Bacteria live in environments containing complex ecologies of other microbes that communicate and survive through the action of a variety of small metabolic compounds. One common yet relatively unstudied metabolite is guanidine. Although it can be toxic to cells, recent studies have revealed that guanidine may function as a cellular metabolite through a specialized RNA sequence known as a riboswitch. Within our overall project on improving algal productivity, the focus of this study is to: (a) describe various guanidine riboswitch sequences in bacteria that interact with biofuel producing algae; and (b) determine if guanidine has a positive or negative influence on the growth of the bacteria containing these riboswitches.

Over 2,000 species across four phyla of bacteria contain genes that help overcome guanidine toxicity. Recently it was discovered that guanidine, a small molecule with three nitrogen linked to a single carbon, regulates some of these genes by specific interactions with a segment of mRNA called a riboswitch. In this investigation, we used the largely uncharacterized cyanobacterium ESFC-1, and others across the four phyla, that contain the guanidine riboswitch, of which there are two subtypes. Both of these two subtypes regulate expression of proteins involved in the export and modification of guanidine inside the bacterial cell.

Genome sequence analysis of our guanidine riboswitches indicate that our test bacteria differ in four key highly conserved residues for a guanidine-binding pocket in the model riboswitch. However, structures of the riboswitches may be similar, indicating their functions and guanidine-binding capabilities may be similar.


Environmental Microbiology and Microbial Ecology | Microbiology


Michael P. Thelen

Lab site

Lawrence Livermore National Laboratory (LLNL)

Funding Acknowledgement

The 2018 STEM Teacher and Researcher Program and this project have been made possible through support from Chevron (www.chevron.com), the National Marine Sanctuary Foundation (www.marinesanctuary.org), the National Science Foundation through the Robert Noyce Program under Grant #1836335 and 1340110, the California State University Office of the Chancellor, and California Polytechnic State University in partnership with Lawrence Livermore National Laboratory. Work at LLNL was performed under the auspices of the U.S. Department of Energy under Contract DE-AC52-07NA-27344. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funders. LLNL-POST-757483



URL: https://digitalcommons.calpoly.edu/star/523


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