02397nas a2200169   4500008004100000245010300041210006900144300001600213490000700229520184400236100001602080700001702096700001602113700001802129700001802147856006202165       2016                        eng d00aSpatial and successional dynamics of microbial biofilm communities in a grassland stream ecosystem0 aSpatial and successional dynamics of microbial biofilm communiti  a4674 - 46880 v253 aBiofilms represent a metabolically active and structurally complex component of freshwater ecosystems. Ephemeral prairie streams are hydrologically harsh and prone to frequent perturbation. Elucidating both functional and structural community changes over time within prairie streams provides a general understanding of microbial responses to environmental disturbance. We examined microbial succession of biofilm communities at three sites in a third-order stream at Konza Prairie over a 2- to 64-day period. Microbial abundance (bacterial abundance, chlorophyll a concentrations) increased and never plateaued during the experiment. Net primary productivity (net balance of oxygen consumption and production) of the developing biofilms did not differ statistically from zero until 64 days suggesting a balance of the use of autochthonous and allochthonous energy sources until late succession. Bacterial communities (MiSeq analyses of the V4 region of 16S rRNA) established quickly. Bacterial richness, diversity and evenness were high after 2 days and increased over time. Several dominant bacterial phyla (Beta-, Alphaproteobacteria, Bacteroidetes, Gemmatimonadetes, Acidobacteria, Chloroflexi) and genera (Luteolibacter, Flavobacterium, Gemmatimonas, Hydrogenophaga) differed in relative abundance over space and time. Bacterial community composition differed across both space and successional time. Pairwise comparisons of phylogenetic turnover in bacterial community composition indicated that early-stage succession (≤16 days) was driven by stochastic processes, whereas later stages were driven by deterministic selection regardless of site. Our data suggest that microbial biofilms predictably develop both functionally and structurally indicating distinct successional trajectories of bacterial communities in this ecosystem.1 aVeach, A.M.1 aStagen, J.C.1 aBrown, S.P.1 aDodds, W., K.1 aJumpponen, A.  uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/mec.1378402088nas a2200253   4500008004100000245008500041210006900126300001300195490000700208520131900215653001001534653003101544653001901575653001401594100001601608700001601624700002201640700001401662700001901676700001701695700001701712700001801729856008701747       2015                        eng d00aScraping the bottom of the barrel: are rare high throughput sequences artifacts?0 aScraping the bottom of the barrel are rare high throughput seque  a221 -2250 v133 a<p>Metabarcoding data generated using next-generation sequencing (NGS) technologies are overwhelmed with rare taxa and skewed in Operational Taxonomic Unit (OTU) frequencies comprised of few dominant taxa. Low frequency OTUs comprise a rare biosphere of singleton and doubleton OTUs, which may include many artifacts. We present an in-depth analysis of global singletons across sixteen NGS libraries representing different ribosomal RNA gene regions, NGS technologies and chemistries. Our data indicate that many singletons (average of 38 % across gene regions) are likely artifacts or potential artifacts, but a large fraction can be assigned to lower taxonomic levels with very high bootstrap support (&sim;32 % of sequences to genus with &ge;90 % bootstrap cutoff). Further, many singletons clustered into rare OTUs from other datasets highlighting their overlap across datasets or the poor performance of clustering algorithms. These data emphasize a need for caution when discarding rare sequence data en masse: such practices may result in throwing the baby out with the bathwater, and underestimating the biodiversity. Yet, the rare sequences are unlikely to greatly affect ecological metrics. As a result, it may be prudent to err on the side of caution and omit rare OTUs prior to downstream analyses.</p>10afungi10aHigh-throughput sequencing10aRare biosphere10aSingleton1 aBrown, S.P.1 aVeach, A.M.1 aRigdon-Huss, A.R.1 aGrond, K.1 aLickteig, S.K.1 aLothamer, K.1 aOliver, A.K.1 aJumpponen, A.  uhttps://www.sciencedirect.com/science/article/abs/pii/S1754504814001068?via%3Dihub