In this paper, we describe the microbial composition and their predictive metabolic profile in the sea urchin Lytechinus variegatus gut ecosystem along with samples from its habitat by using NextGen amplicon sequencing and downstream bioinformatics analyses. The microbial communities of the gut tissue revealed a near-exclusive abundance of Campylobacteraceae, whereas the pharynx tissue consisted of Tenericutes, followed by Gamma-, Alpha- and Epsilonproteobacteria at approximately equal capacities. The gut digesta and egested fecal pellets exhibited a microbial profile comprised of Gammaproteobacteria, mainly Vibrio, and Bacteroidetes. Both the seagrass and surrounding sea water revealed Alpha- and Betaproteobacteria. Bray-Curtis distances of microbial communities indicated a clustering profile with low intrasample variation. Predictive metagenomics performed on the microbial communities revealed that the gut tissue had high relative abundances of metabolisms assigned to the KEGG-Level-2 designation of energy metabolisms compared to the gut digesta, which had higher carbohydrate, amino acid and lipid metabolisms. Overall, the results of this study elaborate the spatial distribution of microbial communities in the gut ecosystem of L. variegatus, and specifically a selective attribute for Campylobacteraceae in the gut tissue. Also, the predictive functional significance of bacterial communities in uniquely compartmentalized gut ecosystems of L. variegatus has been described.

In this study, we have examined the bacterial community composition of the laboratory cultured sea urchin Lytechinus variegatus gut microbiome and its culture environment using NextGen amplicon sequencing of the V4 segment of the 16S rRNA gene, and downstream bioinformatics tools. Overall, the gut and tank water was dominated by Proteobacteria, whereas the feed consisted of a co-occurrence of Proteobacteria and Firmicutes at a high abundance. The gut tissue represented Epsilonproteobacteria as dominant, with order Campylobacterales at the highest relative abundance (>95%). However, the pharynx tissue was dominated by class Alphaproteobacteria. The gut digesta and egested fecal pellets had a high abundance of class Gammaproteobacteria, from which Vibrio was found to be the primary genus, and Epsilonproteobacteria, with genus Arcobacter occurring at a moderate level. At the class level, the tank water was dominated by Gammaproteobacteria, and the feed by Alphaproteobacteria. Multi-Dimensional Scaling analysis showed that the microbial community of the gut tissue clustered together, as did the pharynx tissue to the feed. The gut digesta and egested fecal pellets showed a similarity relationship to the tank water. Further analysis of Campylobacterales at a lower taxonomic level using the oligotyping method revealed 37 unique types across the 10 samples, where Oligotype 1 was primarily represented in the gut tissue. BLAST analysis identified Oligotype 1 to be Arcobacter sp., Sulfuricurvum sp., and Arcobacter bivalviorum at an identity level >90%. This study showed that although distinct microbial communities are evident across multiple components of the sea urchin gut ecosystem, there is a noticeable correlation between the overall microbial communities of the gut with the sea urchin L. variegatus culture environment.

To further understand the impact of antibiotics on the gastrointestinal tract microbial community, the intra-individual recovery pattern of specific microbial strains was determined using metagenomic sequencing coupled with strain-tracking analyses. In a study where 18 individuals were administered a single antibiotic (cefprozil), new microbial genomic variants (herein strains) were transiently detected in 15 individuals, while in a second study that used a cocktail of three antibiotics (meropenem, gentamicin, and vancomycin), all 12 participants had either permanent or transient strain changes. The presence of distinct microbial genomic variants indicates a pattern of strain recovery that is intra-individual specific following disruption of the human gastrointestinal tract with antibiotics.

In this study, we report the distribution of microbial taxa and their predicted metabolic functions observed in the top (U1), middle (U2), and inner (U3) decadal growth laminae of a unique large conical microbial mat from perennially ice-covered Lake Untersee of East Antarctica, using NextGen sequencing of the 16S rRNA gene and bioinformatics tools. The results showed that the U1 lamina was dominated by cyanobacteria, specifically Phormidium sp., Leptolyngbya sp., and Pseudanabaena sp. The U2 and U3 laminae had high abundances of Actinobacteria, Verrucomicrobia, Proteobacteria, and Bacteroidetes. Closely related taxa within each abundant bacterial taxon found in each lamina were further differentiated at the highest taxonomic resolution using the oligotyping method. PICRUSt analysis, which determines predicted KEGG functional categories from the gene contents and abundances among microbial communities, revealed a high number of sequences belonging to carbon fixation, energy metabolism, cyanophycin, chlorophyll, and photosynthesis proteins in the U1 lamina. The functional predictions of the microbial communities in U2 and U3 represented signal transduction, membrane transport, zinc transport and amino acid-, carbohydrate-, and arsenic- metabolisms. The Nearest Sequenced Taxon Index (NSTI) values processed through PICRUSt were 0.10, 0.13, and 0.11 for U1, U2, and U3 laminae, respectively. These values indicated a close correspondence with the reference microbial genome database, implying high confidence in the predicted metabolic functions of the microbial communities in each lamina. The distribution of microbial taxa observed in each lamina and their predicted metabolic functions provides additional insight into the complex microbial ecosystem at Lake Untersee, and lays the foundation for studies that will enhance our understanding of the mechanisms responsible for the formation of these unique mat structures and their evolutionary significance.

The microbiome of sea urchins plays a role in maintaining digestive health and innate immunity. Here, we investigated the effects of long-term (90 day) exposure to elevated seawater temperatures on the microbiome of the common, subtropical sea urchin The community composition and diversity of microbes varied according to the type of sample collected from the sea urchin (seawater, feed, intestines, coelomic fluid, digested pellet and faeces), with the lowest microbial diversity (predominately the order Campylobacterales) located in the intestinal tissue. Sea urchins exposed to near-future seawater temperatures maintained the community structure and diversity of microbes associated with their tissues. However, marginal, non-significant shifts in microbial community structure with elevated temperature resulted in significant changes in predicted metagenomic functions such as membrane transport and amino acid and carbohydrate metabolism. The predicted changes in key metabolic categories suggest that near-future climate-induced increases in seawater temperature could shift microbial community function and impact sea urchin digestive and immune physiology.

BackgroundGiven the increasing realization of the important functions of the gut microbial community in human health, it is important to determine whether the increased age of the host coupled with inevitable environmental changes can alter the stability of individual microbial strains of the gut microbial community. Since early studies demonstrated that pairs of twins possess the related gut microbial communities, to gain insights into the temporal stability of the reservoir of gut microbial strains in humans, we have assessed the strain relatedness of samples from two previously published data sets that were obtained from twin children and adults (36–80 years old) who have been either living together or apart for different times.MethodsWe analyzed the two data sets; twin children (n = 24) and adults (n = 50) using our previously developed strain-tracking program called Window-based Single Nucleotide Variant (SNV) Similarity (WSS) that can distinguish a related strain pair from a non-related strain pair based on the overall genome-wide SNV similarity. To independently substantiate the identification of distinct microbial genomic variants (herein strains) observed from WSS analysis, we used analysis by StrainPhlAn.ResultsAnalysis of the twin children data set revealed a significantly (P-value <0.05) higher number of the shared strain pairs with a predominance of Bacteroides vulgatus between individual sets of twin pairs than the twin adult data set. Additional analysis on the adult twins showed that twins who have been living apart less than 10 years shared significantly more related strain pairs than twins living apart between 10 to 60 years. Eighty-year-old twins who had been living together for 79 years then separated for 1 year showed the highest number of related strain pairs consisting of B. vulgatus, Eubacterium eligens, and Bifidobacterium adolescentis. The next highest number of related strain pairs was found in 56-year-old twins who had been living together for 51 years then separated for 5 years (B. vulgatus and Coprococcus eutactus as related strains), 73-year-old twins living together for 66 years and then separated for 7 years (Bacteroides uniformis and Clostrium sp. L2-50 as related strains) and 36-year-old twins separated for 19 years (shared strains of Alistipes shahii and E. eligens). Finally, a sporadic appearance of a single shared strain that did not show a correlation with time of separation was observed in three twin sets that had separation times between 22 to 54 years.ConclusionWe conclude from our strain-tracking analysis of twins that certain gut microbial strains can be shared between individuals in some cases for decades. Changes in the host environmental conditions over time can impact the stability landscape of the gut microbial community resulting in the appearance of new strains that could potentially impact microbe interactions that are essential for function in human health.

In this study, using NextGen sequencing of the collective 16S rRNA genes obtained from two sets of samples collected from Lake Obersee, Antarctica, we compared and contrasted two bioinformatics tools, PICRUSt and Tax4Fun. We then developed an R script to assess the taxonomic and predictive functional profiles of the microbial communities within the samples. Taxa such as Pseudoxanthomonas, Planctomycetaceae, Cyanobacteria Subsection III, Nitrosomonadaceae, Leptothrix, and Rhodobacter were exclusively identified by Tax4Fun that uses SILVA database; whereas PICRUSt that uses Greengenes database uniquely identified Pirellulaceae, Gemmatimonadetes A1–B1, Pseudanabaena, Salinibacterium and Sinobacteraceae. Predictive functional profiling of the microbial communities using Tax4Fun and PICRUSt separately revealed common metabolic capabilities, while also showing specific functional IDs not shared between the two approaches. Combining these functional predictions using a customized R script revealed a more inclusive metabolic profile, such as hydrolases, oxidoreductases, transferases; enzymes involved in carbohydrate and amino acid metabolisms; and membrane transport proteins known for nutrient uptake from the surrounding environment. Our results present the first molecular-phylogenetic characterization and predictive functional profiles of the microbial mat communities in Lake Obersee, while demonstrating the efficacy of combining both the taxonomic assignment information and functional IDs using the R script created in this study for a more streamlined evaluation of predictive functional profiles of microbial communities.

In this study, we examined the responses by the indigenous bacterial communities in salt-marsh sediment microcosms in vitro following treatment with Mississippi Canyon Block 252 oil (MC252). Microcosms were constructed of sediment and seawater collected from Bayou La Batre located in coastal Alabama on the Gulf of Mexico. We used an amplicon pyrosequencing approach on microcosm sediment metagenome targeting the V3–V5 region of the 16S rRNA gene. Overall, we identified a shift in the bacterial community in three distinct groups. The first group was the early responders (orders Pseudomonadales and Oceanospirillales within class Gammaproteobacteria), which increased their relative abundance within 2 weeks and were maintained 3 weeks after oil treatment. The second group was identified as early, but transient responders (order Rhodobacterales within class Alphaproteobacteria; class Epsilonproteobacteria), which increased their population by 2 weeks, but returned to the basal level 3 weeks after oil treatment. The third group was the late responders (order Clostridiales within phylum Firmicutes; order Methylococcales within class Gammaproteobacteria; and phylum Tenericutes), which only increased 3 weeks after oil treatment. Furthermore, we identified oil-sensitive bacterial taxa (order Chromatiales within class Gammaproteobacteria; order Syntrophobacterales within class Deltaproteobacteria), which decreased in their population after 2 weeks of oil treatment. Detection of alkane (alkB), catechol (C2,3DO) and biphenyl (bph) biodegradation genes by PCR, particularly in oil-treated sediment metacommunity DNA, delineates proliferation of  the hydrocarbon degrading bacterial community. Overall, the indigenous bacterial communities in our salt-marsh sediment in vitro microcosm study responded rapidly and shifted towards members of the taxonomic groups that are capable of surviving in an MC252 oil-contaminated environment.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-014-0233-x) contains supplementary material, which is available to authorized users.