title: Toxin YafQ Reduces Escherichia coli Growth at Low Temperatures.
abstract: Toxin/antitoxin (TA) systems reduce metabolism under stress; for example, toxin YafQ of the YafQ/DinJ Escherichia coli TA system reduces growth by cleaving transcripts with in-frame 5'-AAA-G/A-3' sites, and antitoxin DinJ is a global regulator that represses its locus as well as controls levels of the stationary sigma factor RpoS. Here we investigated the influence on cell growth at various temperatures and found that deletion of the antitoxin gene, dinJ, resulted in both reduced metabolism and slower growth at 18°C but not at 37°C. The reduction in growth could be complemented by producing DinJ from a plasmid. Using a transposon screen to reverse the effect of the absence of DinJ, two mutations were found that inactivated the toxin YafQ; hence, the toxin caused the slower growth only at low temperatures rather than DinJ acting as a global regulator. Corroborating this result, a clean deletion of yafQ in the ΔdinJ ΔKmR strain restored both metabolism and growth at 18°C. In addition, production of YafQ was more toxic at 18°C compared to 37°C. Furthermore, by overproducing all the E. coli proteins, the global transcription repressor Mlc was found that counteracts YafQ toxicity only at 18°C. Therefore, YafQ is more effective at reducing metabolism at low temperatures, and Mlc is its putative target.
authors.affiliation: Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China.|Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, P. R. China.|Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America.
authors.forename: Yueju
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McAnulty
authors.affiliation: Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America.|Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America.
authors.forename: Thomas K
authors.identifier: http://orcid.org/0000-0002-6258-529X
authors.initials: TK
authors.lastname: Wood
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001427:Bacterial Toxins / Q000235:genetics* / Q000378:metabolism*; D003080:Cold Temperature; D004251:DNA Transposable Elements; D004734:Energy Metabolism; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation; D020868:Gene Silencing; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D012808:Sigma Factor; C523350:YafQ protein, E coli; C069567:sigma factor KatF protein, Bacteria