title: Gut-Colonizing Bacteria Promote C. elegans Innate Immunity by Producing Nitric Oxide.
abstract: Many commensal bacteria in the gut are beneficial to the host immune system, but the underlying mechanisms are largely unclear. Using culture-independent Illumina MiSeq sequencing of the bacterial 16S rRNA gene amplicons, we show that bacterial diversity in the intestine of Caenorhabditis elegans, the free-living nematode, is distinct from that in soil. Of these bacteria, Bacillus subtilis is the most prominent species in the worm gut. We demonstrate that B. subtilis confers worm resistance to infection by pathogenic bacteria, such as Pseudomonas aeruginosa, Salmonella enterica, and Enterococcus faecalis, by producing nitric oxide (NO). Deletion of the nos gene, which encodes an NO synthase, reduces the protective effect. NO promotes innate immune responses to P. aeruginosa PA14 by activating a conserved p38 mitogen protein kinase (MAPK) in C. elegans. Our work provides an example of antagonism of commensal bacteria against pathogens and illustrates the importance of commensal bacteria in host immunity.
authors: Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming, Yunnan 650091, China.
authors: Yi
authors: Y
authors: Xiao
authors: Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming, Yunnan 650091, China.
authors: Fang
authors: F
authors: Liu
authors: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.
authors: Zhigang
authors: Z
authors: Zhang
authors: Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming, Yunnan 650091, China.
authors: Jie
authors: J
authors: Tang
authors: Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming, Yunnan 650091, China. Electronic address: chgzou@ynu.edu.cn.
authors: Cheng-Gang
authors: CG
authors: Zou
authors: Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming, Yunnan 650091, China. Electronic address: kqzhang1@aliyun.com.
authors: Ke-Qin
authors: KQ
authors: Zhang