The gastrointestinal tract (GIT) hosts a large number of diverse microorganisms, with mutualistic interactions with the host. Here, in two separate experiments, we investigated whether light at night (LAN) would affect GIT microbiota and, in turn, the host physiology in diurnal zebra finches (Taeniopygia guttata). Experiment I assessed the effects of no-night (LL) and dimly illuminated night (dim light at night, dLAN) on fecal microbiota diversity and host physiology of birds born and raised under 12 h photoperiod (LD; 12 h light: 12 h darkness). Under LL and dLAN, compared to LD, we found a significant increase in the body mass, subcutaneous fat deposition and hepatic accumulation of lipids. Although we found no difference in total 24 h food consumption, LL/ dLAN birds ate also at night, suggesting LAN-induced alteration in daily feeding times. Concurrently, there were marked differences in amplicon sequence and bacterial species richness between LD and LAN, with notable decline in Lactobacillus richness in birds under LL and dLAN. We attributed declined Lactobacillus population as causal (at least partially) to negative effects on the host metabolism. Therefore, in experiment II with similar protocol, birds under LL and dLAN were fed on diet with or without Lactobacillus rhamnosus GG (LGG) supplement. Clearly, LGG supplement ameliorated LL- and dLAN-induced negative effects in zebra finches. These results demonstrate adverse effects of unnatural lighting on GIT bacterial diversity and host physiology, and suggest the role of GIT microbiota in the maintenance of metabolic homeostasis in response to LAN environment in diurnal animals.

胃肠道（GIT）容纳大量各种各样的微生物，并与宿主相互影响。在这里，在两个单独的实验中，我们调查了夜晚的光线（LAN）是否会影响GIT微生物群，进而影响日斑马雀（Taeniopygia guttata）的宿主生理）。实验一评估了在12 h光照周期（LD; 12 h光照：12 ​​h黑暗）下无夜（LL）和昏暗的夜晚（昏暗的灯光，晚上，dLAN）对粪便微生物群多样性和宿主生理的影响。 ）。与LD相比，在LL和dLAN下，我们发现体重，皮下脂肪沉积和肝脏脂质的肝堆积显着增加。尽管我们发现24小时的总食物摄入量没有差异，但是LL / dLAN鸟类也在夜间进食，这表明LAN引起的每日进食时间发生了变化。同时，LD和LAN之间的扩增子序列和细菌种类丰富度存在显着差异，LL和dLAN下家禽的乳酸杆菌丰富度显着下降。我们归因于乳酸杆菌下降导致对宿主代谢的负面影响（至少部分）。因此，在具有类似规程的实验II中，在LL和dLAN下的家禽饲喂有或没有鼠李糖乳杆菌GG（LGG）补充剂的日粮。显然，LGG补充剂改善了斑马雀科中LL和dLAN引起的负面影响。这些结果证明了不自然照明对GIT细菌多样性和宿主生理的不利影响，并暗示了GIT微生物群在维持昼夜动物响应LAN环境的代谢稳态中的作用。