|HARON, MONA - University Of Mississippi|
|PUGH, NIRMAL - University Of Mississippi|
|JACKSON, COLIN - University Of Mississippi|
|PASCO, DAVID - University Of Mississippi|
Submitted to: Food & Function
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2016
Publication Date: 10/25/2016
Citation: Tyler, H.L., Haron, M.H., Pugh, N.D., Jackson, C.R., Pasco, D.S. 2016. Bacterial components are the major contributors to the macrophage stimulating activity exhibited by extracts of common edible mushrooms. Food & Function. 7:4213-4221.
Interpretive Summary: Consumption of medicinal plants and mushrooms is known to provide several health benefits, including enhancing immune function. Previous research indicates that the cell wall components of the bacteria colonizing medicinal plants are a major contributor to their immune enhancing properties. Scientists at the University of Mississippi in Oxford and the USDA-ARS Crop Production Systems Research Unit in Stoneville, MS conducted a study on edible and medicinal mushrooms purchased at supermarkets in Mississippi and Tennessee to determine if the bacteria that colonize mushrooms also contribute to their immune enhancing properties. Mushroom samples with higher immune stimulating activity tended to have higher levels of bacterial colonization and bacterial cell wall components. Levels of two specific genera of bacteria, Pseudomonas and Flavobacterium, were also observed to correlate with higher immune activity. The results of this study demonstrate that the bacteria colonizing mushrooms contribute substantially to their immune enhancing activity and will provide scientists working on medicinal fungi with insight into how their consumption benefits human health.
Technical Abstract: Background: Recent studies have indicated that a major contributor to the innate immune enhancing properties of some medicinal plants is derived from the cell wall components of bacteria colonizing these plants. Purpose: The purpose of the current study was to assess if the bacteria present within edible and medicinal mushrooms substantially contribute to innate immune stimulating potential of these mushrooms. Study Design: Whole mushrooms from thirteen types of edible fungi and individual parts from Agaricus bisporus were analyzed for in vitro macrophage activation as well as bacterial lipopolysaccharides (LPS) content, cell load, and community composition. Methods: In vitro macrophage activation was measured as TNF-alpha production by RAW 264.7 cells exposed to mushroom extracts. Bacterial cell load and community composition were determined by extracting deoxyribonucleic acid (DNA) from mushrooms and analyzing the 16S ribosomal ribonucleic acid (rRNA) gene. Results: Substantial variation between samples was observed in macrophage activation (over 500-fold), total bacterial load (over 200-fold), and LPS content (over 10 million-fold). Both LPS content ('=0.832, p <0.0001) and total bacterial load ('=0.701, p <0.0001) correlated significantly with macrophage activation in the whole mushroom extracts. 16S rRNA gene sequencing demonstrated the bacterial community within whole mushroom samples was frequently dominated by Pseudomonas. Significant correlations between macrophage activation and total bacterial load ('= 0.723, p=0.0001) and LPS content ('=0.951, p<0.0001) were also observed between different tissues of Agaricus bisporus. Pseudomonas and Flavobacterium were the most prevalent genera identified in the different tissue parts and these taxa were significantly correlated with in vitro macrophage activation ('=0.697, p<0.0001 and '=0.659, p=0.0001, respectively). Conclusion: These results indicate that components derived from mushroom associated bacteria contribute substantially to the innate immune enhancing activity exhibited by mushrooms and may result in similar therapeutic actions as reported for ingestion of bacterial preparations such as probiotics.