Intermediate chains of exopolysaccharides from Lactobacillus rhamnosus RW-9595M increase IL-10 production by macrophages.

AIMS: To evaluate the immunosuppressive properties of the exopolysaccharide (EPS) from high-EPS producer Lactobacillus rhamnosus RW-9595M on inflammatory cytokines produced by macrophages. METHODS AND RESULTS: The conditioned media (CM) were produced by macrophages treated with parental Lact. rhamnosus ATCC 9595 and its isogenic variant, the high-EPS producer Lact. rhamnosus RW-9595M, and the levels of TNF-alpha, IL-6, IL-10 and IL-12 were evaluated. Results revealed that CM from parental Lact. rhamnosus induced higher levels of TNF-alpha, IL-6 and IL-12 but inhibited IL-10 production, whereas its mucous variant induced low or no TNF-alpha and IL-6. Addition of purified EPS to macrophages treated with parental Lact. rhamnosus decreased the inflammatory cytokines and inhibited the metabolic activity of lymphocytes. The intermediate polysaccharide chains (16-30 units) produced by time-controlled hydrolysis of EPS increased the IL-10 produced by macrophages. CONCLUSIONS: Polysaccharide chains of EPS induced immunosuppression by the production of macrophagic anti-inflammatory IL-10. SIGNIFICANCE AND IMPACT OF THE STUDY: These results indicate that the EPS from Lact. rhamnosus RW-9595M may be useful as a new immunosuppressive product in dairy food.

Role of Predatory Bacteria in the Termination of a Cyanobacterial Bloom.

Changes in cyanobacterial abundance and in the occurrence of bacteria capable of lysing cyanobacteria were monitored over a period of 6 months (May to October 1998) in eutrophic Brome Lake (Quebec, Canada), in which dense cyanobacterial blooms recur regularly. By screening lake water, we isolated two strains of lytic bacteria from the family Cytophagaceae. When tested on 12 cyanobacteria and 6 heterotrophic bacteria, strain 1 lysed only Anabaena flos-aquae and strain 2 lysed only Synechococcus cedorum, Synechococcus leopoliensis, Synechococcus elongatus, and Anacystis nidulans: both liquid and agar-grown cultures of these cyanobacteria were lysed. The number of plaque-forming units of bacteria increased dramatically during the decline of the bloom. The results are consistent with an important role for these host-specific lytic bacteria in control and elimination of cyanobacterial blooms in this lake.