In many host-microbe symbioses, hosts develop specialized organs that house microbial symbionts. In legume-rhizobium symbiosis, these organs are called root nodules. While many studies have focused on host traits like plant growth, nodule number, and their structural changes, nodule morphology may influence rhizobial benefits (e.g., bacterial population size). Here, we investigated how variation in alfalfa nodule morphologies influences the fitness outcome of both partners. We used 117 strains and 3 alfalfa varieties to test how genetic variation influenced 1) nodule branch number, area, and rhizobial fitness at the individual nodule level and 2) the proportion of branched nodules, nodule number, and plant benefits at the whole plant level. In all tested hosts, larger or more branched nodules tend to release more rhizobia regardless of rhizobial strain, although baseline rhizobial fitness values differed across hosts. From the host perspective, the proportion of branched nodules was strongly negatively correlated with total nodule number and positively correlated with host benefit. Both host and strain genetic variation contributed to the proportion of branched nodules on a plant. Together, these results provide insight into host and rhizobial genetic contributions to nodule morphology and symbiotic outcomes, suggesting a novel direction for research in legume-rhizobium mutualism.

Abstract. Microbial symbioses are the operating system of marine biology. Nearly every macroscopic organism in the ocean exists as a holobiont, the consort

Aging populations face a growing burden of neurodegenerative disease and behavioral decline. The microbiota is increasingly implicated in host physiology, highlighting an urgent need to understand how gut microbes modulate brain function and late life health. Here, we develop a high-throughput microbe-host screening platform to systematically dissect how bacterial genes shape organismal behavior. Using the Escherichia coli Keio library of 3,985 distinct non-essential single-gene deletion mutants in combination with Caenorhabditis elegans, we quantitatively profiled 768 behavioral features per bacterial clone and uncovered a coherent module of bacterial genes involved in iron homeostasis that robustly reprogrammed host behavior. Bacterial omics analyses revealed that alterations in iron homeostasis amplify siderophore production in a TCA cycle-dependent manner, and loss of enterobactin biosynthesis abolished the bacteria-induced changes in worm movement. Transcriptional, molecular and functional studies demonstrated that bacterial enterobactin activates host neuromuscular responses to shape both lifespan and healthspan in a manner dependent on the mitochondrial unfolded protein response. Thermal proteome profiling identified mitochondrial glutaryl-CoA dehydrogenase and the electron-transfer flavoproteins A and B as enterobactin-binding targets that control mitochondrial function. Finally, genetic manipulation of neuronal mitochondrial and cytosolic reactive oxygen species via superoxide dismutase and catalase revealed that redox state modulates enterobactin-driven changes in movement and lifespan through the secretin-family GPCR neuropeptide receptor PDFR-1. Together, these findings establish microbial enterobactin as a non-canonical neurotransmitter regulating neuronal mitochondrial function, behavior and aging, defining a gut bacteria-brain axis with broad implications for maintaining late-life health.

In many host-microbe symbioses, hosts develop specialized organs that house microbial symbionts. In legume-rhizobium symbiosis, these organs are called root nodules. While many studies have focused on host traits like plant growth, nodule number, and their structural changes, nodule morphology may influence rhizobial benefits (e.g., bacterial population size). Here, we investigated how variation in alfalfa nodule morphologies influences the fitness outcome of both partners. We used 117 strains and 3 alfalfa varieties to test how genetic variation influenced 1) nodule branch number, area, and rhizobial fitness at the individual nodule level and 2) the proportion of branched nodules, nodule number, and plant benefits at the whole plant level. In all tested hosts, larger or more branched nodules tend to release more rhizobia regardless of rhizobial strain, although baseline rhizobial fitness values differed across hosts. From the host perspective, the proportion of branched nodules was strongly negatively correlated with total nodule number and positively correlated with host benefit. Both host and strain genetic variation contributed to the proportion of branched nodules on a plant. Together, these results provide insight into host and rhizobial genetic contributions to nodule morphology and symbiotic outcomes, suggesting a novel direction for research in legume-rhizobium mutualism.

Read the full paper: Native pathogen-phage networks reveal multilayered defense and gut-active anti-phage immunity

Aging populations face a growing burden of neurodegenerative disease and behavioral decline. The microbiota is increasingly implicated in host physiology, highlighting an urgent need to understand how gut microbes modulate brain function and late life health. Here, we develop a high-throughput microbe-host screening platform to systematically dissect how bacterial genes shape organismal behavior. Using the Escherichia coli Keio library of 3,985 distinct non-essential single-gene deletion mutants in combination with Caenorhabditis elegans, we quantitatively profiled 768 behavioral features per bacterial clone and uncovered a coherent module of bacterial genes involved in iron homeostasis that robustly reprogrammed host behavior. Bacterial omics analyses revealed that alterations in iron homeostasis amplify siderophore production in a TCA cycle-dependent manner, and loss of enterobactin biosynthesis abolished the bacteria-induced changes in worm movement. Transcriptional, molecular and functional studies demonstrated that bacterial enterobactin activates host neuromuscular responses to shape both lifespan and healthspan in a manner dependent on the mitochondrial unfolded protein response. Thermal proteome profiling identified mitochondrial glutaryl-CoA dehydrogenase and the electron-transfer flavoproteins A and B as enterobactin-binding targets that control mitochondrial function. Finally, genetic manipulation of neuronal mitochondrial and cytosolic reactive oxygen species via superoxide dismutase and catalase revealed that redox state modulates enterobactin-driven changes in movement and lifespan through the secretin-family GPCR neuropeptide receptor PDFR-1. Together, these findings establish microbial enterobactin as a non-canonical neurotransmitter regulating neuronal mitochondrial function, behavior and aging, defining a gut bacteria-brain axis with broad implications for maintaining late-life health.

Abstract. In many host-microbe symbioses, hosts develop specialized organs that house microbial symbionts. In legume-rhizobium symbiosis, these organs are

Wang et al. map >1,000 interactions between Salmonella isolates and bacteriophages to measure the relative contributions of surface features and intracellular defense to phage resistance across a major human pathogen. They further identify AppA, which blocks DNA packaging by targeting the large terminase and restricts phage replication within mammalian hosts.

An oral enzyme-responsive co-delivery nanoplatform is designed to achieve controlled release of tryptophan and the metabolism inhibitor NLG919, specifically in the large intestine. This design redirec...

BackgroundAdipose deposition is a complex trait shaped by both host genetics and environmental factors, including the gut microbiota. While quantitative trai...

Read the full paper: Myo-inositol metabolism counteracts mycotoxin hijacking and confers broad resistance to fungal diseases in crops

Postdoctoral researcher Luka Svet at St. Jude Children’s Research Hospital explores transcriptomic reprogramming and host-microbe interactions in Staphylococcus aureus to reveal tissue-specific mechan...

Postdoctoral researcher Luka Svet at St. Jude Children’s Research Hospital explores transcriptomic reprogramming and host-microbe interactions in Staphylococcus aureus to reveal tissue-specific mechan...

Title: ASSISTANT PROFESSOR IN HOST-MICROBE INTERACTIONS (IMMUNOLOGY, MICROBIOLOGY)Employee Classification: Asst ProfessorDivision Name: Academic AffairsCollege/Unit: College of Arts and SciencesDepart...

Title: ASSISTANT PROFESSOR IN HOST-MICROBE INTERACTIONS (IMMUNOLOGY, MICROBIOLOGY)Employee Classification: Asst ProfessorDivision Name: Academic AffairsCollege/Unit: College of Arts and SciencesDepart...