Supervised extraction of near-complete genomes from metagenomic samples: A new service in PATRIC

Genome sequences of Mycobacterium sp. Elmwood and accompanying phage, isolated from a public swimming pool in Nebraska

Genome sequencing of a non-tuberculosis Mycobacterium species, isolated from a public pool, shows that the genome contains several genes for antibiotic resistance and anti-phage defense, which are absent from other related Mycobacteria. Metagenomic binning also provided the genome of the accompanying phage, which is distinct from other mycobacterial phages.

Genomic characterization, in vitro, and preclinical evaluation of two microencapsulated lytic phages VB_ST_E15 and VB_ST_SPNIS2 against clinical multidrug-resistant Salmonella serovars

BACKGROUND

Salmonella infections continue to be one of the essential public health issues threatening millions of people. With the increasing occurrence of resistance against conventionally used antibiotics, the search for alternatives has become crucial. In this study, we aimed to isolate, characterize, and evaluate two lytic bacteriophages against clinically isolated multidrug-resistant (MDR) Salmonella serovars.

METHODS

Screening for the phage lytic activity was performed using a spot test. Characterization of the isolated phages was done by determining the host range, longevity test, and the effect of temperature, pH, organic solvents, and morphological characterization using a transmission electron microscope. Genomic analysis was performed using Oxford nanopore sequencing. The lytic activities of the free phage lysates and formulated phage as microencapsulated were evaluated both in vitro and in vivo.

RESULTS

Two phages (VB_ST_E15 and VB_ST_SPNIS2) were successfully isolated and showed lytic strong activities against MDR Salmonella (S.) Typhimurium ATCC 14,028, S. Paratyphi A, and S. Typhi. The two phages survived at the tested temperatures, maintained their infectivity for 90 days, and retained their activity until 60 °C with thermal inactivation at 65 °C. They were lytic at a pH range from 3 to 11 but lost their activities at extremely acidic or alkaline pH. The phages could withstand the organic solvents but were completely inactivated by 100% ethanol. Both phages were classified under the order Caudoviricetes, and Genus: Uetakevirus. Their genomic sequences were assembled, annotated, and submitted to the NCBI GenBank database (OR757455 and OR757456). The preclinical evaluation using the murine animal model revealed that the two-phage cocktail managed MDR Salmonella infection as evidenced by the reduction in the bacterial burden, increased animal weight, and histopathological examination.

CONCLUSION

The two encapsulated phage formulas could be considered promising candidates for the management of MDR Salmonella-associated infections and clinical analysis should be undertaken to evaluate their potential use in humans.

Metagenome-assembled bacterial genomes recovered from the datasets of Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae)

Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), also known as the fall armyworm, is an economically important and widespread polyphagous pest. Microorganisms associated to this insect during life cycle play important ecological roles. We report 3 metagenome-assembled bacterial genomes reconstructed from a metagenome dataset obtained from S. frugiperda larvae F3 3rd-instar reared using artificial diet under laboratory conditions. Genome data for Enterococcus casseliflavus indicated a genome length of 3,659,8333 bp and GC content of 42.54%. Genome data for E. mundtii indicated a genome length of 2,921,701 bp and GC content of 38.37%. Finally, genome data for Lactiplantibacillus plantarum indicated a genome length of 3,298,601 bp, GC content of 44.31%. Genome analysis allowed us to identify genus-specific protein families (PLFams), transporters and antibiotic resistance-related genes among others. DNA sequences were deposited in National Center for Biotechnology Information (https://www.ncbi.nlm.nih.gov/) as Bioproject accession PRJNA899064.

Antigenic operon fragmentation and diversification mechanism in Bacteroidota impacts gut metagenomics and pathobionts in Crohn's disease microlesions

Comensal Bacteroidota (Bacteroidota) and Enterobacteriacea are often linked to gut inflammation. However, the causes for variability of pro-inflammatory surface antigens that affect gut commensal/opportunistic dualism in Bacteroidota remain unclear. By using the classical lipopolysaccharide/O-antigen 'rfb operon' in Enterobacteriaceae as a surface antigen model (5-rfb-gene-cluster rfbABCDX), and a recent rfbA-typing strategy for strain classification, we characterized the integrity and conservancy of the entire rfb operon in Bacteroidota. Through exploratory analysis of complete genomes and metagenomes, we discovered that most Bacteroidota have the rfb operon fragmented into nonrandom patterns of gene-singlets and doublets/triplets, termed 'rfb-gene-clusters', or rfb-'minioperons' if predicted as transcriptional. To reflect global operon integrity, contiguity, duplication, and fragmentation principles, we propose a six-category (infra/supra-numerary) cataloging system and a Global Operon Profiling System for bacteria. Mechanistically, genomic sequence analyses revealed that operon fragmentation is driven by intra-operon insertions of predominantly Bacteroides-DNA (thetaiotaomicron/fragilis) and likely natural selection in gut-wall specific micro-niches or micropathologies. Bacteroides-insertions, also detected in other antigenic operons (fimbriae), but not in operons deemed essential (ribosomal), could explain why Bacteroidota have fewer KEGG-pathways despite large genomes. DNA insertions, overrepresenting DNA-exchange-avid (Bacteroides) species, impact our interpretation of functional metagenomics data by inflating by inflating gene-based pathway inference and by overestimating 'extra-species' abundance. Of disease relevance, Bacteroidota species isolated from cavitating/cavernous fistulous tract (CavFT) microlesions in Crohn's Disease have supra-numerary fragmented operons, stimulate TNF-alpha from macrophages with low potency, and do not induce hyperacute peritonitis in mice compared to CavFT Enterobacteriaceae. The impact of 'foreign-DNA' insertions on pro-inflammatory operons, metagenomics, and commensalism/opportunism requires further studies to elucidate their potential for novel diagnostics and therapeutics, and to elucidate the role of co-existing pathobionts in Crohn's disease microlesions.

The basis of antigenic operon fragmentation in Bacteroidota and commensalism

The causes for variability of pro-inflammatory surface antigens that affect gut commensal/opportunistic dualism within the phylum Bacteroidota remain unclear (1, 2). Using the classical lipopolysaccharide/O-antigen 'rfb operon' in Enterobacteriaceae as a surface antigen model (5-gene-cluster rfbABCDX), and a recent rfbA-typing strategy for strain classification (3), we characterized the architecture/conservancy of the entire rfb operon in Bacteroidota. Analyzing complete genomes, we discovered that most Bacteroidota have the rfb operon fragmented into non-random gene-singlets and/or doublets/triplets, termed 'minioperons'. To reflect global operon integrity, duplication, and fragmentation principles, we propose a five-category (infra/supernumerary) cataloguing system and a Global Operon Profiling System for bacteria. Mechanistically, genomic sequence analyses revealed that operon fragmentation is driven by intra-operon insertions of predominantly Bacteroides-DNA (thetaiotaomicron/fragilis) and likely natural selection in specific micro-niches. Bacteroides-insertions, also detected in other antigenic operons (fimbriae), but not in operons deemed essential (ribosomal), could explain why Bacteroidota have fewer KEGG-pathways despite large genomes (4). DNA insertions overrepresenting DNA-exchange-avid species, impact functional metagenomics by inflating gene-based pathway inference and overestimating 'extra-species' abundance. Using bacteria from inflammatory gut-wall cavernous micro-tracts (CavFT) in Crohn's Disease (5), we illustrate that bacteria with supernumerary-fragmented operons cannot produce O-antigen, and that commensal/CavFT Bacteroidota stimulate macrophages with lower potency than Enterobacteriaceae, and do not induce peritonitis in mice. The impact of 'foreign-DNA' insertions on pro-inflammatory operons, metagenomics, and commensalism offers potential for novel diagnostics and therapeutics.

Exploring antibiotic resistance genes, mobile gene elements, and virulence gene factors in an urban freshwater samples using metagenomic analysis

Antibiotic resistance genes (ARGs) and antimicrobial resistance elements (AMR) are novel environmental contaminants that pose a significant risk to human health globally. Freshwater contains a variety of microorganisms that might affect human health; its quality must be assessed before use. However, the dynamics of mobile genetic elements (MGEs) and ARG propagation in freshwater have rarely been studied in Singapore. Therefore, this study used metagenomics to compare diversity, virulence factor composition, and ARG and MGE co-occurrence with bacterial communities in paired (n = 8) environmental freshwater samples. KneadData, FMAP, and Kraken2 were used for bioinformatics analysis and R (v4.1.1) for statistical analysis. Sequence reads with a total of 9043 species were taxonomically classified into 66 phyla, 130 classes, 261 orders, 584 families, and 2477 genera. Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes were found the Phyla in all samples. Analysis of QIIME output by PICRUSt and ß-diversity showed unique clusters and functional microbial community structures. A total of 2961 ARGs were found that conferred resistance to multidrug, aminoglycosides, tetracyclines, elfamycins, and more. The classified ARG mechanism revealed significant distribution of virulence factors in bacterial cells. Transposes and transposon were highly correlated to ARG gene transfer. Co-occurrence network analysis showed several MGEs appear to use the same ARGs (intI and rho) and were dominant in all samples. Furthermore, ARGs are also highly correlated with bacteria like Campylobacter and Escherichia. This study enhances the understanding of antibiotic risk assessment and provides a new perspective on bacterial assembly contamination and the functional prevalence of ARGs and MGEs with antibiotic resistance bacteria. Moreover, it raises public awareness because these contaminants put people's lives at risk of acquiring bacterial infections. In addition, it can also help propose hybrid water treatment approaches.

Interactive Web-Based Services for Metagenomic Data Analysis and Comparisons

Recently, sequencing technologies have become readily available, and scientists are more motivated to conduct metagenomic research to unveil the potential of a myriad of ecosystems and biomes. Metagenomics studies the composition and functions of microbial communities and paves the way to multiple applications in medicine, industry, and ecology. Nonetheless, the immense amount of sequencing data of metagenomics research and the few user-friendly analysis tools and pipelines carry a new challenge to the data analysis.Web-based bioinformatics tools are now being developed to facilitate the analysis of complex metagenomic data without prior knowledge of any programming languages or special installation. Specialized web tools help answer researchers' main questions on the taxonomic classification, functional capabilities, discrepancies between two ecosystems, and the probable functional correlations between the members of a specific microbial community. With an Internet connection and a few clicks, researchers can conveniently and efficiently analyze the metagenomic datasets, summarize results, and visualize key information on the composition and the functional potential of metagenomic samples under study. This chapter provides a simple guide to a few of the fundamental web-based services used for metagenomic data analyses, such as BV-BRC, RDP, MG-RAST, MicrobiomeAnalyst, METAGENassist, and MGnify.

In Vitro and Pre-Clinical Evaluation of Locally Isolated Phages, vB_Pae_SMP1 and vB_Pae_SMP5, Formulated as Hydrogels against Carbapenem-Resistant Pseudomonas aeruginosa

The inadequate therapeutic opportunities associated with carbapenem-resistant Pseudomonas aeruginosa (CRPA) clinical isolates impose a search for innovative strategies. Therefore, our study aimed to characterize and evaluate two locally isolated phages formulated in a hydrogel, both in vitro and in vivo, against CRPA clinical isolates. The two phages were characterized by genomic, microscopic, phenotypic characterization, genomic analysis, in vitro and in vivo analysis in a Pseudomonas aeruginosa-infected skin thermal injury rat model. The two siphoviruses belong to class Caudovirectes and were named vB_Pae_SMP1 and vB_Pae_SMP5. Each phage had an icosahedral head of 60 ± 5 nm and a flexible, non-contractile tail of 170 ± 5 nm long, while vB_Pae_SMP5 had an additional base plate containing a 35 nm fiber observed at the end of the tail. The hydrogel was prepared by mixing 5% w/v carboxymethylcellulose (CMC) into the CRPA propagated phage lysate containing phage titer 10⁸ PFU/mL, pH of 7.7, and a spreadability coefficient of 25. The groups were treated with either Phage vB_Pae_SMP1, vB_Pae_SMP5, or a two-phage cocktail hydrogel cellular subepidermal granulation tissues with abundant records of fibroblastic activity and mixed inflammatory cell infiltrates and showed 17.2%, 25.8%, and 22.2% records of dermal mature collagen fibers, respectively. In conclusion, phage vB_Pae_SMP1 or vB_Pae_SMP5, or the two-phage cocktails formulated as hydrogels, were able to manage the infection of CRPA in burn wounds, and promoted healing at the injury site, as evidenced by the histopathological examination, as well as a decrease in animal mortality rate. Therefore, these phage formulae can be considered promising for clinical investigation in humans for the management of CRPA-associated skin infections.