Project description:Human skin microbiome dysbiosis can have clinical consequences. Characterizing taxonomic composition of bacterial communities associated with skin disorders is important for dermatological advancement in both diagnosis and novel treatments. This study aims to analyze and improve the accuracy of taxonomic classification of skin bacteria with MinION™ nanopore sequencing using a defined skin mock community and a skin microbiome sample. We compared the Oxford Nanopore Technologies recommended procedures and concluded that their protocols highly bias the relative abundance of certain skin microbiome genera, most notably a large overrepresentation of Staphylococcus and underrepresentation of Cutibacterium and Corynebacterium. We demonstrated that changes in the amplification protocols improved the accuracy of the taxonomic classification for these three main skin bacterial genera. This study shows that MinION™ nanopore could be an efficient technology for full-length 16S rRNA sequencing; however, the analytical advantage is strongly influenced by the methodologies. The suggested alternatives in the sample processing improved characterization of a complex skin microbiome community using MinION™ nanopore sequencing.
Project description:The emergence of massively parallel sequencing technology has revolutionized microbial profiling, allowing the unprecedented comparison of microbial diversity across time and space in a wide range of host-associated and environmental ecosystems. Although the high-throughput nature of such methods enables the detection of low-frequency bacteria, these advances come at the cost of sequencing read length, limiting the phylogenetic resolution possible by current methods. Here, we present a generic approach for integrating short reads from large genomic regions, thus enabling phylogenetic resolution far exceeding current methods. The approach is based on a mapping to a statistical model that is later solved as a constrained optimization problem. We demonstrate the utility of this method by analyzing human saliva and Drosophila samples, using Illumina single-end sequencing of a 750 bp amplicon of the 16S rRNA gene. Phylogenetic resolution is significantly extended while reducing the number of falsely detected bacteria, as compared with standard single-region Roche 454 Pyrosequencing. Our approach can be seamlessly applied to simultaneous sequencing of multiple genes providing a higher resolution view of the composition and activity of complex microbial communities.
Project description:Amphibian populations around the world are threatened by an emerging infectious pathogen, the chytrid fungus Batrachochytrium dendrobatidis (Bd). How can a fungal skin infection kill such a broad range of amphibian hosts? And why are certain species particularly susceptible to the impacts of Bd? Here we use a genomics approach to understand the genetic response of multiple susceptible frog species to Bd infection. We characterize the transcriptomes of two closely-related endangered frog species (Rana muscosa and Rana sierrae) and analyze whole genome expression profiles from frogs in controlled Bd-infection experiments. We integrate the Rana results with a comparable dataset from a more distantly-related susceptible species (Silurana tropicalis). We demonstrate that Bd-infected frogs show massive disruption of skin function and show no evidence of a robust immune response. The genetic response to infection is shared across the focal susceptible species, suggesting a common effect of Bd on susceptible frogs. A total of five (12-plex) chips were analyzed from 60 samples comprising 2 conditions (control and infected), 3 tissues (skin, liver and spleen) and 2 timepoints (early and late). Three biological replicates were used for each condition and tissue at each time point. Twentyfour arrays were analyzed for skin samples, 24 for liver, and 12 for spleen. The same dye, Cy5, was used for all samples.
Project description:Many terrestrial ectotherms have gone to great evolutionary lengths to adapt to long cold winters; some have even evolved the ability to tolerate the freezing of most of the water in the body. Now, however, high-elevation, and high-latitude winters are experiencing an accelerated period of warming. Specialized winter adaptations that promoted fitness in a seasonally frozen environment may soon be superfluous or even maladaptive. We ask whether winter adaptations include changes in immune functions, and whether changing winter conditions could exert disparate effects on populations of a wide-ranging terrestrial ectotherm, the wood frog (Lithobates sylvaticus). By rearing wood frogs from ancestral winter environments that vary in length and temperature in a common garden, and reciprocally crossing post-metamorphic frogs into unfrozen and frozen artificial winter conditions in the lab, we were able to decompose transcriptomic differences in ventral skin gene expression into those that were environmentally induced (responsive to temperature), genetically determined, and those that varied as an interaction between genotype and environment. We found that frogs from harsh ancestral winter environments upregulated immune processes, including cellular immunity, inflammatory processes, and adaptive immune processes, as compared to frogs from mild ancestral winter environments. Further, we saw that expression of several genes varied in an interaction between genotype and artificial winter environment, a pattern that was recapitulated at the level of hepatosomatic index (the proportion of body mass comprising liver). We suggest that just as winter climates likely served as the selective force resulting in remarkable winter adaptations such as freeze tolerance, they also induced constitutive changes in immune gene expression.
Project description:BackgroundUsefulness of next-generation sequencing (NGS) in assessing bacteria associated with oral squamous cell carcinoma (OSCC) has been undermined by inability to classify reads to the species level.ObjectiveThe purpose of this study was to develop a robust algorithm for species-level classification of NGS reads from oral samples and to pilot test it for profiling bacteria within OSCC tissues.MethodsBacterial 16S V1-V3 libraries were prepared from three OSCC DNA samples and sequenced using 454's FLX chemistry. High-quality, well-aligned, and non-chimeric reads ≥350 bp were classified using a novel, multi-stage algorithm that involves matching reads to reference sequences in revised versions of the Human Oral Microbiome Database (HOMD), HOMD extended (HOMDEXT), and Greengene Gold (GGG) at alignment coverage and percentage identity ≥98%, followed by assignment to species level based on top hit reference sequences. Priority was given to hits in HOMD, then HOMDEXT and finally GGG. Unmatched reads were subject to operational taxonomic unit analysis.ResultsNearly, 92.8% of the reads were matched to updated-HOMD 13.2, 1.83% to trusted-HOMDEXT, and 1.36% to modified-GGG. Of all matched reads, 99.6% were classified to species level. A total of 228 species-level taxa were identified, representing 11 phyla; the most abundant were Proteobacteria, Bacteroidetes, Firmicutes, Fusobacteria, and Actinobacteria. Thirty-five species-level taxa were detected in all samples. On average, Prevotella oris, Neisseria flava, Neisseria flavescens/subflava, Fusobacterium nucleatum ss polymorphum, Aggregatibacter segnis, Streptococcus mitis, and Fusobacterium periodontium were the most abundant. Bacteroides fragilis, a species rarely isolated from the oral cavity, was detected in two samples.ConclusionThis multi-stage algorithm maximizes the fraction of reads classified to the species level while ensuring reliable classification by giving priority to the human, oral reference set. Applying the algorithm to OSCC samples revealed high diversity. In addition to oral taxa, a number of human, non-oral taxa were also identified, some of which are rarely detected in the oral cavity.
Project description:Here we present clear patterns of age-associated changes in DNA methylation in the aquatic vertebrate species Xenopus tropicalis. We selected approximately 3500 sites highly correlated with age from WGBS data from 9 frogs of 3 different age groups (young, approx. 1 year old; mature, approx. 5 years old; old, approx. 9 years old - GSE221656) and designed probes for the development of cost effective targeted bisulfite sequencing (TBSeq) assay. Here, we present the TBSeq assay in sixteen different frogs as a pilot experiment to validate our previous findings.