Search

SummaryTurquoise killifish (Nothobranchius furzeri) are naturally short-lived vertebrates, with a lifespan in captivity ranging from 4 to 8 months. Aging in turquoise killifish recapitulates several aspects of human aging, including protein aggregation, telomere shortening, neurodegeneration, cellular senescence, increased cancer incidence, age-dependent gut dysbiosis, decline in antibody diversity, and more. The mechanistic causes or systemic aging in killifish are still poorly understood. Here we ask whether killifish undergo significant age-dependent changes in the main hematopoietic organ, which together could contribute to systemic aging. We employed single-cell RNA sequencing, proteomics and cytometry, and provide an R Shiny app (KIAMO) to visualize and compare omics changes occurring during killifish aging. We find that old killifish display increased inflammatory markers both in plasma and in the main hematopoietic organ (kidney marrow). Immune cells from adult killifish display increased markers of proliferation and replication-independent DNA repair in progenitor-like cell clusters, while progenitors from old killifish display extensive markers of DNA double-strand breaks. In less than 10 weeks, from adulthood to geriatric age, killifish recapitulate several markers of aging of the immune niche, which could be functionally linked with its extensive systemic aging and serve as a target for anti-aging interventions.

Biological aging results from the age-dependent change in the force of natural selection, which increases the probability of germline variants that limit survival to accumulate in genes acting predominantly in late life1. The evolutionary mechanisms underlying the accumulation of neutral mutations and antagonistically pleiotropic gene variants that cause biological aging have been analyzed to date under the assumption of infinitely large population size. However, even though population size importantly shapes genetic and phenotype variation via drift and selection2,3, we still have a limited understanding of how finite population size impacts the evolution of mortality at the population level. Here, we study the impact of population size on lifespan evolution under mutation accumulation and antagonistic pleiotropy. We found that larger population size leads to lower age-independent, as well as age-dependent mortality under mutation accumulation, due to more effective purifying selection against deleterious germline variants. Strikingly, large population size can lead to extended lifespan under antagonistic pleiotropy, due to more effective positive selection on gene variants increasing survival in early-life, while leading to increased post-maturation mortality. Our findings provide a comprehensive numerical framework for the two major evolutionary genetic theories of aging and reveal a fundamental and yet non-appreciated role for population size in the evolution of mortality trajectories.

Whether freshwater fish colonize remote islands following tectonic or transoceanic dispersal remains an evolutionary puzzle. Integrating dating of known tectonic events with phylogenomics and current species distribution, we find that killifish species distribution is not explained by species dispersal by tectonic drift only. Investigating the colonization of a nonannual killifish (golden panchax, Pachypanchax playfairii) on the Seychelle islands, we found genetic support for transoceanic dispersal and experimentally discovered an adaptation to complete tolerance to seawater. At the macroevolutionary scale, despite their long-lasting isolation, nonannual golden panchax show stronger genome-wide purifying selection than annual killifishes from continental Africa. However, progressive decline in effective population size over a more recent timescale has probably led to the segregation of slightly deleterious mutations across golden panchax populations, which represents a potential threat for species preservation in the long term.

Ejaculate collection from live animals is a fundamental technique used to perform repeated measures on the same individual—for instance, to test the effect of different treatments/conditions on the same animal or to conduct longitudinal studies. Moreover, collecting the ejaculate allows one to perform in vitro fertilizations (IVFs) or sperm cryopreservation from valuable individuals (e.g., mutant, transgenic animals) without the need to kill the animals. We developed a noninvasive protocol based on a stripping procedure for collecting the ejaculate from live males of the African turquoise killifish (Nothobranchius furzeri). The proposed procedure allows the retrieval of mature sperm along with the seminal fluid. The ejaculate can be used within 1 h of the collection to perform in vitro fertilizations and/or sperm quality measurements. Contamination by mucus, water, urine, or feces can activate the sperm and/or negatively affect sperm quality, so special care is needed to avoid contamination and thus prolong sperm viability. Since in small fish the amount of ejaculate collected is limited to a few microliters, in the present protocol we also provide recommendations on housing conditions to maximize the probability to obtain ejaculate samples.

Aging is the single largest risk factor for most chronic diseases, and thus possesses large socioeconomic interest to continuously aging societies. Consequently, the field of aging research is expanding alongside a growing focus from the industry and investors in aging research. This year's 8th Annual Aging Research and Drug Discovery (ARDD) meeting was organized as a hybrid meeting from August 30th to September 3rd 2021 with more than 130 attendees participating on-site at the Ceremonial Hall at University of Copenhagen, Denmark, and 1800 engaging online. The conference comprised of presentations from 75 speakers focusing on new research in topics including mechanisms of aging and how these can be modulated as well as the use of AI and new standards of practices within aging research. This year, a longevity workshop was included to build stronger connections with the clinical community., Aging, 14 (2), ISSN:1945-4589

B cells undergo a process of somatic recombination leading to the synthesis of a staggering diversity of transmembrane and secreted antibodies. This process dates back to the evolution of jawed vertebrates and is pivotal to the origin of lymphocyte-based adaptive immune responses. Here, we optimized a sequencing-based protocol to characterize B-cell-specific IgH transcripts from bulk RNA in the African turquoise killifish, an emerging model organism characterized by naturally short life span and by a vast range of age-dependent dysfunctions.

BackgroundDiapause is a key adaptation that enabled the colonization of ephemeral habitats subject to the alternation of dry and wet seasons by annual killifishes. Upon desiccation of the ponds, killifish embryos remain vital but quiescent in the clay, where they can survive months or even years. Diapause can occur at three different developmental stages, but Diapause II (DII), which occurs at mid-somitogenesis, is the primary point of developmental arrest. However, diapause is not obligatory, and some embryos can proceed to direct development, skipping one or more diapauses. The precise molecular mechanisms that regulate entry and exit from diapause are beginning to be investigated, but this knowledge is yet fragmentary. Diapause has evolved independently several times in killifish clades from Africa and South America, enabling the identification of possible molecular determinants of diapause by comparative expression analysis. MicroRNAs are small RNAs that represent central nodes in the control of gene expression at the post-transcriptional level and are involved in many developmental processes. Here, we compare microRNA expression profiles of annual killifishes during DII with non-annual killifish in a comparable stage of morphological development. ResultsWe used smallRNA-Seq to quantify microRNA expression from four annual- and four non-annual killifish species from three independent clades and from direct-developing embryos of the annual fish Nothobranchius furzeri. We analyzed the expression of broadly conserved microRNAs and microRNAs that appear to have evolved in the killifish lineage.We found several microRNAs that showed convergent regulation in the three different clades, and for some microRNAs also a phenomenon of switch in the prevalent form between 3p and 5p or vice versa was noted. In addition, we detected a significant overlap between the microRNA regulation during diapause and aging. Particularly interesting is the regulation of the miR-430 family. These microRNAs represent the second most expressed microRNA family in the killifish embryos, and diapause is associated with dramatic down-regulation of the prevalent -3p form and up-regulation of the -5p form. Members of the miR-430 family are contained in a large repetitive cluster whose organization is variable among teleost. Analysis of recently sequenced 45 low-coverage killifish genomes revealed that the miR-430 locus contains a lower number of copies in annual- as opposed to non-annual killifish. ConclusionsThe Evolution of diapause is reflected in the convergent evolution of microRNA regulation in killifishes. A prominent feature is a dramatic down-regulation of miR-430 expression that could be partially explained with a reduction of its copy numbers in the genome.

Insects use sex pheromones as a reproductive isolating mechanism to attract conspecifics and repel heterospecifics. Despite the profound knowledge of sex pheromones, little is known about the coevolutionary mechanisms and constraints on their production and detection. Using whole-genome sequences to infer the kinship among 99 drosophilids, we investigate how phylogenetic and chemical traits have interacted at a wide evolutionary timescale. Through a series of chemical syntheses and electrophysiological recordings, we identify 52 sex-specific compounds, many of which are detected via olfaction. Behavioral analyses reveal that many of the 43 male-specific compounds are transferred to the female during copulation and mediate female receptivity and/or male courtship inhibition. Measurement of phylogenetic signals demonstrates that sex pheromones and their cognate olfactory channels evolve rapidly and independently over evolutionary time to guarantee efficient intra- and inter-specific communication systems. Our results show how sexual isolation barriers between species can be reinforced by species-specific olfactory signals., Despite the profound knowledge of sex pheromones, little is known about the coevolutionary mechanisms and constraints on their production and detection. Whole-genome sequences from 99 drosophilids, with chemical and behavioural data, show that sex pheromones and their cognate olfactory channels evolve rapidly and independently.

Aging individuals exhibit a pervasive decline in adaptive immune function, with important implications for health and lifespan. Previous studies have found a pervasive loss of immune-repertoire diversity in human peripheral blood during aging; however, little is known about repertoire aging in other immune compartments, or in species other than humans. Here, we perform the first study of immune-repertoire aging in an emerging model of vertebrate aging, the African turquoise killifish (Nothobranchius furzeri). Despite their extremely short lifespans, these killifish exhibit complex and individualized heavy-chain repertoires, with a generative process capable of producing millions of distinct productive sequences. Whole-body killifish repertoires decline rapidly in within-individual diversity with age, while between-individual variability increases. Large, expanded B-cell clones exhibit far greater diversity loss with age than small clones, suggesting important differences in how age affects different B cell populations. The immune repertoires of isolated intestinal samples exhibit especially dramatic age-related diversity loss, related to an elevated prevalence of expanded clones. Lower intestinal repertoire diversity was also associated with transcriptomic signatures of reduced B-cell activity, supporting a functional role for diversity changes in killifish immunosenescence. Our results highlight important differences in systemic vs. organ-specific aging dynamics in the adaptive immune system.Significance StatementImmune function declines dramatically with age, with important consequences for health in the elderly. Changes in the diversity and composition of the body’s antibody repertoire are an important contributor to this age-related dysfunction. However, studying repertoire aging at high spatial and temporal resolution is hampered by the long lifespans of humans and other vertebrate models, and the difficulty of acquiring human samples other than peripheral blood. Here, we characterize the aging of the antibody repertoire in a naturally short-lived vertebrate, the turquoise killifish (Nothobranchius furzeri). We found that aging killifish undergo rapid loss of repertoire diversity in both whole-body and intestinal samples within four months of hatching. Loss of repertoire diversity in the gut was also associated with broader gene-expression changes indicative of reduced B-cell activity. As such, killifish represent a powerful laboratory model to study adaptive immune aging.

How freshwater fish colonize remote islands remains an evolutionary puzzle. Tectonic drift and trans-oceanic dispersal models have been proposed as possible alternative mechanisms. Integrating dating of known tectonic events with population genetics and experimental test of salinity tolerance in the Seychelles islands golden panchax (Pachypanchax playfairii), we found support for trans-oceanic dispersal being the most likely scenario. At the macroevolutionary scale, the non-annual killifish golden panchax shows stronger genome-wide purifying selection compared to annual killifishes from continental Africa. Reconstructing past demographies in isolated golden panchax populations provides support for decline in effective population size, which could have allowed slightly deleterious mutations to segregate in the population. Unlike annual killifishes, where relaxed selection preferentially targets aging-related genes, relaxation of purifying selection in golden panchax affects genes involved in developmental processes, including fgf10.

Occupying the interface between host and environment, host-associated microbes play fundamental roles in nutrient absorption, essential metabolite synthesis, development of the immune system, defence against pathogens and pathogenesis. Microbiota composition and function is rather stable during adulthood, while it dramatically changes during early development, frailty and disease. Ageing is associated with progressive decrease of homeostasis, often resulting in disruption of the physiological balance between host and commensal microbes, ultimately leading to dysbiosis and host demise. Generally, high microbial diversity is associated with health and a youthful state, while low individual microbial diversity and larger inter-individual microbial diversity is associated with ageing and disease states. Different species are equipped with species-specific commensal, symbiotic and pathogenic microbial communities. How and whether the specific host–microbiota consortia co-evolved with host physiology to ensure homeostasis and promote individual fitness remains an open question. In this essay, we propose that the evolution of vertebrate-specific immune adaptations may have enabled the establishment of highly diverse, species-specific commensal microbial communities. We discuss how the maintenance of intact immune surveillance mechanisms, which allow discrimination between commensal and pathogenic bacteria, fail during ageing and lead to the onset of known ageing-related diseases. We discuss how host–microbiota interactions are key to maintaining homeostasis despite external perturbations, but also how they affect a range of host-specific ageing-related phenotypes. This article is part of the theme issue ‘The role of the microbiome in host evolution’.

The evolution of the adaptive immune system has provided vertebrates with a uniquely sophisticated immune toolkit, enabling them to mount precise immune responses against a staggeringly diverse range of antigens. Like other vertebrates, teleost fishes possess a complex and functional adaptive immune system; however, our knowledge of the complex antigen-receptor genes underlying its functionality has been restricted to a small number of experimental and agricultural species, preventing systematic investigation into how these crucial gene loci evolve. Here, we analyse the genomic structure of the immunoglobulin heavy chain ( IGH ) gene loci in the cyprinodontiforms, a diverse and important group of teleosts present in many different habitats across the world. We reconstruct the complete IGH loci of the turquoise killifish ( Nothobranchius furzeri ) and the southern platyfish ( Xiphophorus maculatus ) and analyse their in vivo gene expression, revealing the presence of species-specific splice isoforms of transmembrane IGHM . We further characterize the IGH constant regions of 10 additional cyprinodontiform species, including guppy, Amazon molly, mummichog and mangrove killifish. Phylogenetic analysis of these constant regions suggests multiple independent rounds of duplication and deletion of the teleost-specific antibody class IGHZ in the cyprinodontiform lineage, demonstrating the extreme volatility of IGH evolution. Focusing on the cyprinodontiforms as a model taxon for comparative evolutionary immunology, this work provides novel genomic resources for studying adaptive immunity and sheds light on the evolutionary history of the adaptive immune system.

Lifespan is a remarkably diverse trait in nature, ranging from just hours in adult mayflies to hundreds of years in the Greenland shark and quahog clam. Great disparities in lifespan are often observed even among somewhat closely related species; for example, in the laboratory, wild-derived strains of the common house mouse have a maximum observed lifespan of approximately 6 years, while a similarly sized rodent, the naked mole rat, can live for over 30 years. Comparative biology of aging across the tree of life provides a tremendous opportunity for understanding the molecular and genetic basis underlying lifespan and aging. However, a lack of molecular and laboratory tools has limited the ability of researchers to take full advantage of the incredible diversity of aging phenotypes in nature. Recent developments in genomic technology have made it increasingly possible to study non-canonical model organisms for aging. One promising new genetic model organism amenable to a range of experimental interventions is the turquoise killifish (Nothobranchius furzeri). This fish species has a naturally short lifespan and undergoes a wide range of aging-related transformations. These fish have a fully sequenced genome and transcriptome, and killifish embryos are accessible to transgenesis and genome editing. Furthermore, different killifish species and populations show striking differences in lifespan, providing the opportunity for comparative analysis of aging. This Review introduces the natural life history of the turquoise killifish, its emerging applicability as an aging model system, the genetic tools that have been developed to study aging for this species and a summary of recent studies facilitated by these new tools.

Aging is emerging as a druggable target with growing interest from academia, industry and investors. New technologies such as artificial intelligence and advanced screening techniques, as well as a strong influence from the industry sector may lead to novel discoveries to treat age-related diseases. The present review summarizes presentations from the 7th Annual Aging Research and Drug Discovery (ARDD) meeting, held online on the 1st to 4th of September 2020. The meeting covered topics related to new methodologies to study aging, knowledge about basic mechanisms of longevity, latest interventional strategies to target the aging process as well as discussions about the impact of aging research on society and economy. More than 2000 participants and 65 speakers joined the meeting and we already look forward to an even larger meeting next year. Please mark your calendars for the 8th ARDD meeting that is scheduled for the 31st of August to 3rd of September, 2021, at Columbia University, USA., Aging, 12 (24), ISSN:1945-4589

The evolution of the adaptive immune system has provided vertebrates with a uniquely sophisticated immune toolkit, enabling them to mount precise immune responses against a staggeringly diverse range of antigens. Like other vertebrates, teleost fishes possess a complex and functional adaptive immune system; however, our knowledge of the complex antigen-receptor genes underlying its functionality has been restricted to a small number of experimental and agricultural species, preventing a systematic investigation of how these crucial gene loci evolve. Here, we analyse the genomic structure of the immunoglobulin heavy chain (IGH) gene loci in the cyprinodontiforms, a diverse and important group of teleosts present in many different habitats across the world. We reconstruct the complete IGH loci of the turquoise killifish (Nothobranchius furzeri) and the southern platyfish (Xiphophorus maculatus) and analyse their in vivo gene expression, revealing the presence of species-specific splice isoforms of transmembrane IGHM. We further characterise the IGH constant regions of ten additional cyprinodontiform species, including guppy, amazon molly, mummichog and mangrove killifish. Phylogenetic analysis of these constant regions reveals multiple independent rounds of duplication and deletion of the teleost-specific antibody class IGHZ in the cyprinodontiform lineage, demonstrating the extreme volatility of IGH evolution. Focusing on the cyprinodontiforms as a model taxon for comparative evolutionary immunology, this work provides novel genomic resources for studying adaptive immunity and sheds light on the evolutionary history of the adaptive immune system.

Divergent populations across different environments are exposed to critical sensory information related to locating a host or mate, as well as avoiding predators and pathogens. These sensory signals generate evolutionary changes in neuroanatomy and behavior; however, few studies have investigated patterns of neural architecture that occur between sensory systems, or that occur within large groups of closely-related organisms. Here we examine 62 species within the genus Drosophila and describe an inverse resource allocation between vision and olfaction, which we consistently observe at the periphery, within the brain, as well as during larval development. This sensory variation was noted across the entire genus and appears to represent repeated, independent evolutionary events, where one sensory modality is consistently selected for at the expense of the other. Moreover, we provide evidence of a developmental genetic constraint through the sharing of a single larval structure, the eye-antennal imaginal disc. In addition, we examine the ecological implications of visual or olfactory bias, including the potential impact on host-navigation and courtship., Neural architecture may be shaped by selection, but is likely also constrained by development. Here, Keesey and colleagues find an inverse relationship between allocation towards visual and olfactory sensory systems across the genus Drosophila, which may reflect a developmental trade-off.

CircRNAs are a subgroup of RNAs which form a circular molecule. During the splicing process the 3’ splice donor loops back to form a covalent bond with an upstream 5’ splice acceptor instead of the downstream 5’ acceptor. The majority of circRNAs are non-coding splice isoforms of protein coding genes showing tissue and time specific expression. Because circRNAs have no 5’ cap nor 3’ poly-A tail, they degrade slower than their linear host genes. Only few studies were able to show a specific function for circRNAs.In this work we sequenced 23 samples from three tissues (brain, muscle, and gut) at three (two for gut) time points throughout the life of the naturally short-lived African turquoise killifish (Nothobranchius furzeri). We identified 1810 unique circRNAs, half of which are conserved with humans and mice. With this study we provide a comprehensive atlas to the circRNA landscape in the ageing African turquoise killifish, which serves as a novel resource to the circRNA as well as the ageing community.

Human ageing is a fundamental biological process that leads to functional decay, increased risk for various diseases and, ultimately, death. Some of the basic biological mechanisms underlying human ageing are shared with other organisms; thus, animal models have been invaluable in providing key mechanistic and molecular insights into the common bases of biological ageing. In this Review, we briefly summarise the major applications of the most commonly used model organisms adopted in ageing research and highlight their relevance in understanding human ageing. We compare the strengths and limitations of different model organisms and discuss in detail an emerging ageing model, the short-lived African turquoise killifish. We review the recent progress made in using the turquoise killifish to study the biology of ageing and discuss potential future applications of this promising animal model., Summary: The short-lived African turquoise killifish is an emerging experimental vertebrate model organism, ideal for studies aimed at discovering the basic mechanisms underlying vertebrate ageing and adult phenotypes.

African killifishes independently evolved annual life cycles at least three times, offering a unique natural experiment of diversification of life history strategies. Using a comprehensive whole-genome sampling of 46 species of African killifishes, we found that genome size correlates with annual life style and climate. Annual species underwent genome-wide expansion of transposable elements, higher gene family turn-over rates and relaxed selection in genes in known aging pathways, such as mitochondrial replication and translation, mTOR pathway and DNA repair. Whole-genome resequencing in wild Nothobranchius populations showed bottle-necks and a genome-wide signature of relaxation of selection in populations evolved in dryer climates. In conclusion, evolution in ephemeral environments in African killifishes caused an extensive relaxation of selective constraints at genome-wide level. We discovered that, in African killifishes, ecology drove the evolution of short life span, associated to tens of thousands of slightly deleterious mutations driven to intermediate to high frequencies.

The development of husbandry practices in non-model laboratory fish used for experimental purposes has greatly benefited from the establishment of reference fish model systems, such as zebrafish and medaka. In recent years, an emerging fish – the turquoise killifish (Nothobranchius furzeri) – has been adopted by a growing number of research groups in the fields of biology of aging and ecology. With a captive life span of 4 - 8 months, this species is the shortest-lived vertebrate raised in captivity and allows the scientific community to test – in a short time – experimental interventions that can lead to alterations of the aging rate and life expectancy. Given the unique biology of this species, characterized by embryonic diapause, explosive sexual maturation, marked morphological and behavioral sexual dimorphism - and their relatively short adult life span - ad hoc husbandry practices are in urgent demand. This protocol reports a set of key husbandry measures that allow optimal turquoise killifish laboratory care, enabling the scientific community to adopt this species as a powerful laboratory animal model.

The turquoise killifish (Nothobranchius furzeri) has recently been brought to the attention of the scientific community as a promising, new animal model system for studying the biology of vertebrate aging. Due to its unique combination of favorable traits, which include a naturally short life span, explosive sexual maturation, and a wide spectrum of aging-related dysfunctions, it constitutes an ideal vertebrate system to study the onset and progression of complex aging symptoms. Its genome has recently been sequenced and assembled, and along with several genetic maps, it is available for the broad scientific community. The killifish's small size and the recently developed laboratory protocols, allow scientists to efficiently raise, breed, and experimentally manipulate a large number of individuals in a laboratory setting, making this species an increasingly accessible model system for a rapidly expanding scientific community.

Summary Aging is a complex process that affects multiple organs. Modeling aging and age-related diseases in the lab is challenging because classical vertebrate models have relatively long lifespans. Here, we develop the first platform for rapid exploration of age-dependent traits and diseases in vertebrates, using the naturally short-lived African turquoise killifish. We provide an integrative genomic and genome-editing toolkit in this organism using our de-novo-assembled genome and the CRISPR/Cas9 technology. We mutate many genes encompassing the hallmarks of aging, and for a subset, we produce stable lines within 2–3 months. As a proof of principle, we show that fish deficient for the protein subunit of telomerase exhibit the fastest onset of telomere-related pathologies among vertebrates. We further demonstrate the feasibility of creating specific genetic variants. This genome-to-phenotype platform represents a unique resource for studying vertebrate aging and disease in a high-throughput manner and for investigating candidates arising from human genome-wide studies. Video Abstract

Aging is one of the greatest challenges for biomedical research in the developed world. The continuing increase in lifespan without accompanying increases in health span has extreme economic and societal implications for an aging society. The majority of adult-onset diseases such as cancer, cardiovascular disease, and Alzheimer's are a direct consequence of aging, and with changing demographics, more and more people are afflicted. If we knew how to slow down the negative effects of aging, we could delay or prevent all of these diseases at once. We therefore need to understand the underlying molecular mechanisms of aging and longevity so as to develop applications that ultimately improve health span.

Gut bacteria occupy the interface between the organism and the external environment, contributing to homeostasis and disease. Yet, the causal role of the gut microbiota during host aging is largely unexplored. Here, using the African turquoise killifish (Nothobranchius furzeri), a naturally short-lived vertebrate, we show that the gut microbiota plays a key role in modulating vertebrate life span. Recolonizing the gut of middle-age individuals with bacteria from young donors resulted in life span extension and delayed behavioral decline. This intervention prevented the decrease in microbial diversity associated with host aging and maintained a young-like gut bacterial community, characterized by overrepresentation of the key genera Exiguobacterium, Planococcus, Propionigenium and Psychrobacter. Our findings demonstrate that the natural microbial gut community of young individuals can causally induce long-lasting beneficial systemic effects that lead to life span extension in a vertebrate model. DOI: http://dx.doi.org/10.7554/eLife.27014.001, eLife digest Our bodies are home to lots of microorganisms, many of which are found throughout the gut. Gut microbes play important roles in human health, where they cooperate with our own cells to develop the immune system, synthesize essential vitamins, and help to absorb nutrients. When the cooperation between our own cells and the gut microbes fails, the microbial community within the gut can become a source of infection, sometimes leading to life-threatening diseases. Healthy individuals typically have many different types gut microbes, whereas people with poor health, or older individuals, will often have less diverse and a higher percentage of disease-causing microbes. For example, African turquoise killifish only live a few months, during which the composition of their gut microbes undergoes dramatic changes. While young fish harbor highly diverse microbial communities, older fish have less diverse communities and more microbes associated with disease. Until now, it was not known whether manipulating the gut composition could affect the aging process. By using the killifish as a model for their study, Smith et al. revealed that gut microbes affect how the fish survived and aged. When the guts of middle-aged fish were colonized with microbes transferred from younger fish, the older fish lived longer and were more active later in life. These fish also maintained a more diverse microbial community throughout their adulthood and shared key microbes with young fish – possibly associated with the improved health benefits. These results suggest that controlling the composition of the gut microbes can improve health and increase life span. The model system used in this study could provide new ways to manipulate the gut microbial community and gain key insights into how the gut microbes affect aging. Manipulating gut microbes to resemble a community found in young individuals could be a strategy to delay the onset of age-related diseases. DOI: http://dx.doi.org/10.7554/eLife.27014.002