[WS4] Selected from Oral Session: Microbial Taxonomy, Physiology, Structure and Ecology / Application of Microorganisms

[WS4-7/ODP-008] A symbiotic relationship between intestinal lymphoid tissue resident Alcaligenes and dendritic cells

○Koji Hosomi¹, Naoko Shibata^1,2,3, Atsushi Shimoyama⁴, Tomoya Uto⁴, Takahiro Nagatake¹, Haruko Takeyama³, Koichi Fukase⁴, Hiroshi Kiyono², Jun Kunisawa^1,2,3,4,5 (¹National Institutes of Biomedical Innovation, Health, and Nutrition, ²The Univ. of Tokyo, ³Waseda Univ., ⁴Osaka Univ., ⁵Kobe Univ.)

We previously found unique bacterial communities inside intestinal lymphoid tissues including Peyer’s patches (PPs). Alcaligenes spp. including A. faecalis are a dominant genus among lymphoid-tissue-resident commensal bacteria (LRCs). LRCs modulate the host immune system including intestinal IgA production through persisting in dendritic cells (DCs) in the PPs without inducing an excessive inflammatory response. Here, we show Alcaligenes establish an intracellular symbiotic relationship with DCs and this symbiosis induces a unique energy metabolic shift in DCs that are associated with less induction of apoptosis. DCs showed reduced levels of mitochondrial respiration when they were co-cultured with non-symbiotic E. coli, whereas DCs carrying A. faecalis maintained high levels of mitochondrial respiration. Furthermore, E. coli induced apoptosis of DCs, while A. faecalis did not. An underlying mechanism included a different activity in the induction of intracellular nitric oxide (NO) production due to the different activity of LPS. E. coli induced high levels of NO production that inhibited mitochondrial function, in contrast, A. faecalis elicited little NO production in DCs, resulting in the low rate of apoptosis together with the increased mitochondrial respiration. These are novel symbiotic mechanisms of LRCs including A. faecalis in PPs.