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Title: Light Regimes Shape Utilization of Extracellular Organic C and N in a Cyanobacterial Biofilm

Here it is becoming clear that many microbial primary producers can also play a role as organic consumers, we know very little about the metabolic regulation of photoautotroph organic matter consumption. Cyanobacteria in phototrophic biofilms can reuse extracellular organic carbon, but the metabolic drivers of extracellular processes are surprisingly complex. We investigated the metabolic foundations of organic matter reuse by comparing exoproteome composition and incorporation of 13C-labeled and 15N-labeled cyanobacterial extracellular organic matter (EOM) in a unicyanobacterial biofilm incubated using different light regimes. In the light and the dark, cyanobacterial direct organic C assimilation accounted for 32% and 43%, respectively, of all organic C assimilation in the community. Under photosynthesis conditions, we measured increased excretion of extracellular polymeric substances (EPS) and proteins involved in micronutrient transport, suggesting that requirements for micronutrients may drive EOM assimilation during daylight hours. This interpretation was supported by photosynthesis inhibition experiments, in which cyanobacteria incorporated N-rich EOM-derived material. In contrast, under dark, C-starved conditions, cyanobacteria incorporated C-rich EOM-derived organic matter, decreased excretion of EPS, and showed an increased abundance of degradative exoproteins, demonstrating the use of the extracellular domain for C storage. Sequence-structure modeling of one of these exoproteins predicted a specific hydrolytic activity thatmore » was subsequently detected, confirming increased EOM degradation in the dark. Associated heterotrophic bacteria increased in abundance and upregulated transport proteins under dark relative to light conditions. Taken together, our results indicate that biofilm cyanobacteria are successful competitors for organic C and N and that cyanobacterial nutrient and energy requirements control the use of EOM.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [1] ;  [2] ;  [3] ;  [1] ; ORCiD logo [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. NASA Ames Research Center, Moffett Field, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-682499
Journal ID: ISSN 2150-7511
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
mBio (Online)
Additional Journal Information:
Journal Name: mBio (Online); Journal Volume: 7; Journal Issue: 3; Journal ID: ISSN 2150-7511
Publisher:
American Society for Microbiology
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 59 BASIC BIOLOGICAL SCIENCES; 09 BIOMASS FUELS
OSTI Identifier:
1367966

Stuart, Rhona K., Mayali, Xavier, Boaro, Amy A., Zemla, Adam, Everroad, R. Craig, Nilson, Daniel, Weber, Peter K., Lipton, Mary, Bebout, Brad M., Pett-Ridge, Jennifer, and Thelen, Michael P.. Light Regimes Shape Utilization of Extracellular Organic C and N in a Cyanobacterial Biofilm. United States: N. p., Web. doi:10.1128/mBio.00650-16.
Stuart, Rhona K., Mayali, Xavier, Boaro, Amy A., Zemla, Adam, Everroad, R. Craig, Nilson, Daniel, Weber, Peter K., Lipton, Mary, Bebout, Brad M., Pett-Ridge, Jennifer, & Thelen, Michael P.. Light Regimes Shape Utilization of Extracellular Organic C and N in a Cyanobacterial Biofilm. United States. doi:10.1128/mBio.00650-16.
Stuart, Rhona K., Mayali, Xavier, Boaro, Amy A., Zemla, Adam, Everroad, R. Craig, Nilson, Daniel, Weber, Peter K., Lipton, Mary, Bebout, Brad M., Pett-Ridge, Jennifer, and Thelen, Michael P.. 2016. "Light Regimes Shape Utilization of Extracellular Organic C and N in a Cyanobacterial Biofilm". United States. doi:10.1128/mBio.00650-16. https://www.osti.gov/servlets/purl/1367966.
@article{osti_1367966,
title = {Light Regimes Shape Utilization of Extracellular Organic C and N in a Cyanobacterial Biofilm},
author = {Stuart, Rhona K. and Mayali, Xavier and Boaro, Amy A. and Zemla, Adam and Everroad, R. Craig and Nilson, Daniel and Weber, Peter K. and Lipton, Mary and Bebout, Brad M. and Pett-Ridge, Jennifer and Thelen, Michael P.},
abstractNote = {Here it is becoming clear that many microbial primary producers can also play a role as organic consumers, we know very little about the metabolic regulation of photoautotroph organic matter consumption. Cyanobacteria in phototrophic biofilms can reuse extracellular organic carbon, but the metabolic drivers of extracellular processes are surprisingly complex. We investigated the metabolic foundations of organic matter reuse by comparing exoproteome composition and incorporation of 13C-labeled and 15N-labeled cyanobacterial extracellular organic matter (EOM) in a unicyanobacterial biofilm incubated using different light regimes. In the light and the dark, cyanobacterial direct organic C assimilation accounted for 32% and 43%, respectively, of all organic C assimilation in the community. Under photosynthesis conditions, we measured increased excretion of extracellular polymeric substances (EPS) and proteins involved in micronutrient transport, suggesting that requirements for micronutrients may drive EOM assimilation during daylight hours. This interpretation was supported by photosynthesis inhibition experiments, in which cyanobacteria incorporated N-rich EOM-derived material. In contrast, under dark, C-starved conditions, cyanobacteria incorporated C-rich EOM-derived organic matter, decreased excretion of EPS, and showed an increased abundance of degradative exoproteins, demonstrating the use of the extracellular domain for C storage. Sequence-structure modeling of one of these exoproteins predicted a specific hydrolytic activity that was subsequently detected, confirming increased EOM degradation in the dark. Associated heterotrophic bacteria increased in abundance and upregulated transport proteins under dark relative to light conditions. Taken together, our results indicate that biofilm cyanobacteria are successful competitors for organic C and N and that cyanobacterial nutrient and energy requirements control the use of EOM.},
doi = {10.1128/mBio.00650-16},
journal = {mBio (Online)},
number = 3,
volume = 7,
place = {United States},
year = {2016},
month = {6}
}