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1. Cultivable, Host-Specific Bacteroidetes Symbionts Exhibit Diverse Polysaccharolytic Strategies

   https://doi.org/10.1128/AEM.00091-20  

   Vera-Ponce de León, Arturo ; Jahnes, Benjamin C. ; Duan, Jun ; Camuy-Vélez, Lennel A. ; Sabree, Zakee L. ( April 2020 , Applied and Environmental Microbiology)

   Drake, Harold L. (Ed.)

   ABSTRACT Beneficial gut microbes can facilitate insect growth on diverse diets. The omnivorous American cockroach, Periplaneta americana (Insecta: Blattodea), thrives on a diet rich in plant polysaccharides and harbors a species-rich gut microbiota responsive to host diet. Bacteroidetes are among the most abundant taxa in P. americana and other cockroaches, based on cultivation-independent gut community profiling, and these potentially polysaccharolytic bacteria may contribute to host diet processing. Eleven Bacteroidetes isolates were cultivated from P. americana digestive tracts, and phylogenomic analyses suggest that they were new Bacteroides , Dysgonomonas , Paludibacter , and Parabacteroides species distinct from those previously isolated from other insects, humans, and environmental sources. In addition, complete genomes were generated for each isolate, and polysaccharide utilization loci (PULs) and several non-PUL-associated carbohydrate-active enzyme (CAZyme)-coding genes that putatively target starch, pectin, and/or cellulose were annotated in each of the isolate genomes. Type IX secretion system (T9SS)- and CAZyme-coding genes tagged with the corresponding T9SS recognition and export C-terminal domain were observed in some isolates, suggesting that these CAZymes were deployed via non-PUL outer membrane translocons. Additionally, single-substrate growth and enzymatic assays confirmed genomic predictions that a subset of the Bacteroides and Dysgonomonas isolates could degrade starch, pectin, and/or cellulose and grow in the presence of these substrates as a single sugar source. Plant polysaccharides enrich P. americana diets, and many of these gut isolates are well equipped to exploit host dietary inputs and potentially contribute to gut community and host nutrient accessibility. IMPORTANCE Gut microbes are increasingly being recognized as critical contributors to nutrient accessibility in animals. The globally distributed omnivorous American cockroach ( Periplaneta americana ) harbors many bacterial phyla (e.g., Bacteroidetes ) that are abundant in vertebrates. P. americana thrives on a highly diverse plant-enriched diet, making this insect a rich potential source of uncharacterized polysaccharolytic bacteria. We have cultivated, completely sequenced, and functionally characterized several novel Bacteroidetes species that are endemic to the P. americana gut, and many of these isolates can degrade simple and complex polysaccharides. Cultivation and genomic characterization of these Bacteroidetes isolates further enable deeper insight into how these taxa participate in polysaccharide metabolism and, more broadly, how they affect animal health and development. 

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2. Global Composition of the Bacteriophage Community in Honey Bees

   https://doi.org/10.1128/msystems.01195-21  

   Busby, Taylor J. ; Miller, Craig R. ; Moran, Nancy A. ; Van Leuven, James T. ( April 2022 , mSystems)

   Gambino, Michela (Ed.)

   ABSTRACT The microbial communities in animal digestive systems are critical for host development and health. They stimulate the immune system during development, synthesize important chemical compounds like hormones, aid in digestion, competitively exclude pathogens, etc. Compared to the bacterial and fungal components of the microbiome, we know little about the temporal and spatial dynamics of bacteriophage communities in animal digestive systems. Recently, the bacteriophages of the honey bee gut were characterized in two European bee populations. Most of the bacteriophages described in these two reports were novel, harbored many metabolic genes in their genomes, and had a community structure that suggests coevolution with their bacterial hosts. To describe the conservation of bacteriophages in bees and begin to understand their role in the bee microbiome, we sequenced the virome of Apis mellifera from Austin, TX, and compared bacteriophage compositions among three locations around the world. We found that most bacteriophages from Austin are novel, sharing no sequence similarity with anything in public repositories. However, many bacteriophages are shared among the three bee viromes, indicating specialization of bacteriophages in the bee gut. Our study, along with the two previous bee virome studies, shows that the bee gut bacteriophage community is simple compared to that of many animals, consisting of several hundred types of bacteriophages that primarily infect four of the dominant bacterial phylotypes in the bee gut. IMPORTANCE Viruses that infect bacteria (bacteriophages) are abundant in the microbial communities that live on and in plants and animals. However, our knowledge of the structure, dynamics, and function of these viral communities lags far behind our knowledge of their bacterial hosts. We sequenced the first bacteriophage community of honey bees from the United States and compared the U.S. honey bee bacteriophage community to those of samples from Europe. Our work is an important characterization of an economically critical insect species and shows how bacteriophage communities can contain highly conserved individuals and be highly variable in composition across a wide geographic range. 

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3. Dietary and plasma carotenoids are positively associated with alpha diversity in the fecal microbiota of pregnant women

   https://doi.org/10.1111/1750-3841.15586  

   Schmidt, Kristen M. ; Haddad, Eliot N. ; Sugino, Kameron Y. ; Vevang, Karin R. ; Peterson, Lisa A. ; Koratkar, Revati ; Gross, Myron D. ; Kerver, Jean M. ; Comstock, Sarah S. ( January 2021 , Journal of Food Science)

   Because microbes use carotenoids as an antioxidant for protection, dietary carotenoids could be associated with gut microbiota composition. We aimed to determine associations among reported carotenoid intake, plasma carotenoid concentrations, and fecal bacterial communities in pregnant women. Pregnant women (n= 27) were enrolled in a two‐arm study designed to assess feasibility of biospecimen collection and delivery of a practical nutrition intervention. Plasma and fecal samples were collected and women were surveyed with a 24‐hr dietary checklist and recalls. Plasma carotenoids were analyzed by HPLC using photodiode array detection. Fecal bacteria were analyzed by 16S rRNA DNA sequencing. Results presented are cross‐sectional from the 36‐week gestational study visit combined across both study arms due to lack of significant differences between intervention and usual care groups (n= 23 women with complete data). Recent intake of carotenoid‐containing foods included carrots, sweet potatoes, mangos, apricots, and/or bell peppers for 48% of women; oranges/orange juice (17%); egg (39%); tomato/tomato‐based sauces (52%); fruits (83%); and vegetables (65%). Average plasma carotenoid concentrations were 6.4 µg/dL α‐carotene (AC), 17.7 µg/dL β‐carotene (BC), 11.4 µg/dL cryptoxanthin, 39.0 µg/dL trans‐lycopene, and 29.8 µg/dL zeaxanthin and lutein. AC and BC concentrations were higher in women who recently consumed foods high in carotenoids. CR concentrations were higher in women who consumed oranges/orange juice. Microbiota α‐diversity positively correlated with AC and BC. Microbiota β‐diversity differed significantly across reported intake of carotenoid containing foods and plasma concentrations of AC. This may reflect an effect of high fiber or improved overall dietary quality, rather than a specific effect of carotenoids.

   Little is known about the association between the gut microbiome and specific dietary microconstituents, such as carotenoids, especially during pregnancy. This research demonstrates that a carotenoid‐rich diet during pregnancy supports a diverse microbiota, which could be one mechanism by which carotenoids promote health.

    

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4. Improvements in Metabolic Syndrome by Xanthohumol Derivatives Are Linked to Altered Gut Microbiota and Bile Acid Metabolism

   https://doi.org/10.1002/mnfr.201900789  

   Zhang, Yang ; Bobe, Gerd ; Revel, Johana S. ; Rodrigues, Richard R. ; Sharpton, Thomas J. ; Fantacone, Mary L. ; Raslan, Kareem ; Miranda, Cristobal L. ; Lowry, Malcolm B. ; Blakemore, Paul R. ; et al ( December 2019 , Molecular Nutrition & Food Research)

   Two hydrogenated xanthohumol (XN) derivatives, α,β‐dihydro‐XN (DXN) and tetrahydro‐XN (TXN), improved parameters of metabolic syndrome (MetS), a critical risk factor of cardiovascular disease (CVD) and type 2 diabetes, in a diet‐induced obese murine model. It is hypothesized that improvements in obesity and MetS are linked to changes in composition of the gut microbiota, bile acid metabolism, intestinal barrier function, and inflammation.

   To test this hypothesis, 16S rRNA genes were sequenced and bile acids were measured in fecal samples from C57BL/6J mice fed a high‐fat diet (HFD) or HFD containing XN, DXN or TXN. Expression of genes associated with epithelial barrier function, inflammation, and bile acid metabolism were measured in the colon, white adipose tissue (WAT), and liver, respectively. Administration of XN derivatives decreases intestinal microbiota diversity and abundance—specifically Bacteroidetes and Tenericutes—alters bile acid metabolism, and reduces inflammation. In WAT, TXN supplementation decreases pro‐inflammatory gene expression by suppressing macrophage infiltration. Transkingdom network analysis connects changes in the microbiota to improvements in MetS in the host.

   Changes in the gut microbiota and bile acid metabolism may explain, in part, the improvements in obesity and MetS associated with administration of XN and its derivatives.

    

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5. Maternal Dietary Protein Intake Influences Milk and Offspring Gut Microbial Diversity in a Rat (Rattus norvegicus) Model

   https://doi.org/10.3390/nu11092257  

   Warren, Matthew ; Hallowell, Haley ; Higgins, Keah ; Liles, Mark ; Hood, Wendy ( September 2019 , Nutrients)

   null (Ed.)

   Historically, investigators have assumed microorganisms identified in mother’s milk to be contaminants, but recent data suggest that milk microbiota may contribute to beneficial maternal effects. Microorganisms that colonize the gastrointestinal tracts of newborn mammals are derived, at least in part, from the maternal microbial population. Milk-derived microbiota is an important source of this microbial inocula and we hypothesized that the maternal diet contributes to variation in this microbial community. To evaluate the relationship between a mother’s diet and milk microbiome, we fed female rats a low- or high-protein diet and mated all individuals. Milk and cecal contents were collected from dams at peak lactation (14-day post-partum), and the bacterial composition of each community was assessed by 16S rRNA gene amplicon sequencing. Our findings revealed higher dietary protein intake decreased fecal microbial diversity but increased milk microbial and pup cecum diversity. Further, the higher dietary protein intake resulted in a greater abundance of potentially health-promoting bacteria, such as Lactobacillus spp. These data suggest that dietary protein levels contribute to significant shifts in the composition of maternal milk microbiota and that the functional consequences of these changes in microbial inocula might be biologically important and should be further explored. 

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