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Open AccessArticle

Physiological Response of Corynebacterium glutamicum to Indole

1
Genetics of Prokaryotes, Faculty of Biology and CeBiTec, Bielefeld University, 33615 Bielefeld, Germany
2
Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
3
BU Bioscience, Wageningen University & Research, 6700AA Wageningen, The Netherlands
4
Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, 33615 Bielefeld, Germany
*
Author to whom correspondence should be addressed.
Current address: Department of Horticultural Science, Faculty of Agriculture, Tarbiat Modares University, 14115-111 Tehran, Iran.
Microorganisms 2020, 8(12), 1945; https://doi.org/10.3390/microorganisms8121945
Received: 23 November 2020 / Revised: 4 December 2020 / Accepted: 5 December 2020 / Published: 8 December 2020
(This article belongs to the Special Issue Genetics and Physiology of Corynebacteria)
The aromatic heterocyclic compound indole is widely spread in nature. Due to its floral odor indole finds application in dairy, flavor, and fragrance products. Indole is an inter- and intracellular signaling molecule influencing cell division, sporulation, or virulence in some bacteria that synthesize it from tryptophan by tryptophanase. Corynebacterium glutamicum that is used for the industrial production of amino acids including tryptophan lacks tryptophanase. To test if indole is metabolized by C. glutamicum or has a regulatory role, the physiological response to indole by this bacterium was studied. As shown by RNAseq analysis, indole, which inhibited growth at low concentrations, increased expression of genes involved in the metabolism of iron, copper, and aromatic compounds. In part, this may be due to iron reduction as indole was shown to reduce Fe3+ to Fe2+ in the culture medium. Mutants with improved tolerance to indole were selected by adaptive laboratory evolution. Among the mutations identified by genome sequencing, mutations in three transcriptional regulator genes were demonstrated to be causal for increased indole tolerance. These code for the regulator of iron homeostasis DtxR, the regulator of oxidative stress response RosR, and the hitherto uncharacterized Cg3388. Gel mobility shift analysis revealed that Cg3388 binds to the intergenic region between its own gene and the iolT2-rhcM2D2 operon encoding inositol uptake system IolT2, maleylacetate reductase, and catechol 1,2-dioxygenase. Increased RNA levels of rhcM2 in a cg3388 deletion strain indicated that Cg3388 acts as repressor. Indole, hydroquinone, and 1,2,4-trihydroxybenzene may function as inducers of the iolT2-rhcM2D2 operon in vivo as they interfered with DNA binding of Cg3388 at physiological concentrations in vitro. Cg3388 was named IhtR. View Full-Text
Keywords: Corynebacterium glutamicum; amino acids; indole; adaptive laboratory evolution; iron homeostasis; oxidative stress; aromatic compound catabolism Corynebacterium glutamicum; amino acids; indole; adaptive laboratory evolution; iron homeostasis; oxidative stress; aromatic compound catabolism
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MDPI and ACS Style

Walter, T.; Veldmann, K.H.; Götker, S.; Busche, T.; Rückert, C.; Kashkooli, A.B.; Paulus, J.; Cankar, K.; Wendisch, V.F. Physiological Response of Corynebacterium glutamicum to Indole. Microorganisms 2020, 8, 1945. https://doi.org/10.3390/microorganisms8121945

AMA Style

Walter T, Veldmann KH, Götker S, Busche T, Rückert C, Kashkooli AB, Paulus J, Cankar K, Wendisch VF. Physiological Response of Corynebacterium glutamicum to Indole. Microorganisms. 2020; 8(12):1945. https://doi.org/10.3390/microorganisms8121945

Chicago/Turabian Style

Walter, Tatjana; Veldmann, Kareen H.; Götker, Susanne; Busche, Tobias; Rückert, Christian; Kashkooli, Arman B.; Paulus, Jannik; Cankar, Katarina; Wendisch, Volker F. 2020. "Physiological Response of Corynebacterium glutamicum to Indole" Microorganisms 8, no. 12: 1945. https://doi.org/10.3390/microorganisms8121945

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