http://www.fasebj.org/content/30/1_Supplement/1143.2.short
+ Author Affiliations
Abstract
Plant-microbe interactions have been the
focus of extensive research over decades. Several benefits of symbiotic
bacteria
to plants have been reported, for instance, as
growth-promoters and pest control agents. Recently, the presence of
bacteria
in association with medicinal plants, and the
correlation with their immune-boosting properties has been suggested. We
call
these bacteria as “immune-boosting”. Pasco and
co-workers, successfully demonstrated not just bacteria being present in
a
herb, Echinacea purpurea, used for common cold treatment, but also correlated the total bacterial load with its immune-boosting activity. A more recent
study by Cech’s group also found immune-boosting compounds in Echinacea, contributed by endophytic bacteria.
Independently, we have demonstrated the
presence of such bacteria in association with Juzen-taiho-to (JTT), an
immune-boosting
formulation of ten medicinal plants used widely in
East Asia. Immunostimulatory factors were purified from JTT and
subjected
to mass spectrometric analysis and the main active
factors were found to be lipopolysachharides (LPS) of Gram-negative
bacteria.
This led us to our hypothesis: bacteria are enriched in medicinal plants, and they contribute to the immunostimulatory activity of these plants.
However, little is known about the identities of these immune-boosting
bacteria. To this end, we conducted metagenomic analysis
of the 16S ribosomal RNA obtained from the dried
roots of Angelica sinensis, the most potent herb among the ten JTT components. The 16S sequencing revealed a water and soil-borne bacterium, Rahnella aquatilis as the most predominant species associated with A. sinensis. The abundance of Rahnella in different batches of A. sinensis tested also seemed to correlate with their corresponding immunostimulatory activities. This further strengthened our hypothesis
as well as indicated Rahnella to be an immune-boosting bacterial species.
Rahnella, being a Gram-negative
bacterium, presents LPS on the surface of its cell wall. LPS is a
well-known potent immunostimulant.
The endotoxic or potent component of LPS is Lipid A
(LA). We then sought to isolate the LPS and subsequently LA from Rahnella aquatilis.
The different “LA-like species” obtained were analyzed for their
immunostimulatory activities and showed significant activities.
The activities were estimated by quantitative Real
Time-Polymerase Chain Reaction (qRT-PCR) of intercellular adhesion
molecule
1 (ICAM-1) in THP-1 monocytes. The toxicity levels
of these LA-like species were estimated by the Limulus amebocyte lysate
(LAL) assay, an endotoxin detection assay. The
comparison of the immunostimatory activities of the Rahnella
LA-like factors and their endotoxin levels revealed some species with
high activity but low endotoxicity. Taken together,
these results corroborate the notion that bacteria
are associated with medicinal herbs and their bacterial components like
LPS and LA contribute immune-boosting activities to
us.
In conclusion, this work supports the possibility of immune-boosting bacteria such as Rahnella
being enriched in herbal plants. For centuries, people have consumed
medicinal herbs for the treatment of several symptoms
and ailments. We now believe that, in addition to
the benefits derived from the herbs, they may be unknowingly consuming
and
benefiting from these immune-boosting bacteria as
well.
Support or Funding Information
NIGMS/NIH SC3 GM094070 (Research Support); NIMHD/NIH G12 MD007599-27 (Hunter College CTBR)
Footnotes
-
This abstract is from the Experimental Biology 2016 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
