water gets contaminated by sewage water. When that water is used in the field, the soil becomes the portal for Salmonella to enter,” said Karmakar.

According to him, this is the first time it is proven how different the bacteria are from other plant pathogens, based on its ability to colonise the roots.

The study goes on to say, “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.”

It has also been found that when salt concentration in the soil increases, plants produce more lateral roots, therefore, rendering them highly vulnerable to Salmonella infections.