"Endomicrobia" and Other Bacteria Associated with the Hindgut of Dermolepida albohirtum Larvae

Symbiotic bacteria residing in the hindgut chambers of scarab beetle larvae may be useful in paratransgenic approaches to reduce larval root-feeding activities on agricultural crops. We compared the bacterial community profiles associated with the hindgut walls of individual Dermolepida albohirtum third-instar larvae over 2 years and those associated with their plant root food source among different geographic regions. Denaturing gradient gel electrophoresis analysis was used with universal and Actinobacteria-specific 16S rRNA primers to reveal a number of taxa that were found consistently in all D. albohirtum larvae but not in samples from their food source, sugarcane roots. These taxa included representatives from the "Endomicrobia," Firmicutes, Proteobacteria, and Actinobacteria and were related to previously described bacteria from the intestines of other scarab larvae and termites. These universally distributed taxa have the potential to form vertically transmitted symbiotic associations with these insects

Human genetic and metabolite variation reveals that methylthioadenosine is a prognostic biomarker and an inflammatory regulator in sepsis.

Sepsis is a deleterious inflammatory response to infection with high mortality. Reliable sepsis biomarkers could improve diagnosis, prognosis, and treatment. Integration of human genetics, patient metabolite and cytokine measurements, and testing in a mouse model demonstrate that the methionine salvage pathway is a regulator of sepsis that can accurately predict prognosis in patients. Pathway-based genome-wide association analysis of nontyphoidal Salmonella bacteremia showed a strong enrichment for single-nucleotide polymorphisms near the components of the methionine salvage pathway. Measurement of the pathway's substrate, methylthioadenosine (MTA), in two cohorts of sepsis patients demonstrated increased plasma MTA in nonsurvivors. Plasma MTA was correlated with levels of inflammatory cytokines, indicating that elevated MTA marks a subset of patients with excessive inflammation. A machine-learning model combining MTA and other variables yielded approximately 80% accuracy (area under the curve) in predicting death. Furthermore, mice infected with Salmonella had prolonged survival when MTA was administered before infection, suggesting that manipulating MTA levels could regulate the severity of the inflammatory response. Our results demonstrate how combining genetic data, biomolecule measurements, and animal models can shape our understanding of disease and lead to new biomarkers for patient stratification and potential therapeutic targeting

Semele: A Killer-Male, Rescue-Female System for Suppression and Replacement of Insect Disease Vector Populations

Two strategies to control mosquito-borne diseases, such as malaria and dengue fever, are reducing mosquito population sizes or replacing populations with disease-refractory varieties. We propose a genetic system, Semele, which may be used for both. Semele consists of two components: a toxin expressed in transgenic males that either kills or renders infertile wild-type female recipients and an antidote expressed in females that protects them from the effects of the toxin. An all-male release results in population suppression because wild-type females that mate with transgenic males produce no offspring. A release that includes transgenic females results in gene drive since females carrying the allele are favored at high population frequencies. We use simple population genetic models to explore the utility of the Semele system. We find that Semele can spread under a wide range of conditions, all of which require a high introduction frequency. This feature is desirable since transgenic insects released accidentally are unlikely to persist, transgenic insects released intentionally can be spatially confined, and the element can be removed from a population through sustained release of wild-type insects. We examine potential barriers to Semele gene drive and suggest molecular tools that could be used to build the Semele system

Assessment of Gut Bacteria for a Paratransgenic Approach To Control Dermolepida albohirtum Larvae▿

Bacteria from the hindguts of Dermolepida albohirtum larvae were assessed for their potential to be used in paratransgenic strategies that target scarab pests of sugarcane. Bacteria isolated in pure culture from the hindguts of D. albohirtum larvae were from the Proteobacteria, Firmicutes, and Actinobacteria phyla and matched closely with taxa from intestinal and rhizosphere environments. However, these isolates were not the most common gut-associated bacteria identified in denaturing gradient gel electrophoresis (DGGE) hindgut profiles. Subsequently, eight species of gut bacteria were fed to larvae, and RNA-based DGGE analysis of 16S rRNA was used to detect the persistence of these isolates in the hindgut environment. One of these isolates (Da-11) remained metabolically active in the hindgut for 19 days postconsumption. Da-11 most likely forms a new genus within the Burkholderiales order, along with taxa independently identified from larvae of the European scarab pest, Melolontha melolontha. Using the EZ::Tn5 transposon system, a kanamycin resistance gene was inserted into the chromosome of Da-11, thus establishing a stable transformation technique for this species. A second feeding trial that included inoculating approximately 400 transgenic Da-11 cells onto a food source resulted in a density of 1 × 106 transgenic Da-11 cells/ml in the hindguts of larvae at 9 days postconsumption. These populations were maintained in the hindgut for at least another 12 days. The successful isolation, genetic transformation, and establishment of transgenic Da-11 cells in the hindguts of D. albohirtum larvae fulfill fundamental requirements for the future development of a paratransgenic approach to control scarab pests of sugarcane