Role of Carbon Monoxide in Host–Gut Microbiome Communication

Abstract

Nature is full of examples of symbiotic relationships. The critical symbiotic relation between host and mutualistic bacteria is attracting increasing attention to the degree that the gut microbiome is proposed by some as a new organ system. The microbiome exerts its systemic effect through a diverse range of metabolites, which include gaseous molecules such as H2, CO2, NH3, CH4, NO, H2S, and CO. In turn, the human host can influence the microbiome through these gaseous molecules as well in a reciprocal manner. Among these gaseous molecules, NO, H2S, and CO occupy a special place because of their widely known physiological functions in the host and their overlap and similarity in both targets and functions. The roles that NO and H2S play have been extensively examined by others. Herein, the roles of CO in host–gut microbiome communication are examined through a discussion of (1) host production and function of CO, (2) available CO donors as research tools, (3) CO production from diet and bacterial sources, (4) effect of CO on bacteria including CO sensing, and (5) gut microbiome production of CO. There is a large amount of literature suggesting the “messenger” role of CO in host–gut microbiome communication. However, much more work is needed to begin achieving a systematic understanding of this issue.

Carbon Monoxide Induced Metabolic Shift in the Carboxydotrophic Parageobacillus thermoglucosidasius DSM 6285

“…Various life forms, including bacteria, show a wide range of physiological responses to CO. The gas either interferes with central metabolic pathways resulting in deprivation of energy and suppression of immune response or serves as sole or alternative source of energy and/or carbon [ 31 ]. P. thermoglucosidasius oxidises CO strictly under anaerobic conditions [ 10 ], which implies that during initial aerobic growth, the bacterium had to cope with the toxicity of CO to its terminal oxidases.…”

Biome-specific distribution of Ni-containing carbon monoxide dehydrogenases

“…Especially, in human gut microbiomes, the Ni-CODHs in the order Lachnospirales such as Blautia hydrogenotrophica are used for H 2 -dependent acetogenesis via WLP (Rey et al 2010 ; Laverde Gomez et al 2019 ). Moreover, luminal CO emission occurs via various microbial metabolic pathways as well as the host and carbon cycling is performed by CO-utilizing microbiomes (Hopper et al 2020 ) where CO oxidation by Ni-CODH might be coupled with ECH or CooF/FNOR. Similarly, CO emission occurs via organic solid waste degradation processes (Haarstad et al 2006 ; Stegenta-Dąbrowska et al 2019 ), whereas most MAGs constructed in anaerobic digesters encode the Ni-CODH genes performing carbon cycle via methanogenesis and acetogenesis (Treu et al 2018 ; Zhu et al 2019 ; Campanaro et al 2020 ).…”

Recent advances on endogenous gasotransmitters in inflammatory dermatological disorders

“…Furthermore, CO can also target immune responses by regulating T cell proliferation and differentiation [130] . Also, CO has been reported to be a potential messenger with communication from host to bacteria in human, especially in GI tract [131] . Hence, CO plays critical roles in biological processes, such as chronic pain, mitochondrial biogenesis, cellular proliferation, inflammation, and immune responses [127] , [132] .…”

“…In addition, gaseous molecules such as CO and H 2 S have been reported to be potential messengers in communication in the direction from host to bacteria and microbiota also appears to be an important target of these molecules in human, especially GI tract [131] , [177] . Similar to microbes in GI tract, the skin is populated with millions of microbes, which participant in both the innate and adaptive responses of the cutaneous immune system [178] .…”