GToTree: a user-friendly workflow for phylogenomics

Human milk oligosaccharide metabolism and antibiotic resistance in early gut colonizers: insights from bifidobacteria and lactobacilli in the maternal-infant microbiome

Breast milk, rich in human milk oligosaccharides (HMOs), supports the early-life colonization of beneficial bacteria such as bifidobacteria and lactobacilli, potentially reducing early-life antibiotic resistance. However, antibiotic treatment may interfere with the beneficial functions of HMO-degrading bacteria. This study investigated the metabolism of HMOs by bifidobacteria and lactobacilli isolated from human milk and mother-infant paired fecal samples, along with their antibiotic resistance profiles. Understanding these species- and sample-type-specific interactions will provide valuable insights into how bioactive components in human milk may shape the infant resistome during early life. A total of 39 Bifidobacterium and 14 Lactobacillaceae strains were isolated from paired mother-infant fecal and breast milk samples. Whole genome sequencing (WGS) allowed functional predictions on the HMO metabolism abilities and the resistance genotype of each strain. In vitro HMO utilization was assessed using growth kinetics assays combined with HMO glycoprofiling in culture supernatant. The minimum inhibitory concentration (MIC) was also determined for each strain. HMO metabolism by the bifidobacteria was species-specific. Bifidobacterium bifidum (B. bifidum) and Bifidobacterium longum subsp. infantis (B. infantis) exhibited the highest capacity for HMO degradation, consistent with genomic predictions. In contrast, lactobacilli were unable to degrade HMOs in vitro but were predicted to metabolize the by-products of HMO degradation. Phenotypic analysis revealed that B. bifidum strains had the lowest levels of antibiotic resistance, while Bifidobacterium animalis subsp. lactis (B. lactis) strains were resistant to most tested antibiotics. Overall, B. bifidum demonstrated the strongest HMO-degrading ability while remaining the most antibiotic-susceptible species. Early-life colonizing bifidobacterial species possess the essential machinery required to degrade HMOs and are highly susceptible to antibiotics. A better understanding of these dynamics could inform clinical strategies to protect and restore the infant gut microbiome, particularly in neonates exposed to antibiotics.

Arsenic mobilization by Bathyarchaeia in subsurface sediments at the Jianghan Plain, China

As one of the most abundant microorganisms on Earth, Bathyarchaeia with diverse abilities to degrade complex organic carbon play a vital role in the global carbon cycle. However, the role of Bathyarchaeia in arsenic (As) metabolism and their contribution to As mobilization in aquifers remain unclear. In this study, we recovered 15 Bathyarchaeota metagenome-assembled genomes (MAGs) from metagenomes of borehole sediments in the Jianghan Plain (JHP), China. Together with 374 representative Bathyarchaeia MAGs from public databases, six As metabolism genes i.e. arrA, arsR, arsA, arsB, arsC (Trx) and arsM were identified, accounting for 4.4, 47.6, 20.3, 38.3, 37.5 and 49.4 % of total Bathyarchaeia MAGs, respectively. Heterologous expression of multiple arsC and arsM genes of Bathyarchaeia MAGs obtained from JHP sediments validated their abilities for As(V) reduction and As(III) methylation at environmentally relevant As concentration. These results indicate that in addition to providing bioavailable carbon sources for other microbial functional populations, Bathyarchaeia directly participate in As mobilization in the JHP aquifer via As(V) reduction and As(III) methylation. The diversified distribution of arsC and arsM in the class Bathyarchaeia suggests that Bathyarchaeia may contribute to As cycling in other As-rich environments, such as hot spring, saline lakes, marine hydrothermal sediments and soils.

Phylogenomic and Pangenomic Assessment of a Mediterranean Strain of Raphidiopsis raciborskii Extends Knowledge of the Global Distribution and Characteristics of a Potentially Toxigenic Cyanobacterium

Among potentially toxigenic cyanobacteria, Raphidiopsis raciborskii has attracted considerable attention due to its ability to produce massive blooms and its recent spread to temperate regions. In this work, we reported for the first time a taxonomic and functional assessment of a R. raciborskii strain isolated from the Mediterranean region, contributing to filling a gap in the global distribution and characteristics of this species. The strain LT_0923 was isolated from Lake Trasimeno, a large and shallow lake in central Italy. The phylogenomic analyses based on selected marker genes and the core genome obtained from a pangenomic analysis based on a selection of available high-quality genomes showed a strong correspondence of the Lake Trasimeno strain with the North American and, at a lower average nucleotide identity, with the South American genomes. The LT_0923 genome did not show the presence of gene clusters encoding legacy cyanotoxins or emerging toxigenic compounds. The open pangenome and the large fraction of distinct gene families identified in the cloud and partly shell genome, enriched with genes specialised in environmental-specific functions and defence mechanisms, are consistent with the development of Raphidiopsis in geographically distinct regions.

Genome-resolved transcriptomics reveals novel PCE-dehalogenating bacteria from Aarhus Bay sediments

Organohalide-respiring bacteria (OHRB) are keystone microbes in bioremediation of sites contaminated with organohalides and in natural halogen cycling. Known OHRB belong to distinct genera within the phyla Chloroflexota, Proteobacteria, and Firmicutes, whereas information about novel OHRB mediating natural halogen cycling remains scarce. In this study, we applied a genome-resolved transcriptomic approach to characterize the identity and activity of OHRB from tetrachloroethene respiring cultures previously enriched from sediments of Aarhus Bay. Combining short- and long-read sequencing approaches, we assembled 37 medium-quality bins with over 75% completeness and less than 5% contamination. Sixteen bins harbored RDase genes and were affiliated taxonomically to the class of Bacilli and phyla of Bacteroidota, Synergistota, and Spirochaetota, which have not been reported to catalyze reductive dehalogenation. Among the 16 bins, bin.26, phylogenetically close to the genus Vulcanibacillus (phylum Firmicutes), contained an unprecedented 97 reductive dehalogenase (RDase) genes. Of these, 84 RDase genes of bin.26 were transcribed during tetrachloroethene dechlorination in addition to RDase genes from the members of Synergistales (bin.5 and bin.32) and Bacteroidales (bin.18 and bin.24). Moreover, metatranscriptome analysis suggested that the RDase genes were likely under the regulation of transcriptional regulators not previously associated with organohalide respiration, such as HrcA and SigW, which are known to respond to abiotic environmental stresses, such as temperature changes. Combined application of genomic methods enabled us to pinpoint novel OHRB from pristine environments not previously known to mediate reductive dechlorination and to add to the current knowledge of the diversity, activity, and regulation of RDase genes.IMPORTANCEPristine marine environment is the major reservoir for naturally produced organohalides, in which reductive dehalogenation underneath plays an important role in the overall cycling of these compounds. Here, we obtain some novel OHRB genomes from Aarhus Bay marine sediments, which are phylogenetically distant to the well-documented OHRB and widely distributed across the bacterial phyla, such as Bacteroidota, Synergistota, and Spirochaetota. Furthermore, transcriptional profiles unravel that these RDase genes are induced differently, and their activity is controlled by diverse regulatory systems. Accordingly, elucidating the reductive dehalogenation of pristine marine environments substantially advances our understanding of the diversity, phylogeny, and regulatory variety of dehalogenating bacteria contributing to the global halogen cycle.

Genomic description of Microbacterium mcarthurae sp. nov., a bacterium collected from the International Space Station that exhibits unique antimicrobial-resistant and virulent phenotype

A novel bacterial strain, designated as 1F8SW-P5T, was isolated from the wall of the crew quarters on the International Space Station. Cells were Gram-staining-positive, strictly aerobic, non-spore-forming, chemoheterotrophic, and mesophilic rods exhibiting catalase-positive and oxidase-negative reactivity. Strain 1F8SW-P5T shared the highest 16S rRNA gene similarity with Microbacterium proteolyticum CECT 8356T (99.34%) and the highest gyrB gene similarity with Microbacterium algihabitans KSW2-21T (91.34%). Its strongest matches via average nucleotide identity and DNA-DNA hybridization were to Microbacterium hydrothermale CGMCC_1.12512T (84.36% and 25.80%, respectively). 1F8SW-P5T formed a distinct lineage during phylogenetic and phylogenomic analysis. The biochemical, phenotypic, chemotaxonomic, and phylogenomic features substantiated the affiliation to 1F8SW-P5T as a new species of Microbacterium, for which we propose the name Microbacterium mcarthurae, with the type strain 1F8SW-P5T (=DSM 115934T =NRRL B-65667T). Based on metagenomic data collected during the Microbial Tracking mission series, M. mcarthurae was identified from all surfaces (n = 8) over an 8-year period, with an increase in relative abundance over time. This is of potential concern, as we observed resistance to all tested fluoroquinolone antibiotics (n = 6), two β-lactam antibiotics, and one macrolide antibiotic, which was not predicted based on isolate or plasmid genotype alone. Furthermore, we found an increase in virulence, compared to Escherichia coli, when tested within a Caenorhabditis elegans model. This pathogenic profile highlights the importance of continued characterization of spacecraft-associated microbes, the characterization of previously unidentified antimicrobial resistance and virulence genes, and the implementation of targeted mitigation strategies during spaceflight.

IMPORTANCE

Crew members are at an increased risk for exposure to and infection by pathogenic microbes during spaceflight. Therefore, it is imperative to characterize the species that are able to colonize and persist on spacecraft, how those organisms change in abundance and distribution over time, and their genotypic potential for and phenotypic expression of pathogenic traits (i.e., whether they encode for or exhibit traits associated with antibiotic resistance and/or virulence). Here, we describe a novel species of Microbacterium collected from the crew quarters on the International Space Station (ISS), 1F8SW-P5T, for which we propose the name Microbacterium mcarthurae. M. mcarthurae was found to be distributed throughout the ISS with an increase in relative abundance over time. Additionally, this bacterium exhibits a unique antibiotic resistance phenotype that was not predicted from whole-genome sequencing, as well as increased virulence, suggesting the need for the identification of previously undescribed antimicrobial resistance genes and monitoring/mitigation during spaceflight.

Microbial diversity and capacity for arsenic biogeochemical cycling in aquifers associated with thermal mobilization

Thermal recovery technologies for in-situ bitumen extraction can result in the heating of surrounding aquifers, potentially mobilizing arsenic naturally present in the sediments to the groundwater. The relative toxicity of dissolved arsenic is related to its speciation, with As(V) being less toxic than As(III). Microorganisms have various mechanisms of arsenic detoxification and metabolism, which include genes for efflux, methylation, and reduction/oxidation of As(V)/As(III). We characterized the microbial communities along two aquifer transects associated with thermally mobilized arsenic near Northeastern Alberta oil sands deposits. 16S rRNA amplicons and metagenomic sequencing data of biomass from filtered groundwater indicated major changes in the dominant taxa between wells, especially those currently experiencing elevated arsenic concentrations. Annotation of arsenic-related genes indicated that efflux pumps (arsB, acr3), intracellular reduction (arsC) and methylation (arsM) genes were widespread among community members but comparatively few organisms encoded genes for arsenic respiratory reductases (arrA) and oxidases (arxA, aioA). While this indicates that microbes have the capacity to exacerbate arsenic toxicity by increasing the relative concentration of As(III), some populations of iron oxidizing and sulfate reducing bacteria (including novel Gallionella and Thermodesulfovibrionia populations) show potential for indirect bioremediation through formation of insoluble iron/sulfide minerals which adsorb or coprecipitate arsenic. An unusually high proportional abundance of a single Paceibacteria population that lacked arsenic resistance genes was identified in one high‑arsenic well, and we discuss hypotheses for its ability to persist. Overall, this study describes how aquifer microbial communities respond to thermal and arsenic plumes, and predicts potential contributions of microbes to arsenic biogeochemical cycling under this disturbance.

Genomic and transcriptomic insights into vertebrate host-specific Lactobacillus johnsonii adaptation in the gastrointestinal tract

We conducted a comparative genomic analysis of Lactobacillus johnsonii strains isolated from the gastrointestinal tract of diverse vertebrate hosts to explore the genetic basis of host specificity. We then utilized transcriptomics analysis to investigate the expression profile of identified rodent-specific genes in mouse isolate MR1 during in vitro and in vivo growth conditions. There was significant heterogeneity among strains, in both genome sequence and content, with phylogenetic clustering of strains into distinct clades associated with rodent or avian sources. There were not sufficient genomes to identify whether porcine isolates formed their own genetic clade. However, human isolates did not form a distinct clade. Functional enrichment analysis revealed significant enrichment of several genes, including surface proteins and accessory secretory pathway-related genes, as well as tyrosine decarboxylase genes in rodent isolates compared to avian isolates, including in mouse isolate MR1. A total of 40 genes were identified as rodent-associated, and all were transcriptionally active in L. johnsonii MR1. The global transcriptomic analysis of L. johnsonii MR1 was done using cells grown anaerobically, at 37˚C, under both the late-exponential phase and stationary phase, as well as during in vivo growth in the cecum of mono-colonized germ-free mice. Several of these genes were uniquely regulated during late exponential vs stationary phase growth and in vivo colonization in mice, highlighting their potential role in nutrient adaptation and host-microbe interactions.IMPORTANCELactobacillus johnsonii is a well-known probiotic species with health-beneficial properties, including host immunomodulation and pathogen inhibition. Its growing relevance in the medical industry highlights the need to understand its biology, particularly how it adapts to different host environments. In bacteria, niche adaptation is often accompanied by the loss or gain of coding sequences along with changes in the genome size. In this study, we explored the genetic diversity of L. johnsonii strains from the gastrointestinal tracts of various vertebrates such as rodents, birds, swine, and humans. We found associations between genome content and host species of origin and could conceptually demonstrate that these genes are being differentially transcribed under varying conditions. Several functions were associated with specific host groups, suggesting that L. johnsonii strains have adapted to their hosts over time.

Genomic insights into novel extremotolerant bacteria isolated from the NASA Phoenix mission spacecraft assembly cleanrooms

BACKGROUND

Human-designed oligotrophic environments, such as cleanrooms, harbor unique microbial communities shaped by selective pressures like temperature, humidity, nutrient availability, cleaning reagents, and radiation. Maintaining the biological cleanliness of NASA's mission-associated cleanrooms, where spacecraft are assembled and tested, is critical for planetary protection. Even with stringent controls such as regulated airflow, temperature management, and rigorous cleaning, resilient microorganisms can persist in these environments, posing potential risks for space missions.

RESULTS

During the Phoenix spacecraft mission, genomes of 215 bacterial isolates were sequenced and based on overall genome-related indices, 53 strains belonging to 26 novel species were recognized. Metagenome mapping indicated less than 0.1% of the reads associated with novel species, suggesting their rarity. Genes responsible for biofilm formation, such as BolA (COG0271) and CvpA (COG1286), were predominantly found in proteobacterial members but were absent in other non-spore-forming and spore-forming species. YqgA (COG1811) was detected in most spore-forming members but was absent in Paenibacillus and non-spore-forming species. Cell fate regulators, COG1774 (YaaT), COG3679 (YlbF, YheA/YmcA), and COG4550 (YmcA, YheA/YmcA), controlling sporulation, competence, and biofilm development processes, were observed in all spore-formers but were missing in non-spore-forming species. COG analyses further revealed resistance-conferring proteins in all spore-formers (n = 13 species) and eight actinobacterial species, responsible for enhanced membrane transport and signaling under radiation (COG3253), transcription regulation under radiation stress (COG1108), and DNA repair and stress responses (COG2318). Additional functional analysis revealed that Agrococcus phoenicis, Microbacterium canaveralium, and Microbacterium jpeli contained biosynthetic gene clusters (BGCs) for ε-poly-L-lysine, beneficial in food preservation and biomedical applications. Two novel Sphingomonas species exhibited for zeaxanthin, an antioxidant beneficial for eye health. Paenibacillus canaveralius harbored genes for bacillibactin, crucial for iron acquisition. Georgenia phoenicis had BGCs for alkylresorcinols, compounds with antimicrobial and anticancer properties used in food preservation and pharmaceuticals.

CONCLUSION

Despite stringent decontamination and controlled environmental conditions, cleanrooms harbor unique bacterial species that form biofilms, resist various stressors, and produce valuable biotechnological compounds. The reduced microbial competition in these environments enhances the discovery of novel microbial diversity, contributing to the mitigation of microbial contamination and fostering biotechnological innovation. Video Abstract.

Virulence and infectious assessment of a Campylobacter jejuni strain isolated from California gull

Wild birds are a major source of Campylobacter jejuni, but there is limited information on its virulence, infectivity, and its human health risks associated with exposure to wild bird infested surface waters. This study focused on understanding the virulence of C. jejuni 63A isolated from California gull excreta. Whole-genome analyses revealed its multilocus sequence typing (ST2654) and high similarity of DNA sequences (97%-99%) with other pathogenic Campylobacter spp. strains, particularly those isolated from patients suffering from Guillain-Barre´ syndrome (GBS). Furthermore, analyses revealed that the lipooligosaccharide (LOS) biosynthesis gene cluster, capsular polysaccharide (CPS) gene cluster, and the genes responsible for producing cytolethal distending toxin (CDT) operons/genes (cdtABC) were all present and shared high sequence conservation with the same clinical isolates collected from GBS patients. The unique LOS genes (neuA1, neuB1, neuC1, and cstIII) to GBS patient isolates were identified and categorized 63A as group 1 LOS locus type. The presence of an intact CPS gene cluster and cdtABC genes in 63A along with their high sequence similarity to clinical isolates was strikingly different from many other wild-bird isolates. These findings suggest the high possibility of significant virulence associated with the new isolate. Additionally, 63A may not be limited to only California gull. Phylogenetic analysis of 63A with other hosts including waterfowl such as sandhill cranes shows that the 63A isolate is closely related to a diverse range of hosts acting as reservoirs and/or vectors. Lastly, dose-response analyses of this isolate estimated a median infectious dose of 7.16 × 107 CFU, further suggesting that the 63A isolate has zoonotic potential.IMPORTANCEC. jejuni is one of the most common foodborne zoonotic pathogens worldwide. This study focused on the virulence and infection of C. jejuni derived from California gull. We found that C. jejuni 63A shares high genetic similarity with other pathogenic C. jejuni strains. These strains are particularly associated with patients suffering from GBS. Whole-genome analyses revealed virulence factors like lipooligosaccharide, capsular polysaccharide, and cytolethal distending toxin operons/genes present in 63A. These genes showed high sequence conservation with clinical isolates collected from GBS patients. We also analyzed its presence in other avian feces, like those of sandhill cranes. Our chick infection experiment and dose-response analyses indicate that the 63A isolate has zoonotic potential and could infect humans. These findings highlight the importance of understanding the virulence and potential health risks associated with C. jejuni strains of wild birds.

A chemical radar allows bacteria to detect and kill predators

Amoebal predation exerts a strong evolutionary selection pressure on bacteria, thus driving the development of effective predator-defense strategies. However, little is known about the molecular interplay between bacteria and predators, particularly how bacteria can sense and kill their microbial predators. We show how the ubiquitous bacterium Pseudomonas syringae detects and kills the social amoeba Polysphondylium pallidum. Combining comparative genomics, molecular biology, and chemical analyses, we identified a chemical radar system. The system relies on P. syringae secreting the lipopeptide syringafactin, which is deacylated by the amoeba. The resulting peptides are sensed via the bacterial sensor protein chemical radar regulator (CraR) that activates genes for converting the predator-derived signal into the amoebicide pyrofactin. This system is widespread in P. syringae and enables bacteria to infect A. thaliana in the presence of amoebae. Our study advances the understanding of microbial sensing and opens new avenues for the discovery of natural products.

Metagenomic insights into cyanotoxin dynamics in a Mexican subtropical lake

Valle de Bravo is a vital water supply for part of the metropolitan area of the Valle de Mexico megacity, providing 30% of Mexico City's water demand. This water body has experienced an acceleration in its trophic status, going from oligotrophic to eutrophic in just a few years. This temperate lake (at a tropical latitude) is in a persistent bloom dominated by a variety of co-occurring cyanobacteria, many of which have toxigenic potential based on microscopic identification, that makes it difficult or even impractical to identify the cyanotoxin producers. To unravel this complexity and directly identify the toxigenic genera, we showed that integrating classical approaches with metagenomic is required. We first characterized, from genes to metagenomes assembled genomes, the toxigenic Cyanobacteria. We found that Microcystis was the most dominant cyanobacterial genus and the sole carrier of the mcy operon, making it the only microcystin producer. We then quantified twenty-one different cyanopeptides, including twelve microcystin congeners using a high-performance liquid chromatography-high-resolution. Nine microcystins (MCs) and the emerging cyanotoxin anabaenopeptin-A and -B were found at varying concentrations throughout the year, with MC-LA being the most common and abundant. Our findings, constrained by our sampling strategy, indicate that conventional cyanotoxin biomarkers (e.g., toxin mcy genes) were not consistently reliable indicators of cyanotoxin concentrations in this freshwater system. In this study, we followed the dynamics of the cyanobacterial community and the associated cyanopeptides with unprecedented resolution. Our results have implications for better management of toxic blooms in this freshwater system, which supplies drinking water to more than 7 million people in the megalopolis of Valle de México.

Genomic Repertoire of Twenty-Two Novel Vibrionaceae Species Isolated from Marine Sediments

The genomic repertoire of vibrios has been extensively studied, particularly regarding their metabolic plasticity, symbiotic interactions, and resistance mechanisms to environmental stressors. However, little is known about the genomic diversity and adaptations of vibrios inhabiting deep-sea marine sediments. In this study, we investigated the genomic diversity of vibrios isolated from deep-sea core sediments collected using a manned submersible off Japan. A total of 50 vibrio isolates were obtained and characterized phenotypically, and by genome sequencing. From this total, we disclosed 22 novel species examining genome-to-genome distance, average amino acid identity, and phenotypes (Alivibrio: 1; Enterovibrio: 1; Photobacterium: 8; Vibrio: 12). The novel species have fallen within known clades (e.g., Fisheri, Enterovibrio, Profundum, and Splendidus) and novel clades (JAMM0721, JAMM0388, JAMM0395). The 28 remainder isolates were identified as known species: Aliivibrio sifiae (2), A. salmonicida (1), Enterovibrio baiacu (1), E. norvegicus (1), Photobacterium profundum (3), P. angustum (1), P. chitiniliticum (1), P. frigidiphilum (1), Photobacterium indicum (1), P. sanguinicancri (1). P. swingsii (2), Vibrio alginolyticus (3), V. anguillarum (1), V. campbellii (1), V. fluvialis (1), V. gigantis (1), V. lentus (1), V. splendidus (4), and V. tasmaniensis (1). Genomic analyses revealed that all 50 vibrios harbored genes associated with high-pressure adaptation, including sensor kinases, chaperones, autoinducer-2 (AI-2) signaling, oxidative damage repair, polyunsaturated fatty acid biosynthesis, and stress response mechanisms related to periplasmic and outer membrane protein misfolding under heat shock and osmotic stress. Additionally, alternative sigma factors, trimethylamine oxide (TMAO) respiration, and osmoprotectant acquisition pathways were identified, further supporting their ability to thrive in deep-sea environments. Notably, the genomes exhibited a high prevalence of antibiotic resistance genes, with antibiotic efflux pumps being the most abundant group. The ugd gene expanded in number in some novel species (Photobacterium satsumensis sp. nov. JAMM1754: 4 copies; Vibrio makurazakiensis sp. nov. JAMM1826: 3 copies). This gene may confer antibiotic (polymyxin) resistance to these vibrios.

Genomic Identification and Characterization of Saxitoxin Producing Cyanobacteria in Western Lake Erie Harmful Algal Blooms

Saxitoxins (STXs), a group of closely related neurotoxins, are among the most potent natural toxins known. While genes encoding STX biosynthesis have been observed in Lake Erie, the organism(s) responsible for producing STXs in the Laurentian Great Lakes have not been identified. We identified a full suite of STX biosynthesis genes in a Dolichospermum metagenome-assembled genome (MAG). The content of sxt genes suggest that this organism can produce STX, decarbamoyl and deoxy-decarbamoyl saxitoxins, and other congeners. The absence of sxtX indicates this organism is unable to produce neosaxitoxin, a potent congener. However, a distinct, lower abundance sxt operon from an unidentified organism did contain sxtX, indicating neosaxitoxin biosynthesis potential. Metatranscriptomic data confirmed STX biosynthesis gene expression. We also recovered highly similar Dolichospermum MAGs lacking sxt genes, implying gene loss or horizontal gene transfer. sxtA was detected by quantitative polymerase chain reaction during 47 of 76 sampling dates between 2015 and 2019, demonstrating higher sensitivity than metagenomic approaches. sxtA gene abundance was positively correlated with temperature and particulate nitrogen:phosphorus ratio and negatively correlated with ammonium concentration. All Dolichospermum MAGs had genes required for nitrogen fixation. Collectively, this study provides a foundation for understanding potential new threats to Lake Erie water quality.

FastAAI: efficient estimation of genome average amino acid identity and phylum-level relationships using tetramers of universal proteins

Estimation of whole-genome relatedness and taxonomic identification are two important bioinformatics tasks in describing environmental or clinical microbiomes. The genome-aggregate Average Nucleotide Identity is routinely used to derive the relatedness of closely related (species level) microbial and viral genomes, but it is not appropriate for more divergent genomes. Average Amino-acid Identity (AAI) can be used in the latter cases, but no current AAI implementation can efficiently compare thousands of genomes. Here we present FastAAI, a tool that estimates whole-genome pairwise relatedness using shared tetramers of universal proteins in a matter of microseconds, providing a speedup of up to 5 orders of magnitude when compared with current methods for calculating AAI or alternative whole-genome metrics. Further, FastAAI resolves distantly related genomes related at the phylum level with comparable accuracy to the phylogeny of ribosomal RNA genes, substantially improving on a known limitation of current AAI implementations. Our analysis of the resulting AAI matrices also indicated that bacterial lineages predominantly evolve gradually, rather than showing bursts of diversification, and that AAI thresholds to define classes, orders, and families are generally elusive. Therefore, FastAAI uniquely expands the toolbox for microbiome analysis and allows it to scale to millions of genomes.

Bacteroides maternus sp. nov., a novel species isolated from human faeces

A novel bacterial strain, MSB163, was isolated from the stool sample of a healthy mother, 4 weeks after giving birth via vaginal delivery. Taxonomic identification tools revealed that MSB163 belongs to the genus Bacteroides, but it is distinct from any currently known species. The closest related species is Bacteroides cellulosilyticus strain BFG- 250, with an average nucleotide identity (fastANI) of 94.51%. The genome length of MSB163 is 6,440,948 bp and the GC content 42.95%. Two plasmids were identified in the whole genome sequence. MSB163 is a Gram-negative, rod-shaped, non-motile anaerobic bacterium. The optimum growth conditions were at 37 °C, pH 7 and 0% (w/v) NaCl. The respiratory quinones were the menaquinones MK- 10 and MK- 11 and C15:0 ANTEISO was the major fatty acid. The predominant polar lipids were phosphatidylethanolamine, diphosphatidylglycerol and phospholipid. According to the taxonomic results and physiological analysis, strain MSB163 represents a novel species of the genus Bacteroides, for which we propose the name Bacteroides maternus, since the type strain was isolated from the stool sample of a mother. B. maternus type strain (MSB163) sequencing can be accessed under the biosample ID SAMN3953129 on NCBI. The strain was deposited on BCCM/LMG Bacteria Collection under the accession number LMG 33,374 and Leibniz Institut DSMZ GMBH under the accession number DSM 117,047.

Novel Insights and Genomic Characterization of Coral-Associated Microorganisms from Maldives Displaying Antimicrobial, Antioxidant, and UV-Protectant Activities

Coral reef survival is crucial for the socio-ecological interest of many countries, particularly for the Republic of Maldives, whose reef integrity influences the country's livelihoods and economy. These ecosystems are being severely impacted by multiple stressors, leading to declines in biodiversity. In the last few decades, researchers have focused on studying coral-associated microorganisms (CAMs) and their symbiotic role in coral health and resilience. Metabarcoding analysis has been widely utilized to study CAM diversity under various conditions but provides limited information on their functional roles. Therefore, cultivation of bacterial strains remains indispensable for validating ecological and biotechnological hypotheses. In this study, we investigated the microbial community associated with two abundant corals in Maldives, Porites lobata and Acropora gemmifera, and evaluated the antimicrobial, antioxidant, and UV-protectant properties of 10 promising isolated strains. The selected CAMs, Pseudoalteromonas piscicida 39, Streptomyces parvus 79, Microbacterium sp. 92 (a potential novel species), and Micromonospora arenicola 93, exhibited antibiotic activity against a panel of pathogenic strains (MIC from 0.01 to 500 µg/mL), antioxidant (comparable effect to that of Trolox and ascorbic acid), and UV-screen activities (protection of human keratinocytes at 200 µg/mL). Genomes revealed their dual potential in contributing to coral restoration and drug discovery strategies. These findings highlight the biotechnological relevance of CAMs, representing an important step toward the identification of novel and bioactive bacterial species beneficial for coral reef ecosystems and human health.

Resolution of MALDI-TOF compared to whole genome sequencing for identification of Bacillus species isolated from cleanrooms at NASA Johnson Space Center

Introduction

Bacteria are frequently isolated from surfaces in cleanrooms, where astromaterials are curated, at NASA's Lyndon B. Johnson Space Center (JSC). Bacillus species are of particular interest because endospores can endure extreme conditions. Current monitoring programs at JSC rely on culturing microbes from swabs of surfaces followed by identification by 16S rRNA sequencing and the VITEK 2 Compact bacterial identification system. These methods have limited power to resolve Bacillus species. Whole genome sequencing (WGS) is the current standard for bacterial identification but is expensive and time-consuming. Matrix-assisted laser desorption - time of flight mass spectrometry (MALDI-TOF MS), provides a rapid, low-cost, method of identifying bacterial isolates and has a higher resolution than 16S rRNA sequencing, particularly for Bacillus species; however, few studies have compared this method to WGS for identification of Bacillus species isolated from cleanrooms.

Methods

To address this, we selected 15 isolates for analysis with WGS and MALDI-TOF MS. Hybrid next-generation (Illumina) and 3rd-generation (nanopore) sequencing were used to draft genomes. Mass spectra, generated with MALDI-TOF MS, were processed with custom scripts to identify clusters of closely related isolates.

Results

MALDI-TOF MS and WGS identified 13/15 and 9/14 at the species level, respectively, and clusters of species generated from MALDI-TOF MS showed good agreement, in terms of congruence of partitioning, with phylotypes generated with WGS. Pairs of strains that were > 94% similar to each other, in terms of average amino acid identity (AAI) predicted by WGS, consistently showed cosine similarities of mass spectra >0.8. The only discordance was for a pair of isolates that were classified as Paenibacillus species. This pair showed relatively high similarity (0.85) in terms of MALDI-TOF MS but only 85% similarity in terms of AAI. In addition, some strains isolated from cleanrooms at the JSC appeared closely related to strains isolated from spacecraft assembly cleanrooms.

Discussion

Since MALDI-TOF MS costs less than whole genome sequencing and offers a throughput of hundreds of isolates per hour, this approach appears to offer a cost-efficient option for identifying Bacillus species, and related microbes, isolated during routine monitoring of cleanrooms and similar built environments.

Spatial ecology of the Neisseriaceae family in the human oral cavity

The human oral microbiome is a diverse ecosystem in which bacterial species have evolved to occupy specific niches within the oral cavity. The Neisseriaceae family, which includes human oral species in the genera Neisseria, Eikenella, Kingella, and Simonsiella, plays a significant role in both commensal and pathogenic relationships. In this study, we investigate the distribution and functional adaptations of Neisseriaceae species across oral habitats, focusing on their site tropisms and ecological roles. We employed a metapangenomic approach in which a curated set of reference genomes representing Neisseriaceae diversity was used for competitive mapping of metagenomic reads. Our analysis revealed distinct habitat preferences among Neisseriaceae species, with Kingella oralis, Neisseria elongata, and Neisseria mucosa primarily found in dental plaque; Neisseria subflava on the tongue dorsum; and Neisseria cinerea in the keratinized gingiva. Functional enrichment analyses identified genes and pathways underpinning habitat-specific adaptations. Plaque specialists showed metabolic versatility, with adaptations in nitrogen metabolism, including nitrate reduction and denitrification, lysine degradation, and galactose metabolism. Tongue dorsum specialists exhibited adaptations including enhanced capabilities for amino acid biosynthesis, short-chain fatty acid and glycerol transport, as well as lipopolysaccharide glycosylation, which may aid in resisting antimicrobial peptides and maintaining membrane integrity. These findings provide insights into the ecological roles and adaptive strategies of Neisseriaceae species within the human oral microbiome and establish a foundation for exploring functional specialization and microbial interactions in these niches.IMPORTANCEUnraveling the distribution and functional adaptations of Neisseriaceae within the human oral microbiome is essential for understanding the roles of these abundant and prevalent commensals in both health and disease. Through a metapangenomic approach, we uncovered distinct habitat preferences of various Neisseriaceae taxa across the oral cavity and identified key genetic traits that may drive their habitat specialization and role in host-microbe interactions. These insights enhance our understanding of the microbial dynamics that shape oral microbial ecology, offering potential pathways for advancing oral health research.

Kineothrix sedimenti sp. nov., a 3-hydroxybutyrate-producing bacterium isolated from sediment of the meromictic Lake Pavin

An anaerobic, spore-forming, 3-hydroxybutyrate (3-HB)-producing bacterium, strain IPX_CKT, was isolated from sediment of a meromictic lake located in Massif Central (France). Cells were rods, forming filamentous chains which were observed moving under the microscope. Strain IPX_CKT utilized a wide variety of carbohydrates, but not raffinose, rhamnose and starch. Hydrogen (H2), 3-HB, acetate and ethanol were the main fermentative end-products from growth in medium containing glucose. Strain IPX_CKT grew optimally at 37 °C and pH 7. Its closest phylogenetic relative was Kineothrix alysoides (16S rRNA gene sequence identity 98.7%, isDDH 34.6%, ANIb 87.4%). The genomic DNA G+C content was 43.0 mol%. As for K. alysoides, whole-genome sequencing suggested that strain IPX_CKT is capable of fixing nitrogen (N2). However, strain IPX_CKT carried a five-nif-gene-set (nifHDKEB), not present in K. alysoides. Genome sequence also showed a high number of encoded chemotaxis receptors (42 genes, the second highest in the family Lachnospiraceae after K. alysoides). Based on phenotypic, genomic, phylogenetic and chemotaxonomic analyses, it is proposed that a novel species, Kineothrix sedimenti sp. nov., be created, with strain IPX_CKT (DSM 118044T, CIP 112511T) as the type strain.

Dethiothermospora halolimnae gen. nov., sp. nov., a novel moderately halophilic, thermotolerant, bacterium isolated from a brine lake

A novel, strictly anaerobic, slightly alkaliphilic, halotolerant, peptide- and amino acid-utilizing bacterial strain, SD1T, was isolated from a hypersaline lake in Western Australia. The strain stained Gram-negative and was a motile, spore-forming rod. The strain grew between 15 and 50 °C (optimum 40 °C), 1-15% w/v sodium chloride (optimum 5%) and pH 6.0-10.0 (optimum 9.0). Major fatty acids included anteiso-C15 : 0 (24.9%), C14 : 0 dimethyl acetyl (13.2%), anteiso-C15 : 0 dimethyl acetyl (11.5%) and iso-C15 : 0 (10.4%). The DNA G+C content was 30.3 mol%. The isolate did not grow using any tested sugars but grew well on arginine and glycine. It is capable of using elemental sulfur and thiosulfate as alternate electron acceptors, but not sulfide, sulfate, nitrate or nitrite. 16S rRNA gene similarity indicates that the isolate is related to Sporosalibacterium tautonense MRo-4T (94.33% identity). SD1T showed 76.18%-76.31% average nucleotide identity with other strains within the family Thermohalobacteraceae. Phylogenetics, based on the 16S rRNA gene and whole-genome sequence, as well as phenotypic analysis, differentiates the isolate from close neighbors. We propose that SD1T represents a novel species in a new genus, which we have named Dethiothermospora halolimnae gen. nov., sp. nov., type strain SD1T (DSM 117405T = TSD-443T). From this work, we also propose repositioning of the genus Anaeromonas to the family Thermohalobacteraceae.

Environmental instability reduces shock resistance by enriching specialist taxa with distinct two component regulatory systems

Different microbial communities are impacted disproportionately by environmental disturbances. The degree to which a community can remain unchanged under a disturbance is referred to as resistance1. However, the contributing ecological factors, which infer a community's resistance are unknown. In this study, the impact of historical environmental stability on ecological phenomena and microbial community resistance to shocks was investigated. Three separate methanogenic bioreactor consortia, which were subjected to varying degrees of historical environmental stability, and displayed different levels of resistance to an organic loading rate (OLR) shock were sampled. Their community composition was assessed using high throughput sequencing of 16S rRNA genes and assembly based metagenomics. The effect environmental instability on ecological phenomena such as microbial community assembly, microbial niche breadth and the rare biosphere were assessed in the context of each reactor's demonstrated resistance to an OLR shock. Additionally, metagenome assembled genomes were analysed for functional effects of prolonged stability/instability. The system which was subjected to more environmental instability experienced more temporal variation in community beta diversity and a proliferation of specialists, with more abundant two component regulatory systems. This community was more susceptible to deterministic community assembly and demonstrated a lower degree of resistance, indicating that microbial communities experiencing longer term environmental instability (e.g. variations in pH or temperature) are less able to resist a large disturbance.

Recovery of 679 metagenome-assembled genomes from different soil depths along a precipitation gradient

Soil contains a diverse community of organisms; these can include archaea, fungi, viruses, and bacteria. In situ identification of soil microorganisms is challenging. The use of genome-centric metagenomics enables the assembly and identification of microbial populations, allowing the categorization and exploration of potential functions living in the complex soil environment. However, the heterogeneity of the soil-inhabiting microbes poses a tremendous challenge, with their functions left unknown, and difficult to culture in lab settings. In this study, using genome assembling strategies from both field core samples and enriched monolith samples, we assembled 679 highly complete metagenome-assembled genomes (MAGs). The ability to identify these MAGs from samples across a precipitation gradient in the state of Kansas (USA) provided insights into the impact of precipitation levels on soil microbial populations. Metabolite modeling of the MAGs revealed that more than 80% of the microbial populations possessed carbohydrate-active enzymes, capable of breaking down chitin and starch.

Tryptic oncopeptide secreted from the gut bacterium Cronobacter malonaticus PO3 promotes colorectal cancer

The involvement of Cronobacter, which is frequently associated with meningitis and necrotizing enterocolitis, in human colorectal cancer remains unexplored. In this study, we isolate and characterize a novel strain of C. malonaticus designated PO3 from a fecal sample of a colon cancer patient and demonstrate its proliferative effects on colorectal cancer both in vitro and in vivo. The secretome of PO3 significantly promoted cell proliferation, as evidenced by increased cell viability, fluorescence intensity, and Ki-67 expression, without inducing cell death. Furthermore, using high-resolution mass spectrometry (HRMS), we identified a novel tryptic oncopeptide designated P506, in the PO3 secretome that promotes colorectal cancer. Synthetic P506 further stimulated human colorectal adenocarcinoma cell line HT-29 cell proliferation in a dose-dependent manner. Experiments with the BALB/c mouse model in vivo revealed that both the PO3 secretome and P506 contributed to the development of colorectal polyps and associated histological changes, including dysplasia and altered colonic architecture. These findings suggest that P506, a potent peptide from the PO3 secretome, may have oncogenic potential, promoting colorectal cancer progression.

Bumble bee gut microbial community structure differs between species and commercial suppliers, but metabolic potential remains largely consistent

Bumble bees are key pollinators for natural and agricultural plant communities. Their health and performance are supported by a core gut microbiota composed of a few bacterial taxa. However, the taxonomic composition and community structure of bumble bee gut microbiotas can vary with bee species, environment, and origin (i.e., whether colonies come from the wild or a commercial rearing facility), and it is unclear whether metabolic capabilities therefore vary as well. Here we used metagenomic sequencing to examine gut microbiota community composition, structure, and metabolic potential across bumble bees from two different commercial Bombus impatiens suppliers, wild B. impatiens, and three other wild bumble bee species sampled from sites within the native range of all four species. We found that the community structure of gut microbiotas varied between bumble bee species, between populations from different origins within species, and between commercial suppliers. Notably, we found that Apibacter is consistently present in some wild bumble bee species-suggesting it may be a previously unrecognized core phylotype of bumble bees-and that commercial B. impatiens colonies can lack core phylotypes consistently found in wild populations. However, despite variation in community structure, the high-level metabolic potential of gut microbiotas was largely consistent across all hosts, including for metabolic capabilities related to host performance, though metabolic activity remains to be investigated.IMPORTANCEOur study is the first to compare genome-level taxonomic structure and metabolic potential of whole bumble bee gut microbiotas between commercial suppliers and between commercial and wild populations. In addition, we profiled the full gut microbiotas of three wild bumble bee species for the first time. Overall, our results provide new insight into bumble bee gut microbiota community structure and function and will help researchers evaluate how well studies conducted in one bumble bee population will translate to other populations and species. Research on taxonomic and metabolic variation in bumble bee gut microbiotas across species and origins is of increasing relevance as we continue to discover new ways that social bee gut microbiotas influence host health, and as some bumble bee species decline in range and abundance.

Pre-exposure to stress reduces loss of community and genetic diversity following severe environmental disturbance

Environmental stress caused by anthropogenic impacts is increasing worldwide. Understanding the ecological and evolutionary consequences for biodiversity will be crucial for our ability to respond effectively. Historical exposure to environmental stress is expected to select for resistant species, shifting community composition toward more stress-tolerant taxa. Concurrent with this species sorting process, genotypes within resistant taxa that have the highest relative fitness under severe stress are expected to increase in frequency, leading to evolutionary adaptation. However, empirical demonstrations of these dual ecological and evolutionary processes in natural communities are rare. Here, we provide evidence for simultaneous species sorting and evolutionary adaptation across multiple species within a natural freshwater bacterial community. Using a two-phase stressor experimental design (acidification pre-exposure followed by severe acidification) in aquatic mesocosms, we show that pre-exposed communities were more resistant than naive communities to taxonomic loss when faced with severe acid stress. However, after sustained severe acidification, taxonomic richness of both pre-exposed and naive communities eventually converged. All communities experiencing severe acidification became dominated by an acidophilic bacterium, Acidiphilium rubrum, but this species retained greater genetic diversity and followed distinct evolutionary trajectories in pre-exposed relative to naive communities. These patterns were shared across other acidophilic species, providing repeated evidence for the impact of pre-exposure on evolutionary outcomes despite the convergence of community profiles. Our results underscore the need to consider both ecological and evolutionary processes to accurately predict the responses of natural communities to environmental change.

Tabrizicola caldifontis sp. nov., Isolated from Hot Spring Sediment Sample

A Gram-stain-negative, ovoid to rod-shaped, aerobic, non-motile bacterial strain, designated YIM 73028T, was isolated from a sediment sample collected from a hot spring in Tibet, China. Phylogenetic analysis (based on the 16S rRNA gene sequences) indicated that strain YIM 73028T belongs to the genus Tabrizicola and showed the highest sequence similarity to the type strain of Tabrizicola aquatica (97.0%). Growth occurred at 30-50 °C (optimum, 37-45 °C) and pH 6.5-8.5 (optimum, pH 7.0-7.5). The respiratory isoprenoid quinone was ubiquinone Q-10. The polar lipids consisted of phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, unidentified amino lipid and unidentified lipid. The major cellular fatty acids (> 10%) were C18:1 ω7c, C18:1 ω7c 11-methyl, C16:0 and C18:0. The genomic DNA G + C content was 65.7%. The average nucleotide identity value between strain YIM 73028T and type species of Tabrizicola aquatica was lower than 95-96% threshold recommended for distinguishing novel prokaryotic species. Based on the phenotypic, physiological, chemotaxonomic, genotypic, and phylogenetic data, strain YIM 73028T represents a novel species of the genus Tabrizicola, for which the name Tabrizicola caldifontis sp. nov. is proposed. The type strain is YIM 73028T (= KCTC 52713T = CGMCC 1.16151T).

Clonal Candida auris and ESKAPE pathogens on the skin of residents of nursing homes

Antimicrobial resistance is a public health threat associated with increased morbidity, mortality and financial burden in nursing homes and other healthcare settings1. Residents of nursing homes are at increased risk of pathogen colonization and infection owing to antimicrobial-resistant bacteria and fungi. Nursing homes act as reservoirs, amplifiers and disseminators of antimicrobial resistance in healthcare networks and across geographical regions2. Here we investigate the genomic epidemiology of the emerging, multidrug-resistant human fungal pathogen Candida auris in a ventilator-capable nursing home. Coupling strain-resolved metagenomics with isolate sequencing, we report skin colonization and clonal spread of C. auris on the skin of nursing home residents and throughout a metropolitan region. We also report that most Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Entobacter species (ESKAPE) pathogens and other high-priority pathogens (including Escherichia coli, Providencia stuartii, Proteus mirabilis and Morganella morganii) are shared in a nursing home. Integrating microbiome and clinical microbiology data, we detect carbapenemase genes at multiple skin sites on residents identified as carriers of these genes. We analyse publicly available shotgun metagenomic samples (stool and skin) collected from residents with varying medical conditions living in seven other nursing homes and provide additional evidence of previously unappreciated bacterial strain sharing. Taken together, our data suggest that skin is a reservoir for colonization by C. auris and ESKAPE pathogens and their associated antimicrobial-resistance genes.

Metagenomics reveals spatial variation in cyanobacterial composition, function, and biosynthetic potential in the Winam Gulf, Lake Victoria, Kenya

The Winam Gulf in the Kenyan region of Lake Victoria experiences prolific, year-round cyanobacterial harmful algal blooms (cyanoHABs) which pose threats to human, livestock, and ecosystem health. To our knowledge, there is limited molecular research on the gulf's cyanoHABs, and thus, the strategies employed for survival and proliferation by toxigenic cyanobacteria in this region remain largely unexplored. Here, we used metagenomics to analyze the Winam Gulf's cyanobacterial composition, function, and biosynthetic potential. Dolichospermum was the dominant bloom-forming cyanobacterium, co-occurring with Microcystis at most sites. Microcystis and Planktothrix were more abundant in shallow and turbid sites. Metagenome-assembled genomes (MAGs) of Dolichospermum harbored nitrogen fixation genes, suggesting diazotrophy as a potential mechanism supporting the proliferation of Dolichospermum in the nitrogen-limited gulf. Over 300 biosynthetic gene clusters (BGCs) putatively encoding the synthesis of toxins and other secondary metabolites were identified across the gulf, even at sites where there were no visible cyanoHAB events. Almost all BGCs identified had no known synthesis product, indicating a diverse and novel biosynthetic repertoire capable of synthesizing harmful or potentially therapeutic metabolites. Microcystis MAGs contained mcy genes encoding the synthesis of hepatotoxic microcystins which are a concern for drinking water safety. These findings illustrate the spatial variation of bloom-forming cyanobacteria in the Winam Gulf and their available strategies to dominate different ecological niches. This study underscores the need for further use of genomic techniques to elucidate the dynamics and mitigate the potentially harmful effects of cyanoHABs and their associated toxins on human, environmental, and economic health.IMPORTANCEThe Winam Gulf (Kenya) is a vital resource that experiences prolific cyanobacterial harmful algal blooms (cyanoHABs). Bloom-forming cyanobacteria produce cyanotoxins, threatening human and environmental health, recreation, and fishing. However, cyanotoxin production in the gulf has not been linked to a specific type of cyanobacteria. We used DNA sequencing of whole microbial communities to track the species of cyanobacteria present across the gulf and investigate the genes responsible for synthesis of known and novel toxins. Our results reveal Dolichospermum as the main bloom-forming cyanobacteria in the gulf, often co-occurring with high abundance of toxigenic Microcystis. Over 300 unique gene clusters were found, with most predicted to encode the synthesis of uncharacterized molecules. These results provide initial insights into the diverse biosynthetic potential encoded by cyanobacteria in the Winam Gulf and underscore the need to further elucidate and investigate the effects of known and novel molecules produced in cyanoHABs in this region.

High-quality PacBio draft genome sequences of 17 free-living Bradyrhizobium and four related Nitrobacteraceae strains isolated from arid soils in the Santa Catalina Mountains of Southern Arizona

Non-symbiotic Bradyrhizobium are among the most abundant and ubiquitous microbes in bulk soils globally. Despite this, most available genomic resources for Bradyrhizobium are derived from plant-associated strains. We present high-quality draft genomes for 17 Bradyrhizobium and four Nitrobacteraceae cultures isolated from bulk semiarid soils in Arizona, USA. The genome sizes range from 5.99 to 10.4 Mbp. Phylogenomic analysis of the 21 genomes indicates they fall into four clades. Two of the clades are nested within the Bradyrhizobium genus. The other two clades were associated with Nitrobacteraceae outgroups basal to Bradyrhizobium. All genomes lack genes coding for molybdenum or vanadium nitrogenases, and nod genes that code for proteins involved in nodulation, suggesting these isolates are free-living, non-symbiotic and do not fix dinitrogen gas. These genomes offer new resources for investigating free-living Bradyrhizobium lineages.

Draft genome sequences of six high pH adapted Marinobacter shengliensis strains isolated from Mariana forearc serpentinite mud volcanoes

Six marine bacterial isolates were obtained from fluid and sediments collected at alkaline serpentinite mud volcanoes of the Mariana forearc to examine life at high pH in a marine environment. Here, we present the draft genome sequences of these six isolates, classified as strains of the species Marinobacter shengliensis.

Multi-omics unveils strain-specific neuroactive metabolite production linked to inflammation modulation by Bacteroides and their extracellular vesicles

Bacteroides species are key members of the human gut microbiome and play crucial roles in gut ecology, metabolism, and host-microbe interactions. This study investigated the strain-specific production of neuroactive metabolites by 18 Bacteroidetes (12 Bacteroides, 4 Phocaeicola, and 2 Parabacteroides) using multi-omics approaches. Genomic analysis revealed a significant potential for producing GABA, tryptophan, tyrosine, and histidine metabolism-linked neuroactive compounds. Using untargeted and targeted metabolomics, we identified key neurotransmitter-related or precursor metabolites, including GABA, l-tryptophan, 5-HTP, normelatonin, kynurenic acid, l-tyrosine, and norepinephrine, in a strain- and media-specific manner, with GABA (1-2 mM) being the most abundant. Additionally, extracellular vesicles (EVs) produced by Bacteroides harbor multiple neuroactive metabolites, mainly GABA, and related key enzymes. We used CRISPR/Cas12a-based gene engineering to create a knockout mutant lacking the glutamate decarboxylase gene (gadB) to demonstrate the specific contribution of Bacteroides finegoldii-derived GABA in modulating intestinal homeostasis. Cell-free supernatants from wild-type (WT, GABA+) and ΔgadB (GABA-) provided GABA-independent reinforcement of epithelial membrane integrity in LPS-treated Caco-2/HT29-MTX co-cultures. EVs from WT and ΔgadB attenuated inflammatory immune response of LPS-treated RAW264.7 macrophages, with reduced pro-inflammatory cytokines (IL-1β and IL-6), downregulation of TNF-α, and upregulation of IL-10 and TGF-β. GABA production by B. finegoldii had a limited impact on gut barrier integrity but a significant role in modulating inflammation. This study is the first to demonstrate the presence of a myriad of neuroactive metabolites produced by Bacteroides species in a strain- and media-specific manner in supernatant and EVs, with GABA being the most dominant metabolite and influencing immune responses.

Metabolic redundancy and specialisation of novel sulfide-oxidizing Sulfurimonas and Sulfurovum along the brine-seawater interface of the Kebrit Deep

BACKGROUND

Members of the Campylobacterota phylum are dominant key players in sulfidic environments, where they make up a stable portion of sulfide-oxidizing bacterial communities. Despite the significance of these bacteria in primary production being well recognised in several ecosystems, their genomic and metabolic traits in sulfidic deep hypersaline anoxic basins (DHABs) remain largely unexplored. This knowledge gap not only hampers our understanding of their adaptation and functional role in DHABs but also their ecological interactions with other microorganisms in these unique ecosystems.

RESULTS

Metabolic reconstructions from metagenome-assembled genomes (MAGs) of sulfide-oxidizing Campylobacterota were conducted at 10 cm spatial resolution within the halocline of the brine-seawater interface (BSI, salinity 91-155 PSU) of the 1466 m deep sulfidic Kebrit Deep in the Red Sea. Fifty-four Campylobacterota MAGs were assembled and dereplicated into three distinct groups, with the highest-quality genome retained as representative. These genomes represent novel sulfide-oxidizing species within the Sulfurimonas and Sulfurovum genera, which differ from those found in mildly saline deep-sea sulfidic pools. They are stratified along the BSI and utilise the reductive tricarboxylic acid cycle to fix carbon dioxide, acting as primary producers. Their energy generation processes include aerobic or anaerobic-nitrate-dependent sulfide oxidation, as well as hydrogen oxidation. In addition to the osmoprotectant pathways commonly observed in Campylobacterota, such as the synthesis and uptake of proline and glutamate, the two Kebrit Deep Sulfurovum species exhibit genomic signatures for ectoine synthesis, further aiding their adaptation to high salinity. This combination of metabolic redundancy and specialisation within the confined spatial boundaries (~1 m) of the BSI is pivotal in governing microbial interactions, including those with sulfate-reducers, heterotrophs, and other primary producers.

CONCLUSIONS

These results show how the selective pressures mediated by the sulfidic and hypersaline conditions of Kebrit Deep have resulted in novel, adapted and metabolically redundant Sulfurimonas and Sulfurovum species that contribute to the energy coupling, nutrient turnover and metabolic continuity along the physico-chemical gradient of the BSI.

Floridanema gen. nov. (Aerosakkonemataceae, Aerosakkonematales ord. nov., Cyanobacteria) from benthic tropical and subtropical fresh waters, with the description of four new species

Cyanobacteria exhibit a vast diversity from polar to tropical environments. Though much work has been done on elucidating their biodiversity, knowledge on the occurrence, diversity and toxicity of benthic cyanobacteria is limited when compared to the planktonic forms. Integrating molecular techniques with ecological and morphological analyses has become essential in untangling cyanobacterial diversity, particularly for benthic taxa such as the cryptic "Lyngbya." Molecular markers such as the 16S rRNA gene and whole genome sequencing have significantly improved the taxonomy of cyanobacteria. Building on these advancements, this study characterizes benthic cyanobacterial isolates from various locations in Florida, USA, and Orange Walk, Belize, resulting in the identification of a novel genus, Floridanema, and four new species (F. aerugineum, F. evergladense, F. flaviceps, and F. fluviatile). This new genus commonly occurs in canals, ponds, lakes and rivers. By integrating ecological, morphological, and genomic analyses, this study provides support for the family Aerosakkonemataceae and the establishment of the order Aerosakkonematales. The LC-MS data revealed that Floridanema strains do not produce microcystins, nodularin-R, or anabaenopeptins.

Energetic and genomic potential for hydrogenotrophic, formatotrophic, and acetoclastic methanogenesis in surface-expressed serpentinized fluids of the Samail Ophiolite

Serpentinization, the reaction of water with ultramafic rock, produces reduced, hyperalkaline, and H2-rich fluids that support a variety of hydrogenotrophic microbial metabolisms. Previous work indicates the occurrence of methanogenesis in fluids from the actively serpentinizing Samail Ophiolite in the Sultanate of Oman. While those fluids contain abundant H2 to fuel hydrogenotrophic methanogenesis (CO2 + 4H2 ➔ CH4 + 2H2O), the concentration of CO2 is very low due to the hyperalkalinity (> pH 11) and geochemistry of the fluids. As a result, species such as formate and acetate may be important as alternative methanogenic substrates. In this study we quantified the impact of inorganic carbon, formate and acetate availability for methanogenic metabolisms, across a range of fluid chemistries, in terms of (1) the potential diffusive flux of substrates to the cell, (2) the Affinity (Gibbs energy change) associated with methanogenic metabolism, and (3) the energy "inventory" per kg fluid. In parallel, we assessed the genomic potential for the conduct of those three methanogenic modes across the same set of fluids and consider the results within the quantitative framework of energy availability. We find that formatotrophic methanogenesis affords a higher Affinity (greater energetic yield) than acetoclastic and hydrogenotrophic methanogenesis in pristine serpentinized fluids and, in agreement with previous studies, find genomic evidence for a methanogen of the genus Methanobacterium to carry out formatotrophic and hydrogenotrophic methanogenesis, with the possibility of even using bicarbonate as a supply of CO2. Acetoclastic methanogenesis is also shown to be energetically favorable in these fluids, and we report the first detection of a potential acetoclastic methanogen of the family Methanosarcinaceae, which forms a distinct clade with a genome from the serpentinizing seafloor hydrothermal vent field, Lost City. These results demonstrate the applicability of an energy availability framework for interpreting methanogen ecology in serpentinizing systems.

Ecological features of microbial community linked to stochastic and deterministic assembly processes in acid mine drainage

Ecological processes greatly shape microbial community assembly, but the driving factors remain unclear. Here, we compiled a metagenomic data set of microbial communities from global acid mine drainage (AMD) and explored the ecological features of microbial community linked to stochastic and deterministic processes from the perspective of species niche position, interaction patterns, gene functions, and viral infection. Our results showed that dispersal limitation (DL) (48.5%~93.5%) dominated the assembly of phylogenetic bin in AMD microbial community, followed by homogeneous selection (HoS) (3.1%~39.2%), heterogeneous selection (HeS) (1.4%~22.2%), and drift (DR) (0.2%~2.7%). The dominant process of dispersal limitation was significantly influenced by niche position in temperature (r = -0.518, P = 0.007) and dissolved oxygen (r = 0.471, P = 0.015). Network stability had a significantly negative correlation with the relative importance of dispersal limitation, while it had a positive correlation with selection processes, implying changes in network properties could be mediated by ecological processes. Furthermore, we found that ecological processes were mostly related to the gene functions of energy production and conversion (C), and amino acid transport and metabolism (E). Meanwhile, our results showed that the number of proviruses and viral genes involved in arsenic (As) resistance is negatively associated with the relative importance of ecological drift in phylogenetic bin assembly, implying viral infection might weaken ecological drift. Taken together, these results highlight that ecological processes are associated with ecological features at multiple levels, providing a novel insight into microbial community assembly in extremely acidic environments.

IMPORTANCE

Unraveling the forces driving community assemblage is a core issue in microbial ecology, but how ecological constraints impose stochasticity and determinism remains unknown. This study presents a comprehensive investigation to uncover the association of ecological processes with species niche position, interaction patterns, microbial metabolisms, and viral infections, which provides novel insights into community assembly in extreme environments.

Impact of commercial gut health interventions on caecal metagenome and broiler performance

BACKGROUND

Maintaining gut health is a persistent and unresolved challenge in the poultry industry. Given the critical role of gut health in chicken performance and welfare, there is a pressing need to identify effective gut health intervention (GHI) strategies to ensure optimal outcomes in poultry farming. In this study, across three broiler production cycles, we compared the metagenomes and performance of broilers provided with ionophores (as the control group) against birds subjected to five different GHI combinations involving vaccination, probiotics, prebiotics, essential oils, and reduction of ionophore use.

RESULTS

Using a binning strategy, 84 (≥ 75% completeness, ≤ 5% contamination) metagenome-assembled genomes (MAGs) from 118 caecal samples were recovered and annotated for their metabolic potential. The majority of these (n = 52, 61%) had a differential response across all cohorts and are associated with the performance parameter - European poultry efficiency factor (EPEF). The control group exhibited the highest EPEF, followed closely by the cohort where probiotics are used in conjunction with vaccination. The use of probiotics B, a commercial Bacillus strain-based formulation, was determined to contribute to the superior performance of birds. GHI supplementation generally affected the abundance of microbial enzymes relating to carbohydrate and protein digestion and metabolic pathways relating to energy, nucleotide synthesis, short-chain fatty acid synthesis, and drug-transport systems. These shifts are hypothesised to differentiate performance among groups and cycles, highlighting the beneficial role of several bacteria, including Rikenella microfusus and UBA7160 species.

CONCLUSIONS

All GHIs are shown to be effective methods for gut microbial modulation, with varying influences on MAG diversity, composition, and microbial functions. These metagenomic insights greatly enhance our understanding of microbiota-related metabolic pathways, enabling us to devise strategies against enteric pathogens related to poultry products and presenting new opportunities to improve overall poultry performance and health. Video Abstract.

zol and fai: large-scale targeted detection and evolutionary investigation of gene clusters

Many universally and conditionally important genes are genomically aggregated within clusters. Here, we introduce fai and zol, which together enable large-scale comparative analysis of different types of gene clusters and mobile-genetic elements, such as biosynthetic gene clusters (BGCs) or viruses. Fundamentally, they overcome a current bottleneck to reliably perform comprehensive orthology inference at large scale across broad taxonomic contexts and thousands of genomes. First, fai allows the identification of orthologous instances of a query gene cluster of interest amongst a database of target genomes. Subsequently, zol enables reliable, context-specific inference of ortholog groups for individual protein-encoding genes across gene cluster instances. In addition, zol performs functional annotation and computes a variety of evolutionary statistics for each inferred ortholog group. Importantly, in comparison to tools for visual exploration of homologous relationships between gene clusters, zol can scale to handle thousands of gene cluster instances and produce detailed reports that are easy to digest. To showcase fai and zol, we apply them for: (i) longitudinal tracking of a virus in metagenomes, (ii) performing population genetic investigations of BGCs for a fungal species, and (iii) uncovering evolutionary trends for a virulence-associated gene cluster across thousands of genomes from a diverse bacterial genus.

Reclassification of Salinisphaera halophila Zhang et al. 2012 as a Later Heterotypic Synonym of Salinisphaera orenii Park et al. 2012

In the present study, the taxonomic position of Salinisphaera halophila (NZ_AYKF00000000) and Salinisphaera orenii (NZ_AYKH00000000) was re-evaluated. In addition, their metabolic potentials and mechanisms for mitigating stress conditions were determined. Comparisons of 16S rRNA gene sequences, analysis of the phylogenetic tree, phylogenomic tree, average nucleotide identity (ANI), and digital DNA-DNA hybridization (dDDH) values were conducted. The 16S rRNA gene sequence similarity between Salinisphaera halophila YIM 95161T and Salinisphaera orenii MK-B5T was 100%. In phylogenetic and phylogenomic trees, Salinisphaera halophila YIM 95161T and Salinisphaera orenii MK-B5Tclustered together. Both species encode genes for glycolysis, citrate cycle, pentose phosphate pathway, Entner-Doudoroff pathway, nitrate assimilation, and assimilatory sulfate reduction. They employ salt-in and salt-out strategies to mitigate salt stress. The ANI and dDDH values between Salinisphaera halophila YIM 95161Tand Salinisphaera orenii MK-B5Twere 96.6 and 72.1%, respectively, above the cut-off (95-96% for ANI and 70% for dDDH) for species delineation. Based on the above results, we propose to reclassify Salinisphaera halophila Zhang et al. 2012 as a later heterotypic synonym of Salinisphaera orenii Park et al. 2012.

Reclassification of Salisediminibacterium haloalkalitolerans Sultanpuram et al. 2015 as a Later Heterotypic Synonym of Salisediminibacterium halotolerans Jiang et al. 2012

In the present study, the taxonomic position of Salisediminibacterium haloalkalitolerans was evaluated by determining the 16S rRNA gene sequence similarity, genome relatedness, and phylogenetic analyses. The 16S rRNA gene sequences extracted from the genomes of Salisediminibacterium haloalkalitolerans 10nlgT and Salisediminibacterium halotolerans DSM 26530T showed 100% similarity, supporting their classification as the same species. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between S. haloalkalitolerans and S. halotolerans were 97.7 and 80.2%, respectively, above the cutoff value (95-96% ANI; 70% dDDH) for species delineation. S. haloalkalitolerans and S. halotolerans should be classified as the same species because the 16S rRNA gene phylogeny and phylogenomic tree (based on 71 bacterial single-copy genes) showed no genetic divergence between them. Based on the above results and the rule of priority in nomenclature, we propose to reclassify Salisediminibacterium haloalkalitolerans Sultanpuram et al. 2015 as a later heterotypic synonym of Salisediminibacterium halotolerans Jiang et al. 2012.

Comparative genomics analyses of Actinobacteriota identify Golgi phosphoprotein 3 (GPP34) as a widespread ancient protein family associated with sponge symbiosis

BACKGROUND

Sponges harbor microbial communities that play crucial roles in host health and ecology. However, the genetic adaptations that enable these symbiotic microorganisms to thrive within the sponge environment are still being elucidated. To understand these genetic adaptations, we conducted a comparative genomics analysis on 350 genomes of Actinobacteriota, a phylum commonly associated with sponges.

RESULTS

Our analysis uncovered several differences between symbiotic and free-living bacteria, including an increased abundance of genes encoding prokaryotic defense systems (PDSs) and eukaryotic-like proteins (ELPs) in symbionts. Furthermore, we identified GPP34 as a novel symbiosis-related gene family, found in two symbiotic Actinobacteriota clades, but not in their closely related free-living relatives. Analyses of a broader set of microbes showed that members of the GPP34 family are also found in sponge symbionts across 16 additional bacterial phyla. While GPP34 proteins were thought to be restricted to eukaryotes, our phylogenetic analysis shows that the GPP34 domain is found in all three domains of life, suggesting its ancient origin. We also show that the GPP34 family includes genes with two main structures: a short form that includes only the GPP34 domain and a long form that encompasses a GPP34 domain coupled with a cytochrome P450 domain, which is exclusive to sponge symbiotic bacteria.

CONCLUSIONS

Given previous studies showing that GPP34 is a phosphatidylinositol-4-phosphate (PI4P)-binding protein in eukaryotes and that other PI4P-binding proteins from bacterial pathogens can interfere with phagolysosome maturation, we propose that symbionts employ GPP34 to modulate phagocytosis to colonize and persist within sponge hosts. Video Abstract.

Neobacillus driksii sp. nov. isolated from a Mars 2020 spacecraft assembly facility and genomic potential for lasso peptide production in Neobacillus

During microbial surveillance of the Mars 2020 spacecraft assembly facility, two novel bacterial strains, potentially capable of producing lasso peptides, were identified. Characterization using a polyphasic taxonomic approach, whole-genome sequencing and phylogenomic analyses revealed a close genetic relationship among two strains from Mars 2020 cleanroom floors (179-C4-2-HS, 179-J1A1-HS), one strain from the Agave plant (AT2.8), and another strain from wheat-associated soil (V4I25). All four strains exhibited high 16S rRNA gene sequence similarity (>99.2%) and low average nucleotide identity (ANI) with Neobacillus niacini NBRC 15566T, delineating new phylogenetic branches within the genus. Detailed molecular analyses, including gyrB (90.2%), ANI (86.4%), average amino acid identity (87.8%) phylogenies, digital DNA-DNA hybridization (32.6%), and percentage of conserved proteins (77.7%) indicated significant divergence from N. niacini NBRC 15566T. Consequently, these strains have been designated Neobacillus driksii sp. nov., with the type strain 179-C4-2-HST (DSM 115941T = NRRL B-65665T). N. driksii grew at 4°C to 45°C, pH range of 6.0 to 9.5, and 0.5% to 5% NaCl. The major cellular fatty acids are iso-C15:0 and anteiso-C15:0. The dominant polar lipids include diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and an unidentified aminolipid. Metagenomic analysis within NASA cleanrooms revealed that N. driksii is scarce (17 out of 236 samples). Genes encoding the biosynthesis pathway for lasso peptides were identified in all N. driksii strains and are not commonly found in other Neobacillus species, except in 7 out of 26 recognized species. This study highlights the unique metabolic capabilities of N. driksii, underscoring their potential in antimicrobial research and biotechnology.

IMPORTANCE

The microbial surveillance of the Mars 2020 assembly cleanroom led to the isolation of novel N. driksii with potential applications in cleanroom environments, such as hospitals, pharmaceuticals, semiconductors, and aeronautical industries. N. driksii genomes were found to possess genes responsible for producing lasso peptides, which are crucial for antimicrobial defense, communication, and enzyme inhibition. Isolation of N. driksii from cleanrooms, Agave plants, and dryland wheat soils, suggested niche-specific ecology and resilience under various environmentally challenging conditions. The discovery of potent antimicrobial agents from novel N. driksii underscores the importance of genome mining and the isolation of rare microorganisms. Bioactive gene clusters potentially producing nicotianamine-like siderophores were found in N. driksii genomes. These siderophores can be used for bioremediation to remove heavy metals from contaminated environments, promote plant growth by aiding iron uptake in agriculture, and treat iron overload conditions in medical applications.

Antarctic Geothermal Soils Exhibit an Absence of Regional Habitat Generalist Microorganisms

Active geothermal systems are relatively rare in Antarctica and represent metaphorical islands ideal to study microbial dispersal. In this study, we tested the macro-ecological concept that high dispersal rates result in communities being dominated by either habitat generalists or specialists by investigating the microbial communities on four geographically separated geothermal sites on three Antarctic volcanoes (Mts. Erebus, Melbourne, and Rittman). We found that the microbial communities at higher temperature (max 65°C) sites (Tramway Ridge on Erebus and Rittmann) were unique from each other and were dominated by a variety of novel Archaea from class Nitrososphaeria, while lower temperature (max 50°C) sites (Western Crater on Erebus and Melbourne) had characteristically mesophilic communities (Planctomycetes, Acidobacteriota, etc.) that were highly similar. We found that 97% of the detected microbial taxa were regional habitat specialists, with no generalists, with community assembly driven by high dispersal rates and drift (25% and 30% of community assembly, respectively), not environmental selection. Our results indicate that for microbial communities experiencing high dispersal rates between isolated communities, habitat specialists may tend to out-compete habitat generalists.

Metagenomic immunoglobulin sequencing reveals IgA coating of microbial strains in the healthy human gut

IgA, the primary human antibody secreted from the gut mucosa, shapes the intestinal microbiota. Methodological limitations have hindered defining which microbial strains are targeted by IgA and the implications of binding. Here we develop a technique, metagenomic immunoglobulin sequencing (MIg-seq), that provides strain-level resolution of microbes coated by IgA and use it to determine IgA coating levels for 3,520 gut microbiome strains in healthy human faeces. We find that both health and disease-associated bacteria are targeted by IgA. Microbial genes are highly predictive of IgA binding levels; in particular, mucus degradation genes are correlated with high binding, and replication rates are significantly reduced for microbes bound by IgA. We demonstrate that IgA binding is more correlated with host immune status than traditional relative abundance measures of microbial community composition. This study introduces a powerful technique for assessing strain-level IgA binding in human stool, paving the way for deeper understanding of IgA-based host-microbe interactions.

Description of six novel species Bacillus bruguierae sp. nov., Bacillus kandeliae sp. nov., Bacillus yunxiaonensis sp. nov., Metabacillus rhizosphaerae sp. nov., Metabacillus sediminis sp. nov. and Psychrobacillus mangrovi sp. nov., isolated from mangrove ecosystem

Six Gram-stain-positive and rod-shaped strains, designated FJAT-51614T, FJAT-51639T, FJAT-52054T, FJAT-52991T, FJAT-53654T and FJAT-53711T, were isolated from a mangrove ecosystem. The condition for growth among the strains varied (pH ranging 5.0-11.0 and temperature 15-45 °C). These strains showed the highest 16S rRNA gene sequence similarity to the genera Bacillus, Metabacillus and Psychrobacillus. Menaquinone MK-7 (100%) was present in all strains except strain FJAT-51614T, which contained MK-7 (32%) and MK-8 (68%). The major fatty acids (>10%) in strains FJAT-52054T and FJAT-51614T were anteiso-C15 : 0 and iso-C14 : 0. The major fatty acid (>10%) in strain FJAT-53654T was anteiso-C15 : 0, while in strain FJAT-51639T were iso-C15 : 0 and iso-C17 : 0. The major fatty acids in strains FJAT-52991T and FJAT-53711T were iso-C15 : 0 and iso-C16 : 0. The major polar lipids in strains FJAT-51639T, FJAT-52991T and FJAT-51614T were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine, while strains FJAT-53711T, FJAT-52054T and FJAT-53654T consist of diphosphatidylglycerol and phosphatidylglycerol. The genome-relatedness values among the present study strains and the closest species were below the recognized cutoff levels for species delineation. The polyphasic analysis comparison results represent six strains as novel species for which the names Bacillus bruguierae sp. nov. (FJAT-51639T=GDMCC 1.3073T=JCM 35615T), Bacillus kandeliae sp. nov. (FJAT-52991T=GDMCC 1.3069T=JCM 35619T), Bacillus yunxiaonensis sp. nov. (FJAT-53711T=GDMCC 1.3068T=JCM 35616T), Metabacillus rhizosphaerae sp. nov. (FJAT-53654T=GDMCC 1.3075T=JCM 35614T), Metabacillus sediminis sp. nov. (FJAT-52054T=GDMCC 1.3074T=JCM 35620T) and Psychrobacillus mangrovi sp. nov. (FJAT-51614T=GDMCC 1.3072T=JCM35478T) are proposed.

Whole-genome sequencing and genomic analysis of four Akkermansia strains newly isolated from human feces

Background

Numerous studies have demonstrated that Akkermansia is closely associated with human health. These bacteria colonize the mucus layer of the gastrointestinal tract and utilize mucin as their sole source of carbon and nitrogen. Akkermansia spp. exhibit potential as probiotics under specific conditions. However, the gene accumulation curve derived from pan-genome analysis suggests that the genome of Akkermansia strains remains open. Consequently, current genome mining efforts are insufficient to fully capture the intraspecific and interspecific characteristics of Akkermansia, necessitating continuous exploration of the genomic and phenotypic diversity of new isolates.

Methods

Based on this finding, we sequenced, assembled, and functionally annotated the whole genomes of four new human isolates from our laboratory: AKK-HX001, AKK-HX002, AKK-HX003, and AKK-HX004.

Results

Phylogenetic analysis revealed that all four isolates belonged to the AmII phylogroup, whereas the type strain DSM 22959 is classified within the AmI phylogroup. Moreover, 2,184 shared homologous genes were identified among the four isolates. Functional annotation using the COG, KEGG, and CAZy databases indicated that the functional genes of the four isolates were primarily associated with metabolism. Two antibiotic resistance genes were identified in AKK-HX001 and AKK-HX002, while three resistance genes were detected in AKK-HX003 and AKK-HX004. Additionally, each of the four isolates possessed two virulence genes and three pathogenicity genes, none of which were associated with pathogenicity. The prediction of mobile genetic elements indicated unequal distributions of GIs among the isolates, and a complete CRISPR system was identified in all isolates except AKK-HX003. Two annotated regions of secondary metabolite biosynthesis genes, both belonging to Terpene, were detected using the antiSMASH online tool.

Conclusion

These findings indicate that the four Akkermansia isolates, which belong to a phylogroup distinct from the model strain DSM 22959, exhibit lower genetic risk and may serve as potential probiotic resources for future research.

Genome sequences of toxigenic cyanobacteria from a bloom in Lake Mattamuskeet, North Carolina (United States)

Lake Mattamuskeet, the largest lake in North Carolina, USA, has undergone decades-long eutrophication causing reduced water quality and promoting cyanobacterial blooms that may produce toxins. It is therefore necessary to evaluate the cyanobacterial diversity of the lake and their toxigenic potential. We present draft genomes of Microcystis, Pelatocladus, Raphidiopsis, and Umezakia strains isolated from Lake Mattamuskeet. The whole-genome shotgun projects for Umezakia ovalisporum BLCC-F208, Microcystis sp. BLCC-F209, Microcystis sp. BLCC-F210, Pelatocladus sp. BLCC-F211, U. ovalisporum BLCC-F215, and Raphidiopsis BLCC-F218 have been deposited in GenBank under accession numbers JBHFLK000000000, JBHFLL000000000, CP169647, JBHFLM000000000, JBHFLN000000000, and JBHFLO000000000, respectively. Based on the genomic analysis, several biosynthetic gene clusters (BCGs) with varying degrees of similarity to known toxic and bioactive compound gene clusters were identified across the different cyanobacterial strains.

Draft genome sequence of Sanguibacter species strain 25GB23B1, cultivated from arctic surface seawater

We report a draft genome sequence for Sanguibacter species strain 25GB23B1, isolated from arctic surface seawater off the coast of Alaska. The whole genome sequence will provide knowledge of the bacteria's relationship to its environment and possibly a new species of Sanguibacter.

Large-scale investigation for antimicrobial activity reveals novel defensive species across the healthy skin microbiome

The human skin microbiome constitutes a dynamic barrier that can impede pathogen invasion by producing antimicrobial natural products. Gene clusters encoding for production of secondary metabolites, biosynthetic gene clusters (BGCs), that are enriched in the human skin microbiome relative to other ecological settings, position this niche as a promising source for new natural product mining. Here, we introduce a new human microbiome isolate collection, the EPithelial Isolate Collection (EPIC). It includes a large phylogenetically diverse set of human skin-derived bacterial strains from eight body sites. This skin collection, consisting of 980 strains is larger and more diverse than existing resources, includes hundreds of rare and low-abundance strains, and hundreds of unique BGCs. Using a large-scale co-culture screen to assess 8,756 pairwise interactions between skin-associated bacteria and potential pathogens, we reveal broad antifungal activity by skin microbiome members. Integrating 287 whole isolate genomes and 268 metagenomes from sampling sites demonstrates that while the distribution of BGC types is stable across body sites, specific gene cluster families (GCFs), each predicted to encode for a distinct secondary metabolite, can substantially vary. Sites that are dry or rarely moist harbor the greatest potential for discovery of novel bioactive metabolites. Among our discoveries are four novel bacterial species, three of which exert significant and broad-spectrum antifungal activity. This comprehensive isolate collection advances our understanding of the skin microbiomes biosynthetic capabilities and pathogen-fighting mechanisms, opening new avenues towards antimicrobial drug discovery and microbiome engineering.

An intranuclear bacterial parasite of deep-sea mussels expresses apoptosis inhibitors acquired from its host

A limited number of bacteria are able to colonize the nuclei of eukaryotes. 'Candidatus Endonucleobacter' infects the nuclei of deep-sea mussels, where it replicates to ≥80,000 bacteria per nucleus and causes nuclei to swell to 50 times their original size. How these parasites are able to replicate and avoid apoptosis is not known. Dual RNA-sequencing transcriptomes of infected nuclei isolated using laser-capture microdissection revealed that 'Candidatus Endonucleobacter' does not obtain most of its nutrition from nuclear DNA or RNA. Instead, 'Candidatus Endonucleobacter' upregulates genes for importing and digesting sugars, lipids, amino acids and possibly mucin from its host. It likely prevents apoptosis of host cells by upregulating 7-13 inhibitors of apoptosis, proteins not previously seen in bacteria. Comparative phylogenetic analyses revealed that 'Ca. Endonucleobacter' acquired inhibitors of apoptosis through horizontal gene transfer from their hosts. Horizontal gene transfer from eukaryotes to bacteria is assumed to be rare, but may be more common than currently recognized.

Ketone body oxidation and susceptibility to ethyl acetoacetate in a novel hemolytic multidrug-resistant strain Leptospira interrogans KeTo originated from sewage water

Terrestrial and aquatic environments contaminated with animal urine may contribute to the transmission of Leptospira, a causative agent of leptospirosis in humans and wild/domesticated animals. Although enormous amounts of work have been done decoding the ecophysiology, the factors governing the cell growth and virulence in Leptospires derived from environmental samples still remain elusive. Here, we show oxidation of a wide array of organic acids including acetoacetate by a new strain of Leptospira interrogans designated as KeTo, isolated from a sewage sample originating from a wildlife enclosure located at Mangalore, India. We further demonstrate the susceptibility of KeTo to ethyl ester of acetoacetate (ethyl acetoacetate, EA). A 4.7 Mbp genome of KeTo shared the highest relatedness to pathogenic L. interrogans RGAT (99.3%), followed by L. kirschneri 3522CT (91.3%) and other related species of Leptospira (80.8‒74.3%), and harbored genes encoding acetoacetyl-CoA synthetase and acetoacetate decarboxylase respectively involved in the acetoacetate utilization and acetone formation. In line with this, strain KeTo oxidized acetoacetate when supplied as a sole carbon. Aqueous EA suppressed biofilm formation (p < 0.0001) of KeTo in basal Ellinghausen-McCullough-Johnson-Harris (EMJH) medium. Similarly, significant inhibition in the growth/biofilm of Leptospira was recorded in semisolid EMJH with/without blood supplementation when exposed to volatile EA. The extent of ketone body oxidation and susceptibility to EA was found to vary with strain as evident through the analysis of L. interrogans serogroup Australis sv. Australis strain Ballico and L. interrogans serogroup Icterohaemorrhagiae sv. Lai Like strain AF61. In conclusion, our study demonstrated the ketone body metabolic ability and susceptibility to an esterified derivative of a major ketone body in the tested strains of L. interrogans. Molecular aspects governing EA-driven growth inhibition warrant further investigations to develop optimal therapeutics for leptospirosis.