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K-State Today

October 25, 2018

University of Nebraska Medical Center's Laurey Steinke to present Division of Biology Seminar Oct. 26

Submitted by Division of Biology

Laurey Steinke, University of Nebraska Medical Center, will present "Demonstration of carbon fixation using short-term, stable-isotope probing of proteins in members of a thermophilic microbial biofilm associated with Mushroom Spring, Yellowstone National Park" as part of the Division of Biology Seminar series at 4 p.m. Friday, Oct. 26, in 221 Ackert Hall.

Steinke will lecture on the sunlight-fueled microbial mat associated with Mushroom Spring, an alkaline siliceous hot spring of Yellowstone National Park is a biofilm consisting eight major taxa. Synechococcus spp. (oxygenic, photoautotrophic, cyanobacteria) are the major community members that fix inorganic carbon, but some evidence suggests that anoxygenic Roseiflexus spp. also contribute to carbon fixation during low-light anoxic morning periods. To test this hypothesis, and to follow the light-dependent pathway of inorganic carbon incorporation into different taxa, mat samples were incubated in situ with 13C-bicarbonate for 3 h while the mat was shaded between sunrise and illumination by direct sunlight. Extracted proteins were treated with trypsin and analyzed by mass spectrometry, leading to peptide identifications and peptide isotopic profile signatures containing evidence of 13C-label incorporation. A total of 25,483 peptides, corresponding to 7,221 proteins, were identified from spectral features and associated with mat taxa by comparison to metagenomic assembly sequences. 1,417 peptides, derived from 720 proteins, were labeled by 13C. Incorporation of 13C was observed for proteins from both Synechococcus spp. and Roseiflexus spp.; chaperones and proteins of carbohydrate metabolism were most abundantly labeled. No bias toward labeling of particular amino acids was observed and abundant proteins were not all labeled, while some less abundant proteins exhibited labeling. The described metaproteomics-stable-isotope-labeling approach provides a way to demonstrate which proteins are synthesized by specific taxa under the incubation conditions. Total proteins identified are compared to the proteins synthesized in the early morning time period. In Roseiflexus spp., peptides associated with protein folding and protein synthesis were labeled in the early-morning incubation, along with the hydroxypropionate pathway of carbon fixation. In Synechococcus spp. labeled peptides associated with carbohydrate metabolism and protein folding were detected, along with proteins associated with nitrogen fixation, photosynthesis and transport.

In conclusion, both Synechococcus and Roseiflexus spp. incorporate inorganic carbon during the early morning anoxic time period, however the proteins synthesized are not all associated with the same functions in the two organisms.

If you would like to visit with Steinke, please contact Ari Jumpponen at ari@k-state.edu