Influence of Antimicrobial Feed Additives on Broiler Commensal Posthatch Gut Microbiota Development and Performance

ABSTRACTThe effects of avilamycin, zinc bacitracin, and flavophospholipol on broiler gut microbial community colonization and bird performance in the first 17 days posthatch were investigated. Significant differences in gut microbiota associated with gut section, dietary treatment, and age were identified by terminal restriction fragment length polymorphism (T-RFLP), although no performance-related differences between dietary treatments were detected. Similar age-related shifts in the gut microbiota were identified regardless of diet but varied between the ilea and ceca. Interbird variabilities in ileal bacterial communities were reduced (3 to 7 days posthatch) in chicks fed with feed containing antimicrobial agents. Avilamycin and flavophospholipol had the most consistent effect on gut microbial communities. Operational taxonomic units (OTU) linked to changes in gut microbiota in birds on antimicrobial-supplemented diets were characterized and identified. Some OTUs could be identified to the species level; however, the majority could be only tentatively classified to the genus, family, order, or domain level. OTUs 140 to 146 (Lachnospiraceae), OTU 186/188 (Lactobacillus johnsonii), OTU 220 (Lachnospiraceae), OTUs 284 to 288 (unclassified bacterial spp. orRuminococcaceae), OTU 296/298 (unclassified bacterium orClostridiales), and OTU 480/482 (Oxalobacteraceae) were less prevalent in the guts of chicks fed antimicrobial-supplemented diets. OTU 178/180 (Lactobacillus crispatus), OTU 152 (Lactobacillus reuterior unclassifiedClostridiales), OTU 198/200 (Subdoligranulumspp.), and OTU 490/492 (unclassified bacterium orEnterobacteriaceae) were less prevalent in the gut of chicks raised on the antimicrobial-free diet. The identification of key bacterial species influenced by antimicrobial-supplemented feed immediately posthatch may assist in the formulation of diets that facilitate beneficial gut microbial colonization and, hence, the development of alternatives to current antimicrobial agents in feed for sustainable poultry production.

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Immune Response of Chicken Gut to Natural Colonization by Gut Microflora and to Salmonella enterica Serovar Enteritidis Infection

Infection and Immunity ◽

10.1128/iai.01375-10 ◽

2011 ◽

Vol 79 (7) ◽

pp. 2755-2763 ◽

Cited By ~ 149

Author(s):

Magdalena Crhanova ◽

Helena Hradecka ◽

Marcela Faldynova ◽

Marta Matulova ◽

Hana Havlickova ◽

...

Keyword(s):

Immune Response ◽

Immune System ◽

Gut Microbiota ◽

Salmonella Enterica ◽

Microbial Colonization ◽

Poultry Production ◽

Content Type ◽

Gut Immune System ◽

Chicken Gut Microbiota ◽

Chicken Cecum

ABSTRACTIn commercial poultry production, there is a lack of natural flora providers since chickens are hatched in the clean environment of a hatchery. Events occurring soon after hatching are therefore of particular importance, and that is why we were interested in the development of the gut microbial community, the immune response to natural microbial colonization, and the response toSalmonella entericaserovar Enteritidis infection as a function of chicken age. The complexity of chicken gut microbiota gradually increased from day 1 to day 19 of life and consisted ofProteobacteriaandFirmicutes. For the first 3 days of life, chicken cecum was protected by increased expression of chicken β-defensins (i.e., gallinacins 1, 2, 4, and 6), expression of which dropped from day 4 of life. On the other hand, a transient increase in interleukin-8 (IL-8) and IL-17 expression could be observed in chicken cecum on day 4 of life, indicating physiological inflammation and maturation of the gut immune system. In agreement, the response of chickens infected withS. Enteritidis on days 1, 4, and 16 of life shifted from Th1 (characterized mainly by induction of gamma interferon [IFN-γ] and inducible nitric oxide synthase [iNOS]), observed in younger chickens, to Th17, observed in 16-day-old chickens (characterized mainly by IL-17 induction). Active modification of chicken gut microbiota in the future may accelerate or potentiate the maturation of the gut immune system and increase its resistance to infection with different pathogens.

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Differential Metabolism of Exopolysaccharides from Probiotic Lactobacilli by the Human Gut Symbiont Bacteroides thetaiotaomicron

Applied and Environmental Microbiology ◽

10.1128/aem.00149-15 ◽

2015 ◽

Vol 81 (12) ◽

pp. 3973-3983 ◽

Cited By ~ 30

Author(s):

Alicia Lammerts van Bueren ◽

Aakanksha Saraf ◽

Eric C. Martens ◽

Lubbert Dijkhuizen

Keyword(s):

Gastrointestinal Tract ◽

Carbohydrate Metabolism ◽

Lactobacillus Reuteri ◽

Bacterial Species ◽

Transport Systems ◽

Bacteroides Thetaiotaomicron ◽

Human Gut ◽

Positive Health ◽

Content Type ◽

Commensal Species

ABSTRACTProbiotic microorganisms are ingested as food or supplements and impart positive health benefits to consumers. Previous studies have indicated that probiotics transiently reside in the gastrointestinal tract and, in addition to modulating commensal species diversity, increase the expression of genes for carbohydrate metabolism in resident commensal bacterial species. In this study, it is demonstrated that the human gut commensal speciesBacteroides thetaiotaomicronefficiently metabolizes fructan exopolysaccharide (EPS) synthesized by probioticLactobacillus reuteristrain 121 while only partially degrading reuteran and isomalto/malto-polysaccharide (IMMP) α-glucan EPS polymers.B. thetaiotaomicronmetabolized these EPS molecules via the activation of enzymes and transport systems encoded by dedicated polysaccharide utilization loci specific for β-fructans and α-glucans. Reduced metabolism of reuteran and IMMP α-glucan EPS molecules may be due to reduced substrate binding by components of the starch utilization system (sus). This study reveals that microbial EPS substrates activate genes for carbohydrate metabolism inB. thetaiotaomicronand suggests that microbially derived carbohydrates provide a carbohydrate-rich reservoir forB. thetaiotaomicronnutrient acquisition in the gastrointestinal tract.

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Antimicrobial Susceptibility Testing and Tentative Epidemiological Cutoff Values for FiveBacillusSpecies Relevant for Use as Animal Feed Additives or for Plant Protection

Applied and Environmental Microbiology ◽

10.1128/aem.01108-18 ◽

2018 ◽

Vol 84 (19) ◽

Cited By ~ 7

Author(s):

Yvonne Agersø ◽

Birgitte Stuer-Lauridsen ◽

Karin Bjerre ◽

Michelle Geervliet Jensen ◽

Eric Johansen ◽

...

Keyword(s):

Antimicrobial Resistance ◽

Resistance Genes ◽

Pathogenic Bacteria ◽

Animal Feed ◽

Bacterial Species ◽

Feed Additives ◽

Content Type ◽

Cutoff Values ◽

Antimicrobial Resistance Genes ◽

Species Specific

ABSTRACTBacillus megaterium(n= 29),Bacillus velezensis(n= 26),Bacillus amyloliquefaciens(n= 6),Bacillus paralicheniformis(n= 28), andBacillus licheniformis(n= 35) strains from different sources, origins, and time periods were tested for the MICs for nine antimicrobial agents by the CLSI-recommended method (Mueller-Hinton broth, 35°C, for 18 to 20 h), as well as with a modified CLSI method (Iso-Sensitest [IST] broth, 37°C [35°C forB. megaterium], 24 h). This allows a proposal of species-specific epidemiological cutoff values (ECOFFs) for the interpretation of antimicrobial resistance in these species. MICs determined by the modified CLSI method were 2- to 16-fold higher than with the CLSI-recommended method for several antimicrobials. The MIC distributions differed between species for five of the nine antimicrobials. Consequently, use of the modified CLSI method and interpretation of resistance by use of species-specific ECOFFs is recommended. The genome sequences of all strains were determined and used for screening for resistance genes against the ResFinder database and for multilocus sequence typing. A putative chloramphenicol acetyltransferase (cat) gene was found in oneB. megateriumstrain with an elevated chloramphenicol MIC compared to the otherB. megateriumstrains. InB. velezensisandB. amyloliquefaciens, a putative tetracycline efflux gene,tet(L), was found in all strains (n= 27) with reduced tetracycline susceptibility but was absent in susceptible strains. AllB. paralicheniformisand 23% ofB. licheniformisstrains had elevated MICs for erythromycin and harboredermD. The presence of these resistance genes follows taxonomy suggesting they may be intrinsic rather than horizontally acquired. Reduced susceptibility to chloramphenicol, streptomycin, and clindamycin could not be explained in all species.IMPORTANCEWhen commercializing bacterial strains, likeBacillusspp., for feed applications or plant bioprotection, it is required that the strains are free of acquired antimicrobial resistance genes that could potentially spread to pathogenic bacteria, thereby adding to the pool of resistance genes that may cause treatment failures in humans or animals. Conversely, if antimicrobial resistance is intrinsic to a bacterial species, the risk of spreading horizontally to other bacteria is considered very low. Reliable susceptibility test methods and interpretation criteria at the species level are needed to accurately assess antimicrobial resistance levels. In the present study, tentative ECOFFs for fiveBacillusspecies were determined, and the results showed that the variation in MICs followed the respective species. Moreover, putative resistance genes, which were detected by whole-genome sequencing and suggested to be intrinsic rather that acquired, could explain the resistance phenotypes in most cases.

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Intestinal IgA Regulates Expression of a Fructan Polysaccharide Utilization Locus in Colonizing Gut Commensal Bacteroides thetaiotaomicron

mBio ◽

10.1128/mbio.02324-19 ◽

2019 ◽

Vol 10 (6) ◽

Cited By ~ 4

Author(s):

Payal Joglekar ◽

Hua Ding ◽

Pablo Canales-Herrerias ◽

Pankaj Jay Pasricha ◽

Justin L. Sonnenburg ◽

...

Keyword(s):

Gut Microbiota ◽

Ex Vivo ◽

Microbial Colonization ◽

Bacteroides Thetaiotaomicron ◽

Content Type ◽

Microbial Utilization ◽

Polysaccharide Utilization Locus ◽

The Impact

ABSTRACT Gut-derived immunoglobulin A (IgA) is the most abundant antibody secreted in the gut that shapes gut microbiota composition and functionality. However, most of the microbial antigens targeted by gut IgA remain unknown, and the functional effects of IgA targeting these antigens are currently understudied. This study provides a framework for identifying and characterizing gut microbiota antigens targeted by gut IgA. We developed a small intestinal ex vivo culture assay to harvest lamina propria IgA from gnotobiotic mice, with the aim of identifying antigenic targets in a model human gut commensal, Bacteroides thetaiotaomicron VPI-5482. Colonization by B. thetaiotaomicron induced a microbe-specific IgA response that was reactive against diverse antigens, including capsular polysaccharides, lipopolysaccharides, and proteins. IgA against microbial protein antigens targeted membrane and secreted proteins with diverse functionalities, including an IgA specific against proteins of the polysaccharide utilization locus (PUL) that are necessary for utilization of fructan, which is an important dietary polysaccharide. Further analyses demonstrated that the presence of dietary fructan increased the production of fructan PUL-specific IgA, which then downregulated the expression of fructan PUL in B. thetaiotaomicron, both in vivo and in vitro. Since the expression of fructan PUL has been associated with the ability of B. thetaiotaomicron to colonize the gut in the presence of dietary fructans, our work suggests a novel role for gut IgA in regulating microbial colonization by modulating their metabolism. IMPORTANCE Given the significant impact that gut microbes have on our health, it is essential to identify key host and environmental factors that shape this diverse community. While many studies have highlighted the impact of diet on gut microbiota, little is known about how the host regulates this critical diet-microbiota interaction. In our present study, we discovered that gut IgA targeted a protein complex involved in the utilization of an important dietary polysaccharide: fructan. While the presence of dietary fructans was previously thought to allow unrestricted growth of fructan-utilizing bacteria, our work shows that gut IgA, by targeting proteins responsible for fructan utilization, provides the host with tools that can restrict the microbial utilization of such polysaccharides, thereby controlling their growth.

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Lactobacillus reuteri DSM 17938 feeding of healthy newborn mice regulates immune responses while modulating gut microbiota and boosting beneficial metabolites

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00107.2019 ◽

2019 ◽

Vol 317 (6) ◽

pp. G824-G838 ◽

Cited By ~ 7

Author(s):

Yuying Liu ◽

Xiangjun Tian ◽

Baokun He ◽

Thomas K. Hoang ◽

Christopher M. Taylor ◽

...

Keyword(s):

Gut Microbiota ◽

Oral Administration ◽

Relative Abundance ◽

Lactobacillus Reuteri ◽

Tca Cycle ◽

Microbial Colonization ◽

Plasma Metabolites ◽

Early Administration ◽

Newborn Mice ◽

Breastfed Infants

Early administration of Lactobacillus reuteri DSM 17938 (LR) prevents necrotizing enterocolitis and inhibits regulatory T-cell (Treg)-deficiency-associated autoimmunity in mice. In humans, LR reduces crying time in breastfed infants with colic, modifies severity in infants with acute diarrheal illnesses, and improves pain in children with functional bowel disorders. In healthy breastfed newborns with evolving microbial colonization, it is unclear if early administration of LR can modulate gut microbiota and their metabolites in such a way as to promote homeostasis. We gavaged LR (107 colony-forming units/day, daily) to C57BL/6J mice at age of day 8 for 2 wk. Both male and female mice were investigated in these experiments. We found that feeding LR did not affect clinical phenotype or inflammatory biomarkers in plasma and stool, but LR increased the proportion of Foxp3+ regulatory T cells (Tregs) in the intestine. LR also increased bacterial diversity and the relative abundance of p_Firmicutes, f_Lachnospiraceae, f_Ruminococcaceae, and genera Clostridium and Candidatus arthromitus, while decreasing the relative abundance of p_Bacteriodetes, f_Bacteroidaceae, f_Verrucomicrobiaceae, and genera Bacteroides, Ruminococcus, Akkermansia, and Sutterella. Finally, LR exerted a major impact on the plasma metabolome, upregulating amino acid metabolites formed via the urea, tricarboxylic acid, and methionine cycles and increasing tryptophan metabolism. In conclusion, early oral administration of LR to healthy breastfed mice led to microbial and metabolic changes which could be beneficial to general health. NEW & NOTEWORTHY Oral administration of Lactobacillus reuteri DSM 17938 (LR) to healthy breastfed mice promotes intestinal immune tolerance and is linked to proliferation of beneficial gut microbiota. LR upregulates plasma metabolites that are involved in the urea cycle, the TCA cycle, methionine methylation, and the polyamine pathway. Herein, we show that LR given to newborn mice specifically increases levels of tryptophan metabolites and the purine nucleoside adenosine that are known to enhance tolerance to inflammatory stimuli.

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A Cross-Sectional Study of Compositional and Functional Profiles of Gut Microbiota in Sardinian Centenarians

mSystems ◽

10.1128/msystems.00325-19 ◽

2019 ◽

Vol 4 (4) ◽

Cited By ~ 10

Author(s):

Lu Wu ◽

Tiansheng Zeng ◽

Angelo Zinellu ◽

Salvatore Rubino ◽

David J. Kelvin ◽

...

Keyword(s):

Gut Microbiota ◽

Healthy Aging ◽

High Capacity ◽

Functional Independence ◽

Metagenomic Sequencing ◽

Bifidobacterium Adolescentis ◽

Content Type ◽

Age Related ◽

Genes Encoding ◽

Functional Profiles

ABSTRACT Sardinia, Italy, has a high prevalence of residents who live more than 100 years. The reasons for longevity in this isolated region are currently unknown. Gut microbiota may hold a clue. To explore the role gut microbiota may play in healthy aging and longevity, we used metagenomic sequencing to determine the compositional and functional differences in gut microbiota associated with populations of different ages in Sardinia. Our data revealed that the gut microbiota of both young and elderly Sardinians shared similar taxonomic and functional profiles. A different pattern was found in centenarians. Within the centenarian group, the gut microbiota was correlated with the functional independence measurement of the host. Centenarians had a higher diversity of core microbiota species and microbial genes than those in the young and elderly. We found that the gut microbiota in Sardinian centenarians displayed a rearranged taxonomic pattern compared with those of the young and elderly, featured by depletion of Faecalibacterium prausnitzii and Eubacterium rectale and enriched for Methanobrevibacter smithii and Bifidobacterium adolescentis. Moreover, functional analysis revealed that the microbiota in centenarians had high capacity for central metabolism, especially glycolysis and fermentation to short-chain fatty acids (SCFAs), although the gut microbiota in centenarians was low in genes encoding enzymes involved in degradation of carbohydrates, including fibers and galactose. IMPORTANCE The gut microbiota has been proposed as a promising determinant for human health. Centenarians as a model for extreme aging may help us understand the correlation of gut microbiota with healthy aging and longevity. Here we confirmed that centenarians had microbiota elements usually associated with benefits to health. Our finding of a high capacity of glycolysis and related SCFA production represented a healthy microbiome and environment that is regarded as beneficial for host gut epithelium. The low abundance of genes encoding components of pathways involved in carbohydrate degradation was also found in the gut microbiota of Sardinian centenarians and is often associated with poor gut health. Overall, our study here represents an expansion of previous research investigating the age-related changes in gut microbiota. Furthermore, our study provides a new prospective for potential targets for gut microbiota intervention directed at limiting gut inflammation and pathology and enhancing a healthy gut barrier.

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Potentiation of Tobramycin by Silver Nanoparticles against Pseudomonas aeruginosa Biofilms

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00415-17 ◽

2017 ◽

Vol 61 (11) ◽

Cited By ~ 20

Author(s):

Marc B. Habash ◽

Mara C. Goodyear ◽

Amber J. Park ◽

Matthew D. Surette ◽

Emily C. Vis ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Silver Nanoparticles ◽

Bacterial Infections ◽

Pathogenic Bacteria ◽

Antimicrobial Agents ◽

Bacterial Species ◽

Acute Infection ◽

Public Health Problem ◽

Chronic Infections ◽

Content Type

ABSTRACT Increasing antibiotic resistance among pathogenic bacterial species is a serious public health problem and has prompted research examining the antibacterial effects of alternative compounds and novel treatment strategies. Compounding this problem is the ability of many pathogenic bacteria to form biofilms during chronic infections. Importantly, these communities are often recalcitrant to antibiotic treatments that show effectiveness against acute infection. The antimicrobial properties of silver have been known for decades, but recently silver and silver-containing compounds have seen renewed interest as antimicrobial agents for treating bacterial infections. The goal of this study was to assess the ability of citrate-capped silver nanoparticles (AgNPs) of various sizes, alone and in combination with the aminoglycoside antibiotic tobramycin, to inhibit established Pseudomonas aeruginosa biofilms. Our results demonstrate that smaller 10-nm and 20-nm AgNPs were more effective at synergistically potentiating the activity of tobramycin. Visualization of biofilms treated with combinations of 10-nm AgNPs and tobramycin reveals that the synergistic bactericidal effect may be caused by disrupting cellular membranes. Minimum biofilm eradication concentration (MBEC) assays using clinical P. aeruginosa isolates shows that small AgNPs are more effective than larger AgNPs at inhibiting biofilms, but that the synergy effect is likely a strain-dependent phenomenon. These data suggest that small AgNPs synergistically potentiate the activity of tobramycin against P. aeruginosa in vitro and may reveal a potential role for AgNP/antibiotic combinations in treating patients with chronic infections in a strain-specific manner.

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Metaproteomics Analysis Reveals the Adaptation Process for the Chicken Gut Microbiota

Applied and Environmental Microbiology ◽

10.1128/aem.02472-13 ◽

2013 ◽

Vol 80 (2) ◽

pp. 478-485 ◽

Cited By ~ 42

Author(s):

Yue Tang ◽

Anthony Underwood ◽

Adriana Gielbert ◽

Martin J. Woodward ◽

Liljana Petrovska

Keyword(s):

16S Rrna ◽

Gut Microbiota ◽

High Throughput Sequencing ◽

Bacterial Species ◽

Abundant Species ◽

Fecal Microbiota ◽

Rrna Gene ◽

Sequencing Analysis ◽

Content Type ◽

Chicken Gut Microbiota

ABSTRACTThe animal gastrointestinal tract houses a large microbial community, the gut microbiota, that confers many benefits to its host, such as protection from pathogens and provision of essential metabolites. Metagenomic approaches have defined the chicken fecal microbiota in other studies, but here, we wished to assess the correlation between the metagenome and the bacterial proteome in order to better understand the healthy chicken gut microbiota. Here, we performed high-throughput sequencing of 16S rRNA gene amplicons and metaproteomics analysis of fecal samples to determine microbial gut composition and protein expression. 16 rRNA gene sequencing analysis identifiedClostridiales,Bacteroidaceae, andLactobacillaceaespecies as the most abundant species in the gut. For metaproteomics analysis, peptides were generated by using the Fasp method and subsequently fractionated by strong anion exchanges. Metaproteomics analysis identified 3,673 proteins. Among the most frequently identified proteins, 380 proteins belonged toLactobacillusspp., 155 belonged toClostridiumspp., and 66 belonged toStreptococcusspp. The most frequently identified proteins were heat shock chaperones, including 349 GroEL proteins, from many bacterial species, whereas the most abundant enzymes were pyruvate kinases, as judged by the number of peptides identified per protein (spectral counting). Gene ontology and KEGG pathway analyses revealed the functions and locations of the identified proteins. The findings of both metaproteomics and 16S rRNA sequencing analyses are discussed.

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Decreased Ecological Resistance of the Gut Microbiota in Response to Clindamycin Challenge in Mice Colonized with the Fungus Candida albicans

mSphere ◽

10.1128/msphere.00982-20 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Laura Markey ◽

Antonia Pugliese ◽

Theresa Tian ◽

Farrah Roy ◽

Kyongbum Lee ◽

...

Keyword(s):

Candida Albicans ◽

Gut Microbiota ◽

Bacterial Species ◽

Species Abundance ◽

Alpha Diversity ◽

Human Gut ◽

Content Type ◽

Ecological Resistance ◽

Bacterial Microbiota ◽

Host Health

ABSTRACT The mammalian gut microbiota is a complex community of microorganisms which typically exhibits remarkable stability. As the gut microbiota has been shown to affect many aspects of host health, the molecular keys to developing and maintaining a “healthy” gut microbiota are highly sought after. Yet, the qualities that define a microbiota as healthy remain elusive. We used the ability to resist change in response to antibiotic disruption, a quality we refer to as ecological resistance, as a metric for the health of the bacterial microbiota. Using a mouse model, we found that colonization with the commensal fungus Candida albicans decreased the ecological resistance of the bacterial microbiota in response to the antibiotic clindamycin such that increased microbiota disruption was observed in C. albicans-colonized mice compared to that in uncolonized mice. C. albicans colonization resulted in decreased alpha diversity and small changes in abundance of bacterial genera prior to clindamycin challenge. Strikingly, co-occurrence network analysis demonstrated that C. albicans colonization resulted in sweeping changes to the co-occurrence network structure, including decreased modularity and centrality and increased density. Thus, C. albicans colonization resulted in changes to the bacterial microbiota community and reduced its ecological resistance. IMPORTANCE Candida albicans is the most common fungal member of the human gut microbiota, yet its ability to interact with and affect the bacterial gut microbiota is largely uncharacterized. Previous reports showed limited changes in microbiota composition as defined by bacterial species abundance as a consequence of C. albicans colonization. We also observed only a few bacterial genera that were significantly altered in abundance in C. albicans-colonized mice; however, C. albicans colonization significantly changed the structure of the bacterial microbiota co-occurrence network. Additionally, C. albicans colonization changed the response of the bacterial microbiota ecosystem to a clinically relevant perturbation, challenge with the antibiotic clindamycin.

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Substrate Use Prioritization by a Coculture of Five Species of Gut Bacteria Fed Mixtures of Arabinoxylan, Xyloglucan, β-Glucan, and Pectin

Applied and Environmental Microbiology ◽

10.1128/aem.01905-19 ◽

2019 ◽

Vol 86 (2) ◽

Cited By ~ 4

Author(s):

Yafei Liu ◽

Anne-Louise Heath ◽

Barbara Galland ◽

Nancy Rehrer ◽

Lynley Drummond ◽

...

Keyword(s):

Gut Microbiota ◽

Dietary Fiber ◽

Bacterial Species ◽

Short Chain ◽

Emergent Properties ◽

Human Gut ◽

Fermentation Products ◽

Plant Polysaccharides ◽

Content Type ◽

Human Gut Microbiota

ABSTRACT Dietary fiber provides growth substrates for bacterial species that belong to the colonic microbiota of humans. The microbiota degrades and ferments substrates, producing characteristic short-chain fatty acid profiles. Dietary fiber contains plant cell wall-associated polysaccharides (hemicelluloses and pectins) that are chemically diverse in composition and structure. Thus, depending on plant sources, dietary fiber daily presents the microbiota with mixtures of plant polysaccharides of various types and complexity. We studied the extent and preferential order in which mixtures of plant polysaccharides (arabinoxylan, xyloglucan, β-glucan, and pectin) were utilized by a coculture of five bacterial species (Bacteroides ovatus, Bifidobacterium longum subspecies longum, Megasphaera elsdenii, Ruminococcus gnavus, and Veillonella parvula). These species are members of the human gut microbiota and have the biochemical capacity, collectively, to degrade and ferment the polysaccharides and produce short-chain fatty acids (SCFAs). B. ovatus utilized glycans in the order β-glucan, pectin, xyloglucan, and arabinoxylan, whereas B. longum subsp. longum utilization was in the order arabinoxylan, arabinan, pectin, and β-glucan. Propionate, as a proportion of total SCFAs, was augmented when polysaccharide mixtures contained galactan, resulting in greater succinate production by B. ovatus and conversion of succinate to propionate by V. parvula. Overall, we derived a synthetic ecological community that carries out SCFA production by the common pathways used by bacterial species for this purpose. Systems like this might be used to predict changes to the emergent properties of the gut ecosystem when diet is altered, with the aim of beneficially affecting human physiology. IMPORTANCE This study addresses the question as to how bacterial species, characteristic of the human gut microbiota, collectively utilize mixtures of plant polysaccharides such as are found in dietary fiber. Five bacterial species with the capacity to degrade polymers and/or produce acidic fermentation products detectable in human feces were used in the experiments. The bacteria showed preferential use of certain polysaccharides over others for growth, and this influenced their fermentation output qualitatively. These kinds of studies are essential in developing concepts of how the gut microbial community shares habitat resources, directly and indirectly, when presented with mixtures of polysaccharides that are found in human diets. The concepts are required in planning dietary interventions that might correct imbalances in the functioning of the human microbiota so as to support measures to reduce metabolic conditions such as obesity.

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