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

Abstract

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.

Gut Bacteria Associated With Monochamus saltuarius (Coleoptera: Cerambycidae) and Their Possible Roles in Host Plant Adaptations

“…Moreover, some dominant bacterial genera in the gut of M. saltuarius larvae were also reported in soil and pine tissues (e.g., Burkholderia , Dyella , and Mycobacterium ) ( Guo et al, 2020 ), and there are also examples in previous studies showing that insects can obtain beneficial microbiota from the environment to better adapt to the host (e.g., Bemisia tabaci improves its fitness on unsuitable hosts by changing the composition and abundance of its gut microbiota) ( Santos-Garcia et al, 2020 ). These findings raise the possibility that some environmental bacteria can establish a beneficial symbiotic relationship with longhorn beetles, and some of them can become consistent gut residents.…”

Multi-Omics of Pine Wood Nematode Pathogenicity Associated With Culturable Associated Microbiota Through an Artificial Assembly Approach

“…Four of them (X.3alpha. 6alpha.Mannotriose, Malt triose, Cellobiose, and Stachyose) are products of plant polymer decomposition and are important substrates for the growth of insect intestinal bacteria (Mussatto and Mancilha, 2007;Rotte et al, 2009;Hu et al, 2015).These multi-omics data show that the accumulation of pine tree ROS is beneficial to insects but not PWN, thus modulating the insect feeding behavior, which explains the host preference of the Monochamus beetle to those PWN invaded pine trees (Guo et al, 2020). Meanwhile, the rising ROS level led to the accumulation of Tyramine, which can inactivate insect immunoreaction to its parasite and enhance the mobility of nematodes in its hosts (Rotte et al, 2009).…”

Microbiome Associated with the Mycangia of Female and Male Adults of the Ambrosia Beetle Platypus cylindrus Fab. (Coleoptera: Curculionidae)

“…Therefore, these bacteria might be responsible for facilitating the excavation of the first tunnel made by adult male beetles and in tannin detoxification throughout the galleries. Moreover, both adult male and female beetles harbored bacterial taxa that are described in the literature as having a role in cellulose degradation; females showed high values in relative abundance for the genera Gryllotalpicola, Pseudoxanthomonas [57] and for members of the Micrococcinae suborder (e.g., Cellulomonadaceae, Microbacteriaceae; [58,59]). The transport of symbiotic fungi is done in specialized organs located on the prothorax as described by Cassier et al [4], and our study confirmed its structure.…”