Analysis of gut bacterial diversity and exploration of cellulose-degrading bacteria in xylophagous insects

Hao

Wei

et al. 2020

Insects

Monochamus alternatus is an important insect pest in pine forests of southern China and the dispersing vector of the pine wood nematode, Bursaphelenchus xylophilus, which leads to pine wilt disease (PWD). Microbiome of M. alternatus may contribute to survival of larvae in the host pine trees. In order to investigate the intestinal bacterial structure of M. alternatus during the larvae and pupae stages in host trees, and infer the function of symbiotic bacteria, we used 16S rRNA gene Illumina sequencing to obtain and compare the bacterial community composition in the foregut, midgut, and hindgut of larvae, pupal intestines, larval galleries, and pupal chambers of M. alternatus. The diversity of the bacterial community in larval intestines and pupal intestines were similar, as well as was significantly greater in larval galleries and pupal chambers. Although there were differences in bacterial compositions in different samples, similar components were also found. Proteobacteria and Firmicutes were the two most dominant phyla in all samples, and genera Enterobacter, Raoultella, Serratia, Lactococcus, and Pseudomonas were dominant in both the intestinal samples and plant tissue samples. Enterobacter was the most abundant genus in larval intestines, and Serratia was dominant in pupal intestine. The functions of these dominant and specific bacteria were also predicted through metagenomic analyses. These bacteria may help M. alternatus degrade cellulose and pinene. The specific role of symbiotic bacteria in the infection cycle of PWD also warrants further study in the future.

Section: Discussionmentioning

confidence: 99%

Bacterial Communities Associated with the Pine Wilt Disease Insect Vector Monochamus alternatus (Coleoptera: Cerambycidae) during the Larvae and Pupae Stages

Hao

Wei

et al. 2020

Insects

“…could be an ideal agent for expressing insecticidal protein in M. alternatus midguts, which would represent a new use of microbes to control M. alternatus. Furthermore, the cellulose-degrading bacterial genera Stenotrophomonas, Gryllotalpicola, and Pseudoxanthomonas [49,52] were positively correlated with Serratia. In contrast, the genera Gp1, Gp2, Gp3, Saccharibacteria, Escherichia/Shigella, Bradyrhizobium, Sphingomonas, Terriglobus, Burkholderia, and Mucilaginibacter were negatively correlated with Serratia, and they are associated with soil pH, plant growth, and cellulose degradation [39,42,44,45].…”

Section: Discussionmentioning

confidence: 97%

“…It has been reported that the genus Gryllotalpicola was isolated from the midguts of Megopis sinica, M. alternatus, and Reticulitermes speratus, while the genus Cellulomonas was isolated from both the midgut and hindgut of M. sinica and M. alternatus [52, 53] and from the stem of P. contorta and the needles of Thuja plicata [29]. In this study, however, Gryllotalpicola had a relative abundance of only 0.25% in the midgut of M. alternatus, and Cellulomonas was not found in the midgut of M. alternatus.Both Gryllotalpicola and Cellulomonas can degrade cellulose[52], which is the main nutrient component in the food of wood-boring insects and plays an important role in the growth and development of pests[54]. Therefore, Gryllotalpicola sp.…”

mentioning

confidence: 99%

Characterization of bacterial communities associated with the pinewood nematode insect vector Monochamus alternatus Hope and the host tree Pinus massoniana

Guo

Lin

et al. 2020

Preprint

Background Monochamus alternatus Hope is one of the insect vectors of pinewood nematode ( Bursaphelenchus xylophilus ), which causes the destructive pine wilt disease. The microorganisms within the ecosystem, comprising plants, their environment, and insect vectors, form complex networks. This study presents a systematic analysis of the bacterial microbiota in the M. alternatus midgut and its habitat niche. Methods Total DNA was extracted from 20 types of samples (with three replicates each) from M. alternatus and various tissues of healthy and infected P. massoniana (pines). 16S rDNA amplicon sequencing was conducted to determine the composition and diversity of the bacterial microbiota in each sample. Moreover, the relative abundances of bacteria in the midgut of M. alternatus larvae were verified by counting the colony-forming units. Results Pinewood nematode infection increased the microbial diversity in pines. Bradyrhizobium , Burkholderia , Dyella , Mycobacterium , and Mucilaginibacter were the dominant bacterial genera in the soil and infected pines. These results indicate that the bacterial community in infected pines may be associated with the soil microbiota. Interestingly, the abundance of the genus Gryllotalpicola was highest in the bark of infected pines. The genus Cellulomonas was not found in the midgut of M. alternatus , but it peaked in the phloem of infected pines, followed by the phloem of heathy pines. Moreover, the genus Serratia was not only present in the habitat niche, but it was also enriched in the M. alternatus midgut. The colony-forming unit assays showed that the relative abundance of Serratia sp. peaked in the midgut of instar II larvae (81%). Conclusions Overall, the results indicate that the bacterial microbiota in the soil and in infected pines are correlated. The Gryllotalpicola sp. and Cellulomonas sp. are potential microbial markers of pine wilt disease. Additionally, Serratia sp. could be an ideal agent for expressing insecticidal protein in the insect midgut by genetic engineering, which represents a new use of microbes to control M. alternatus .

“…Shi et al found that pinewood nematode infection changes the physical and chemical properties of the soil and the bacterial community composition and diversity; however, Acidobacteria was the predominant bacteria in nematodeinfected soil, which had a lower pH than the uninfected soil [35]. It has been reported that the genus Gryllotalpicola was isolated from the midguts of Megopis sinica, M. alternatus, and Reticulitermes speratus, while the genus Cellulomonas was isolated from both the midgut and hindgut of M. sinica and M. alternatus [52,53] and from the stem of P. contorta and the needles of Thuja plicata [29]. In this study, however, Gryllotalpicola had a relative abundance of only 0.25% in the midgut of M. alternatus, and Cellulomonas was not found in the midgut of M. alternatus.…”

Section: Discussionmentioning

confidence: 99%

“…Both Gryllotalpicola and Cellulomonas can degrade cellulose [52], which is the main nutrient component in the food of wood-boring insects and plays an important role in the growth and development of pests [54]. Therefore, Gryllotalpicola sp.…”

Section: Discussionmentioning

confidence: 99%

Characterization of bacterial communities associated with the pinewood nematode insect vector Monochamus alternatus Hope and the host tree Pinus massoniana

Guo

Lin

et al. 2020

Preprint

Background: Monochamus alternatus Hope is one of the insect vectors of pinewood nematode (Bursaphelenchus xylophilus), which causes the destructive pine wilt disease. The microorganisms within the ecosystem, comprising plants, their environment, and insect vectors, form complex networks. This study presents a systematic analysis of the bacterial microbiota in the M. alternatus midgut and its habitat niche.Methods: Total DNA was extracted from 20 types of samples (with three replicates each) from M. alternatus and various tissues of healthy and infected P. massoniana (pines). 16S rDNA amplicon sequencing was conducted to determine the composition and diversity of the bacterial microbiota in each sample. Moreover, the relative abundances of bacteria in the midgut of M. alternatus larvae were verified by counting the colony-forming units.Results: Pinewood nematode infection increased the microbial diversity in pines. Bradyrhizobium, Burkholderia, Dyella, Mycobacterium, and Mucilaginibacter were the dominant bacterial genera in the soil and infected pines. These results indicate that the bacterial community in infected pines may be associated with the soil microbiota. Interestingly, the abundance of the genus Gryllotalpicola was highest in the bark of infected pines. The genus Cellulomonas was not found in the midgut of M. alternatus, but it peaked in the phloem of infected pines, followed by the phloem of heathy pines. Moreover, the genus Serratia was not only present in the habitat niche, but it was also enriched in the M. alternatus midgut. The colony-forming unit assays showed that the relative abundance of Serratia sp. peaked in the midgut of instar II larvae (81%).Conclusions: Overall, the results indicate that the bacterial microbiota in the soil and in infected pines are correlated. The Gryllotalpicola sp. and Cellulomonas sp. are potential microbial markers of pine wilt disease. Additionally, Serratia sp. could be an ideal agent for expressing insecticidal protein in the insect midgut by genetic engineering, which represents a new use of microbes to control M. alternatus.