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

Abstract

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.

Fig 1. Gross anatomy of the bactrian camel stomach [26].

1: Anterior gland area; 2: Posterior gland area; 3: Third gland area; 4: Cardia gland area; 5: Gastric fundic gland area; 6: Pyloric gland area.

Fig 2. The dots in the figure indicate each sample, and different colors indicate that the samples belong to different groups.

2A: The closer the sample distance, the more similar the composition of the samples. 2B: The closer the distance between the two points of the sample indicates the smaller the difference in community composition between the two.

Fig 3. The OUT rank curve.

The length of the horizontal axis of the curve reflects the richness of species in the sample, and the wider the curve, the richer the species composition in the sample. The vertical axis of the curve reflects the homogeneity of species in the sample; the wider the curve, the higher the homogeneity of species composition in the sample.

Fig 4

Profiling histogram of water products of sample phylum (A) and genus (B) The different colors represent different species.

Fig 5. Alpha-Diversity box plot between groups.

The box plot shows the minimum value, the first quartile, the median, the third median and the maximum 5 statistics from bottom to top, and "。" indicates an outlier.

Fig 6. Unweighted-UniFrac index chart.

The samples of the same color belong to the same group, and the closer the samples are, the shorter the branch length is, and the more similar the species composition of the two samples is.

Fig 7. Differences between groups of Phyllobacterium and Fibrobacter.

For each indicator, the same lowercase letters represent no significant difference between groups (p > 0.05), while different lowercase letters represent significant difference between groups (p < 0.05). The letter "a" represents the maximum value and "a, b, c," in descending order.

Fig 8. The scanning electron microscope results.

A-F are the anterior gland area, posterior gland area, third gland area, cardia gland area, gastric fundic gland area and pyloric gland area.

Fig 9. The results of AB&PAS staining in different glandular regions of the stomach.

A, B, C, D, E and F indicate the anterior, posterior, third, cardia, fundic, and pyloric gland regions, respectively; neutral, acidic, and moderately acidic mucus is red, blue, and purplish-red, respectively.

Fig 10. H&E staining of different glandular areas of the stomach.

A, B, C, D, E and F indicate the anterior, posterior, third, cardia, fundic, and pyloric gland regions.

Fig 11. The characterization of IgA+ distribution in different glandular regions of the stomach.

A, B, C, D, E and F indicate the anterior, posterior, third, cardia, fundic, and pyloric gland regions.

Fig 12. The differential analysis of IgA+ distribution in different glandular regions of the stomach.

_* indicates significant difference (0.01< p <0.05).