Structure and dynamics of the gut bacterial microbiota of the bark beetle, Dendroctonus rhizophagus (Curculionidae: Scolytinae) across their life stages

Abstract

Bark beetles play an important role as agents of natural renovation and regeneration in coniferous forests. Several studies have documented the metabolic capacity of bacteria associated with the gut, body surface, and oral secretions of these insects; however, little is known about how the bacterial community structure changes during the life cycle of the beetles. This study represents the first comprehensive analysis of the bacterial community of the gut of the bark beetle D. rhizophagus during the insect’s life cycle using 454 pyrosequencing. A total of 4 bacterial phyla, 7 classes, 15 families and 23 genera were identified. The α-diversity was low, as demonstrated in previous studies. The dominant bacterial taxa belonged to the Enterobacteriaceae and Pseudomonadaceae families. This low α-diversity can be attributed to the presence of defensive chemical compounds in conifers or due to different morpho-physiological factors in the gut of these insects acting as strong selective factors. Members of the genera Rahnella, Serratia, Pseudomonas and Propionibacterium were found at all life stages, and the first three genera, particularly Rahnella, were predominant suggesting the presence of a core microbiome in the gut. Significant differences in β-diversity were observed, mainly due to bacterial taxa present at low frequencies and only in certain life stages. The predictive functional profiling indicated metabolic pathways related to metabolism of amino acids and carbohydrates, and membrane transport as the most significant in the community. These differences in the community structure might be due to several selective factors, such as gut compartmentalization, physicochemical conditions, and microbial interactions.

Divergence in Gut Bacterial Community Among Life Stages of the Rainbow Stag Beetle Phalacrognathus muelleri (Coleptera: Lucanidae)

“…Firmicutes and Proteobacteria were the dominant phyla in Anoplophora glabripennis [ 12 ], Hylobius abietis [ 48 ], Monochamus alternatus and Psacothea hilaris [ 4 ], Nicrophorus vespilloides [ 26 ], and Popillia japonica [ 7 ]. Firmicutes, Proteobacteria and Bacteroidetes were also the dominant phyla in Holotrichia parallela [ 47 ], Dendroctonus valens [ 13 ], and Dendroctonus rhizophagus [ 10 ], and Tenericutes also was the dominant phylum in Odontolabis fallaciosa (Lucanidae) [ 34 ]. Prior research demonstrated that intestinal Firmicutes play significant role in the degradation of complex plant carbohydrates.…”

“…Previous studies have focused on the gut bacterial community of coleopteran pests to advance progress in pest control [ 10 , 11 ], including invasive bark beetles (Scolytidae) and longhorn beetles (Cerambycidae), that mainly feed on tree xylem and phloem. These species are considered to be serious pests of forests, as they grow and develop while feeding on lignocellulose [ 12 , 13 ].…”

“…The aim of these studies was to identify how to damage and alter the core microbiota to cause the death of pests, thereby developing new pest control strategies [ 16 , 17 , 18 , 19 ]. Further, gut bacteria in these pests contributed to understand the degrading functions by digesting cellulose and lignin (i.e., wood, litter, and humus) to promote host growth [ 10 , 11 , 12 , 20 , 21 ].…”

Gut Microbial Divergence between Two Populations of the Hadal Amphipod Hirondellea gigas

“…In a more recent study of the amphipod gut microbiota from the Mariana Trench, the draft genome of a Psychromonas strain (CDP1) was analyzed, which revealed a significant genome reduction driven by host association (22). Members of the genus Propionibacterium were found in the gut of the bark beetle Dendroctonus rhizophagus and are persistent in all life stages of this insect (23). Members of Pseudoalteromonas were detected in the gut microbiota of a variety of marine animals, such as the sea cucumber Apostichopus japonicus (24) and the small abalone Haliotis diversicolor (25).…”

Gut Bacterial Communities of Dendroctonus valens and D. mexicanus (Curculionidae: Scolytinae): A Metagenomic Analysis across Different Geographical Locations in Mexico

“…Several studies using conventional techniques and massive parallel sequencing technologies have allowed the determination of the bacterial community structure associated with the inside (e.g., gut and mycangium) and the outside (e.g., mouthparts and cuticle) of the bark beetles body [ 7 , 12 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ], galleries [ 29 ], and specific developmental stages of some species [ 30 , 31 ]. In addition, the presence of two core bacteriomes, one strict (composed by Enterobacter , Serratia , Rahnella , Pantoea , Raoultella , and Pseudomonas ) and another relaxed (constituted of the strict core plus Acinetobacter , Propionibacterium , Providencia , Stenotrophomonas , Erwinia , Kluyvera , Paenibacillus , and Ralstonia ) in the gut has been recently determined in different Dendroctonus species [ 28 ], which suggests that some of these taxa probably support basic metabolic processes that benefit these bark beetles.…”