Interspecies Competition Impacts Targeted Manipulation of Human Gut Bacteria by Fiber-Derived Glycans.

Development of microbiota-directed foods (MDFs) that selectively increase the abundance of beneficial human gut microbes, and their expressed functions, requires knowledge of both the bioactive components of MDFs and the mechanisms underlying microbe-microbe interactions. Here, gnotobiotic mice were colonized with a defined consortium of human-gut-derived bacterial strains and fed different combinations of 34 food-grade fibers added to a representative low-fiber diet consumed in the United States. Bioactive carbohydrates in fiber preparations targeting particular Bacteroides species were identified using community-wide quantitative proteomic analyses of bacterial gene expression coupled with forward genetic screens. Deliberate manipulation of community membership combined with administration of retrievable artificial food particles, consisting of paramagnetic microscopic beads coated with dietary polysaccharides, disclosed the contributions of targeted species to fiber degradation. Our approach, including the use of bead-based biosensors, defines nutrient-harvesting strategies that underlie, as well as alleviate, competition between Bacteroides and control the selectivity of MDF components.

Single-Cell Map of Diverse Immune Phenotypes in the Breast Tumor Microenvironment.

Knowledge of immune cell phenotypes in the tumor microenvironment is essential for understanding mechanisms of cancer progression and immunotherapy response. We profiled 45,000 immune cells from eight breast carcinomas, as well as matched normal breast tissue, blood, and lymph nodes, using single-cell RNA-seq. We developed a preprocessing pipeline, SEQC, and a Bayesian clustering and normalization method, Biscuit, to address computational challenges inherent to single-cell data. Despite significant similarity between normal and tumor tissue-resident immune cells, we observed continuous phenotypic expansions specific to the tumor microenvironment. Analysis of paired single-cell RNA and T cell receptor (TCR) sequencing data from 27,000 additional T cells revealed the combinatorial impact of TCR utilization on phenotypic diversity. Our results support a model of continuous activation in T cells and do not comport with the macrophage polarization model in cancer. Our results have important implications for characterizing tumor-infiltrating immune cells.

Effective green treatment of sewage sludge from Fenton reactions: Utilizing MoS2 for sustainable resource recovery.

Effectively managing sewage sludge from Fenton reactions in an eco-friendly way is vital for Fenton technology's viability in pollution treatment. This study focuses on sewage sludge across various treatment stages, including generation, concentration, dehydration, and landfill, and employs chemical composite MoS2 to facilitate green resource utilization of all types of sludge. MoS2, with exposed Mo4+ and low-coordination sulfur, enhances iron cycling and creates an acidic microenvironment on the sludge surface. The MoS2-modified iron sludge exhibits outstanding (>95%) phenol and pollutant degradation in hydrogen peroxide and peroxymonosulfate-based Fenton systems, unlike unmodified sludge. This modified sludge maintains excellent Fenton activity in various water conditions and with multiple anions, allowing extended phenol degradation for over 14 d. Notably, the generated chemical oxygen demand (COD) in sludge modification process can be efficiently eliminated through the Fenton reaction, ensuring effluent COD compliance and enabling eco-friendly sewage sludge resource utilization.

Local O2 concentrating boosts the electro-Fenton process for energy-efficient water remediation.

The electro-Fenton process is a state-of-the-art water treatment technology used to remove organic contaminants. However, the low O2 utilization efficiency (OUE, <1%) and high energy consumption remain the biggest obstacles to practical application. Here, we propose a local O2 concentrating (LOC) approach to increase the OUE by over 11-fold compared to the conventional simple O2 diffusion route. Due to the well-designed molecular structure, the LOC approach enables direct extraction of O2 from the bulk solution to the reaction interface; this eliminates the need to pump O2/air to overcome the sluggish O2 mass transfer and results in high Faradaic efficiencies (~50%) even under natural air diffusion conditions. Long-term operation of a flow-through pilot device indicated that the LOC approach saved more than 65% of the electric energy normally consumed in treating actual industrial wastewater, demonstrating the great potential of this system-level design to boost the electro-Fenton process for energy-efficient water remediation.

Global decarbonization potential of CO2 mineralization in concrete materials.

CO2 mineralization products are often heralded as having outstanding potentials to reduce CO2-eq. emissions. However, these claims are generally undermined by incomplete consideration of the life cycle climate change impacts, material properties, supply and demand constraints, and economic viability of CO2 mineralization products. We investigate these factors in detail for ten concrete-related CO2 mineralization products to quantify their individual and global CO2-eq. emissions reduction potentials. Our results show that in 2020, 3.9 Gt of carbonatable solid materials were generated globally, with the dominant material being end-of-life cement paste in concrete and mortar (1.4 Gt y-1). All ten of the CO2 mineralization technologies investigated here reduce life cycle CO2-eq. emissions when used to substitute comparable conventional products. In 2020, the global CO2-eq. emissions reduction potential of economically competitive CO2 mineralization technologies was 0.39 Gt CO2-eq., i.e., 15% of that from cement production. This level of CO2-eq. emissions reduction is limited by the supply of end-of-life cement paste. The results also show that it is 2 to 5 times cheaper to reduce CO2-eq. emissions by producing cement from carbonated end-of-life cement paste than carbon capture and storage (CCS), demonstrating its superior decarbonization potential. On the other hand, it is currently much more expensive to reduce CO2-eq. emissions using some CO2 mineralization technologies, like carbonated normal weight aggregate production, than CCS. Technologies and policies that increase recovery of end-of-life cement paste from aged infrastructure are key to unlocking the potential of CO2 mineralization in reducing the CO2-eq. footprint of concrete materials.

Prospective, multi-site study of healthcare utilization after actionable monogenic findings from clinical sequencing.

As large-scale genomic screening becomes increasingly prevalent, understanding the influence of actionable results on healthcare utilization is key to estimating the potential long-term clinical impact. The eMERGE network sequenced individuals for actionable genes in multiple genetic conditions and returned results to individuals, providers, and the electronic health record. Differences in recommended health services (laboratory, imaging, and procedural testing) delivered within 12 months of return were compared among individuals with pathogenic or likely pathogenic (P/LP) findings to matched individuals with negative findings before and after return of results. Of 16,218 adults, 477 unselected individuals were found to have a monogenic risk for arrhythmia (n = 95), breast cancer (n = 96), cardiomyopathy (n = 95), colorectal cancer (n = 105), or familial hypercholesterolemia (n = 86). Individuals with P/LP results more frequently received services after return (43.8%) compared to before return (25.6%) of results and compared to individuals with negative findings (24.9%; p < 0.0001). The annual cost of qualifying healthcare services increased from an average of $162 before return to $343 after return of results among the P/LP group (p < 0.0001); differences in the negative group were non-significant. The mean difference-in-differences was $149 (p < 0.0001), which describes the increased cost within the P/LP group corrected for cost changes in the negative group. When stratified by individual conditions, significant cost differences were observed for arrhythmia, breast cancer, and cardiomyopathy. In conclusion, less than half of individuals received billed health services after monogenic return, which modestly increased healthcare costs for payors in the year following return.

Micellar catalysis: Polymer bound palladium catalyst for carbon-carbon coupling reactions in water.

Metallosurfactants, defined here as hydrophobic metal-containing groups embedded in hydrophilic units when dispersed in water, emanate in the formation of metallomicelles. This approach continues to attract great interest for its ability to serve as micellar catalysts for various metal-mediated chemical transformations in water. Indeed, relevant to green chemistry, micellar catalysis plays a preeminent function as a replacement for organic solvents in a variety of chemical reactions. There are several methods for the interaction of metal complexes (catalysts or catalyst precursors) and surfactants for producing micellar aggregates. A very effective manner for achieving this involves the direct bonding of the metal center to the amphiphilic polymeric materials. Herein, we describe the synthesis of a metallosurfactant containing a palladium complex covalently incorporated into a CO2-based triblock polycarbonate derived using a dicarboxylic acid chain-transfer agent. This amphiphilic polycarbonate was shown to self-assemble in water to provide uniform and spherical micelles, where the catalytic metal center is located in the hydrophobic portion of the micelle. The resulting metallosurfactant was demonstrated to effectively catalyze carbon-carbon coupling reactions at very low catalyst loadings.

Dead-zone-compensated design as general method of flow field optimization for redox flow batteries.

One essential element of redox flow batteries (RFBs) is the flow field. Certain dead zones that cause local overpotentials and side effects are present in all conventional designs. To lessen the detrimental effects, a dead-zone-compensated design of flow field optimization is proposed. The proposed architecture allows for the detection of dead zones and their compensation on existing flow fields. Higher reactant concentrations and uniformity factors can be revealed in the 3D multiphysical simulation. The experiments also demonstrate that at an energy efficiency (EE) of 80%, the maximum current density of the novel flow field is 205 mA cm-2, which is much higher than the values for the previous ones (165 mA cm-2) and typical serpentine flow field (153 mA cm-2). Extensions of the design have successfully increased system EE (2.7 to 4.3%) for a variety of flow patterns. As a result, the proposed design is demonstrated to be a general method to support the functionality and application of RFBs.

Engineering a universal and efficient platform for terpenoid synthesis in yeast.

Engineering microbes for the production of valuable natural products is often hindered by the regulation of native competing metabolic networks in host. This is particularly evident in the case of terpenoid synthesis in yeast, where the canonical terpenoid precursors are tightly coupled to the biosynthesis of sterols essential for yeast viability. One way to circumvent this limitation is by engineering product pathways less connected to the host native metabolism. Here, we introduce a two-step isopentenol utilization pathway (IUP) in Saccharomyces cerevisiae to augment the native mevalonate pathway by providing a shortcut to the synthesis of the common terpenoid precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). As such, the IUP was capable of elevating the IPP/DMAPP pool by 147-fold compared with the native pathway. We further demonstrate that cofeeding isoprenol and prenol enhances geranyl diphosphate (GPP) content for monoterpene biosynthesis. More importantly, we established a synthetic three-step route for efficient synthesis of di-and tetraterpene precursor geranylgeranyl diphosphate (GGPP), circumventing the competition with farnesyl diphosphate (FPP) for sterol biosynthesis and elevating the GGPP level by 374-fold. We combine these IUP-supported precursor-forming platforms with downstream terpene synthases to harness their potential and improve the production of industrially relevant terpenoids by several fold. Our exploration provides a universal and effective platform for supporting terpenoid synthesis in yeast.

Inducible CRISPR-targeted "knockdown" of human gut Bacteroides in gnotobiotic mice discloses glycan utilization strategies.

Understanding how members of the human gut microbiota prioritize nutrient resources is one component of a larger effort to decipher the mechanisms defining microbial community robustness and resiliency in health and disease. This knowledge is foundational for development of microbiota-directed therapeutics. To model how bacteria prioritize glycans in the gut, germfree mice were colonized with 13 human gut bacterial strains, including seven saccharolytic Bacteroidaceae species. Animals were fed a Western diet supplemented with pea fiber. After community assembly, an inducible CRISPR-based system was used to selectively and temporarily reduce the absolute abundance of Bacteroides thetaiotaomicron or B. cellulosilyticus by 10- to 60-fold. Each knockdown resulted in specific, reproducible increases in the abundances of other Bacteroidaceae and dynamic alterations in their expression of genes involved in glycan utilization. Emergence of these "alternate consumers" was associated with preservation of community saccharolytic activity. Using an inducible system for CRISPR base editing in vitro, we disrupted translation of transporters critical for utilizing dietary polysaccharides in Phocaeicola vulgatus, a B. cellulosilyticus knockdown-responsive taxon. In vitro and in vivo tests of the resulting P. vulgatus mutants allowed us to further characterize mechanisms associated with its increased fitness after knockdown. In principle, the approach described can be applied to study utilization of a range of nutrients and to preclinical efforts designed to develop therapeutic strategies for precision manipulation of microbial communities.

OsbZIP1 regulates phosphorus uptake and nitrogen utilization, contributing to improved yield.

Increasing nutrient uptake and use efficiency in plants can contribute to improved crop yields and reduce the demand for fertilizers in crop production. In this study, we characterized a rice mutant, 88n which showed long roots under low nitrogen (N) or phosphorus (P) conditions. Low expression levels of N transporter genes were observed in 88n root, and total N concentration in 88n shoots were decreased, however, C concentrations and shoot dry weight in 88n were comparable to that in WT. Therefore, 88n showed high nitrogen utilization efficiency (NUtE). mRNA accumulation of Pi transporter genes was higher in 88n roots, and Pi concentration and uptake activity were higher in 88n than in WT. Therefore, 88n also showed high phosphorus uptake efficiency (PUpE). Molecular genetic analysis revealed that the causal gene of 88n phenotypes was OsbZIP1, a monocot-specific ortholog of the A. thaliana bZIP transcription factor HY5. Similar to the hy5 mutant, chlorophyll content in roots was decreased and root angle was shallower in 88n than in WT. Finally, we tested the yield of 88n in paddy fields over 3 years because 88n mutant plants showed higher PUpE and NUtE activity and different root architecture at the seedling stage. 88n showed large panicles and increased panicle weight/plant. Taken together, a mutation in OsbZIP1 could contribute to improved crop yields.

A versatile genetic toolbox for Prevotella copri enables studying polysaccharide utilization systems.

Prevotella copri is a prevalent inhabitant of the human gut and has been associated with plant-rich diet consumption and diverse health states. The underlying genetic basis of these associations remains enigmatic due to the lack of genetic tools. Here, we developed a novel versatile genetic toolbox for rapid and efficient genetic insertion and allelic exchange applicable to P. copri strains from multiple clades. Enabled by the genetic platform, we systematically investigated the specificity of polysaccharide utilization loci (PULs) and identified four highly conserved PULs for utilizing arabinan, pectic galactan, arabinoxylan, and inulin, respectively. Further genetic and functional analysis of arabinan utilization systems illustrate that P. copri has evolved two distinct types of arabinan-processing PULs (PULAra ) and that the type-II PULAra is significantly enriched in individuals consuming a vegan diet compared to other diets. In summary, this genetic toolbox will enable functional genetic studies for P. copri in future.

Single crystal spectroscopy and multiple structures from one crystal (MSOX) define catalysis in copper nitrite reductases.

Many enzymes utilize redox-coupled centers for performing catalysis where these centers are used to control and regulate the transfer of electrons required for catalysis, whose untimely delivery can lead to a state incapable of binding the substrate, i.e., a dead-end enzyme. Copper nitrite reductases (CuNiRs), which catalyze the reduction of nitrite to nitric oxide (NO), have proven to be a good model system for studying these complex processes including proton-coupled electron transfer (ET) and their orchestration for substrate binding/utilization. Recently, a two-domain CuNiR from a Rhizobia species (Br2DNiR) has been discovered with a substantially lower enzymatic activity where the catalytic type-2 Cu (T2Cu) site is occupied by two water molecules requiring their displacement for the substrate nitrite to bind. Single crystal spectroscopy combined with MSOX (multiple structures from one crystal) for both the as-isolated and nitrite-soaked crystals clearly demonstrate that inter-Cu ET within the coupled T1Cu-T2Cu redox system is heavily gated. Laser-flash photolysis and optical spectroscopy showed rapid ET from photoexcited NADH to the T1Cu center but little or no inter-Cu ET in the absence of nitrite. Furthermore, incomplete reoxidation of the T1Cu site (∼20% electrons transferred) was observed in the presence of nitrite, consistent with a slow formation of NO species in the serial structures of the MSOX movie obtained from the nitrite-soaked crystal, which is likely to be responsible for the lower activity of this CuNiR. Our approach is of direct relevance for studying redox reactions in a wide range of biological systems including metalloproteins that make up at least 30% of all proteins.

Species divergence in gut-restricted bacteria of social bees.

Host-associated microbiomes, particularly gut microbiomes, often harbor related but distinct microbial lineages, but how this diversity arises and is maintained is not well understood. A prerequisite for lineage diversification is reproductive isolation imposed by barriers to gene flow. In host-associated microbes, genetic recombination can be disrupted by confinement to different hosts, for example following host speciation, or by niche partitioning within the same host. Taking advantage of the simple gut microbiome of social bees, we explore the diversification of two groups of gut-associated bacteria, Gilliamella and Snodgrassella, which have evolved for 80 million y with honey bees and bumble bees. Our analyses of sequenced genomes show that these lineages have diversified into discrete populations with limited gene flow. Divergence has occurred between symbionts of different host species and, in some cases, between symbiont lineages within a single host individual. Populations have acquired genes to adapt to specific hosts and ecological niches; for example, Gilliamella lineages differ markedly in abilities to degrade dietary polysaccharides and to use the resulting sugar components. Using engineered fluorescent bacteria in vivo, we show that Gilliamella lineages localize to different hindgut regions, corresponding to differences in their abilities to use spatially concentrated nitrogenous wastes of hosts. Our findings show that bee gut bacteria can diversify due to isolation in different host species and also due to spatial niche partitioning within individual hosts, leading to barriers to gene flow.

Nonsteroidal anti-inflammatory drug "allergy" labeling is associated with increased postpartum opioid utilization.

BACKGROUND: Current guidelines recommend a stepwise approach to postpartum pain management, beginning with acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs), with opioids added only if needed. Report of a prior NSAID-induced adverse drug reaction (ADR) may preclude use of first-line analgesics, despite evidence that many patients with this allergy label may safely tolerate NSAIDs. OBJECTIVE: We assessed the association between reported NSAID ADRs and postpartum opioid utilization. METHODS: We performed a retrospective cohort study of birthing people who delivered within an integrated health system (January 1, 2017, to December 31, 2020). Study outcomes were postpartum inpatient opioid administrations and opioid prescriptions at discharge. Statistical analysis was performed on a propensity score-matched sample, which was generated with the goal of matching to the covariate distributions from individuals with NSAID ADRs. RESULTS: Of 38,927 eligible participants, there were 883 (2.3%) with an NSAID ADR. Among individuals with reported NSAID ADRs, 49.5% received inpatient opioids in the postpartum period, compared to 34.5% of those with no NSAID ADRs (difference = 15.0%, 95% confidence interval 11.4-18.6%). For patients who received postpartum inpatient opioids, those with NSAID ADRs received a higher total cumulative dose between delivery and hospital discharge (median 30.0 vs 22.5 morphine milligram equivalents [MME] for vaginal deliveries; median 104.4 vs 75.0 MME for cesarean deliveries). The overall proportion of patients receiving an opioid prescription at the time of hospital discharge was higher for patients with NSAID ADRs compared to patients with no NSAID ADRs (39.3% vs 27.2%; difference = 12.1%, 95% confidence interval 8.6-15.6%). CONCLUSION: Patients with reported NSAID ADRs had higher postpartum inpatient opioid utilization and more frequently received opioid prescriptions at hospital discharge compared to those without NSAID ADRs, regardless of mode of delivery.

Asthma morbidity measures across Black ethnic subgroups.

BACKGROUND: Black adults are disproportionately affected by asthma and are often considered a homogeneous group in research studies despite cultural and ancestral differences. OBJECTIVE: We sought to determine if asthma morbidity differs across adults in Black ethnic subgroups. METHODS: Adults with moderate-severe asthma were recruited across the continental United States and Puerto Rico for the PREPARE (PeRson EmPowered Asthma RElief) trial. Using self-identifications, we categorized multiethnic Black (ME/B) participants (n = 226) as Black Latinx participants (n = 146) or Caribbean, continental African, or other Black participants (n = 80). African American (AA/B) participants (n = 518) were categorized as Black participants who identified their ethnicity as being American. Baseline characteristics and retrospective asthma morbidity measures (self-reported exacerbations requiring systemic corticosteroids [SCs], emergency department/urgent care [ED/UC] visits, hospitalizations) were compared across subgroups using multivariable regression. RESULTS: Compared with AA/B participants, ME/B participants were more likely to be younger, residing in the US Northeast, and Spanish speaking and to have lower body mass index, health literacy, and <1 comorbidity, but higher blood eosinophil counts. In a multivariable analysis, ME/B participants were significantly more likely to have ED/UC visits (incidence rate ratio [IRR] = 1.34, 95% CI = 1.04-1.72) and SC use (IRR = 1.27, 95% CI = 1.00-1.62) for asthma than AA/B participants. Of the ME/B subgroups, Puerto Rican Black Latinx participants (n = 120) were significantly more likely to have ED/UC visits (IRR = 1.64, 95% CI = 1.22-2.21) and SC use for asthma (IRR = 1.43, 95% CI = 1.06-1.92) than AA/B participants. There were no significant differences in hospitalizations for asthma among subgroups. CONCLUSIONS: ME/B adults, specifically Puerto Rican Black Latinx adults, have higher risk of ED/UC visits and SC use for asthma than other Black subgroups.

Cogeneration of Clean Water and Valuable Energy/Resources via Interfacial Solar Evaporation.

Water, covering over two-thirds of the Earth's surface, holds immense potential for generating clean water, sustainable energy, and metal resources, which are the cornerstones of modern society and future development. It is highly desired to produce these crucial elements through eco-friendly processes with minimal carbon footprints. Interfacial solar evaporation, which utilizes solar energy at the air-liquid interface to facilitate water vaporization and solute separation, offers a promising solution. In this review, we systematically report the recent progress of the cogeneration of clean water and energy/resources including electricity, hydrogen, and metal resources via interfacial solar evaporation. We first gain insight into the energy and mass transport for a typical interfacial solar evaporation system and reveal the residual energy and resources for achieving the cogeneration goal. Then, we summarize the recent advances in materials/device designs for efficient cogeneration. Finally, we discuss the existing challenges and potential opportunities for the further development of this field.

The deacylase sirtuin 5 reduces malonylation in nonmitochondrial metabolic pathways in diabetic kidney disease.

Early diabetic kidney disease (DKD) is marked by dramatic metabolic reprogramming due to nutrient excess, mitochondrial dysfunction, and increased renal energy requirements from hyperfiltration. We hypothesized that changes in metabolism in DKD may be regulated by Sirtuin 5 (SIRT5), a deacylase that removes posttranslational modifications derived from acyl-coenzyme A and has been demonstrated to regulate numerous metabolic pathways. We found decreased malonylation in the kidney cortex (∼80% proximal tubules) of type 2 diabetic BKS db/db mice, associated with increased SIRT5 expression. We performed a proteomics analysis of malonylated peptides and found that proteins with significantly decreased malonylated lysines in the db/db cortex were enriched in nonmitochondrial metabolic pathways: glycolysis and peroxisomal fatty acid oxidation. To confirm relevance of these findings in human disease, we analyzed diabetic kidney transcriptomic data from a cohort of Southwestern American Indians, which revealed a tubulointerstitial-specific increase in Sirt5 expression. These data were further corroborated by immunofluorescence data of SIRT5 from nondiabetic and DKD cohorts. Furthermore, overexpression of SIRT5 in cultured human proximal tubules demonstrated increased aerobic glycolysis. Conversely, we observed reduced glycolysis with decreased SIRT5 expression. These findings suggest that SIRT5 may lead to differential nutrient partitioning and utilization in DKD. Taken together, our findings highlight a previously unrecognized role for SIRT5 in metabolic reprogramming in DKD.

Bacteroidota polysaccharide utilization system for branched dextran exopolysaccharides from lactic acid bacteria.

Dextran is an α-(1→6)-glucan that is synthesized by some lactic acid bacteria, and branched dextran with α-(1→2)-, α-(1→3)-, and α-(1→4)-linkages are often produced. Although many dextranases are known to act on the α-(1→6)-linkage of dextran, few studies have functionally analyzed the proteins involved in degrading branched dextran. The mechanism by which bacteria utilize branched dextran is unknown. Earlier, we identified dextranase (FjDex31A) and kojibiose hydrolase (FjGH65A) in the dextran utilization locus (FjDexUL) of a soil Bacteroidota Flavobacterium johnsoniae and hypothesized that FjDexUL is involved in the degradation of α-(1→2)-branched dextran. In this study, we demonstrate that FjDexUL proteins recognize and degrade α-(1→2)- and α-(1→3)-branched dextrans produced by Leuconostoc citreum S-32 (S-32 α-glucan). The FjDexUL genes were significantly upregulated when S-32 α-glucan was the carbon source compared with α-glucooligosaccharides and α-glucans, such as linear dextran and branched α-glucan from L. citreum S-64. FjDexUL glycoside hydrolases synergistically degraded S-32 α-glucan. The crystal structure of FjGH66 shows that some sugar-binding subsites can accommodate α-(1→2)- and α-(1→3)-branches. The structure of FjGH65A in complex with isomaltose supports that FjGH65A acts on α-(1→2)-glucosyl isomaltooligosaccharides. Furthermore, two cell surface sugar-binding proteins (FjDusD and FjDusE) were characterized, and FjDusD showed an affinity for isomaltooligosaccharides and FjDusE for dextran, including linear and branched dextrans. Collectively, FjDexUL proteins are suggested to be involved in the degradation of α-(1→2)- and α-(1→3)-branched dextrans. Our results will be helpful in understanding the bacterial nutrient requirements and symbiotic relationships between bacteria at the molecular level.

Transcriptomic analysis of polysaccharide utilization loci reveals substrate preferences in ruminal generalists Segatella bryantii TF1-3 and Xylanibacter ruminicola KHP1.

Bacteria of the genera Xylanibacter and Segatella are among the most dominant groups in the rumen microbiota. They are characterized by the ability to utilize different hemicelluloses and pectin of plant cell-wall as well as plant energy storage polysaccharides. The degradation is possible with the use of cell envelope bound multiprotein apparatuses coded in polysaccharide utilization loci (PULs), which have been shown to be substrate specific. The knowledge of PUL presence in rumen Xylanibacter and Segatella based on bioinformatic analyses is already established and transcriptomic and genetic approaches confirmed predicted PULs for a limited number of substrates. In this study, we transcriptomically identified additional different PULs in Xylanibacter ruminicola KHP1 and Segatella bryantii TF1-3. We also identified substrate preferences and found that specific growth rate and extent of growth impacted the choice of substrates preferentially used for degradation. These preferred substrates were used by both strains simultaneously as judged by their PUL upregulation. Lastly, ß-glucan and xyloglucan were used by these strains in the absence of bioinformatically and transcriptomically identifiable PUL systems.