Degradation Of Plant Polysaccharides Research Articles

Substrate complexity buffers negative interactions in a synthetic community of leaf litter degraders.

Leaf litter microbes collectively degrade plant polysaccharides, influencing land-atmosphere carbon exchange. An open question is how substrate complexity - defined as the structure of the saccharide and the amount of external processing by extracellular enzymes - influences species interactions. We tested the hypothesis that monosaccharides (i.e., xylose) promote negative interactions through resource competition, and polysaccharides (i.e., xylan) promote neutral or positive interactions through resource partitioning or synergism among extracellular enzymes. We assembled a three-species community of leaf litter-degrading bacteria isolated from a grassland site in Southern California. In the polysaccharide xylan, pairs of species stably coexisted and grew equally in co-culture and in monoculture. Conversely, in the monosaccharide xylose, competitive exclusion and negative interactions prevailed. These pairwise dynamics remained consistent in a three-species community: all three species coexisted in xylan, while only two species coexisted in xylose, with one species capable of using peptone. A mathematical model showed that in xylose these dynamics could be explained by resource competition. Instead, the model could not predict the coexistence patterns in xylan, suggesting other interactions exist during biopolymer degradation. Overall, our study shows that substrate complexity influences species interactions and patterns of coexistence in a synthetic microbial community of leaf litter degraders.

Impact of rumen microbiome on cattle carcass traits

Rumen microbes are crucial in the anaerobic fermentation of plant polysaccharides to produce volatile fatty acids. However, limited information exists about the specific microbial species and strains in the rumen that affect carcass traits, and it is unclear whether there is a relationship between rumen metabolic functions and these traits. This study investigated the relationship between the rumen microbiome and carcass traits in beef cattle using 16S rRNA amplicon and shotgun sequencing. Metagenomic sequencing was used to compare the rumen microbiome between high-carcass weight (HW) and low-carcass weight (LW) cattle, and high-marbling (HM) and low-marbling (LM) cattle. Prokaryotic communities in the rumen of HW vs. LW and HM vs. LM were separated using 16S rRNA amplicon sequencing. Notably, shotgun metagenomic sequencing revealed that HW cattle had more methane-producing bacteria and ciliate protozoa, suggesting higher methane emissions. Additionally, variations were observed in the abundances of certain glycoside hydrolases and polysaccharide lyases involved in the ruminal degradation of plant polysaccharides between HW and LW. From our metagenome dataset, 807 non-redundant metagenome-assembled genomes (MAGs) of medium to high quality were obtained. Among these, 309 and 113 MAGs were associated with carcass weight and marbling, respectively.

Transcriptional response of the white-rot fungus Dichomitus squalens to polysaccharides reveals a co-expression network of plant biomass conversion related genes

Wood-degrading white-rot fungi can efficiently degrade all plant biomass components, but the molecular mechanisms behind the degradation of plant polysaccharides remain poorly understood. For example, the gene sets and expression levels induced by the plant polysaccharide-derived monosaccharides in white-rot fungi do not reflect those induced by crude plant biomass substrates. To explore the molecular response of the white-rot fungus Dichomitus squalens to plant-derived oligo- and polysaccharides, we investigated the transcriptomes from mono- and dikaryotic strains of the fungus on 10 substrates and compared the expression of carbohydrate-active enzyme-encoding genes to that previously reported for different monosaccharides and cellobiose. Our results revealed that in D. squalens, a robust response to cellulose leads to its effective depolymerization, with an orthologue of the ascomycete Trichoderma reesei ACE3 likely acting as a central transcriptional regulator. The conserved response between cellulose and cellobiose further confirms cellobiose as the main cellulase inducer in D. squalens. Surprisingly, despite low abundance of pectin in the natural wood substrate of D. squalens, we identified polygalacturonic acid as a major inducer of a broad-targeted pectinolytic response including pectinase, pectin-related sugar transporter and catabolism genes, and four fungal specific transcription factors. This indicates that D. squalens has not only maintained its ability to degrade minor polysaccharide components in its biotope, but also a regulatory system spanning from extracellular degradation to metabolic conversion. Our study contributes to a deeper understanding of the molecular mechanisms behind white-rot fungal plant polysaccharide degradation and provides leads for functional studies of potential transcriptional regulators in basidiomycetes.

Impact of feeding dried distillers' grains with solubles diet on microbiome and metabolome of ruminal and cecal contents in Guanling yellow cattle.

Dried distillers' grains with solubles (DDGS) are rich in nutrients, and partially alternative feeding of DDGS effectively reduces cost of feed and improves animals' growth. We used 16S rDNA gene sequencing and LC/MS-based metabolomics to explore the effect of feeding cattle with a basal diet (BD) and a Jiang-flavor DDGS diet (replaces 25% concentrate of the diet) on microbiome and metabolome of ruminal and cecal contents in Guanling yellow cattle. The results showed that the ruminal and cecal contents shared the same dominance of Bacteroidetes, Firmicutes and Proteobacteria in two groups. The ruminal dominant genera were Prevotella_1, Rikenellaceae_RC9_gut_group, and Ruminococcaceae_UCG-010; and the cecal dominant genera were Ruminococcaceae_UCG-005, Ruminococcaceae_UCG-010, and Rikenellaceae_RC9_gut_group. Linear discriminant analysis effect size analysis (LDA > 2, P < 0.05) revealed the significantly differential bacteria enriched in the DDGS group, including Ruminococcaceae_UCG_012, Prevotellaceae_UCG_004 and Anaerococcus in the ruminal contents, which was associated with degradation of plant polysaccharides. Besides, Anaerosporobacter, Anaerovibrio, and Caproiciproducens in the cecal contents were involved in fatty acid metabolism. Compared with the BD group, 20 significantly different metabolites obtained in the ruminal contents of DDGS group were down-regulated (P < 0.05), and based on them, 4 significantly different metabolic pathways (P < 0.05) were enriched including "Linoleic acid metabolism," "Biosynthesis of unsaturated fatty acids," "Taste transduction," and "Carbohydrate digestion and absorption." There were 65 significantly different metabolites (47 were upregulated, 18 were downregulated) in the cecal contents of DDGS group when compared with the BD group, and 4 significantly different metabolic pathways (P < 0.05) were enriched including "Longevity regulating pathway," "Bile secretion," "Choline metabolism in cancer," and "HIF-1 signaling pathway." Spearman analysis revealed close negative relationships between the top 20 significantly differential metabolites and Anaerococcus in the ruminal contents. Bacteria with high relevance to cecal differential metabolites were Erysipelotrichaceae_UCG-003, Dielma, and Solobacterium that affect specific metabolic pathways in cattle. Collectively, our results suggest that feeding cattle with a DDGS diet improves the microbial structure and the metabolic patterns of lipids and carbohydrates, thus contributing to the utilization efficiency of nutrients and physical health to some extent. Our findings will provide scientific reference for the utilization of DDGS as feed in cattle industry.

A meta-omics approach to explore the biofuel-producing enzyme potential from extreme environmental conditions

Geothermally warmed spring water contaminated with decomposed leaf biomass are unique hot spring ecosystems , are expected to support the recycling of various nutrients and to host lignocellulose degrading thermostable enzymes, genes and bacteria. An attempt is made in the present study to explore CAZymes in a carbohydrate-contaminated unique environment at Deulajhari spring through a multi-omics approach using an indigenous consortium developed from the spring sediment. Co-assembly of shotgun metagenome and metatranscriptome libraries from the Deulajhari hot spring consortia sample recovered seventeen refined, high-quality near-complete genomes. The predominant recovery of thermophilic aerobic chemo-heterotrophic Meiothermus and Rhodothermus has been observed through genome reconstruction. The reported production of an array of enzymes, including xylanase, β-xylosidase, endoglucanase and polysaccharide deacetylase, establishes their lignocellulose-degrading ability. The unexpected strong positive correlation between predominating Meiothermus and less prevailing members of Acetobacteraceae, unclassified Gaiellaceae, unclassified Burkholderiaceae and Tepidimonas of the consortium signifies their unexplored role in biomass degradation. Furthermore, the synergistic involvement of the diverse enzymes represented by a vast gene repertoire is responsible for the degradation of complex plant polysaccharides by the group of bacteria. The novelty of the present study stems from the identification of a diverse range of potential lignocellulose-digesting enzymes expressed by the bacterial consortium. This finding emphasizes the significant potential of these enzymes in facilitating industrial-scale production of biofuel, making it a notable contribution to the field.

Comparative Genomics and Transcriptomics Analyses Reveal Divergent Plant Biomass-Degrading Strategies in Fungi.

Plant biomass is one of the most abundant renewable carbon sources, which holds great potential for replacing current fossil-based production of fuels and chemicals. In nature, fungi can efficiently degrade plant polysaccharides by secreting a broad range of carbohydrate-active enzymes (CAZymes), such as cellulases, hemicellulases, and pectinases. Due to the crucial role of plant biomass-degrading (PBD) CAZymes in fungal growth and related biotechnology applications, investigation of their genomic diversity and transcriptional dynamics has attracted increasing attention. In this project, we systematically compared the genome content of PBD CAZymes in six taxonomically distant species, Aspergillus niger, Aspergillus nidulans, Penicillium subrubescens, Trichoderma reesei, Phanerochaete chrysosporium, and Dichomitus squalens, as well as their transcriptome profiles during growth on nine monosaccharides. Considerable genomic variation and remarkable transcriptomic diversity of CAZymes were identified, implying the preferred carbon source of these fungi and their different methods of transcription regulation. In addition, the specific carbon utilization ability inferred from genomics and transcriptomics was compared with fungal growth profiles on corresponding sugars, to improve our understanding of the conversion process. This study enhances our understanding of genomic and transcriptomic diversity of fungal plant polysaccharide-degrading enzymes and provides new insights into designing enzyme mixtures and metabolic engineering of fungi for related industrial applications.

Genomic and Transcriptomic Survey Provides Insights into Molecular Basis of Pathogenicity of the Sunflower Pathogen Phoma macdonaldii

Phoma macdonaldii (teleomorph Leptosphaeria lindquistii) is the causal agent of sunflower (Helianthus annuus L.) black stem. In order to investigate the molecular basis for the pathogenicity of P. ormacdonaldii, genomic and transcriptomic analyses were performed. The genome size was 38.24 Mb and assembled into 27 contigs with 11,094 putative predicted genes. These include 1133 genes for CAZymes specific for plant polysaccharide degradation, 2356 for the interaction between the pathogen and host, 2167 for virulence factors, and 37 secondary metabolites gene clusters. RNA-seq analysis was conducted at the early and late stages of the fungal spot formation in infected sunflower tissues. A total of 2506, 3035, and 2660 differentially expressed genes (DEGs) between CT and each treatment group (LEAF-2d, LEAF-6d, and STEM) were retrieved, respectively. The most significant pathways of DEGs from these diseased sunflower tissues were the metabolic pathways and biosynthesis of secondary metabolites. Overall, 371 up-regulated DEGs were shared among LEAF-2d, LEAF-6d, and STEM, including 82 mapped to DFVF, 63 mapped to PHI-base, 69 annotated as CAZymes, 33 annotated as transporters, 91 annotated as secretory proteins, and a carbon skeleton biosynthetic gene. The most important DEGs were further confirmed by RT-qPCR. This is the first report on the genome-scale assembly and annotation for P. macdonaldii. Our data provide a framework for further revealing the underlying mechanism of the pathogenesis of P. macdonaldii, and also suggest the potential targets for the diseases caused by this fungal pathogen.

Microwave assisted free radical degradation of Schisandra polysaccharides: Optimization, identification and application

In order to establish structural-fingerprinting of polysaccharides for improvement of quality assessment, a sample preparation method based on microwave assisted free radical degradation (MFRD) of plant polysaccharides was proposed to produce oligosaccharides and small Mw polysaccharides. As a case study of Schisandra chinensis and S. sphenanthera fruit polysaccharides (SCP and SSP), the MFRD condition (i.e., 100 °C, 30 s and 80 W) was confirmed to be optimal. The potential structures of the MFRD products of SCP and SSP were further discussed by combinations of HILIC-ESI−-QTOF-MSE and HILIC-ESI−-Q-OT-IT-MS/MS. As followed, multivariable statistical analysis shows a clear separation of SCP and the SSP in PCA and OPLS-DA plots based HILIC-ESI−-QTOF-MSE data. The VIP plot unveils several key Q-markers (e.g., peaks 3, 8, 9, 10, 15, 25, 26, 28, 29 and 30) with significant differences and stable emergences. Furthermore, a low-polymerization compositional fingerprinting was successfully constructed for SCP and SSP using a high-performance anion-exchange chromatography with pulsed amperometric detection. Compared to the conventional sample preparation methods, the MFRD took only a few thousandth of the time to accomplish degradations of plant polysaccharides. It significantly improves sample preparations and is generally applicable to various polysaccharide samples.

Effectiveness of ruminal xylanase with an extra proline-rich C-terminus on lignocellulosic biomass degradation

The efficient degradation of plant polysaccharides in agricultural waste requires xylanases with high catalytic activity. In this study, the C-terminal proline-rich GH10 xylanase XynA from sheep rumen was investigated using product analysis, structural characterization, truncated and site-directed mutagenesis, molecular dynamics simulation, and application evaluation, revealing that the proline-rich C-terminus contributes to the interaction at the substrate-binding pocket to reduce the binding free energy. Compared to the C-terminally truncated enzyme XynA-Tr, XynA has a more favorable conformation for proton transfer and affinity attack, facilitating the degradation of oligomeric and beechwood xylan without altering the hydrolysis pattern. Moreover, both the reduced sugar yield and weight loss of the pretreated wheat bran, corn cob, and corn stalk hydrolyzed by XynA for 12 h increased by more than 30 %. These findings are important to better understand the relationship between enzyme activities and their terminal regions and suggest candidate materials for lignocellulosic biomass utilization.

Whole-Genome Sequence Resource of Fusarium oxysporum Strain TH15, a Plant Growth Promoting Endophytic Fungus Isolated from Tetrastigma hemsleyanum

Whole-Genome Sequence Resource of <i>Fusarium oxysporum</i> Strain TH15, a Plant Growth Promoting Endophytic Fungus Isolated from <i>Tetrastigma hemsleyanum</i>

Genomic Analyses of the Fungus Paraconiothyrium sp. Isolated from the Chinese White Wax Scale Insect Reveals Its Symbiotic Character.

The Chinese white wax scale, Ericerus pela, is an insect native to China. It harbors a variety of microbes. The Paraconiothyrium fungus was isolated from E. pela and genome sequenced in this study. A fungal cytotoxicity assay was performed on the Aedes albopictus cell line C6/36. The assembled Paraconiothyrium sp. genome was 39.55 Mb and consisted of 14,174 genes. The coding sequences accounted for 50.75% of the entire genome. Functional pathway analyses showed that Paraconiothyrium sp. possesses complete pathways for the biosynthesis of 20 amino acids, 10 of which E. pela lacks. It also had complementary genes in the vitamin B groups synthesis pathways. Secondary metabolism prediction showed many gene clusters that produce polyketide. Additionally, a large number of genes associated with ‘reduced virulence’ in the genome were annotated with the Pathogen–Host Interaction database. A total of 651 genes encoding carbohydrate-active enzymes were predicted to be mostly involved in plant polysaccharide degradation. Pan-specific genomic analyses showed that genes unique to Paraconiothyrium sp. were enriched in the pathways related to amino acid metabolism and secondary metabolism. GO annotation analysis yielded similar results. The top COG categories were ‘carbohydrate transport and metabolism’, ‘lipid transport and metabolism’, and ‘secondary metabolite biosynthesis, transport and catabolism’. Phylogenetic analyses based on gene family and pan genes showed that Paraconiothyrium sp is clustered together with species from the Didymosphaeriaceae family. A multi-locus sequence analysis showed that it converged with the same branch as P. brasiliense and they formed one group with fungi from the Paraconiothyrium genus. To validate the in vitro toxicity of Paraconiothyrium sp., a cytotoxicity assay was performed. The results showed that medium-cultured Paraconiothyrium sp. had no harmful effect on cell viability. No toxins were secreted by the fungus during growth. Our results imply that Paraconiothyrium sp. may establish a symbiotic relationship with the host to supply complementary nutrition to E. pela.

Gut microbiome of the largest living rodent harbors unprecedented enzymatic systems to degrade plant polysaccharides

The largest living rodent, capybara, can efficiently depolymerize and utilize lignocellulosic biomass through microbial symbiotic mechanisms yet elusive. Herein, we elucidate the microbial community composition, enzymatic systems and metabolic pathways involved in the conversion of dietary fibers into short-chain fatty acids, a main energy source for the host. In this microbiota, the unconventional enzymatic machinery from Fibrobacteres seems to drive cellulose degradation, whereas a diverse set of carbohydrate-active enzymes from Bacteroidetes, organized in polysaccharide utilization loci, are accounted to tackle complex hemicelluloses typically found in gramineous and aquatic plants. Exploring the genetic potential of this community, we discover a glycoside hydrolase family of β-galactosidases (named as GH173), and a carbohydrate-binding module family (named as CBM89) involved in xylan binding that establishes an unprecedented three-dimensional fold among associated modules to carbohydrate-active enzymes. Together, these results demonstrate how the capybara gut microbiota orchestrates the depolymerization and utilization of plant fibers, representing an untapped reservoir of enzymatic mechanisms to overcome the lignocellulose recalcitrance, a central challenge toward a sustainable and bio-based economy.

Comparative Genomics Reveal the Animal-Associated Features of the Acanthopleuribacteraceae Bacteria, and Description of Sulfidibacter corallicola gen. nov., sp., nov.

Members of the phylum Acidobacteria are ubiquitous in various environments. Soil acidobacteria have been reported to present a variety of strategies for their success in terrestrial environments. However, owing to lack of pure culture, information on animal-associated acidobacteria are limited, except for those obtained from 16S rRNA genes. To date, only two acidobacteria have been isolated from animals, namely strain M133T obtained from coral Porites lutea and Acanthopleuribacter pedis KCTC 12899T isolated from chiton. Genomics and physiological characteristics of strain M133T and A. pedis KCTC 12899T were compared with 19 other isolates (one strain from each genus) in the phylum Acidobacteria. The results revealed that strain M133T represents a new species in a new genus in the family Acanthopleuribacteraceae. To date, these two Acanthopleuribacteraceae isolates have the largest genomes (10.85–11.79 Mb) in the phylum Acidobacteria. Horizontal gene transfer and gene duplication influenced the structure and plasticity of these large genomes. Dissimilatory nitrate reduction and abundant secondary metabolite biosynthetic gene clusters (including eicosapentaenoic acid de novo biosynthesis) are two distinct features of the Acanthopleuribacteraceae bacteria in the phylum Acidobacteria. The absence of glycoside hydrolases involved in plant polysaccharide degradation and presence of animal disease-related peptidases indicate that these bacteria have evolved to adapt to the animal hosts. In addition to low- and high-affinity respiratory oxygen reductases, enzymes for nitrate to nitrogen, and sulfhydrogenase were also detected in strain M133T, suggesting the capacity and flexibility to grow in aerobic and anaerobic environments. This study highlighted the differences in genome structure, carbohydrate and protein utilization, respiration, and secondary metabolism between animal-associated acidobacteria and other acidobacteria, especially the soil acidobacteria, displaying flexibility and versatility of the animal-associated acidobacteria in environmental adaption.

CAZyme prediction in ascomycetous yeast genomes guides discovery of novel xylanolytic species with diverse capacities for hemicellulose hydrolysis

BackgroundAscomycetous yeasts from the kingdom fungi inhabit every biome in nature. While filamentous fungi have been studied extensively regarding their enzymatic degradation of the complex polymers comprising lignocellulose, yeasts have been largely overlooked. As yeasts are key organisms used in industry, understanding their enzymatic strategies for biomass conversion is an important factor in developing new and more efficient cell factories. The aim of this study was to identify polysaccharide-degrading yeasts by mining CAZymes in 332 yeast genomes from the phylum Ascomycota. Selected CAZyme-rich yeasts were then characterized in more detail through growth and enzymatic activity assays.ResultsThe CAZyme analysis revealed a large spread in the number of CAZyme-encoding genes in the ascomycetous yeast genomes. We identified a total of 217 predicted CAZyme families, including several CAZymes likely involved in degradation of plant polysaccharides. Growth characterization of 40 CAZyme-rich yeasts revealed no cellulolytic yeasts, but several species from the Trichomonascaceae and CUG-Ser1 clades were able to grow on xylan, mixed-linkage β-glucan and xyloglucan. Blastobotrys mokoenaii, Sugiyamaella lignohabitans, Spencermartinsiella europaea and several Scheffersomyces species displayed superior growth on xylan and well as high enzymatic activities. These species possess genes for several putative xylanolytic enzymes, including ones from the well-studied xylanase-containing glycoside hydrolase families GH10 and GH30, which appear to be attached to the cell surface. B. mokoenaii was the only species containing a GH11 xylanase, which was shown to be secreted. Surprisingly, no known xylanases were predicted in the xylanolytic species Wickerhamomyces canadensis, suggesting that this yeast possesses novel xylanases. In addition, by examining non-sequenced yeasts closely related to the xylanolytic yeasts, we were able to identify novel species with high xylanolytic capacities.ConclusionsOur approach of combining high-throughput bioinformatic CAZyme-prediction with growth and enzyme characterization proved to be a powerful pipeline for discovery of novel xylan-degrading yeasts and enzymes. The identified yeasts display diverse profiles in terms of growth, enzymatic activities and xylan substrate preferences, pointing towards different strategies for degradation and utilization of xylan. Together, the results provide novel insights into how yeast degrade xylan, which can be used to improve cell factory design and industrial bioconversion processes.

Purification and characterization of novel, thermostable and non-processive GH5 family endoglucanase from Fomitopsis meliae CFA 2

Endoglucanases from glycoside hydrolase family 5 (GH5) are the key enzymes in degradation of diverse plant polysaccharides. Present study reports purification, characterization and partial sequencing of novel thermostable GH5 family endoglucanase from a newly isolated brown rot fungi Fomitopsis meliae CFA 2. Endoglucanase was purified 34.18 fold with a specific activity of 302.90 U/mg. The molecular weight of the endoglucanase was 37.87 kDa as determined by SDS PAGE. LC MS/MS analysis identified the protein to be a member of GH5_5 family. The temperature and pH optima for endoglucanase activity were 70 °C and 4.8, respectively. The enzyme catalyzed the hydrolysis of carboxymethyl-cellulose with a Km of 12.0 mg/ml, Vmax of 556.58 μmol/min/mg and Kcat of 129.41/sec. The enzyme was stimulated by Zn+2 and K+ metal ions and DTT. Half-life (t1/2) for endoglucanase was found to be 11.36 h with decimal reduction time (D) of 37.75 h at 70 °C. The activation energy for endoglucanase was found to be 30.76 kJ/mol (50 °C–70 °C). Looking at the results, the endoglucanase from Fomitopsis meliae CFA 2 seems to be a promising thermostable enzyme which may be applicable in applications like biomass hydrolysis.

Enzymatic degradation of xyloglucans by Aspergillus species: a comparative view of this genus.

Aspergillus species are closely associated with humanity through fermentation, infectious disease, and mycotoxin contamination of food. Members of this genus produce various enzymes to degrade plant polysaccharides, including starch, cellulose, xylan, and xyloglucan. This review focus on the machinery of the xyloglucan degradation using glycoside hydrolases, such as xyloglucanases, isoprimeverose-producing oligoxyloglucan hydrolases, and α-xylosidases, in Aspergillus species. Some xyloglucan degradation-related glycoside hydrolases are well conserved in this genus; however, other enzymes are not. Cooperative actions of these glycoside hydrolases are crucial for xyloglucan degradation in Aspergillus species. KEY POINTS: •Xyloglucan degradation-related enzymes of Aspergillus species are reviewed. •Each Aspergillus species possesses a different set of glycoside hydrolases. •The machinery of xyloglucan degradation of A. oryzae is overviewed.

Comparative genome analyses suggest a hemibiotrophic lifestyle and virulence differences for the beech bark disease fungal pathogens Neonectria faginata and Neonectria coccinea

Neonectria faginata and Neonectria coccinea are the causal agents of the insect-fungus disease complex known as beech bark disease (BBD), known to cause mortality in beech forest stands in North America and Europe. These fungal species have been the focus of extensive ecological and disease management studies, yet less progress has been made toward generating genomic resources for both micro- and macro-evolutionary studies. Here, we report a 42.1 and 42.7 mb highly contiguous genome assemblies of N. faginata and N. coccinea, respectively, obtained using Illumina technology. These species share similar gene number counts (12,941 and 12,991) and percentages of predicted genes with assigned functional categories (64 and 65%). Approximately 32% of the predicted proteomes of both species are homologous to proteins involved in pathogenicity, yet N. coccinea shows a higher number of predicted mitogen-activated protein kinase genes, virulence determinants possibly contributing to differences in disease severity between N. faginata and N. coccinea. A wide range of genes encoding for carbohydrate-active enzymes capable of degradation of complex plant polysaccharides and a small number of predicted secretory effector proteins, secondary metabolite biosynthesis clusters and cytochrome oxidase P450 genes were also found. This arsenal of enzymes and effectors correlates with, and reflects, the hemibiotrophic lifestyle of these two fungal pathogens. Phylogenomic analysis and timetree estimations indicated that the N. faginata and N. coccinea species divergence may have occurred at ∼4.1 million years ago. Differences were also observed in the annotated mitochondrial genomes as they were found to be 81.7 kb (N. faginata) and 43.2 kb (N. coccinea) in size. The mitochondrial DNA expansion observed in N. faginata is attributed to the invasion of introns into diverse intra- and intergenic locations. These first draft genomes of N. faginata and N. coccinea serve as valuable tools to increase our understanding of basic genetics, evolutionary mechanisms and molecular physiology of these two nectriaceous plant pathogenic species.

Multi-omic Directed Discovery of Cellulosomes, Polysaccharide Utilization Loci, and Lignocellulases from an Enriched Rumen Anaerobic Consortium.

Lignocellulose is one of the most abundant renewable carbon sources, representing an alternative to petroleum for the production of fuel and chemicals. Nonetheless, the lignocellulose saccharification process, to release sugars for downstream applications, is one of the most crucial factors economically challenging to its use. The synergism required among the various carbohydrate-active enzymes (CAZymes) for efficient lignocellulose breakdown is often not satisfactorily achieved with an enzyme mixture from a single strain. To overcome this challenge, enrichment strategies can be applied to develop microbial communities with an efficient CAZyme arsenal, incorporating complementary and synergistic properties, to improve lignocellulose deconstruction. We report a comprehensive and deep analysis of an enriched rumen anaerobic consortium (ERAC) established on sugarcane bagasse (SB). The lignocellulolytic abilities of the ERAC were confirmed by analyzing the depolymerization of bagasse by scanning electron microscopy, enzymatic assays, and mass spectrometry. Taxonomic analysis based on 16S rRNA sequencing elucidated the community enrichment process, which was marked by a higher abundance of Firmicutes and Synergistetes species. Shotgun metagenomic sequencing of the ERAC disclosed 41 metagenome-assembled genomes (MAGs) harboring cellulosomes and polysaccharide utilization loci (PULs), along with a high diversity of CAZymes. The amino acid sequences of the majority of the predicted CAZymes (60% of the total) shared less than 90% identity with the sequences found in public databases. Additionally, a clostridial MAG identified in this study produced proteins during consortium development with scaffoldin domains and CAZymes appended to dockerin modules, thus representing a novel cellulosome-producing microorganism.IMPORTANCE The lignocellulolytic ERAC displays a unique set of plant polysaccharide-degrading enzymes (with multimodular characteristics), cellulosomal complexes, and PULs. The MAGs described here represent an expansion of the genetic content of rumen bacterial genomes dedicated to plant polysaccharide degradation, therefore providing a valuable resource for the development of biocatalytic toolbox strategies to be applied to lignocellulose-based biorefineries.

Complete Genome Sequence of the Polysaccharide-Degrading Rumen Bacterium Pseudobutyrivibrio xylanivorans MA3014 Reveals an Incomplete Glycolytic Pathway.

Bacterial species belonging to the genus Pseudobutyrivibrio are important members of the rumen microbiome contributing to the degradation of complex plant polysaccharides. Pseudobutyrivibrio xylanivorans MA3014 was selected for genome sequencing to examine its ability to breakdown and utilize plant polysaccharides. The complete genome sequence of MA3014 is 3.58 Mb, consists of three replicons (a chromosome, chromid, and plasmid), has an overall G + C content of 39.6%, and encodes 3,265 putative protein-coding genes (CDS). Comparative pan-genomic analysis of all cultivated and currently available P. xylanivorans genomes has revealed a strong correlation of orthologous genes within this rumen bacterial species. MA3014 is metabolically versatile and capable of growing on a range of simple mono- or oligosaccharides derived from complex plant polysaccharides such as pectins, mannans, starch, and hemicelluloses, with lactate, butyrate, and formate as the principal fermentation end products. The genes encoding these metabolic pathways have been identified and MA3014 is predicted to encode an extensive range of Carbohydrate-Active enZYmes with 78 glycoside hydrolases, 13 carbohydrate esterases, and 54 glycosyl transferases, suggesting an important role in solubilization of plant matter in the rumen.

Enterotype identification and its influence on regulating the duodenum metabolism in chickens

Enterotypes are used to describe clusters of specific gut microbial community structures, but few reports exist on the identification of enterotypes in poultry. In addition, there is incomplete understanding on the role of the foregut microbiota in the digestion and absorption of nutrients in poultry. Thus, this study aimed to identify the duodenal enterotypes by examining microbial communities from 206 broilers using 16S rRNA high-throughput sequencing and explore the effects of enterotypes on phenotypic performance and nutrient metabolism with metabolomics. The duodenal microbial communities of the broiler population were partitioned into 3 enterotypes (ET1, ET2, and ET3), and significant differences were observed in α-diversity among the enterotypes (P < 0.01). At the genus level, the ET1 group was over-represented by Bacteroides (9.8%) and Escherichia–Shigella (8.9%), the ET2 group was over-represented by Ochrobactrum (19.4%) and Rhodococcus (14.7%), and the ET3 group was over-represented by Bacillus (23.4%) and Akkermansia (16.2%). The relative abundance of the dominant taxa of each enterotype was significantly higher than that in the other 2 enterotypes (P < 0.01). The results showed that Ochrobactrum and Rhodococcus were positively correlated with cellobiose, alpha-D-glucose, D-mannose, and D-allose (r = 0.429, 0.435, 0.482, and 0.562, respectively; all P < 0.05). Rhodococcus was also positively correlated with tridecanoic acid and glycerol 1-myristate (r = 0.655 and 0.489, respectively; all P < 0.01). In terms of phenotype, the triglyceride level in the ET2 group was significantly higher than that in the ET1 group (P < 0.05), and the subcutaneous fat thickness and abdominal fat weight in the ET2 group were the highest (P > 0.05). Taken together, these results confirmed the presence of enterotypes in broilers and found that the dominant microbes in broilers of the ET2 group might play a major role in the degradation and utilization of plant polysaccharides, which may have an impact on the serum triglyceride level and fat deposition in broilers. These findings lay a foundation for further studies on the gut microbial interactions with the metabolism in broilers and the regulation of the gut microbiota to promote growth and well-being in broilers.