These data demonstrate that obese youth show a different gut flora composition than lean and that short chain fatty acids are associated with body fat partitioning and DNL. Also, the gut microbiota of obese youth have a higher capability than the gut flora of lean to oxidize CHO.
There are trillions of microbes found throughout the human body and they exceed the number of eukaryotic cells by 10-fold. Metagenomic studies have revealed that the majority of these microbes are found within the gut, playing an important role in the host's digestion and nutrition. The complexity of the animal digestive tract, unculturable microbes, and the lack of genetic tools for most culturable microbes make it challenging to explore the nature of these microbial interactions within this niche. The medicinal leech, Hirudo verbana, has been shown to be a useful tool in overcoming these challenges, due to the simplicity of the microbiome and the availability of genetic tools for one of the two dominant gut symbionts, Aeromonas veronii. In this study, we utilize 16S rRNA gene pyrosequencing to further explore the microbial composition of the leech digestive tract, confirming the dominance of two taxa, the Rikenella-like bacterium and A. veronii. The deep sequencing approach revealed the presence of additional members of the microbial community that suggests the presence of a moderately complex microbial community with a richness of 36 taxa. The presence of a Proteus strain as a newly identified resident in the leech crop was confirmed using fluorescence in situ hybridization (FISH). The metagenome of this community was also pyrosequenced and the contigs were binned into the following taxonomic groups: Rikenella-like (3.1 MB), Aeromonas (4.5 MB), Proteus (2.9 MB), Clostridium (1.8 MB), Eryspelothrix (0.96 MB), Desulfovibrio (0.14 MB), and Fusobacterium (0.27 MB). Functional analyses on the leech gut symbionts were explored using the metagenomic data and MG-RAST. A comparison of the COG and KEGG categories of the leech gut metagenome to that of other animal digestive-tract microbiomes revealed that the leech digestive tract had a similar metabolic potential to the human digestive tract, supporting the usefulness of this system as a model for studying digestive-tract microbiomes. This study lays the foundation for more detailed metatranscriptomic studies and the investigation of symbiont population dynamics.
Digestive-tract microbiota exert tremendous influence over host health. Host-symbiont model systems are studied to investigate how symbioses are initiated and maintained, as well as to identify host processes affected by resident microbiota. The medicinal leech, Hirudo verbana, is an excellent model to address such questions owing to a microbiome that is consistently dominated by two species, Aeromonas veronii and Mucinivorans hirudinis, both of which are cultivable and have sequenced genomes. This review outlines current knowledge about the dynamics of the H. verbana microbiome. We discuss in depth the factors required for A. veronii colonization and proliferation in the leech crop and summarize the current understanding of interactions between A. veronii and its annelid host. Lastly, we discuss leech usage in modern medicine and highlight how leech-therapy associated infections, often attributable to Aeromonas spp., are of growing clinical concern due in part to an increased prevalence of fluoroquinolone resistant strains.
Lipopolysaccharide (LPS) is a bacterial endotoxin and a potent B-cell activator capable of inducing a humoral immune response. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a well-established immunotoxicant that can suppress humoral immune responses, including those initiated by LPS stimulation. In murine models, TCDD-induced suppression of the LPS-activated primary immunoglobulin M (IgM) response is observed both in vivo and in vitro and is typically evaluated as a decrease in the number of IgM antibody-forming cells. The TCDD-induced suppression of the primary humoral immune response occurs, at least in part, upstream of IgM production. The current study was designed as an initial test of our hypothesis that altered DNA methylation, an epigenetic event, is involved in the LPS-induced IgM response by splenocytes as is the suppression of this response by TCDD. Splenocyte-derived DNA from mice treated in vivo with sesame oil + PBS, LPS, TCDD, or LPS + TCDD was used for the current investigation. DNA methylation was evaluated using a technique that permits assessment of the methylation status of multiple genomic regions simultaneously in an unbiased fashion (no specific genes or genomic regions are preselected). Additionally, the expression of selected genes was determined. Our results indicate that treatment with LPS or TCDD can alter DNA methylation and, importantly, combined TCDD + LPS results in altered DNA methylation that was not simply the addition of the changes discerned in the individual treatment groups. Thus, we have identified cross talk between LPS and TCDD at the level of DNA methylation and gene expression.
Diseases caused by the fish pathogens Flavobacterium columnare and Flavobacterium psychrophilum are major contributors of preventable losses in the aquaculture industry. The persistent and difficult to control infections caused by these bacteria make timely intervention and prophylactic elimination of pathogen reservoirs important measures to combat these disease-causing agents. In the present study, we present two independent assays for detecting these pathogens in a range of environmental samples. Natural water samples were inoculated with F. columnare and F. psychrophilum over five orders of magnitude, and pathogen levels were detected using Illumina MiSeq sequencing and droplet digital PCR. Both detection methods accurately identified pathogen-positive samples and showed good agreement in quantifying each pathogen. Additionally, the real-world application of these approaches was demonstrated using environmental samples collected at a rainbow trout ( Oncorhynchus mykiss ) aquaculture facility. These results show that both methods can serve as useful tools for surveillance efforts in aquaculture facilities, where the early detection of these flavobacterial pathogens may direct preventative measures to reduce disease occurrence. Importance Early detection of a deadly disease outbreak in a population can be the difference between mass mortality or mitigated effects. In the present study, we evaluated and compared two molecular techniques for detecting economically impactful aquaculture pathogens. We demonstrate that one of these techniques, 16S rRNA gene sequencing using Illumina MiSeq technology, provides the ability to accurately detect two freshwater fish pathogens, F. columnare and F. psychrophilum , while simultaneously profiling the native microbial community. The second technique, droplet digital PCR, is commonly used for pathogen detection, and the results obtained using the assays we designed with this method served to validate those obtained using the MiSeq method. These two methods offer distinct advantages. The MiSeq method pairs pathogen detection and microbial community profiling to answer immediate and long-term fish health concerns, while droplet digital PCR method provides fast and highly sensitive detection that is useful for surveillance and rapid clinical responses.
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