Comparison of intestinal flora structure between starting point and steady point of colonization in workers (Apis mellifera)

Abstract:

[Objective] Now, there is no reports on colonization of intestinal bacteria in insects. Exploration for difference of intestinal bacterial structure and composition between two key time points (The starting point is 0-days and the steady point is 7-days after pupation) of intestinal bacterial colonization in Apis mellifera, deepening understanding of intestinal flora colonization in bees and even insects.[Methods] After pupation, five worker individuals were collected from each of the two time points. Samples of workers were dissected and then DNA of intestinal flora was extracted. High-throughput sequencing for the highly variable region of 16S rDNA of intestinal flora was implemented using illumine platform, and then diversity of intestinal flora was analyzed by bioinformatics. Intestinal flora showing the highest relative abundance at the two time points was statistically analyzed, as well as the relative abundance and composition of intestinal flora were compared. [Results] A total of 515156 quality sequences were obtained, with a total length of 227904953 bp and an average length of 442 bp. According to OTUs-based classification, intestinal bacteria of workers were classified into 34 phylum, 82 classes, 221 orders, 405 families and 799 genera, respectively. In addition, there was a significant difference between Alpha diversity index from the starting point and that from the end point of intestinal flora colonization in workers (ACE, P=0.0014; Chao, P=0.0013; Shannon, P=0.0003; Simpson, P=0.0028). It is found that the relative abundance of Lactobacillus, Gilliamella, Bifidobacterium and Snodgrassella increased significantly, and the relative abundance of Acinetobacter, escherichia-shigella, Sphingomonas, Bacteroides, Nesterenkonia and Thermus decreased significantly (P<0.05) in 7-days workers by comparing to 0-days workers. [Conclusion] Intestinal bacterial diversity of the newly emerged (0-day) adult A. mellifera was significantly higher than that of fully colonized (7-day) workers. The relative abundance of several intestinal bacteria in adult worker bees changed significantly after colonizing. Results of the study not only increase our understanding for colonization rules of intestinal bacteria in bee, and also provide important references for studying colonization rules of intestinal bacteria in other insects.

Key words:Apis mellifera;intestinal flora colonization;16S rDNA;diversity;relative abundance