Biology subjects

Nichols, H. L.

Publications and source records attributed to Nichols, H. L..

4 recordsLinked to original sources

bioRxiv2025

Vertical transmission of mosquito microbiota and its effects on offspring development

BackgroundThe mosquitos gut microbiota plays a crucial role in determining its capacity to transmit harmful viruses and parasites. Accordingly, manipulating mosquito gut microbiota is a promising avenue towards reducing mosquito-borne human pathogen transmission. A successful microbial control campaign will require a thorough understanding of how bacteria are transmitted through mosquito populations. Through two parallel but complementary studies using the yellow fever mosquito Aedes aegypti as a focal host species, we surveyed vertical transmission of bacteria from individual mothers to cohorts of offspring maintained in a closed system. ResultsLaboratory- and field-derived mothers deposited bacteria that support offspring development, and the relative abundance of commonly transmitted taxa correlated with offspring fitness. Maternally transmitted bacteria were detected in both larval and adult offspring, and the relative abundances of specific taxa differed between life stages. Microbiota composition in adult offspring closely resembled microbiota composition in mothers, despite dramatic shifts in the relative abundance of specific microbial community members during the larval stage. Variability in microbiota composition in offspring was also greater than variability across the population of egg-laying mothers. Eggs that underwent a period of desiccation before hatching produced larval communities dominated by endospore-forming bacteria that were rare in maternal samples. ConclusionsOverall, our results demonstrate the vertical transmission of mosquito-associated microbiota across generations, including bacterial taxa that could potentially be leveraged for mosquito and mosquito-borne disease control.

microbiology↗

bioRxiv2023

Pathogen-microbiome interactions and the virulence of an entomopathogenic fungus

AO_SCPLOWBSTRACTC_SCPLOWBacteria shape interactions between hosts and fungal pathogens. In some cases, bacteria associated with fungi are essential for pathogen virulence. In other systems, host associated microbiomes confer resistance against fungal pathogens. We studied an aphid-specific entomopathogenic fungus called Pandora neoaphidis in the context of both host and pathogen microbiomes. Aphids host several species of heritable bacteria, some of which confer resistance against Pandora. We first found that spores that emerged from aphids that harbored protective bacteria were less virulent against subsequent hosts and did not grow on plate media. We then used 16S amplicon sequencing to study the bacterial microbiome of fungal mycelia and spores during plate culturing and host infection. We found that the bacterial community is remarkably stable in culture despite dramatic changes in pathogen virulence. Last, we used an experimentally transformed symbiont of aphids to show that Pandora can acquire hostassociated bacteria during infection. Our results uncover new roles for bacteria in the dynamics of aphidpathogen interactions and illustrate the importance of the broader microbiological context in studies of fungal pathogenesis.

microbiology↗

bioRxiv2023

Establishment and comparative genomics of a high-quality collection of mosquito-associated bacterial isolates -- MosAIC (Mosquito-Associated Isolate Collection)

Mosquitoes transmit medically important human pathogens, including viruses like dengue virus and parasites such as Plasmodium spp., the causative agent of malaria. Mosquito microbiomes are critically important for the ability of mosquitoes to transmit disease-causing agents. However, while large collections of bacterial isolates and genomic data exist for vertebrate microbiomes, the vast majority of work in mosquitoes to date is based on 16S rRNA gene amplicon data that provides limited taxonomic resolution and no functional information. To address this gap and facilitate future studies using experimental microbiome manipulations, we generated a bacterial Mosquito-Associated Isolate Collection (MosAIC) consisting of 392 bacterial isolates with extensive metadata and high-quality draft genome assemblies that are publicly available for use by the scientific community. MosAIC encompasses 142 species spanning 29 bacterial families, with members of the Enterobacteriaceae comprising 40% of the collection. Phylogenomic analysis of three genera, Enterobacter, Serratia, and Elizabethkingia, reveal lineages of mosquito-associated bacteria isolated from different mosquito species in multiple laboratories. Investigation into species pangenomes further reveals clusters of genes specific to these lineages, which are of interest for future work to identify functions underlying mosquito host association. Altogether, we describe the generation of a physical collection of mosquito-associated bacterial isolates, their genomic data, and analyses of selected groups in context of genome data from closely related isolates, providing a unique, highly valuable resource to investigate factors for bacterial colonisation and adaptation within mosquito hosts. Future efforts will expand the collection to include broader geographic and host species representation, especially from individuals collected from field populations, as well as other mosquito-associated microbes, including fungi, archaea, and protozoa.

microbiology↗

bioRxiv2020

Intraspecific variation in immune gene expression and heritable symbiont density

AO_SCPLOWBSTRACTC_SCPLOWHost genetic variation plays an important role in the structure and function of heritable microbial communities. Recent studies have demonstrated that insects use immune mechanisms to regulate heritable symbionts. Here we test the hypothesis that variation in symbiont density within hosts is linked to intraspecific differences in the immune response to harboring symbionts. We show that pea aphids (Acyrthosiphon pisum) harboring the bacterial endosymbiont Regiella insecticola (but not all other species of symbionts) suppress expression of key immune genes. We then functionally link immune suppression with symbiont density using RNAi. The pea aphid species complex is comprised of multiple reproductively-isolated host plant-adapted populations. These biotypes have distinct patterns of heritable symbiont infections: for example, aphids from the Trifolium biotype are strongly associated with Regiella. Using RNAseq, we compare patterns of gene expression in response to Regiella in aphid genotypes from multiple biotypes, and we show that Trifolium aphids experience no immune gene suppression from Regiella and host symbionts at lower densities. We then generated F1 hybrids between two biotypes and found that symbiont density and immune suppression are both intermediate in hybrids. We suggest that in this system, Regiella symbionts are suppressing aphid immune mechanisms to increase their density, but that some hosts have adapted to prevent immune suppression in order to control symbiont numbers. The specific immune mechanisms suppressed by Regiella have been previously demonstrated to combat pathogens in aphids, and thus this work highlights the immune systems complex dual role in interacting with both beneficial and harmful microbes. AO_SCPLOWUTHORC_SCPLOW SO_SCPLOWUMMARYC_SCPLOWHeritable microbes are found in most insects including agriculturally and medically relevant pests. Explaining the variation in the distribution and abundance of symbionts in natural populations is critical to understanding these interactions. This work contributes to our mechanistic understanding of an important model of host-microbe symbiosis and suggests more broadly that variation in insect immune responses plays a role in intraspecific variation in host-symbiont interactions. Our work also suggests that antagonistic coevolution can play a role in host-microbe interactions even when microbes are transmitted vertically and provide a clear benefit to their hosts.

evolutionary biology↗