Nitrogen-Fixing and Uricolytic Bacteria Associated with the Gut of Dendroctonus rhizophagus and Dendroctonus valens (Curculionidae: Scolytinae)

Abstract

The bark beetles of the genus Dendroctonus feed on phloem that is a nitrogen-limited source. Nitrogen fixation and nitrogen recycling may compensate or alleviate such a limitation, and beetle-associated bacteria capable of such processes were identified. Raoultella terrigena, a diazotrophic bacteria present in the gut of Dendroctonus rhizophagus and D. valens, exhibited high acetylene reduction activity in vitro with different carbon sources, and its nifH and nifD genes were sequenced. Bacteria able to recycle uric acid were Pseudomonas fluorescens DVL3A that used it as carbon and nitrogen source, Serratia proteomaculans 2A CDF and Rahnella aquatilis 6-DR that used uric acid as sole nitrogen source. Also, this is the first report about the uric acid content in whole eggs, larvae, and adults (male and female) samples of the red turpentine beetle (Dendroctonus valens). Our results suggest that the gut bacteria of these bark beetles could contribute to insect N balance.

Taxonomy, Physiology, and Natural Products of Actinobacteria

“…The class of Actinobacteria was represented by Ponticoccus gilvus and Kocuria marina, both of which can degrade carboxymethylcellulose in vitro. Neither Actinobacteria species has ever been reported in other bark beetles, suggesting that these bacteria could be involved in the degradation of cellulosic substrates such as pine bark and phloem, enabling them to serve as a carbon source (475). This postulate is supported by the presence of cellulose-degrading bacteria in the gut of insects that feed on woody tree tissues, such as wood-boring beetles, including Saperda vestita and Agrilus planipennis (476,477).…”

Influence of Starvation on the Structure of Gut-Associated Bacterial Communities in the Chinese White Pine Beetle (Dendroctonus armandi)

“…The molecular analysis indicated that the predominant species in the D. armandi bacterial community formed a low complexity group with a different structure after starvation. Low-complexity gut microbial communities have been reported for D. rhizophagus, D. valens and D. ponderosae [31][32][33]. Additionally, as found in all of the D. armandi developmental stages, some taxa were shared among the bacterial communities [12].…”

“…Members of Serratia secrete secondary metabolites and other biomolecules with antibacterial, antifungal, and antiprotozoal activities to outcompete other microbes. Serratia proteomaculans is associated with D. valens and D. rhizophagus guts, which contribute to insect N balance by using uric acid as sole nitrogen source [32]. This ability is crucial for colonizing niches, especially in poor conditions including poor nutrition, competing microbes and so on [41].…”

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

“…In the case of bacteria, these organisms can contribute to the degradation of starch, lipids and esters [15] as well as complex polymers such as cellulose and xylan [15–17]. Bacteria also fix nitrogen [18, 19], recycle nitrogenous metabolic products [19], tolerate and degrade monoterpenes [14, 20, 21], mediate the growth and sporulation of associated fungi [22] and produce antibiotics that inhibit the growth of antagonistic fungi [23– 24]. …”