Biology subjects

Jansson, J. K.

Publications and source records attributed to Jansson, J. K..

3 recordsLinked to original sources

bioRxiv2018

Lactobacillus acidophilus disrupts collaborative multispecies bile acid metabolism

Bile acids are metabolic links between hosts and their gut microbiomes, yet little is known about the roles they play in microbe-to-microbe interactions. Here we present a study designed to investigate the effect that a common probiotic, Lactobacillus acidophilus, has on microbial interactions that lead to formation of secondary bile acids. A model microbial consortium was built from three human gut isolates, Clostridium scindens, Collinsella aerofaciens, and Blautia obeum, and cultured under different bile acid and probiotic treatments. A multi-omics platform that included mass spectrometry-based metabolomics and activity-based proteomic probes was used to produce two major results. The first, was that an uncommon secondary bile acid - ursocholate - was produced by a multi-species chemical synthesis pathway. This result highlights a new microbe-to-microbe interaction mediated by bile acids. The second finding was that the probiotic strain, L. acidophilus, quenched the observed interactions and effectively halted consortial synthesis of ursocholate. Little is known about the role that ursocholate plays in human health and development. However, we did discover that a decrease in ursocholate abundance corresponded with successful weight loss in patients after gastric bypass surgery versus those who did not lose weight after surgery. Hence, this study uncovered basic knowledge that may aid future designs of custom probiotic therapies to combat obesity.

microbiology↗

bioRxiv2018

Dispersal limitation and thermodynamic constraints govern spatial structure of permafrost microbial communities

Understanding drivers of permafrost microbial community composition is critical for understanding permafrost microbiology and predicting ecosystem responses to thaw, however studies describing ecological controls on these communities are lacking. We hypothesize that permafrost communities are uniquely shaped by constraints imposed by prolonged freezing, and decoupled from factors that influence non-permafrost soil communities. To test this hypothesis, we characterized patterns of environmental variation and microbial community composition in permafrost across an Alaskan boreal forest landscape. We used null modeling to estimate the relative importance of selective and neutral assembly processes on community composition, and identified environmental factors influencing ecological selection through regression and structural equation modeling (SEM). Proportionally, the strongest process influencing community composition was dispersal limitation (0.36), exceeding the influence of homogenous selection (0.21), variable selection (0.16), and homogenizing dispersal (0.05). Fe(II) content was the most important factor explaining variable selection, and was significantly associated with total selection by univariate regression (R2=0.14, p=0.003). SEM supported a model in which Fe(II) content mediated influences of the Gibbs free energy of the organic matter pool and organic acid concentration on total selection. These findings reveal that the processes shaping microbial communities in permafrost are distinct from those in non-permafrost soils, as the stability of the permafrost environment imposes dispersal and thermodynamic constraints on permafrost communities. Models of permafrost community composition will need to account for these unique drivers in order to predict community characteristics across permafrost landscapes, and in efforts to understand how pre-thaw conditions will influence post-thaw ecological and biogeochemical processes.

ecology↗

bioRxiv2016

Metabolic and spatio-taxonomic response of uncultivated seafloor bacteria following the Deepwater Horizon oil spill

The release of 700 million liters of oil into the Gulf of Mexico over a few months in 2010 produced dramatic changes in the microbial ecology of the water and sediment. Previous 4 studies have examined the phylogeny and function of these changes, but until now a 5 fundamental examination of the extant hydrocarbon metabolisms that supported these 6 changes had not been performed. Here, we reconstructed the genomes of 57 widespread 7 uncultivated bacteria from post spill sediments, and recovered their gene expression 8 pattern across the seafloor. These genomes comprised a common collection of bacteria 9 that were highly enriched in heavily affected sediments around the wellhead. While rare in distal sediments, some members were still detectable at sites up to 60 km away. Many of these genomes exhibited phylogenetic clustering indicative of common trait selection by the environment, and within half we identified 264 genes associated with hydrocarbon degradation. Observed alkane degradation ability was near ubiquitous among candidate hydrocarbon degraders, while just 3 harbored elaborate gene inventories for the degradation of alkanes and (poly)aromatic hydrocarbons. Differential gene expression profiles revealed a spill-promoted microbial sulfur cycle alongside gene up-regulation associated with polyaromatic hydrocarbon degradation. Gene expression associated with alkane degradation was widespread, although active alkane degrader identities changed along the pollution gradient. The resulting analysis suggests a broad metabolic capacity to respond to oil exists across a large array of usually rare bacteria.

microbiology↗