Distribution characteristics of gastric mucosal colonizing microorganisms in different glandular regions of Bactrian camels and their relationship with local mucosal immunity.

Bactrian camels inhabiting desert and semi-desert regions of China are valuable animal models for studying adaptation to desert environments and heat stress. In this study, 16S rRNA technology was employed to investigate the distribution characteristics and differences of mucosal microorganisms in the anterior gland area, posterior gland area, third gland area, cardia gland area, gastric fundic gland area and pyloric gland area of 5-peak adult healthy Bactrian camels. We aimed to explore the possible reasons for the observed microbial distribution from the aspects of histological structure and mucosal immunity. Bacteroides and Fibrobacteria accounted for 59.54% and 3.22% in the gland area, respectively, and 52.37% and 1.49% in the wrinkled stomach gland area, respectively. The gland area showed higher abundance of Bacteroides and Fibrobacteria than the wrinkled stomach gland area. Additionally, the anterior gland area, posterior gland area, third gland area, and cardia gland area of Bactrian camels mainly secreted acidic mucus, while the gastric fundic gland area mainly secreted neutral mucus and the pyloric region mainly secreted a mixture of acidic and neutral mucus. The results of immunohistochemistry techniques demonstrated that the number of IgA+ cells in the anterior glandular area, posterior glandular area, third glandular area, and cardia gland area was significantly higher than that in the fundic and pyloric gland area (p < 0.05), and the difference in IgA+ between the fundic and pyloric gland area was not significant (p > 0.05). The study revealed a large number of bacteria that can digest and degrade cellulose on the mucosa of the gastric gland area of Bactrian camels. The distribution of IgA+ cells, the structure of the mucosal tissue in the glandular region, and the composition of the mucus secreted on its surface may have a crucial influence on microbial fixation and differential distribution.