Biology subjects

Banfield, J. F.

Publications and source records attributed to Banfield, J. F..

At least 37 records · Page 2Linked to original sources

bioRxiv2023

Model cyanobacterial consortia reveal a consistent core microbiome independent of inoculation source or cyanobacterial host species

Cyanobacteria are integral to biogeochemical cycles, influence climate processes, and hold promise for commercial applications. In natural habitats, they form complex consortia with other microorganisms, where interspecies interactions shape their ecological roles. Although in vitro studies of these consortia have significantly advanced our understanding, they often lack the biological replication needed for robust statistical analysis of shared microbiome features and functions. Moreover, the microbiomes of many model cyanobacterial strains, which are central to our understanding of cyanobacterial biology, remain poorly characterized. Here, we expanded on existing in vitro approaches by co-culturing five well-characterized model cyanobacterial strains with microorganisms filtered from three distinct freshwater sources, generating 108 stable consortia. Metagenomic analyses revealed that, despite host and inoculum diversity, these consortia converged on a similar set of non-cyanobacterial taxa, forming a 25-species core microbiome. The large number of stable consortia in this study enabled statistical validation of both previously observed and newly identified core microbiome functionalities in micronutrient biosynthesis, metabolite transport, and anoxygenic photosynthesis. Furthermore, core species showed significant enrichment of plasmids, and functions encoded on plasmids suggested plasmid-mediated roles in symbiotic interactions. Overall, our findings uncover the potential microbiomes recruited by key model cyanobacteria, demonstrate that laboratory-enriched consortia retain many taxonomic and functional traits observed more broadly in phototroph-heterotroph assemblages, and show that model cyanobacteria can serve as robust hosts for uncovering functional roles underlying cyanobacterial community dynamics.

microbiology↗

bioRxiv2023

Asgard archaea modulate potential methanogenesis substrates in wetland soil

The roles of Asgard archaea in eukaryogenesis and marine biogeochemical cycles are well studied, yet their contributions in soil ecosystems are unknown. Of particular interest are Asgard archaeal contributions to methane cycling in wetland soils. To investigate this, we reconstructed two complete genomes for soil-associated Atabeyarchaeia, a new Asgard lineage, and the first complete genome of Freyarchaeia, and defined their metabolism in situ. Metatranscriptomics highlights high expression of [NiFe]-hydrogenases, pyruvate oxidation and carbon fixation via the Wood-Ljungdahl pathway genes. Also highly expressed are genes encoding enzymes for amino acid metabolism, anaerobic aldehyde oxidation, hydrogen peroxide detoxification and glycerol and carbohydrate breakdown to acetate and formate. Overall, soil-associated Asgard archaea are predicted to be non-methanogenic acetogens, likely impacting reservoirs of substrates for methane production in terrestrial ecosystems. One-Sentence SummaryComplete genomes of Asgard archaea, coupled with metatranscriptomic data, indicate roles in production and consumption of carbon compounds that are known to serve as substrates for methane production in wetlands.

microbiology↗

bioRxiv2023

Eukaryotic RNA-guided endonucleases evolved from a unique clade of bacterial enzymes

RNA-guided endonucleases form the crux of diverse biological processes and technologies, including adaptive immunity, transposition, and genome editing. Some of these enzymes are components of insertion sequences (IS) in the IS200/IS605 and IS607 transposon families. Both IS families encode a TnpA transposase and TnpB nuclease, an RNA-guided enzyme ancestral to CRISPR-Cas12. In eukaryotes and their viruses, TnpB homologs occur as two distinct types, Fanzor1 and Fanzor2. We analyzed the evolutionary relationships between prokaryotic TnpBs and eukaryotic Fanzors, revealing that a clade of IS607 TnpBs with unusual active site arrangement found primarily in Cyanobacteriota likely gave rise to both types of Fanzors. The wide-spread nature of Fanzors imply that the properties of this particular group of IS607 TnpBs were particularly suited to adaptation and evolution in eukaryotes and their viruses. Experimental characterization of a prokaryotic IS607 TnpB and virally encoded Fanzor1s uncovered features that may have fostered coevolution between TnpBs/Fanzors and their cognate transposases. Our results provide insight into the evolutionary origins of a ubiquitous family of RNA-guided proteins that shows remarkable conservation across domains of life.

molecular biology↗

bioRxiv2023

Methanotrophic Methanoperedens archaea host diverse and interacting extrachromosomal elements

Methane emissions that contribute to climate change can be mitigated by anaerobic methane-oxidizing archaea such as Methanoperedens. Some Methanoperedens have huge extrachromosomal genetic elements (ECEs) called Borgs that may modulate their activity, yet the broader diversity of Methanoperedens ECEs is little studied. Here, we report small enigmatic linear ECEs, circular viruses and unclassified ECEs, that we predict replicate within Methanoperedens. The linear ECEs have features such as inverted terminal repeats, pervasive tandem repeats, and coding patterns that are strongly reminiscent of Borgs, but they are only 52 kb to 145 kb in length. They share proteins with Borgs and Methanoperedens. Thus, we refer to them as mini-Borgs. Mini-Borgs are genetically diverse and we assign them to at least five family-level groups. We also identify eight novel families of Methanoperedens viruses, some of which encode multiheme cytochromes, and unclassified circular ECEs that encode TnpB genes. A population-heterogeneous CRISPR array is in close proximity to the TnpB and has spacers that target other Methanoperedens ECEs including previously reported plasmids. The diverse groups of ECEs exchange genetic information with each other and with Methanoperedens, likely impacting the activity and evolution of these environmentally important archaea.

microbiology↗

bioRxiv2023

Extensive and diverse lanthanide-dependent metabolism in the ocean

Lanthanide (Ln)-dependent enzymes have evolved roles in organic carbon metabolism despite low Ln availability in natural environments1-8. The oceans are the major reservoir of dissolved organic carbon (DOC) on the planet, yet the prevalence and diversity of Ln-dependent enzymes in the ocean, and their biogeochemical importance in the ocean carbon cycle is unknown. Here, we analyzed a global ocean metagenomic/metatranscriptomic dataset and found Ln-dependent methanol-, ethanol- and putative sorbose- and glucose-dehydrogenases in all metagenomes and 20% of all resolved microbial genomes, with several individual organisms hosting dozens of unique Ln-dependent genes. We find that biological methanol oxidation in the ocean is overwhelmingly Ln-dependent, and that methanol dehydrogenases are the most highly expressed Ln-dependent genes in most ocean regions, particularly in surface oceans. As Ln availability is a function of phosphate concentration and pH, Ln-dependent metabolism likely underpins complex biogeochemical feedbacks determining the efficiency of organic matter remineralization, thus impacting the oceanic DOC pool and Earths climate system. The widespread biological utility of Ln also explains their nutrient-like vertical concentration profiles observed in ocean waters, and shows that the preferential utilization of light lanthanides by biology must be considered when interpreting patterns of relative Ln concentrations in seawater.

microbiology↗

bioRxiv2023

COBRA improves the quality of viral genomes assembled from metagenomes

Microbial and viral diversity, distribution, and ecological impacts are often studied using metagenome-assembled sequences, but genome incompleteness hampers comprehensive and accurate analyses. Here we introduce COBRA (Contig Overlap Based Re-Assembly), a tool that resolves de Bruijn graph based assembly breakpoints and joins contigs. While applicable to any short-read assembled DNA sequences, we benchmarked COBRA by using a dataset of published complete viral genomes from the ocean. COBRA accurately joined contigs assembled by metaSPAdes, IDBA_UD, and MEGAHIT, outcompeting several existing binning tools and achieving significantly higher genome accuracy (96.6% vs 19.8-59.6%). We applied COBRA to viral contigs that we assembled from 231 published freshwater metagenomes and obtained 7,334 high-quality or complete species-level genomes (clusters with 95% average nucleotide identity) for viruses of bacteria (phages), [~]83% of which represent new phage species. Notably, [~]70% of the 7,334 species genomes were circular, compared to 34% before COBRA analyses. We expanded genomic sampling of [≥] 200 kbp phages (i.e., huge phages), the largest of which was curated to completion (717 kbp in length). The improved phage genomes from Rotsee Lake provided context for metatranscriptomic data and indicated in situ activity of huge phages, WhiB and cysC/cysH encoding phages from this site. In conclusion, COBRA improves the assembly contiguity and completeness of microbial and viral genomes and thus, the accuracy and reliability of analyses of gene content, diversity, and evolution.

genomics↗

bioRxiv2023

Genomic analysis of cultivated infant microbiomes identifies Bifidobacterium 2'-fucosyllactose utilization can be facilitated by co-existing species

Human milk oligosaccharides (HMOs) ensure proper infant gut microbiome establishment. Isolate studies have revealed the genetic basis for HMO metabolism, but they exclude the possibility of HMO assimilation via synergistic interactions involving multiple organisms. Here, we investigated microbiome responses to 2-fucosyllactose (2FL), a prevalent HMO and infant formula additive, by establishing individualized microbiomes using fecal samples from three different infants as the inocula. Bifidobacterium breve, a prominent member of infant microbiomes, typically cannot metabolize 2FL. Using metagenomic data, we predicted that extracellular fucosidases encoded by co-existing members such as Ruminococcus gnavus initiate 2FL breakdown, thus critical for B. breves growth. Using both targeted co-cultures and by supplementation of R. gnavus into one microbiome, we show that R. gnavus can promote extensive growth of B. breve through the release of lactose from 2FL. Overall, microbiome cultivation combined with genome-resolved metagenomics demonstrated that HMO utilization can vary with an individuals microbiome.

microbiology↗

bioRxiv2023

Vitamin interdependencies predicted by metagenomics-informed network analyses validated in microbial community microcosms

Microbial communities are fundamental components of most ecosystems but little is known about the interactions that structure them. Metagenomic data have revolutionized our understanding of complex consortia, yet predicted interactions are rarely explored experimentally. We developed an organism abundance correlation network to investigate factors that control community organization in soil-derived laboratory microbial consortia grown under dozens of conditions. The network was overlaid with metagenomic information about functional capacities to generate testable hypotheses. We developed a metric to predict the importance of each node within its local network environments relative to correlated vitamin auxotrophs and predicted that a Variovorax species is a hub because it is a highly important source of thiamine. Quantification of thiamine during the growth of Variovorax in minimal media conditions showed extraordinarily high levels of production of thiamine, up to 100 mg/L. This over-production of thiamine explains why the auxotrophs correlated with Variovorax are reliant on this organism for thiamine, despite the presence of other predicted thiamine producers in the community. A few of these thiamine auxotrophs are predicted to produce pantothenate that we show that Variovorax requires to grow, implying that a subset of vitamin-dependent interactions are mutualistic. We found that Cryptococcus produces the B-vitamin pantothenate, and co-cultures led to a 90-130-fold fitness increase for both Cryptococcus and Variovorax. This study demonstrates the predictive power of metagenome-informed, microbial consortia-based network analyses for identifying microbial interactions that underpin the structure and functioning of microbial communities.

microbiology↗

bioRxiv2023

Fine scale sampling reveals spatial heterogeneity of rhizosphere microbiome in young Brachypodium plants

For a deeper and comprehensive understanding of the diversity, composition and function of rhizosphere microbiomes, we need to focus at the scale of individual roots in standardized growth containers. Root exudation patterns are known to vary across distinct parts of the root giving rise to spatially distinct microbial niches. To address this, we analyzed microbial community from two spatially distinct zones of the primary root (the tip vs. the base) in Brachypodium distachyon, grown in natural soil using standardized fabricated ecosystems known as EcoFABs as well as in more conventional pot and tubes. 16S rRNA based community analysis showed a stronger rhizosphere effect in the root base vs. bulk soil compared to the root tips vs. bulk soil, resulting in an enrichment of Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria, few OTUs belonging to less characterized lineages such as Verrucomicrobia and Acidobacteria. While the microbial community distributions are similar across growth containers, the EcoFAB displayed higher replicate reproducibility. Genome-resolved and bulk metagenomics revealed that genes associated with transcriptional regulation, transport of nutrients and catabolic enzymes indicating active metabolism, biofilm formation and root colonization were enriched in root tips. On the other hand, genes associated with nutrient-limitation and environmental stress were prominent in the bulk soil compared to the root tips, implying the presence of easily available, labile carbon and nutrients in the rhizosphere relative to bulk soil. Such insights into the relationships between root structure, exudation and microbial communities are critical for developing understanding of plant-microbe interactions.

ecology↗

bioRxiv2022

Host translation machinery is not a barrier to phages that infect both CPR and non-CPR bacteria

Within human microbiomes, Gracilibacteria, Absconditabacteria, and Saccharibacteria, members of Candidate Phyla Radiation (CPR), are increasingly correlated with human oral health and disease. We profiled the diversity of CRISPR-Cas systems in the genomes of these bacteria and sought phages that are capable of infecting them by comparing their spacer inventories to large phage sequence databases. Gracilibacteria and Absconditabacteria recode the typical TGA stop codon to glycine and are infected by phages that share their hosts alternate genetic code. Unexpectedly, however, other predicted phages of Gracilibacteria and Absconditabacteria do not use an alternative genetic code. Some of these phages are predicted to infect both alternatively coded CPR bacteria and standard coded bacteria. These phages rely on other stop codons besides TGA, and thus should be capable of producing viable gene products in either bacterial host type. Interestingly, we predict that phages of Saccharibacteria can replicate in Actinobacteria, which have been shown to act as episymbiotic hosts for Saccharibacteria. Overall, the broad host range of some CPR phages may be advantageous for the production of these phages for microscopic characterization or use as therapy agents, given the current difficulty of CPR cultivation. Absconditabacteria phages and Gracilibacteria phages may have avoided acquisition of in-frame stop codons to increase the diversity of bacteria in which they can replicate.

microbiology↗

bioRxiv2022

Autotrophic biofilms sustained by deeply-sourced groundwater host diverse CPR bacteria implicated in sulfur and hydrogen metabolism

BackgroundCandidate Phyla Radiation (CPR) bacteria are commonly detected yet enigmatic members of diverse microbial communities. Their host associations, metabolic capabilities, and potential roles in biogeochemical cycles remain under-explored. We studied chemoautotrophically-based biofilms that host diverse CPR bacteria and grow in sulfide-rich springs using bulk geochemical analysis, genome-resolved metagenomics and scanning transmission x-ray microscopy (STXM) at room temperature and 87{degrees} K. ResultsCPR-affiliated Gracilibacteria, Absconditabacteria, Saccharibacteria, Peregrinibacteria, Berkelbacteria, Microgenomates, and Parcubacteria are members of two biofilm communities dominated by chemolithotrophic sulfur-oxidizing bacteria including Thiothrix or Beggiatoa. STXM imaging revealed ultra-small cells along the surfaces of filamentous bacteria that we interpret are CPR bacterial episymbionts. STXM and NEXAFS spectroscopy at carbon K and sulfur L2,3 edges show protein-encapsulated elemental sulfur spherical granules associated with filamentous bacteria, indicating that they are sulfur-oxidizers, likely Thiothrix. Berkelbacteria and Moranbacteria in the same biofilm sample are predicted to have a novel electron bifurcating group 3b [NiFe]-hydrogenase, putatively a sulfhydrogenase, potentially linked to sulfur metabolism via redox cofactors. This complex could potentially underpin a symbiosis involving Berkelbacteria and/or Moranbacteria and filamentous sulfur-oxidizing bacteria such as Thiothrix that is based on cryptic sulfur cycling. One Doudnabacteria genome encodes adjacent sulfur dioxygenase and rhodanese genes that may convert thiosulfate to sulfite. We find similar conserved genomic architecture associated with CPR bacteria from other sulfur-rich subsurface ecosystems. ConclusionsOur combined metagenomic, geochemical, spectromicroscopic and structural bioinformatics analyses link some CPR bacteria to sulfur-oxidizing Proteobacteria, likely Thiothrix, and indicate roles for CPR bacteria in sulfur and hydrogen cycling.

microbiology↗

bioRxiv2022

Isotope-enrichment reveals active viruses follow microbial host dynamics during rewetting of a California grassland soil

Viruses are abundant, ubiquitous members of soil communities that kill microbial cells, but how they respond to perturbation of soil ecosystems is essentially unknown. Here, we investigated lineage-specific virus-host dynamics in grassland soil following "wet-up", when resident microbes are both resuscitated and lysed after a prolonged dry period. Quantitative isotope tracing, time-resolved metagenomics and viromic analyses indicated that dry soil held a diverse but low biomass reservoir of virions, of which only a subset thrived following wet-up. Viral richness decreased by 50% within 24 h post wet-up, while viral biomass increased four-fold within one week. Counter to recent hypotheses suggesting temperate viruses predominate in soil, our evidence indicates that wet-up is dominated by viruses in lytic cycles. We estimate that viruses drive a measurable and continuous rate of cell lysis, with up to 46% of microbial death driven by viral lysis one week following wet-up. Thus, viruses contribute to turnover of soil microbial biomass and the widely reported CO2 efflux following wet-up of seasonally dry soils.

microbiology↗

bioRxiv2022

Quantitative stable-isotope probing (qSIP) with metagenomics links microbial physiology and activity to soil moisture in Mediterranean-climate grassland ecosystems

The growth and physiology of soil microorganisms, which play vital roles in biogeochemical cycling, are likely dependent on current and prior soil moisture levels. Here, we developed and applied a genome-resolved metagenomic implementation of quantitative stable isotope probing (qSIP) to an H218O labeling experiment to determine which microbial community members, and with what capacities, are growing under in situ conditions. qSIP enabled measurement of taxon-specific growth because isotopic incorporation into microbial DNA requires production of new genome copies. We studied three Mediterranean grassland soils across a rainfall gradient to evaluate the hypothesis that historic precipitation levels are an important factor controlling trait selection. We used qSIP-informed genome-resolved metagenomics to resolve an active subset of soil community members and identify the ecophysiological traits that characterize them. Higher year-round precipitation levels correlated with higher activity and growth rates of flagellar motile microorganisms. In addition to bacteria that were heavily isotopically labeled, we identified abundant isotope-labeled phages suggesting phage-induced cell lysis likely contributed to necromass production at all three sites. Further, there was a positive correlation between phage activity and the activity of putative phage hosts. Contrary to our expectations, the capabilities to decompose the diverse complex carbohydrates common in soil necromass or oxidize methanol and carbon monoxide were broadly distributed across active and inactive bacteria in all three soils, implying that these traits are not highly selected for by historical precipitation.

microbiology↗

bioRxiv2022

Candidatus Nealsonbacteria (OD1) in a methanogenic benzene-degrading enrichment culture is likely an ectosymbiotic biomass recycler

The Candidate Phyla Radiation (CPR) is a very large group of bacteria with no pure culture representatives, first discovered by metagenomic analyses. Within the CPR, candidate phylum Parcubacteria (previously referred to as OD1) within the candidate superphylum Patescibacteria is prevalent in anoxic sediments and groundwater. Previously, we had identified a specific member of the Parcubacteria (referred to as DGGOD1a) as an important member of a methanogenic benzene-degrading consortium. Phylogenetic analyses herein place DGGOD1a within the Candidate clade Nealsonbacteria. Because of its persistence over many years, we hypothesized that Ca. Nealsonbacteria DGGOD1a must serve an important role in sustaining anaerobic benzene metabolism in the consortium. To try to identify its growth substrate, we amended the culture with a variety of defined compounds (pyruvate, acetate, hydrogen, DNA, phospholipid), as well as crude culture lysate and three subfractions thereof. We observed the greatest (10 fold) increase in the absolute abundance of Ca. Nealsonbacteria DGGOD1a only when the consortium was amended with crude cell lysate. These results implicate Ca. Nealsonbacteria in biomass recycling. Fluorescent in situ hybridization and cryogenic transmission electron microscope images revealed that Ca. Nealsonbacteria DGGOD1a cells were attached to larger archaeal Methanothrix cells. This apparent epibiont lifestyle was supported by metabolic predictions from a manually curated complete genome. This is one of the first examples of bacterial-archaeal episymbiosis and may be a feature of other Ca. Nealsonbacteria found in anoxic environments.

microbiology↗

bioRxiv2022

Do lanthanide-dependent microbial metabolisms drive the release of REEs from weathered granites?

Prior to soil formation, phosphate liberated by rock weathering is often sequestered into highly insoluble lanthanide phosphate minerals. Dissolution of these minerals is critical for the release of phosphate to the biosphere, yet the microorganisms involved, and the genes required for lanthanide metabolism, are poorly understood. Here, we sampled weathered granite and associated soil to identify the zones of lanthanide phosphate mineral solubilization and genomically define the organisms implicated in lanthanide utilisation. We reconstructed 136 genomes from 11 bacterial phyla and found gene clusters implicated in lanthanide-based metabolism of methanol (primarily XoxF3 and XoxF5) are surprisingly common in microbial communities in moderately weathered granite where lanthanide phosphate minerals are dissolving. Notably, XoxF3 systems were found in Verrucomicrobia for the first time, and in Acidobacteria, Gemmatimonadetes, and Alphaproteobacteria. The XoxF-containing gene clusters are shared by diverse Acidobacteria and Gemmatimonadetes, and include conserved hypothetical proteins and transporters not associated with the few well studied XoxF systems. Given that siderophore-like molecules that strongly bind lanthanides may be required to solubilize lanthanide phosphates, it is notable that candidate siderophore biosynthesis systems were most prevalent in bacteria in moderately weathered rock, especially in Acidobacteria with lanthanide-based systems. We conclude that the confluence in the zone of moderate weathering of phosphate mineral dissolution, lanthanide utilisation, and methanol oxidation (thus carbonic acid production) may be important during the conversion of granitic rock to soil.

microbiology↗

bioRxiv2022

A widespread group of large plasmids in methanotrophic Methanoperedens archaea

Anaerobic methanotrophic (ANME) archaea conserve energy from the breakdown of methane, an important driver of global warming, yet the extrachromosomal genetic elements that impact the activities of ANME archaea are little understood. Here we describe large plasmids associated with ANME archaea of the Methanoperedens genus. These have been maintained in two bioreactors that contain enrichment cultures dominated by different Methanoperedens species and co-occur with Methanoperedens species in other anoxic environments. By manual curation we show that two of the plasmids are large (155,607 bp and 191,912 bp), circular, and replicate bidirectionally. The group of Methanoperedens species that carry these plasmids is related to "Ca. Methanoperedens nitroreducens", "Ca. Methanoperedens ferrireducens", "Ca. Methanoperedens manganicus" and the plasmids occur in the same copy number as the main chromosome. The larger plasmid encodes transporters that potentially enhance access to Ni, which is required for the methyl-CoM reductase (Mcr), Co required for the cobalamin cofactor needed for methyltransferases, and amino acid uptake. We show that many plasmid genes are actively transcribed, including genes involved in plasmid chromosome maintenance and segregation, a Co2+/Ni2+ transporter and cell protective proteins. Notably, one plasmid carries three tRNAs and two colocalized genes encoding ribosomal protein uL16 and elongation factor eEF2. These are not encoded in the host Methanoperedens genome and uL16 and eEF2 were highly expressed, indicating an obligate interdependence between this plasmid and its host. The finding of plasmids of Methanoperedens opens the way for the development of genetic vectors that could be used to probe little understood aspects of Methanoperedens physiology. Ultimately, this may provide a route to introduce or alter genes that may enhance growth and overall metabolism to accelerate methane oxidation rates.

microbiology↗

bioRxiv2022

Using strain-resolved analysis to identify contamination in metagenomics data

Metagenomics analyses can be negatively impacted by DNA contamination. While external sources of contamination such as DNA extraction kits have been widely reported and investigated, contamination originating within the study itself remains underreported. Here we applied high-resolution strain-resolved analyses to identify contamination in two large-scale clinical metagenomics datasets. By mapping strain sharing to DNA extraction plates, we identified well-to-well contamination in both negative controls and biological samples in one dataset. Such contamination is more likely to occur among samples that are on the same or adjacent columns or rows of the extraction plate than samples that are far apart. Our strain-resolved workflow also reveals the presence of externally derived contamination, primarily in the other dataset. Overall in both datasets, contamination is more significant in samples with lower biomass. Our work demonstrates that genome-resolved strain tracking, with its essentially genome-wide nucleotide-level resolution, can be used to detect contamination in sequencing-based microbiome studies. Our results underscore the value of strain-specific methods to detect contamination and the critical importance of looking for contamination beyond negative and positive controls.

microbiology↗

bioRxiv2021

Stop codon recoding is widespread in diverse phage lineages and has the potential to regulate translation of late stage and lytic genes

The genetic code is a highly conserved feature of life. However, some "alternative" genetic codes use reassigned stop codons to code for amino acids. Here, we survey stop codon recoding across bacteriophages (phages) in human and animal gut microbiomes. We find that stop codon recoding has evolved in diverse clades of phages predicted to infect hosts that use the standard code. We provide evidence for an evolutionary path towards recoding involving reduction in the frequency of TGA and TAG stop codons due to low GC content, followed by acquisition of suppressor tRNAs and the emergence of recoded stop codons in structural and lysis genes. In analyses of two distinct lineages of recoded virulent phages, we find that lysis-related genes are uniquely biased towards use of recoded stop codons. This convergence supports the inference that stop codon recoding is a strategy to regulate the expression of late stage genes and control lysis timing. Interestingly, we identified prophages with recoded stop codons integrated into genomes of bacteria that use standard code, and hypothesize that recoding may control the lytic-lysogenic switch. Alternative coding has evolved many times, often in closely related lineages, indicating that genetic code is plastic in bacteriophages and adaptive recoding can occur over very short evolutionary timescales.

microbiology↗