A preliminary study on the diversity of butyrate-producing bacteria in response to the treatment of depression with Xiaoyaosan.

Butyrate-producing bacteria generate butyrate, which has antidepressant effects. Xiaoyaosan (XYS), a traditional Chinese medicine (TCM) used to treat depression, may improve depression-like behaviour by modulating the gut microbiota. However, the functional groups and mechanisms of action in the XYS treatment of depression remain unknown. This study aimed to analyse with clone sequencing the changes in intestinal butyrate-producing bacteria in XYS-treated chronic unpredictable mild stress (CUMS) rats. We successfully established the XYS-treated CUMS rat model of depression. Rat faecal samples were collected before, during, and after the experiment, and butyryl-CoA:acetate CoA-transferase gene primers were selected for PCR amplification to determine the diversity of butyrate-producing bacteria. The results showed that XYS increased intestinal butyrate-producing bacterial diversity in CUMS rats regarding phylum and genus numbers; the number of phyla increased to two, distributed in Firmicutes and Bacteroides, and four genera were distributed in Eubacterium sp., Roseburia sp., Clostridium sp. and Bacteroides sp. Only one phylum and two genera were present in the model group without XYS treatment. Our findings indicate that XYS can improve depression-like behaviour by regulating intestinal butyrate-producing bacteria diversity, particularly Roseburia sp. and Eubacterium sp., thus providing new insights into the targeted regulation of the intestinal flora to treat depression.

Isolation and characterization of heterotrophic nitrifying and aerobic denitrifying Klebsiella pneumoniae and Klebsiella variicola strains from various environments.

AIMS: We sought to isolate novel heterotrophic nitrifying and aerobic denitrifying Klebsiella pneumoniae and Klebsiella variicola strains from various natural environments and characterize their nitrogen removal processes. METHODS AND RESULTS: Ten novel Klebsiella strains with heterotrophic nitrification and aerobic denitrification abilities, including seven K. pneumoniae and three K. variicola, were successfully isolated from faeces, sewage, plant surfaces and sludge. A 1674-bp fragment of the hydroxylamine oxidase (hao) gene was successfully amplified from the novel strains. The removal rates of ammonium, nitrate and nitrite of the seven K. pneumoniae isolates were 96·42-97·38%, 61·27-82·78% and 100%, respectively, and the corresponding degradation ratios were 4·82-6·49 (higher than previously reported for K. pneumoniae CF-S9 and EGD-HP19-C), 1·15-1·38 and 1·48-3·33 mg l-1  h-1 , respectively. The removal rates of ammonium, nitrate and nitrite of the three K. variicola isolates were 95·01-96·15%,68·60--78·37% and 100%, respectively, and the corresponding degradation ratios were 4·79-9·5, 1·14-1·74 and 1·67-4·44 mg l-1  h-1 , respectively. The K. variicola strain sd-3 from sludge exhibited the best heterotrophic nitrification and aerobic denitrification abilities among the isolates. Meanwhile, the results of simultaneous nitrification and denitrification assays with all isolated strains showed that ammonium was removed prior to nitrate or nitrite. CONCLUSIONS: Our results indicate that K. pneumoniae and K. variicola (isolated from a novel natural environment) play an important role in the Earth's nitrogen cycle in various natural environments. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is one of only a few works to successfully isolate K. pneumoniae with heterotrophic nitrification and aerobic denitrification abilities in various natural environments. The physiological characterization K. variicola as having abilities to heterotrophically nitrify and aerobically denitrify is the first to be reported. Moreover, this study may provide alternative microbial resources for the removal of nitrogen from wastewater.