Re: [compost_tea] Systemic bacteria..

From: <soilfoodweb_at_aol.com>
Date: Tue, 25 Nov 2003 10:01:51 -0500

Disease occurs when a plant or animal's tissues are invaded by an organism that enters into the plant or animal, grows and is spread, system-wide and therefore systemically, through the host. Typically the result of this is death of the host.

I hope you don't consider that a normal, healthy occurrence. That was what I was talking about. Normally, you do not get the growth of other organisms in what should be a sterile condition inside the tissues of a living organism.
When a bacterium or fungus that will kill the plant or animal enters, the host is not going to be around for long. Not a sustainable situation.

The original question was, are there bacteria that live inside plants. My response was that this is not a normal or healthy condition. In food plants, you notice that the plant material you are about to eat is not consumable. The pathogen has begun to decompose the leaf, and the taste will be un-desirable, and the metabolites of the pathogen as it decomposes the plant material will often produce highly undesirable symptoms in the person eating the contaminated plant material.

The work suggesting that E. coli can move into and colonize plant leaves comes from an experiment where an unusual condition resulted in the bacterium being taken up into the plant tissue. Colonization of plant tissues by any bacterium is an unusual condition - or at least let us try to keep it that way.

A major benefit of a healthy foodweb is protection of plant surfaces. The pathogens cannot find the plant surface, and that great layer of bacteria, fungi, protozoa and nematodes growing on the exudates the plant puts out keep the pathogens from being able to reach infection sites, so that the pathogen can never access either the cell wall or the cell membrane.

Could you please give me the reference to the work the bacterium you were talking about? The one that enters with the mycorrhizal fungus and systemically colonizes the plant. I have not heard of this, and in all my years of looking at mycorrhizal colonization of roots with VAM or ectomycorrhizal fungi, have never observed systemic infection of a plant with beneficial bacteria.

What I do see is reduction in systemic infection by either bacteria or fungi once the root system becomes colonized by mycorrhizal fungi.

We see many associates of mycorrhizal fungi on the root surface, but never anything in the root along with the mycorrhizal fungus.

Elaine Ingham
President, Soil Foodweb Inc.
SFI Corvallis, OR
SFI Port Jefferson, NY
SFI Lismore, NSW, Australia
SFI Hilversum, The Netherlands
SFI Cambridge, New Zealand
www.soilfoodweb.com

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Received on Tue Nov 25 2003 - 11:26:19 EST

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