Biology subjects

Bordenstein, S. R.

Publications and source records attributed to Bordenstein, S. R..

13 recordsLinked to original sources

bioRxiv2026

Dietary fiber-type-specific gut microbiome preconditioning drives differential susceptibility to sporadic colon cancer development

Background: Dietary fiber intake is broadly associated with reduced colorectal cancer (CRC) risk, yet processed fiber supplements exert inconsistent and occasionally opposing effects on colon tumorigenesis. How structurally distinct dietary fibers differentially shape the gut microbiome-metabolome axis to influence carcinogenic susceptibility remains poorly understood. Objective: To determine whether structurally distinct dietary fibers differentially modulate colon tumor development and characterize the underlying gut microbiome and metabolic mechanisms. Design: Four-week-old male mice were maintained on low-fiber control or fiber-supplemented diets (7.5%w/w: cellulose, agar, pectin, or inulin) for 28 weeks and received eight intraperitoneal azoxymethane injections (AOM; 7.5 mg/kg). Temporal fecal microbiomes were profiled by 16S-rRNA sequencing, cecal metabolites quantified by H-NMR spectroscopy, and microbiome-metabolome interactions assessed by co-occurrence networks. Results: Refined inulin supplementation markedly elevated colon tumor incidence (~70%) compared with all other groups (~10-20%), and cecal extracts from inulin-fed mice promoted HT29 cancer-cell proliferation. Longitudinal microbiome profiling identified 36 inulin-specific microbial signatures converging on two axes: depletion of SCFAs and fermentation cross-feeding taxa and reprogramming of amino acid and nitrogen metabolism. Metabolomics confirmed succinate, fumarate, and lactate accumulation alongside propionate and amino acid depletion exclusively under AOM conditions, with no differences in carcinogen-naive animals. Two stable co-occurrence hubs were identified exclusively in AOM-treated animals, structurally integrating both functional axes. Conclusion: Inulin supplementation preconditions the gut microbiome toward functional vulnerability, characterized by disrupted fermentation throughput and reprogrammed amino acid metabolism, that is amplified by carcinogen exposure into a tumor-promoting ecosystem, providing a mechanistic basis for the disproportionately higher tumor prevalence in inulin-fed animals.

microbiology↗

bioRxiv2025

Host and Microbe Scale Processes Shape Spatial Variation in Aphaenogaster (Hymenoptera: Formicidae) Genetics and Their Microbiota

Like all ecological communities, host-associated (HA) microbiota are shaped by environmental selection and dispersal limitation. However, unlike communities of free-living organisms, communities of HA microbes experience selection and dispersal at two separate scales - the scale of the microbes and the scale of their hosts. Thus, HA microbes must tolerate not only the environment created by their host (microbe-scale environment), but also, the environment in which their host resides (host-scale environment). Likewise, HA microbes can disperse between hosts through either horizontal or vertical transmission (microbe-scale dispersal) but can also disperse between locations through host movement (host-scale dispersal). In this paper, we examine how multiscale environmental selection and dispersal limitation shape the genetics and HA microbiota of ants in the Aphaenogaster fulva-rudis-texana (Hymenoptera: Formicidae) complex. We begin by showing how spatial variation in Aphaenogaster genetics is shaped by host-scale environmental selection and dispersal limitation. We then show how this allows both host- and microbe-scale environmental selection to govern spatial variation in Aphaenogaster microbiota. Finally, we discuss the possibility that microbe-scale dispersal limitation also impacts spatial variation in Aphaenogaster microbiota and that this, in turn, may contribute to spatial variation in Aphaenogaster genetics. Ultimately, our results help to shed light on the myriad of interacting factors governing spatial variation in HA microbiota, including the potential for complex, bidirectional interactions between host- and microbe-scale processes.

ecology↗

bioRxiv2024

The holobiont's extracellular microbiome modulates the adaptation of an intracellular endosymbiont

Holobionts contain spatially separated microbes whose interorgan effects are a neglected source of potential, functional variation. Here we show the extracellular gut microbiome modulates the transcriptome and adaptation of the endosymbiont Wolbachia in Drosophila melanogaster testes. Gut bacteria suppress cytoplasmic incompatibility (CI), a sperm-egg lethality trait, by altering endosymbiont pathogenicity gene expression. Transgenic assays identify the enchancer of cytoplasmic incompatibility gene eci as causal to the variation. Restoring the gut microbiome in laboratory and wild-caught, germ-free flies recapitulates CI attenuation and shifts host fitness. Intact holobionts sustain higher densities of the two symbiont types versus isolated rearing, revealing a synergistic, replication interaction between the symbiont classes. The gut-germline axis on symbiont functions has far-reaching implications for the study of holobiont trait variation.

microbiology↗

bioRxiv2022

Nuclease proteins CifA and CifB promote spermatid DNA damage associated with symbiont-induced cytoplasmic incompatibility

The worldwide endosymbiosis between arthropods and Wolbachia bacteria is an archetype for reproductive parasitism. This parasitic strategy rapidly increases the proportion of symbiont-transmitting mothers, and the most common form, cytoplasmic incompatibility (CI), impacts insect evolution and arboviral control strategies. During CI, sperms from symbiotic males kill embryos of aposymbiotic females via two nuclear-targeting proteins, CifA and CifB, that alter sperm chromatin organization in Drosophila melanogaster. Here we hypothesize that Cif proteins metabolize nucleic acids of developing sperm to initiate genome integrity changes. Using in vitro and in situ transgenic, mutant, enzymatic, and cytochemical assays, we show that CifA is a previously-unrecognized DNase and RNase, and CifB is a DNase. Notably, in vitro nuclease activity translates to in situ spermatid DNA damage at the canoe stage of spermiogenesis. Evolution-guided mutations ablate Cif enzymatic activity. Nucleic acid metabolism by Cif enzymes expands a fundamental understanding of the mechanism of symbiont-mediated reproductive parasitism.

biochemistry↗

bioRxiv2022

The cytoplasmic incompatibility Cif proteins from prophage WO modify sperm genome integrity

Inherited microorganisms can selfishly manipulate host reproduction to drive through populations. In Drosophila melanogaster, germline expression of the native Wolbachia prophage WO proteins CifA and CifB cause cytoplasmic incompatibility (CI) in which embryos from infected males and uninfected females suffer catastrophic mitotic defects and lethality; however, in infected females, CifA expression rescues the embryonic lethality and thus imparts a fitness advantage to the maternally-transmitted Wolbachia. Despite widespread relevance to sex determination, evolution, and vector control, the mechanisms underlying when and how CI impairs male reproduction remain unknown and a topic of debate. Here we use cytochemical, microscopic, and transgenic assays in D. melanogaster to demonstrate that CifA and CifB proteins of wMel localize to nuclear DNA throughout the process of spermatogenesis. Cif proteins cause abnormal histone retention in elongating spermatids and protamine deficiency in mature sperms that travel to the female reproductive tract with Cif proteins. Notably, protamine gene knockouts enhance wild type CI. In ovaries, CifA localizes to germ cell nuclei and cytoplasm of early-stage egg chambers, however Cifs are absent in late-stage oocytes and subsequently in fertilized embryos. Finally, CI and rescue are contingent upon a newly annotated CifA bipartite nuclear localization sequence. Together, our results strongly support the Host Modification model of CI in which Cifs initially modify the paternal and maternal gametes to bestow CI-defining embryonic lethality and rescue.

cell biology↗

bioRxiv2021

The Most Widespread Phage in Animals: Genomics and Taxonomic Classification of Phage WO

Wolbachia are the most common obligate, intracellular bacteria in animals. They exist worldwide in arthropod and nematode hosts in which they commonly act as reproductive parasites or mutualists, respectively. Bacteriophage WO, the largest of Wolbachias mobile elements, includes reproductive parasitism genes, serves as a hotspot for genetic divergence and genomic rearrangement of the bacterial chromosome, and uniquely encodes a Eukaryotic Association Module with eukaryotic-like genes and an ensemble of putative host interaction genes. Despite WOs relevance to genome evolution, selfish genetics, and symbiotic applications, relatively little is known about its origin, host range, diversification, and taxonomic classification. Here we analyze the most comprehensive set of 150 Wolbachia and phage WO assemblies to provide a framework for discretely organizing and naming integrated phage WO genomes. We demonstrate that WO is principally in arthropod Wolbachia with relatives in diverse endosymbionts and metagenomes, organized into four variants related by gene synteny, often oriented opposite the origin of replication in the Wolbachia chromosome, and the large serine recombinase is an ideal typing tool to assign taxonomic classification of the four variants. We identify a novel, putative lytic cassette and WOs association with a conserved eleven gene island, termed Undecim Cluster, that is enriched with virulence-like genes. Finally, we evaluate WO-like Islands in the Wolbachia genome and discuss a new model in which Octomom, a notable WO-like Island, arose from a split with WO. Together, these findings establish the first comprehensive Linnaean taxonomic classification of endosymbiont phages that includes distinguishable genera of phage WO, a family of non-Wolbachia phages from aquatic environments, and an order that captures the collective relatedness of these viruses.

genomics↗

bioRxiv2021

A single synonymous nucleotide change impacts the male-killing phenotype of prophage WO gene wmk

Wolbachia are the most widespread bacterial endosymbionts in animals. Within arthropods, these maternally-transmitted bacteria can selfishly hijack host reproductive processes to increase the relative fitness of their transmitting females. One such form of reproductive parasitism called male killing, or the selective killing of infected males, is recapitulated to degrees by transgenic expression of the WO-mediated killing (wmk) gene. Here, we characterize the genotype-phenotype landscape of wmk-induced male killing in D. melanogaster using transgenic expression. While phylogenetically distant wmk homologs induce no sex-ratio bias, closely-related homologs exhibit complex phenotypes spanning no death, male death, or death of all hosts. We demonstrate that alternative start codons, synonymous codons, and notably a single synonymous nucleotide in wmk can ablate killing. These findings reveal previously unrecognized features of transgenic wmk-induced killing and establish new hypotheses for the impacts of post-transcriptional processes in male killing variation. We conclude that synonymous sequence changes are not necessarily silent in nested endosymbiotic interactions with life-or-death consequences.

genomics↗

bioRxiv2021

Genomes of gut bacteria from Nasonia wasps shed light on phylosymbiosis and microbe-assisted hybrid breakdown

Phylosymbiosis is a cross-system trend whereby microbial community relationships recapitulate the host phylogeny. In Nasonia parasitoid wasps, phylosymbiosis occurs throughout development, is distinguishable between sexes, and benefits host development and survival. Moreover, the microbiome shifts in hybrids as a rare Proteus bacteria in the microbiome becomes dominant. The larval hybrids then catastrophically succumb to bacterial-assisted lethality and reproductive isolation between the species. Two important questions for understanding phylosymbiosis and bacterial-assisted lethality in hybrids are: (i) Do the Nasonia bacterial genomes differ from other animal isolates and (ii) Are the hybrid bacterial genomes the same as those in the parental species? Here we report the cultivation, whole genome sequencing, and comparative analyses of the most abundant gut bacteria in Nasonia larvae, Providencia rettgeri and Proteus mirabilis. Characterization of new isolates shows Proteus mirabilis forms a more robust biofilm than Providencia rettgeri and when grown in co-culture, Proteus mirabilis significantly outcompetes Providencia rettgeri. Providencia rettgeri genomes from Nasonia are similar to each other and more divergent to pathogenic, human-associates strains. Proteus mirabilis from N. vitripennis, N. giraulti, and their hybrid offspring are nearly identical and relatively distinct from human isolates. These results indicate that members of the larval gut microbiome within Nasonia are most similar to each other, and the strain of the dominant Proteus mirabilis in hybrids is resident in parental species. Holobiont interactions between shared, resident members of the wasp microbiome and the host underpin phylosymbiosis and hybrid breakdown. IMPORTANCEAnimal and plant hosts often establish intimate relationships with their microbiomes. In varied environments, closely-related host species share more similar microbiomes, a pattern termed phylosymbiosis. When phylosymbiosis is functionally significant and beneficial, microbial transplants between host species or host hybridization can have detrimental consequences on host biology. In the Nasonia parasitoid wasp genus that contains a phylosymbiotic gut community, both effects occur and provide evidence for selective pressures on the holobiont. Here, we show that bacterial genomes in Nasonia differ from other environments and harbor genes with unique functions that may regulate phylosymbiotic relationships. Furthermore, the bacteria in hybrids are identical to parental species, thus supporting a hologenomic tenet that the same members of the microbiome and the host genome impact phylosymbiosis, hybrid breakdown, and speciation.

microbiology↗

bioRxiv2020

Evolution-guided mutagenesis of the cytoplasmic incompatibility proteins: Identifying CifAs complex functional repertoire and new essential regions in CifB

Wolbachia are the worlds most common, maternally-inherited, arthropod endosymbionts. Their worldwide distribution is due in part to a selfish drive system termed cytoplasmic incompatibility (CI) that confers a relative fitness advantage to females that transmit Wolbachia to their offspring. CI results in embryonic death when infected males mate with uninfected females but not infected females. Under the Two-by-One genetic model of CI, males expressing the two phage WO proteins CifA and CifB cause CI, and females expressing CifA rescue CI. While each protein is predicted to harbor three functional domains, there is no knowledge on how sites across these Cif domains, rather than in any one particular domain, contribute to CI and rescue. Here, we use evolution-guided, substitution mutagenesis of conserved amino acids across the Cif proteins, coupled with transgenic expression in uninfected Drosophila melanogaster, to determine the functional impacts of conserved residues evolving mostly under purifying selection. We report that amino acids in CifAs N-terminal unannotated region and annotated catalase-related domain are important for both complete CI and rescue, whereas C-terminal residues in CifAs putative domain of unknown function are solely important for CI. Moreover, conserved CifB amino acids in the predicted nucleases, peptidase, and unannotated regions are essential for CI. Taken together, these findings indicate that (i) all CifA amino acids determined to be involved in rescue are correspondingly involved in CI, (ii) an additional set of CifA amino acids are uniquely important in CI, and (iii) CifB amino acids across the protein, rather than in one particular domain, are all essential for CI. We discuss how these findings advance an expanded view of Cif protein evolution and function, inform the mechanistic and biochemical bases of Cif-induced CI/rescue, and continue to substantiate the Two-by-One genetic model of CI. Article summaryWolbachia are maternally-transmitted, intracellular bacteria that occur in approximately half of arthropod species worldwide. They can spread rapidly though host populations via the cytoplasmic incompatibility (CI) drive system. CI causes embryonic death when infected males mate with infected females, but offspring of infected females are rescued. Two proteins, CifA and CifB, underlie the genetic basis of CI and rescue, but how amino acid sites across these proteins contribute to CI and/or rescue remain unknown. Here, we employed evolution-guided, combinatorial mutagenesis on conserved amino acids to understand their relative contributions to CI and rescue. The results of this study reveal a phenotypic complexity underlying the expression of these proteins and provide relevance to the biochemical and mechanistic bases of CI and rescue.

microbiology↗

bioRxiv2018

Gut Microbiota Diversity across Ethnicities in the United States

Composed of hundreds of microbial species, the composition of the human gut microbiota can vary with chronic diseases underlying health disparities that disproportionally affect ethnic minorities. However, the influence of ethnicity on the gut microbiota remains largely unexplored and lacks reproducible generalizations across studies. By distilling associations between ethnicity and differences in two United States based 16S gut microbiota datasets including 1,673 individuals, we report 12 microbial genera and families that reproducibly vary by ethnicity. Interestingly, a majority of these microbial taxa, including the most heritable bacterial family, Christensenellaceae, overlap with genetically-associated taxa and form co-occurring clusters linked by similar fermentative and methanogenic metabolic processes. These results demonstrate recurrent associations between specific taxa in the gut microbiota and ethnicity, providing hypotheses for examining specific members of the gut microbiota as mediators of health disparities.

microbiology↗

bioRxiv2018

A single prophage WO gene rescues cytoplasmic incompatibility in Drosophila melanogaster

Wolbachia are maternally-inherited, intracellular bacteria at the forefront of vector control efforts to curb arbovirus transmission. In international field trials, the cytoplasmic incompatibility (CI) drive system of wMel Wolbachia is deployed to replace target vector populations, whereby a Wolbachia- induced modification of the sperm genome kills embryos. However, Wolbachia in the embryo rescue the sperm genome impairment, and therefore CI results in a strong fitness advantage for infected females that transmit the bacteria to offspring. The two genes responsible for the wMel-induced sperm modification of CI, cifA and cifB, were recently identified in the eukaryotic association module of prophage WO, but the genetic basis of rescue is unresolved. Here we use transgenic and cytological approaches to demonstrate that cifA independently rescues CI and nullifies embryonic death caused by wMel Wolbachia in Drosophila melanogaster. Discovery of cifA as the rescue gene and previously one of two CI induction genes establishes a new Two-by-One model that underpins the genetic basis of CI. Results highlight the central role of prophage WO in shaping Wolbachia phenotypes that are significant to arthropod evolution and vector control.\n\nSignificance StatementThe World Health Organization recommended pilot deployment of Wolbachia-infected mosquitoes to curb viral transmission to humans. Releases of mosquitoes are underway worldwide because Wolbachia can block replication of these pathogenic viruses and deterministically spread by a drive system termed cytoplasmic incompatibility (CI). Despite extensive research, the underlying genetic basis of CI remains only half-solved. We recently reported that two prophage WO genes recapitulate the modification component of CI in a released strain for vector control. Here we show that one of these genes underpins rescue of CI. Together, our results reveal the complete genetic basis of this selfish trait and pave the way for future studies exploring WO prophage genes as adjuncts or alternatives to current control efforts.

genetics↗

bioRxiv2018

A simple genetic basis for managing maternally transmitted symbionts

Maternal transmission of intracellular microbes is pivotal in establishing long-term, intimate symbioses. For germline microbes that exert negative reproductive effects on their hosts, selection can theoretically favor the spread of host genes that counteract the microbes harmful effects. Here, we leverage a major difference in bacterial (Wolbachia pipientis) titers between closely-related wasp species with forward genetic, transcriptomic, and cytological approaches to map two quantitative trait loci that suppress bacterial titers via a maternal effect. Fine mapping and knockdown experiments identify the gene Wolbachia density suppressor (Wds), which dominantly suppresses bacterial transmission from mother to embryo. Wds evolved by lineage-specific non-synonymous changes driven by positive selection. Collectively, our findings demonstrate that a genetically simple change arose by Darwinian selection in less than a million years to regulate maternally transmitted bacteria via a dominant, maternal effect gene.

evolutionary biology↗

bioRxiv2017

Evolutionary genetics of cytoplasmic incompatibility genes cifA and cifB in prophage WO of Wolbachia

The bacterial endosymbiont Wolbachia manipulates arthropod reproduction to facilitate its maternal spread through populations. The most common manipulation is cytoplasmic incompatibility (CI): Wolbachia-infected males produce modified sperm that cause embryonic mortality, unless rescued by eggs harboring the same Wolbachia. The genes underlying CI, cifA and cifB, were recently identified in the eukaryotic association module of Wolbachias prophage WO. Here, we use transcriptomic and genomic approaches to address three important evolutionary facets of these genes. First, we assess whether or not cifA and cifB comprise a classic toxin-antitoxin operon, and show they do not form an operon in strain wMel. They coevolve but exhibit strikingly distinct expression across host development. Second, we provide new domain and functional predictions across homologs within Wolbachia, and we show amino acid sequences vary substantially across the genus. Lastly, we investigate conservation of cifA and cifB and find degradation and loss of the genes is common in strains that no longer induce CI. Taken together, we find no evidence for the operon hypothesis in wMel, provide functional annotations that broaden the potential mechanisms of CI induction, illuminate recurrent erosion of cifA and cifB in non-CI strains, and advance an understanding of the most widespread form of reproductive parasitism.

evolutionary biology↗