Activities and Prevalence of Proteobacteria Members Colonizing Echinacea purpurea Fully Account for Macrophage Activation Exhibited by Extracts of This Botanical

Abstract

Evidence supports the theory that bacterial communities colonizing Echinacea purpurea contribute to the innate immune enhancing activity of this botanical. Previously we reported that only about half of the variation in in vitro monocyte stimulating activity exhibited by E. purpurea extracts could be accounted for by total bacterial load within the plant material. In the current study we test the hypothesis that the type of bacteria, in addition to bacterial load, is necessary to fully account for extract activity. Bacterial community composition within commercial and freshly harvested (wild and cultivated) E. purpurea aerial samples was determined using high-throughput 16S rRNA gene pyrosequencing. Bacterial isolates representing 38 different taxa identified to be present within E. purpurea were acquired and the activity exhibited by extracts of these isolates varied by over 8,000-fold. Members of the Proteobacteria exhibited the highest potency for in vitro macrophage activation and were the most predominant taxa. Furthermore, the mean activity exhibited by the Echinacea extracts could be solely accounted for by the activities and prevalence of Proteobacteria members comprising the plant-associated bacterial community. The efficacy of E. purpurea material for use against respiratory infections may be determined by the Proteobacterial community composition of this plant, since ingestion of bacteria (probiotics) is reported to have a protective effect against this health condition.

Plant microbiome-dependent immune enhancing action of Echinacea purpurea is enhanced by soil organic matter content

“…In our previous studies we reported that the bacterial components lipopolysaccharide (LPS) and Braun-type lipoproteins within extracts of E. purpurea and other botanicals were responsible for essentially all of the in-vitro activation of monocytes/macrophages 1 . Consistent with these findings, our later studies showed that the level of in vitro macrophage activation exhibited by an E. purpurea extract could be predicted by calculating the sum of activities contributed by the prevalence and types of Proteobacteria within the plant material 4 . Furthermore, we found that root and aerial extracts from E. purpurea and E. angustifolia , obtained from six distinctly different regions in North America, exhibited substantial variation in macrophage stimulatory activity (up to 200-fold).…”

“…Evidence from our lab 1–4 and others 5,6 supports the theory that the efficacy of E. purpurea against respiratory infections is dependent, at least in part, on its bacterial community (microbiome). Bacterial components of this microbiome can directly impact immune function 1–5 and plant-endophyte interactions can alter secondary metabolite production of the anti-inflammatory alkylamides 6 .…”

“…We have also reported that there are two factors that determine Echinacea extract activity – total bacterial load and activity exhibited by each type of bacteria (which can vary by over 8000-fold). Using these two factors, we found that Echinacea extract activity can be accounted for by the activities and prevalence of Proteobacteria members colonizing this plant 4 . In the current study we have suggestive evidence that both bacterial load (Fig.…”

“…The majority of detected activity was due to changes in levels of LPS and bacterial Braun-type lipoproteins, and differences in post-harvesting conditions did not appear to be responsible for the observed variation in activity 2 . Follow-up research indicated that the Echinacea sourced from the six geographical locations also exhibited variation in both total bacterial load (up to 52-fold) and composition of the bacterial community 3,4 .…”

Cell‐line‐based assay for the toxicity/benefit analysis of lipopolysaccharides in plants

“…Recent studies revealed that the immunostimulatory factors in Echinacea and JTT were lipopolysaccharides (LPSs) of plant‐associated Gram‐negative bacteria (Haron et al, ; Kalpana et al, ; Montenegro et al, ; Pugh, Jackson, & Pasco, ; Pugh et al, ; Todd et al, ). These findings opened a possibility that the immunostimulatory activity of other medicinal plants might also arise from LPSs.…”