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Bacterial associates of seed-parasitic wasps (Hymenoptera: Megastigmus).

Paulson AR, von Aderkas P, Perlman SJ - BMC Microbiol. (2014)

Bottom Line: Males and females were infected at similar frequencies, suggesting that these bacteria do not distort sex ratios.The M. spermotrophus microbiome is dominated by five bacterial OTUs, including lineages commonly found in other insect microbiomes and in environmental samples.The bacterial community associated with M. spermotrophus remained constant throughout wasp development and was dominated by a single OTU - a strain of Ralstonia, in the Betaproteobacteria, comprising over 55% of all bacterial OTUs from Megastigmus samples.

View Article: PubMed Central - PubMed

ABSTRACT

Background: The success of herbivorous insects has been shaped largely by their association with microbes. Seed parasitism is an insect feeding strategy involving intimate contact and manipulation of a plant host. Little is known about the microbial associates of seed-parasitic insects. We characterized the bacterial symbionts of Megastigmus (Hymenoptera: Torymidae), a lineage of seed-parasitic chalcid wasps, with the goal of identifying microbes that might play an important role in aiding development within seeds, including supplementing insect nutrition or manipulating host trees. We screened multiple populations of seven species for common facultative inherited symbionts. We also performed culture independent surveys of larvae, pupae, and adults of M. spermotrophus using 454 pyrosequencing. This major pest of Douglas-fir is the best-studied Megastigmus, and was previously shown to manipulate its tree host into redirecting resources towards unfertilized ovules. Douglas-fir ovules and the parasitoid Eurytoma sp. were also surveyed using pyrosequencing to help elucidate possible transmission mechanisms of the microbial associates of M. spermotrophus.

Results: Three wasp species harboured Rickettsia; two of these also harboured Wolbachia. Males and females were infected at similar frequencies, suggesting that these bacteria do not distort sex ratios. The M. spermotrophus microbiome is dominated by five bacterial OTUs, including lineages commonly found in other insect microbiomes and in environmental samples. The bacterial community associated with M. spermotrophus remained constant throughout wasp development and was dominated by a single OTU - a strain of Ralstonia, in the Betaproteobacteria, comprising over 55% of all bacterial OTUs from Megastigmus samples. This strain was also present in unparasitized ovules.

Conclusions: This is the first report of Ralstonia being an abundant and potentially important member of an insect microbiome, although other closely-related Betaproteobacteria, such as Burkholderia, are important insect symbionts. We speculate that Ralstonia might play a role in nutrient recycling, perhaps by redirecting nitrogen. The developing wasp larva feeds on megagametophyte tissue, which contains the seed storage reserves and is especially rich in nitrogen. Future studies using Ralstonia-specific markers will determine its distribution in other Megastigmus species, its mode of transmission, and its role in wasp nutrition.

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Maximum likelihood phylogeny forRalstonia16S rRNA sequence constructed using the Tamura-Nei with invariant sites and gamma distributed rate among sites model of nucleotide substitution. Numbers next to the nodes indicate percentage of bootstrap support from 500 bootstrap replicates. Nodes without numbers received less than 65% bootstrap support.
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Fig4: Maximum likelihood phylogeny forRalstonia16S rRNA sequence constructed using the Tamura-Nei with invariant sites and gamma distributed rate among sites model of nucleotide substitution. Numbers next to the nodes indicate percentage of bootstrap support from 500 bootstrap replicates. Nodes without numbers received less than 65% bootstrap support.

Mentions: A maximum likelihood phylogeny for Ralstonia was created using 16S rRNA sequence from the most abundant Ralstonia OTU in the pyrosequencing data set (Figure 4). Strong bootstrap support (0.99) clusters the Ralstonia isolated from M. spermotrophus with the human pathogen R. pickettii (sequence divergence = 3.3%).Figure 4


Bacterial associates of seed-parasitic wasps (Hymenoptera: Megastigmus).

Paulson AR, von Aderkas P, Perlman SJ - BMC Microbiol. (2014)

Maximum likelihood phylogeny forRalstonia16S rRNA sequence constructed using the Tamura-Nei with invariant sites and gamma distributed rate among sites model of nucleotide substitution. Numbers next to the nodes indicate percentage of bootstrap support from 500 bootstrap replicates. Nodes without numbers received less than 65% bootstrap support.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4197294&req=5

Fig4: Maximum likelihood phylogeny forRalstonia16S rRNA sequence constructed using the Tamura-Nei with invariant sites and gamma distributed rate among sites model of nucleotide substitution. Numbers next to the nodes indicate percentage of bootstrap support from 500 bootstrap replicates. Nodes without numbers received less than 65% bootstrap support.
Mentions: A maximum likelihood phylogeny for Ralstonia was created using 16S rRNA sequence from the most abundant Ralstonia OTU in the pyrosequencing data set (Figure 4). Strong bootstrap support (0.99) clusters the Ralstonia isolated from M. spermotrophus with the human pathogen R. pickettii (sequence divergence = 3.3%).Figure 4

Bottom Line: Males and females were infected at similar frequencies, suggesting that these bacteria do not distort sex ratios.The M. spermotrophus microbiome is dominated by five bacterial OTUs, including lineages commonly found in other insect microbiomes and in environmental samples.The bacterial community associated with M. spermotrophus remained constant throughout wasp development and was dominated by a single OTU - a strain of Ralstonia, in the Betaproteobacteria, comprising over 55% of all bacterial OTUs from Megastigmus samples.

View Article: PubMed Central - PubMed

ABSTRACT

Background: The success of herbivorous insects has been shaped largely by their association with microbes. Seed parasitism is an insect feeding strategy involving intimate contact and manipulation of a plant host. Little is known about the microbial associates of seed-parasitic insects. We characterized the bacterial symbionts of Megastigmus (Hymenoptera: Torymidae), a lineage of seed-parasitic chalcid wasps, with the goal of identifying microbes that might play an important role in aiding development within seeds, including supplementing insect nutrition or manipulating host trees. We screened multiple populations of seven species for common facultative inherited symbionts. We also performed culture independent surveys of larvae, pupae, and adults of M. spermotrophus using 454 pyrosequencing. This major pest of Douglas-fir is the best-studied Megastigmus, and was previously shown to manipulate its tree host into redirecting resources towards unfertilized ovules. Douglas-fir ovules and the parasitoid Eurytoma sp. were also surveyed using pyrosequencing to help elucidate possible transmission mechanisms of the microbial associates of M. spermotrophus.

Results: Three wasp species harboured Rickettsia; two of these also harboured Wolbachia. Males and females were infected at similar frequencies, suggesting that these bacteria do not distort sex ratios. The M. spermotrophus microbiome is dominated by five bacterial OTUs, including lineages commonly found in other insect microbiomes and in environmental samples. The bacterial community associated with M. spermotrophus remained constant throughout wasp development and was dominated by a single OTU - a strain of Ralstonia, in the Betaproteobacteria, comprising over 55% of all bacterial OTUs from Megastigmus samples. This strain was also present in unparasitized ovules.

Conclusions: This is the first report of Ralstonia being an abundant and potentially important member of an insect microbiome, although other closely-related Betaproteobacteria, such as Burkholderia, are important insect symbionts. We speculate that Ralstonia might play a role in nutrient recycling, perhaps by redirecting nitrogen. The developing wasp larva feeds on megagametophyte tissue, which contains the seed storage reserves and is especially rich in nitrogen. Future studies using Ralstonia-specific markers will determine its distribution in other Megastigmus species, its mode of transmission, and its role in wasp nutrition.

Show MeSH
Related in: MedlinePlus