Biology subjects

Enav, H.

Publications and source records attributed to Enav, H..

7 recordsLinked to original sources

bioRxiv2026

StrainVis: interactive visual strain-level analysis of microbiome data

BackgroundMicrobiomes contain multiple conspecific strains whose genomic differences arise from both single nucleotide variants (SNVs) and structural variation (insertions, deletions, recombination). Recently, computational tools to assess strain-level differences became available, based either on average nucleotide identity (ANI) or on the average pairwise synteny (APSS) of strains, which are sensitive, respectively, to either SNVs or to structural variation. However, strain-level analyses remain technically challenging and fragmented across approaches and combining these complementary signals typically requires substantial bioinformatic expertise. ResultsHere we present StrainVis, a web-based analysis and visualization platform that integrates outputs from both ANI- and APSS-based strain tracking tools to enable unified, interactive exploration of within-species diversity. StrainVis allows users to perform per-species and multi-species comparisons, incorporate metadata and gene annotations, and generate statistical summaries and publication-ready figures without programming. ConclusionsBy lowering technical barriers and enabling joint interpretation of sequence and structural variation, StrainVis makes advanced strain-level microbiome analysis accessible to a broader community and facilitates discovery of evolutionary patterns that would be missed by single-method approaches alone.

bioinformatics↗

bioRxiv2025

Fidelity in co-diversified symbiosis

Obligate co-dependence can arise in symbiosis, yielding heritable partnerships. These interactions are considered to be highly specific, but partner fidelity is difficult to quantify owing to the experimental constraints of symbiont exchange between host species. Here, we overcome this challenge by leveraging the unique transmission dynamics of Stammera capleta, the obligate digestive symbiont of tortoise beetles (Chrysomelidae: Cassidinae). Despite its extracellular localization, S. capleta possesses a drastically reduced genome ([~]0.25 Mb) and is vertically transmitted through egg-associated spheres. Manipulating these spheres allowed us to experimentally exchange S. capleta between beetle species to determine their impact on host development. We show that non-native S. capleta can successfully colonize the symbiotic organs of a novel host, but that the interaction outcome correlates with genetic relatedness to the native symbiont. Genetically distant species trigger a more pronounced transcriptional response and can only partially rescue host development. While more closely related symbionts proliferate similarly to the native one and induce a comparable host response, they fail to propagate to the next generation, underscoring how transmission fidelity, host-symbiont compatibility, and local adaptation can further specificity within a Paleocene-aged partnership.

evolutionary biology↗

bioRxiv2023

Tradeoffs between phage resistance and nitrogen fixation drive the evolution of genes essential for cyanobacterial heterocyst functionality

Harmful blooms caused by diazotrophic (nitrogen-fixing) cyanobacteria are becoming increasingly frequent and negatively impact aquatic environments worldwide. Cyanophages (viruses infecting cyanobacteria) can potentially regulate cyanobacterial blooms, yet cyanobacteria can rapidly acquire mutations that provide protection against phage infection. Here, we provide novel insights into cyanophage:cyanobacteria interactions by characterizing the resistance to phages in two species of diazotrophic cyanobacteria: Nostoc sp. and Cylindrospermopsis raciborskii. Our results demonstrate that phage resistance is associated with a fitness tradeoff by which resistant cyanobacteria have reduced ability to fix nitrogen and/or to survive nitrogen starvation. Furthermore, we use whole genome sequence analysis of 58 Nostoc resistant strains to identify several mutations associated with phage resistance, including in cell surface-related genes, and regulatory genes involved in development and function of heterocysts (cells specialized in nitrogen fixation). Finally, we employ phylogenetic analyses to show that most of these resistance genes are accessory genes whose evolution is impacted by lateral gene transfer events. Together, these results further our understanding of the interplay between diazotrophic cyanobacteria and their phages, and suggest that a tradeoff between phage resistance and nitrogen fixation affects the evolution of cell surface-related genes and of genes involved in heterocyst differentiation and nitrogen fixation.

evolutionary biology↗

bioRxiv2021

Codiversification of gut microbiota with humans

Some gut microbes have cospeciated with hominids, but whether they further codiversified with human populations is unclear. Here, we identify predominant gut microbial species sharing a parallel evolutionary history with human populations. Patterns of strain transfer between populations are generally consistent with an African origin, and suggest long-term vertical transmission over thousands of generations. We show the same strains also faithfully transmit between mothers and their children. Consistent with the development of intimate symbiosis, species with strongest patterns of codiversification have the smallest genomes. This study reveals long-term fidelity of gut microbiota with human populations through transmission among individuals living in close proximity. Dominance of specific strains in different populations is based in part on vertical transmission and they may provide population-specific health benefits. One-sentence summaryIdentification of gut microbes that codiversified with human populations.

evolutionary biology↗

bioRxiv2021

SynTracker: a synteny based tool for tracking microbial strains

In the human gut microbiome, specific strains emerge due to within-host evolution and can occasionally be transferred to or from other hosts. Phenotypic variance among such strains can have implications for strain transmission and interaction with the host. Surveilling strains of the same species, within and between individuals, can further our knowledge about the way in which microbial diversity is generated and maintained in host populations. Existing methods to estimate the biological relatedness of similar strains usually rely on either detection of single nucleotide polymorphisms (SNP), which may include sequencing errors, or on the analysis of pangenomes, which can be limited by the requirement for extensive gene databases. To complement existing methods, we developed SynTracker. This strain-comparison tool is based on synteny comparisons between strains, or the comparison of the arrangement of sequence blocks in two homologous genomic regions in pairs of metagenomic assemblies or genomes. Our method is executed in a species-specific manner, has a low sensitivity to SNPs, does not require a pre-existing database, and can correctly resolve strains using complete or draft genomes and metagenomic samples using <5% of the genome length. When applied to metagenomic datasets, we detected person-specific strains with an average sensitivity of 97% and specificity of 99%, and strain-sharing events in mother-infant pairs. SynTracker can be used to study the population structure of specific microbial species between and within environments, to identify evolutionary trajectories in longitudinal datasets, and to further understanding of strain sharing networks.

microbiology↗

bioRxiv2020

Strain-level analysis of Bifidobacterium spp. from gut microbiomes of adults of differing lactase persistence genotypes

One of the strongest associations between human genetics and the gut microbiome is a greater relative abundance of Bifidobacterium in adults with lactase gene (LCT) SNPs associated with lactase-non persistence (GG genotypes), versus lactase persistence (AA/AG genotypes). To gain a finer grained phylogenetic resolution of this association, we interrogated 1,680 16S rRNA libraries and 245 metagenomes from gut microbiomes of adults with varying lactase persistence genotypes. We further employed a novel genome-capture based enrichment of Bifidobacterium DNA from a subset of these metagenomes, including monozygotic (MZ) twin pairs, each sampled 2 or 3 times. B. adolescentis and B. longum were the most abundant Bifidobacterium species regardless of host LCT-genotype. LCT- genotypes could not be discriminated based on relative abundances of Bifidobacterium species or Bifidobacterium community structure. Metagenomic analysis of Bifidobacterium-enriched DNA revealed intra-individual temporal stability of B. longum, B. adolescentis, and B. bifidum strains against the background of a changeable microbiome. We also observed greater strain sharing within MZ twin pairs compared to unrelated individuals, and within GG compared to AA/AG individuals, but no effect of host LCTgenotype on Bifidobacterium strain composition. Our results support a "rising tide lift all boats" model for the dominant Bifidobacteria in the adult gut: their higher abundance in lactase-non persistent compared to lactase-persistent individuals results from an expansion at the genus level. Bifidobacterium species are known to be transmitted from mother to child and stable within individuals in infancy and childhood: our results extend this stability into adulthood. IMPORTANCEWhen human populations domesticated animals to drink their milk they adapted genetically with the ability to digest milk into adulthood (lactase persistence). The gut microbiomes of lactase non-persistent people (LNP) differ from those of lactase-persistent people (LP) by containing more bacteria belonging to the Bifidobacteria. These beneficial gut bacteria, which fall into many species, are known to degrade milk in the baby gut. Here, we asked if adult LP and LNP microbiomes differ in the species of Bifidobacteria present. We studied the gut microbiomes of LP and LNP adults, including twins, sampled at several times. In particular, we used a technique to selectively pull out the DNA belonging to the Bifidobacteria: analysis of these DNA segments allowed us to compare Bifidobacteria at the strain level. Our results show that the LNP enhance the abundance of Bifidobacteria regardless of species. We also noted that a persons specific strains are recoverable several years later, and twins tend to share the same ones. Given that Bifidobacteria are inherited from mother to child, strain stability over time in adulthood suggests long term, multi-generational inheritance.

microbiology↗

bioRxiv2018

Adaptation to sub-optimal hosts is a driver of viral diversification in the ocean

Marine cyanophages are viruses that infect oceanic cyanobacteria, thus affecting global ecological processes. Cyanophages of the Myoviridae family are of great interest since they include generalist viruses capable of infection of a wide range of hosts including those from different cyanobacterial genera. While the influence of phages on host evolution has been studied previously, it is not known how the infection of distinct hosts influences the evolution of cyanophage populations. In marine systems this question is of special interest as the abundance of different Synechococcus and Prochlorococcus hosts constantly changes, temporally and spatially. Here, using an experimental evolution approach, we investigated the adaptation of multiple cyanophage populations to three distinct cyanobacterial hosts. We show that when infecting an \"optimal\" host, whose infection is the most efficient, phage populations accumulated only a few mutations. However, when infecting \"sub-optimal\" hosts, different, largely host-specific sets of mutations, spread in the phage populations, leading to rapid diversification into distinct subpopulations. The mutations included insertions, deletions, SNPs and codon adaptations. Most of the mutations were found in genes encoding for proteins responsible for host recognition, attachment and infection, regardless of their evolutionary conservation. Based on our results, we propose a model demonstrating how shifts in bacterial abundance, which lead to infection of \"sub-optimal\" hosts, act as a driver for rapid diversification of phage populations.

evolutionary biology↗