The Preventive Effect And Mechanism Of Aerosol-derived Bacterium Roseicella Aerolata GB24~T Against Streptococcus Pneumoniae Infection

BackgroundUnder the background of the pandemic of novel coronavirus infection,the infection caused by Streptococcus pneumoniae has become one of the important complications,and the enhancement of antibiotic resistance and the emergence of nonvaccine serotype strains make conventional prevention and control measures difficult to cope with.The discovery of the gut-lung axis and the development of probiotics provide a new intervention target and microbial therapy for the treatment of S.pneumoniae infection,and the complex environment of electronic waste landfill makes it a potential hiding place for various novel bacteria,from which probiotics that can antagonize S.pneumoniae can be screened has great practical significance.ObjectiveA new species of bacteria,Roseicella aerolata GB24T,isolated from the aerosol of an e-waste site in Guangdong Province,was identified by multiphase taxonomy,and its protective effect and related mechanism against S.pneumoniae infection were explored together with the gut-lung axis and extracellular vesicles.Methods1.Systematic taxonomic identification of strain GB24T was performed from various aspects including bacterial phenotype,growth characteristics,physiological and biochemical properties,and comparative genomic analysis.2.An agar diffusion method was used to explore the antagonistic inhibitory ability of strain GB24T on the growth of S.pneumoniae;Bronchial Epithelium transformed with Ad 12-SV40 2B(BEAS-2B)cells and Sprague-Dawley rats models infected with S.pneumoniae were constructed respectively;qPCR was performed to detect the relative gene expression levels of inflammatory cytokines interleukin-1β(IL-1β),interleukin-6(IL-6)and tumor necrosis factor-α(TNF-α);body weight,lung weight,lung tissue organ coefficient,lung wet-to-dry weight ratio,S.pneumoniae colonization,bronchoalveolar lavage fluid,and other related indexes in rats were observed;the 16S rRNA V3-V4 region was sequenced using Illumina high-throughput sequencing platform to detect the microbial composition in rats feces;the content and composition of short-chain fatty acids(SCFAs)in rats feces were determined by gas chromatography-mass spectrometry(GC-MS).3.The effect of sodium acetate and the extracellular vesicles of strain GB24T on the relative gene expression levels of IL-1β,IL-6,and TNF-α in BEAS-2B cells after S.pneumoniae infection was examined by qPCR.Results1.Strain GB24T is a gram-negative,partly anaerobic coccus with an average diameter of 1.0 μm.The optimal growth conditions are a temperature of 37℃ and pH=7.0.The 16S rRNA similarity between strain GB24T and the model strain was 97.5%,and the Average Nucleotide Identity(ANI)and in silico DNA-DNA hybridization(isDDH)values were 83.2%(Ortho ANI),83.3%(ANIb)and 27.0%,respectively,and was defined as a new species of Roseicella and named Roseicella aerolata GB24T.2.Strain GB24T not only inhibited the growth of S.pneumoniae and the average diameter of the inhibition circle formed was 20 mm,but also significantly alleviated the inflammatory damage caused by S.pneumoniae infection;strain GB24T caused a significant decrease in the diversity of the gut microbiota and an increase in the abundance of the beneficial bacteria Lactobacillus;the concentrations of SCFAs tended to increase compared to the model group.3.0.05 mM sodium acetate and the extracellular vesicles of GB24T could significantly alleviate the inflammation of BEAS-2B cells caused by S.pneumoniae infection.Conclusion1.Strain GB24T is a new species of Roseicella.2.Strain GB24T antagonizes S.pneumoniae and exerts protection against S.pneumoniae infection by modulating the lung-gut axis.3.Acetic acid and extracellular vesicles are critical metabolites and active substances in GB24T defense against S.pneumoniae infection.