Researchers show how probiotics boost plant immunity

Aug 27, 2012 by Tracey Bryant
At left, a magnified stomata (pore and surrounding guard cell) on a plant leaf is shown being attacked by pathogens. However, when the beneficial bacterium Bacillus subtilis is added to the plant's soil, the bacteria signal the stomata to close, cutting off the pathogens' access to the plant interior.

(Phys.org)—With the help of beneficial bacteria, plants can slam the door when disease pathogens come knocking, University of Delaware researchers have discovered.

A scientific team under the leadership of Harsh Bais, assistant professor of plant and soil sciences in UD's College of Agriculture and Natural Resources, found that when pathogens attempt to invade a plant through the tiny open pores in its leaves, a surprising ally comes to the rescue. Soil bacteria at the plant's roots signal the leaf pores to close, thwarting infection.

The fascinating defense response is documented in video and micrographs of live taken by confocal and at UD's Bio-Imaging Center at the Delaware Biotechnology Institute.

The research, which explored the interaction between the Bacillus subtilis and the , is published in the August issue of The Plant Journal. The findings underscore both the importance of root-based processes in plant defense and the potential for bolstering plant immunity naturally through the emerging field of probiotics.

Postdoctoral researcher Amutha Sampath Kumar is the lead author of the journal article. In addition to Bais, the co-authors include postdoctoral researcher Venkatachalam Lakshmanan, researchers Jeffrey L. Caplan, Deborah Powell and Kirk J. Czymmek of UD's Bio-Imaging Center, and Delphis F. Levia, associate professor of geography. The National Science Foundation, University of Delaware Research Foundation and Delaware Experimental Program to Stimulate Competitive Research (EPSCoR) provided funding for the study.

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With the help of beneficial bacteria, plants can slam the door when disease pathogens come knocking.

Millions of stomata, consisting of microscopic pores surrounded by guard cells, cover the above-ground parts of plants, from the stems to the . The pores resemble tiny mouths, or doors, which the open and close to allow carbon dioxide, oxygen, water and minerals in and out of the plant.

Pathogens also can slip through these stomata and begin infecting the plant. However, as Bais's team confirmed, this invasion is halted when the beneficial bacterium Bacillus subtilis is present in the soil where the plant is rooted. The finding was based on tests of approximately 3,000 Arabidopsis plants inoculated with the foliar pathogen Pseudomonas syringae pathovar tomato DC3000 (PstDC3000) during a year-long period.

When a foliar pathogen attacks, as shown in previous research by Bais and his group, the plant recruits Bacillus subtilis to help and facilitates its multiplication. The Bacillus subtilis bacteria bind to the plant's roots and invoke abscisic acid and salicylic acid signaling pathways to close the stomata.

Abscisic acid and salicylic acid are both important hormones involved in plant defense. When a plant encounters adverse environmental conditions, such as drought, for example, abscisic acid triggers the stomata to shut tightly to prevent the plant from dehydrating.

In addition to ramping up plant disease resistance, the use of this rhizobacteria to promote drought tolerance in plants could be a very promising avenue, Bais notes.

"Many bacterial pathogens invade plants primarily through stomata on the leaf surface," Bais says. "But how do plants fight off infection? In our studies of the whole plant, we see this active enlistment by Bacillus subtilis, from root to shoot."

Strikingly, the research team's data revealed that of different root-associated tested, only Bacillus species were effective in closing the stomata and for a prolonged period.

"We know only 1 to 5 percent of what this bug can do, but the potential is exciting," Bais notes, pointing out that there is increasing commercial interest in inoculating crop seeds with to reduce pathogen infection. "Just as you can boost your immune system, plants also could be supercharged for immunity."

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Mike_Massen
3 / 5 (2) Aug 28, 2012
The same general paradigm seems to apply to all mammals, in that shifting the bowel bacteria equilibrium away from pathogens and more to helpful bacteria not only improves immune system function as any pathogen generated toxins are minimised but other chemicals from those pathogens not normally considered as toxins are reduced. the suggestion is many of these unknown chemicals (sofar) contribute to the speed of aging.

One way to shift the equilibrium to beneficial bacteria is to take bacteria supplements as in live bacteria of many types. Another way is to eat foods which the good bacteria favour and also to increase zinc and copper intake which tends to impact more on pathogens than good bacteria. Also ensure foods allow the bowels to be a little more acidic, eg vinegars etc as alkaline bowel environments tend to favour pathogens...

Natural raw veges and fruits where possible in conjunction with legumes and rice, nuts are also helpful.

Cheers