title: Characterization of Clostridium ljungdahlii OTA1: a non-autotrophic hyper ethanol-producing strain.
abstract: A Clostridium ljungdahlii lab-isolated spontaneous-mutant strain, OTA1, has been shown to produce twice as much ethanol as the C. ljungdahlii ATCC 55383 strain when cultured in a mixotrophic medium containing fructose and syngas. Whole-genome sequencing identified four unique single nucleotide polymorphisms (SNPs) in the C. ljungdahlii OTA1 genome. Among these, two SNPs were found in the gene coding for AcsA and HemL, enzymes involved in acetyl-CoA formation from CO/CO2. Homology models of the respective mutated enzymes revealed alterations in the size and hydrogen bonding of the amino acids in their active sites. Failed attempts to grow OTA1 autotrophically suggested that one or both of these mutated genes prevented acetyl-CoA synthesis from CO/CO2, demonstrating that its activity was required for autotrophic growth by C. ljungdahlii. An inoperable Wood-Ljungdahl pathway resulted in higher CO2and ethanol yields and lower biomass and acetate yields compared to WT for multiple growth conditions including heterotrophic and mixotrophic conditions. The two other SNPs identified in the C. ljungdahlii OTA1 genome were in genes coding for transcriptional regulators (CLJU_c09320 and CLJU_c18110) and were found to be responsible for deregulated expression of co-localized arginine catabolism and 2-deoxy-D-ribose catabolism genes. Growth medium supplementation experiments suggested that increased arginine metabolism and 2-deoxy-D-ribose were likely to have minor effects on biomass and fermentation product yields. In addition, in silico flux balance analysis simulating mixotrophic and heterotrophic conditions showed no change in flux to ethanol when flux through HemL was changed whereas limited flux through AcsA increased the ethanol flux for both simulations. In characterizing the effects of the SNPs identified in the C. ljungdahlii OTA1 genome, a non-autotrophic hyper ethanol-producing strain of C. ljungdahlii was identified that has utility for further physiology and strain performance studies and as a biocatalyst for industrial applications.
authors.affiliation: Department of Plant and Microbial Biology, North Carolina State University, 4548 Thomas Hall, Campus Box 7615, Raleigh, NC, 27695-7615, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Whitham
authors.affiliation: Department of Chemical and Biomolecular Engineering, 196 Golden LEAF Biomanufacturing Training and Education Center, North Carolina State University, Raleigh, NC, 27695, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Schulte
authors.affiliation: Duke University NMR Center, Duke University Medical Center, Duke University, Durham, NC, 27710, USA.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Bobay
authors.affiliation: Department of Plant and Microbial Biology, North Carolina State University, 4548 Thomas Hall, Campus Box 7615, Raleigh, NC, 27695-7615, USA.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Bruno-Barcena
authors.affiliation: Department of Biological and Agricultural Engineering, North Carolina State University, 277 Weaver Labs, Campus Box 7625, Raleigh, NC, 27695-7625, USA.
authors.forename: Mari S
authors.initials: MS
authors.lastname: Chinn
authors.affiliation: Department of Chemical and Biomolecular Engineering, 196 Golden LEAF Biomanufacturing Training and Education Center, North Carolina State University, Raleigh, NC, 27695, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Flickinger
authors.affiliation: Department of Forest Biomaterials, North Carolina State University, 2028C Biltmore Hall, Campus Box 8001, Raleigh, NC, 27695-8001, USA.
authors.forename: Joel J
authors.initials: JJ
authors.lastname: Pawlak
authors.affiliation: Department of Plant and Microbial Biology, North Carolina State University, 4548 Thomas Hall, Campus Box 7615, Raleigh, NC, 27695-7615, USA. amy_grunden@ncsu.edu.
authors.forename: Amy M
authors.identifier: http://orcid.org/0000-0002-8025-753X
authors.initials: AM
authors.lastname: Grunden
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002248:Carbon Monoxide / Q000378:metabolism; D003013:Clostridium / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism
chemical_list: D009097:Multienzyme Complexes; D002245:Carbon Dioxide; D000431:Ethanol; D000105:Acetyl Coenzyme A; D002248:Carbon Monoxide; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase
keywords: Acetyl-coA; Carbon monoxide dehydrogenase; Clostridium ljungdahlii; Ethanol; Wood-Ljungdahl pathway