Gut-Associated Bacteria Throughout the Life Cycle of the Bark Beetle Dendroctonus rhizophagus Thomas and Bright (Curculionidae: Scolytinae) and Their Cellulolytic Activities

Abstract

Dendroctonus rhizophagus Thomas and Bright (Curculionidae: Scolytinae) is an endemic economically important insect of the Sierra Madre Occidental in Mexico. This bark beetle has an atypical behavior within the genus because just one beetle couple colonizes and kills seedlings and young trees of 11 pine species. In this work, the bacteria associated with the Dendroctonus rhizophagus gut were analyzed by culture-dependent and culture-independent methods. Analysis of 16S rRNA sequences amplified directly from isolates of gut bacteria suggests that the bacterial community associated with Dendroctonus rhizophagus, like that of other Dendroctonus spp. and Ips pini, is limited in number. Nine bacterial genera of γ-Proteobacteria and Actinobacteria classes were detected in the gut of Dendroctonus rhizophagus. Stenotrophomonas and Rahnella genera were the most frequently found bacteria from Dendroctonus rhizophagus gut throughout their life cycle. Stenotrophomonas maltophilia, Ponticoccus gilvus, and Kocuria marina showed cellulolytic activity in vitro. Stenotrophomonas maltophilia, Rahnella aquatilis, Raoultella terrigena, Ponticoccus gilvus, and Kocuria marina associated with larvae or adults of Dendroctonus rhizophagus could be implicated in nitrogen fixation and cellulose breakdown, important roles associated to insect development and fitness, especially under the particularly difficult life conditions of this beetle.

Cellulolytic Bacteria Associated with the Gut of Dendroctonus armandi Larvae (Coleoptera: Curculionidae: Scolytinae)

“…All isolates were active against carboxymethylcellulose; nevertheless, only a S. vestita isolate showed activity against filter paper. A study of the bacterial flora in the guts of Dendroctonus rhizophagus proposed that most of the bacterial genera that were present could be implicated in nitrogen fixation and cellulose breakdown, which are important roles associated with insect development and fitness, particularly given the challenging environment that is inhabited by bark beetles [10]. All of these results indicate that the bacteria in beetle hindguts play an important role in the degradation of plants and other organic matters that are consumed by D. armandi larvae.…”

“…Viable counting demonstrated that the population density of the cellulolytic bacteria in D. armandi larvae was 1.1 ± 0.46 × 10 2 CFU/gut, which was lower than that of other beetles, such as Saperda vestita (2.4 × 10 5 to 3.57 × 10 6 CFU/gut) [9] and D. rhizophagus (2.3 ± 0.43 × 10 3 CFU/gut) [10]. After one month of enrichment, the population density of the bacteria with CMCase activities was 1.5 ± 0.4 × 10 4 CFU/gut, which was also lower than that of other insects, such as Holotrichia parallela (1.14 ± 0.13 × 10 8 CFU/gut) and Pachnoda marginata (2.5 ± 1.1 × 10 8 CFU/mLgut) [4,22].…”

“…have been previously isolated or detected in Dendroctonus spp. [10,24,25]. Known for the ability to produce a myriad of extracellular enzymes such as cellulases [26], Serratia spp.…”

“…The larvae of D. armandi bore into the bark of P. armandi and feed on its nutrient-poor phloem substrates. Symbiotic microbes provide nutritional supplements that benefit their hosts [8], and the intestinal bacteria in the hindgut of bark beetles, such as D. frontalis and D. rhizophagus, might be responsible for the cellulose degradation [9,10].…”

Effect of bacterial probiotics bio encapsulated into Artemia franciscana on weight and length of the shortfin silverside (Chirostoma humboldtianum), and PCR DGGE characterization of its intestinal bacterial community

“…Metagenomic DNA obtained from the intestinal contents of fingerlings from control and probiotic treatments were used as a target for PCR amplification of V3 and V6-V8 regions of 16S rRNA gene. DGGE primers, PCR conditions, and DGGE general methodology were performed following directions previously described (Morales-Jiménez et al, 2012). PCR-DGGE profiles displayed by both 16S rRNA regions and the different experimental groups were grouped using Dice similarity coefficient and UPGMA hierarchical clustering method, the image analysis was made with the software Syngene (Synoptics Ltd., UK).…”