The Effects of <i>Rhodobacter sphaeroides</i> on the Composition of Gut Microbiota<i> </i>and Short-chain Fatty Acids in Mice

Abstract

This study aims to determine the effects of Rhodobacter sphaeroides 8513 on the physiological and biochemical indicators, short-chain fatty acids, and gut microbiota of healthy BALB/c mice. Mice were divided into the control group and R. sphaeroides group (5×10 8 CFU/mL). After 28 days of continuous gavage, fecal samples were collected for high-throughput sequencing, then mice were sacrificed and the serum was taken for biochemical analysis. Liver, kidney, and spleen were obtained for organ coefficient calculation, and cecum contents were collected for short-chain fatty acid analysis by gas chromatography. The results showed that there was no significant difference in body weight gain, alanine aminotransferase (ALT) and urea nitrogen (BUN) levels between the control group and R. sphaeroides group, while R. sphaeroides significantly decreased the aspartate aminotransferase (AST) and creatinine (CRE) level. No side effect of R. sphaeroides treatment on the basic physiological health of mice was observed. R. sphaeroides significantly increased the content of acetic acids in the gut of mice, while there were no significant changes in the concentration of butyric and propionic acid. High-throughput sequencing analysis indicated that there was a significant difference in α-diversity between these 2 groups, while there was no significant difference in β-diversity between them. R. sphaeroides not only increased the abundance of anaerobic bacteria of Rhodospirillaceae, Desulfovibrionaceae, and Helicobacter in the gut of mice, but also increased the abundance of the predominant microflora in the gut such as Bacteroidaceae (Bacteroides), Prevotellaceae, Clostridiales_vadinBB60_group (Closporaceae). These results suggested that R. sphaeroides 8513 could modulate the microbial ecology in the gut of mice.

The Case for Rhodobacter Sphaeroides as a probiotic: Applications for Human Health and Ulcerative Colitis

“…29 Through R. sphaeroides administration, dysbiosis could be alleviated as suggested by data that shows its capacity to modulate microbiota to a certain extent in a murine model. 12 Furthermore, chronic inflammation could be decreased due to R. sphaeroides' Tlr4-antagonizing LPS. Tlr4 activation is also an important subject of discussion to relate intestinal microbiota to the mitochondria in UC.…”

“…The only mammalian studies performed to date are one murine study, which explored the effects of its administration on microbiota and general health parameters like weight, creatinine and aspartate aminotransferase. 12 Furthermore, one bovine study was conducted, which did not study any health parameters but did report increased ubiquinone content in milk. 58 Therefore, more pre-clinical studies examining the effects of R. sphaeroides probiotic administration on health parameters relating to UC (disease expression, cytokine release, mitochondrial function, intestinal microbiota, Goblet cell count, and mucus barrier integrity) are warranted.…”

“…There is an important weakness to the conclusion that the bacteria remain viable after administration, if this conclusion is based on the fact that there is a significant change in biochemical or clinical parameters alone. Since the bacterium contains bioactive membrane-bound components and beneficial metabolites, it could be argued that in the two mammalian studies, 12,58 the observed effects could still happen following bacterial death and release of its contents in the GI tract, especially considering the relatively high and frequent dosing used. However, for a counterargument , it should be noted that R. sphaeroides viability has been tested in simulated human gastric and intestinal conditions.…”

“…1,3,4 R. sphaeroides has been the subject of interest over the past 20 years in bioengineering processes involving mass synthesis of ubiquinone, 2,5,6 environmental detoxification, 7,8 and optimization of animal health in the context of aquaculture. [9][10][11] The viability of R. sphaeroides as a probiotic does appear to extend to mammalian health, as shown by Yang et al (2020) in a murine model where R. sphaeroides administration significantly increased acetate production by the microbiota, increased abundance of predominant microbiota and α-diversity, and decreased creatinine and aspartate aminotransferase levels. 12 To echo the concluding remarks of Yang et al (2020), some interesting next steps would be to determine the effects of R. sphaeroides administration on oxidation parameters in vivo, as the presence of the bacteria with the Caco-2 cell line has already been shown to mitigate H2O2-related oxidative damage via increased endogenous activity of superoxide dismutase, catalase, and glutathione peroxidase in vitro.…”

“…[9][10][11] The viability of R. sphaeroides as a probiotic does appear to extend to mammalian health, as shown by Yang et al (2020) in a murine model where R. sphaeroides administration significantly increased acetate production by the microbiota, increased abundance of predominant microbiota and α-diversity, and decreased creatinine and aspartate aminotransferase levels. 12 To echo the concluding remarks of Yang et al (2020), some interesting next steps would be to determine the effects of R. sphaeroides administration on oxidation parameters in vivo, as the presence of the bacteria with the Caco-2 cell line has already been shown to mitigate H2O2-related oxidative damage via increased endogenous activity of superoxide dismutase, catalase, and glutathione peroxidase in vitro. 13 To further support the therapeutic potential of this bacterium, an R. sphaeroides extract named Lycogen™ already has demonstrated antioxidant and anti-inflammatory effects 14 with significant protective effects against dextran sodium sulfate (DSS)-induced colitis 15 and cisplatin-induced renal injury.…”