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Plants vs. Fungi: Inherent Antimicrobial Activity

Fungi fight back…

 Situ Biosciences – Microbial Test Experts

There is a war being waged by the microorganisms around us.  New research has shown that fungi have evolved proteins that help it avoid plant defenses against microbes.  This research provides another amazing example of the subtle interplay that occurs in nature between a host and the pathogenic organisms that they battle against. 

Plants like all organisms have immune responses that help them fight against infection by microorganisms.  However, in turn, microorganisms have evolved numerous very subtle mechanisms either to simply evade or to directly counteract these host defenses.

In a recent article by De Jonge et al (Science Aug 20, 2010), one such mechanism used by the tomato plant pathogenic fungi Cladosporium fulvum was described.    Cladosporium sp., a fungi commonly associated with the defacement of cellulosic products such as papers and textiles, predominantly plagues agricultural industries.   This article presents how these fungi release a protein that helps the fungi go undetected while invading the tomato plant.   The result is that the plant has a more difficult time in responding to this particular fungal pathogen, lessening its antifungal response.

In the microbial world, immunological defenses (such as antibodies) are keyed into pattern recognition receptors that “see” parts of microbes or small molecules released from microbes that then signals the plant to initiate both biochemical (fast response) and genetic (slower response) changes to stop the invading microbe.  In the case described in this article, the plant would normally detect the release of waste chitin (a fungal cell wall component) and initiate a response against the pathogen.  However, the fungi can “cover its tracks” by releasing a protein to bind the chitin, hiding the waste chitin from the normal plant receptor.

As in combat, evasion of detection for the fungi is key to their ability to thrive.  Plants and fungi are relatively slow in responses to environmental stimuli, so if the fungi can obtain the upper hand is it growth cycle, the host plant is likely to succumb over time.

You may have heard –  Chitin and Chitosan are not the same.  Chitosan is a trade name for a chemically processed form of chitin, which is the sugar polymer derived from chitin. Chitosan derives antimicrobial properties from the processing of chitin making it cationic, which as a polymer has certain antibacterial and antifungal properties.  Chitin for this use is typically derived from shrimp exoskeletons because of their abundance and relative purity as compared to other renewable sources of chitin.

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