Food poisoning is a condition that affects millions of people around the world and the main cause of the problem is said to be poor handling of food and poor standards of hygiene among food handlers. However, a new study by Indian Institution of Science (IISc), and University of Agricultural Sciences (UAS) has now indicated that there might be another way that salmonella bacteria may be finding their way into your salad vegetables- through their roots! The study, published in the journal BMC Plant Biology has explained how the contamination by these bacteria may take place in the fields, even before the crops have been harvested.
The study titled, "Root mediated uptake of Salmonella is different from phyto-pathogen and associated with the colonisation of edible organs" talks about how salad vegetables may already be carrying pathogens for food-borne diseases before they are even harvested from the field. The study explains that salmonella uptake in the plant that is harvested for use in salads, may take place at the "lateral root emerging area", which is the crack in the root, where a lateral root emerges and branches out from the main or primary root. This is why salmonella colonisation is found to be higher in plants with more lateral roots. This happens because salmonella is incapable of degrading the cell wall of the plants and is instead heavily reliant on natural openings in plants. The study concluded, "Salmonella, being unable to degrade plant cell wall material relies heavily on natural openings. Therefore, its invasion is highly dependent on the number of lateral roots which provides an entry point because of the epidermis remodeling."
It added by saying, "Thus, when number of lateral root was enhanced by increasing the soil salinity, plants became susceptible to Salmonella invasion in roots and its transmission to aerial organs." According to the authors, this is the first time that a study has been able to show how salmonella is different from other plant pathogens, as it has the ability to colonise plant roots. In the study's experiments, salmonella was found to be clustered around the points of emergence of lateral roots in the plants. The researchers used fluorescent tagging and imaging to figure out how exactly Salmonella bacteria was using the lateral root opening to enter the root of the plant.