Bacterial invasion proteins could improve detection of live crop pathogens

Scientists, researchers, seed companies and others may soon have a new tool for identifying bacterial pathogens in crops, according to a study published in the Journal of Microbiological Methods. The research, led by Rachel Herschlag from Penn State's College of Agricultural Sciences, introduces a new method called enzyme-linked chaperone assay (ELCA) which can detect living Pseudomonas syringae, a common bacterium that infects various crops, vegetables and woody ornamentals.

The ELCA method is similar in cost to the traditional enzyme-linked immunosorbent assay (ELISA), but it has the advantage of being able to detect only living bacteria, making it more sensitive and accurate. Herschlag explained that the method works by using a bacterial chaperone to recognize and bind to its matching effector protein, which then triggers a color change. This highly specific interaction allows the method to reliably detect its intended target, which is living bacteria capable of causing infections.

Unlike other diagnostic tests that work by detecting specific cell parts like DNA, ELCA relies on the unique process used by bacteria to invade their hosts. When bacteria attack their hosts, they deliver specialized proteins called effectors into the host's cells. These proteins, recognized by host chaperones, help the bacteria overcome the host's immune system and invade the organism.

ELCA takes advantage of this process by using a chaperone to recognize and bind to the bacterial effectors, turning the solution yellow as a visual signal that the target is present.

The researchers emphasize that this new technique is particularly helpful because effectors are only produced by living bacteria, and they degrade quickly, meaning they likely don't survive long in dead bacteria. This feature reduces the likelihood of false positives in ELCA tests. In the future, the researchers aim to optimize the test and adapt the concept for detecting other pathogens with comparable chaperone-effector systems, including those relevant to agriculture, veterinary science and human health.