Abstract
As permanent residents of the normal gut microbiota, bifidobacteria have evolved to adapt to the host’s immune response whose priority is to eliminate pathogenic agents. The mechanisms that ensure the survival of commensals during inflammation and maintain the stability of the core component of the normal gut microbiota in such conditions remain poorly understood. We propose a new in vitro approach to study the mechanisms of resistance to immune response factors based on high-throughput sequencing followed by transcriptome analysis. This approach allowed us to detect differentially expressed genes associated with inflammation. In this study, we demonstrated that the presence of the pro-inflammatory cytokines IL-6 and TNFα to the growth medium of the B. longum subsp. longum GT15 strain changes the latter’s growth rate insignificantly while affecting the expression of certain genes. We identified these genes and performed a COG and a KEGG pathway enrichment analysis. Using phylogenetic profiling we predicted the operons of genes whose expression was triggered by the cytokines TNFα and IL-6 in vitro. By mapping the transcription start points, we experimentally validated the predicted operons. Thus, in this study, we predicted the genes involved in a putative signaling pathway underlying the mechanisms of resistance to inflammatory factors in bifidobacteria. Since bifidobacteria are a major component of the human intestinal microbiota exhibiting pronounced anti-inflammatory properties, this study is of great practical and scientific relevance.
Highlights
Bifidobacteria are a key component of the commensal gut microbiota conferring considerable health benefits and supporting the normal functioning of the host organism [1].Bifidobacteria exert many immunomodulatory properties that became the subject of many in vitro and in vivo studies [2]
To test the effects of pro-inflammatory cytokines on the growth of the bacterial culture, B. longum subsp. longum GT15 was incubated with various concentrations of IL-6 and tumor necrosis factor a (TNFa) while OD600 values were measured at different timepoints
We showed that the presence of IL-6 [100pg/ml] and TNFa [10 ng/ml] in the growth medium led to moderate changes in the growth rate of the culture (Figure S1)
Summary
Bifidobacteria are a key component of the commensal gut microbiota conferring considerable health benefits and supporting the normal functioning of the host organism [1].Bifidobacteria exert many immunomodulatory properties that became the subject of many in vitro and in vivo studies [2]. Bifidobacteria are a key component of the commensal gut microbiota conferring considerable health benefits and supporting the normal functioning of the host organism [1]. As the predominant component of the commensal microbiota of infants [3], bifidobacteria contribute significantly to the formation of the human immune system in the early stages of postnatal development [4, 5]. The key factor in this process, ostensibly, is the ability to communicate with the immune system, which results in the regulation of both antiinflammatory and pro-inflammatory cytokines and other factors of the immune response [2, 6]. As permanent residents of the normal gut microbiota, bifidobacteria have evolved to adapt the host’s immune response whose priority is to eliminate pathogenic agents. The mechanisms that ensure the survival of commensals during inflammation and maintain the stability of the core component of the normal gut microbiota in such conditions remain poorly understood
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