Unique and Shared Responses of the Gut Microbiota to Prolonged Fasting: A Comparative Study Across Five Classes of Vertebrate Hosts.,Reporter:xxx Date：20171119,INTRODUCTION,1、Gut microorganisms provide a number of nutritional functions to their hosts, such as fermenting fiber and synthesizing essential amino acids . In return, hosts provide symbiotic microorganisms with a stable, protected, and nutrient-rich environment.,2、Food limitation is a physiological challenge faced by many animals that may affect their gut microbiota. First, fasting represents an energy crisis for microorganisms due to a reduction in the availability of nutrients . Second, many animals reduce the size of their intestines in response to fasting thereby generating a housing crisis for the microbiota.,3、There may be universal responses of the gut microbiota to fasting. The absence of free nutrients or physiological responses of hosts to fasting may exert similar selection on resident microorganisms and cause complementary shifts in diversity and abundances of taxa.,4、Understanding the responses of gut microorganisms to fasting is imperative, given that the gut microbiota promote host survival during periods of fasting. For example,mice and rats lacking gut microbiota (germ-free) incur higher mortality rates than conventional hosts when starved, despite similar rates of body mass loss.,5、The author compared the effects of fasting on the microbial communities of hosts from five vertebrate classes:Osteichthyes,Amphibia,Reptilia, Aves, and Mammalia. The author investigated changes in the microbial communities of two gut chambers: the colon and the cecum.,methods,The fasting time frame was divided in thirds to determine the early-fasting and mid-fastingtime points. Within ten minutes of euthanasia, the gas trointestinal tract from the distal esophagus to the rectum was removed intact. A central section (approximately 12 cm in length) of each colon was removed from all host species and promptly frozen.,1、Tilapia exhibited a continual increase in phylogenetic diversity.,Fig. 1. 1.Phylogenetic diversity of the colonic microbial communities of various hosts at different time points over prolonged fasting.,Colonic samples results,2、In toads, microbial diversity was 33% higher in early-fasted individuals and 51% higher in late-fasted individuals compared with nourished toads.,Fig. 1. 2.Phylogenetic diversity of the colonic microbial communities of various hosts at different time points over prolonged fasting.,3、There were no differences in phylogenetic diversity among the fasting geckos.,Fig. 1. 3 Phylogenetic diversity of the colonic microbial communities of various hosts at different time points over prolonged fasting.,4、Quail exhibited a variable response, with late-fasted individuals exhibiting 37% less phylogenetic diversity compared with nourished individuals .,Fig. 1.4. Phylogenetic diversity of the colonic microbial communities of various hosts at different time points over prolonged fasting.,5、Last, fasted mice exhibited 1522%higher phylogenetic diversity compared with nourished mice . These trends were also reflected in estimated measurements of species richness .,Fig. 1. 5 Phylogenetic diversity of the colonic microbial communities of various hosts at different time points over prolonged fasting.,Shared responses of the microbiota,In the colon, we were unable to identify any microbial genera that met our criteria for shared responses across allfive host species. Across tetrapods (toads, geckos, quail,mice), there were shared responses such that these animalsexhibited decreases in the abundances of Coprobacillus(P = 0.008) and Ruminococcus (P = 0.012). These decreases remained significant when investigating the colonic responses across amniotes (geckos, quail, mice;Coprococcus: P = 0.015; Ruminococcus: P = 0.036). We did not find any additional shared responses across amniotes.,谢谢聆听,