l-Glutamine as a nitrogen source for Corynebacterium glutamicum: derepression of the AmtR regulon and implications for nitrogen sensing

Abstract

Corynebacterium glutamicum, a Gram-positive soil bacterium employed in the industrial production of various amino acids, is able to use a number of different nitrogen sources, such as ammonium, urea or creatinine. This study shows that l-glutamine serves as an excellent nitrogen source for C. glutamicum and allows similar growth rates in glucose minimal medium to those in ammonium. A transcriptome comparison revealed that the nitrogen starvation response was elicited when glutamine served as the sole nitrogen source, meaning that the target genes of the global nitrogen regulator AmtR were derepressed. Subsequent growth experiments with a variety of mutants defective in nitrogen metabolism showed that glutamate synthase is crucial for glutamine utilization, while a putative glutaminase is dispensable under the experimental conditions used. The gltBD operon encoding the glutamate synthase is a member of the AmtR regulon. The observation that the nitrogen starvation response was elicited at high intracellular l-glutamine levels has implications for nitrogen sensing. In contrast with other Gram-positive and Gram-negative bacteria such as Bacillus subtilis, Salmonella enterica serovar Typhimurium and Klebsiella pneumoniae, a drop in glutamine concentration obviously does not serve as a nitrogen starvation signal in C. glutamicum.

Deletion of Type I glutamine synthetase deregulates nitrogen metabolism and increases ethanol production in Clostridium thermocellum

“…In addition to α-ketoglutarate, other effector molecules also regulate nitrogen metabolism through gene expression and/or protein activity, including ammonium in Actinobacteria such as Corynebacterium glutamicum (Muller et al, 2006;Nolden et al, 2001;Rehm and Burkovski, 2011;Rehm et al, 2010) and glutamine in Proteobacteria (Ikeda et al, 1996;Jiang et al, 1998;Reitzer, 2003) and Firmicutes such as Bacillus subtilis (Wray et al, 2001). While high α-ketoglutarate levels in the latter organisms indicate nitrogen starvation, high glutamine and low αketoglutarate levels are typically indicative of nitrogen-rich conditions.…”

PIIsignal transduction proteins: nitrogen regulation and beyond

“…Furthermore, the signals controlling the opposing adenylyltransferase/adenylyl‐removing activities of GlnD remain to be elucidated. Unlike the situation in most Proteobacteria , glutamine seems not to be a major nitrogen signal in C. glutamicum (Nolden et al ., ; Rehm et al ., ), rather the evidence suggests that the primary signal is accumulation of 2‐OG which indicates nitrogen deficiency (Muller et al ., ).…”

Single-Domain Peptidyl-Prolyl cis / trans Isomerase FkpA from Corynebacterium glutamicum Improves the Biomass Yield at Increased Growth Temperatures

“…2A) and exhibiting a classical FKBP fold as well as high PPIase activity (47). The two amino acids that provide the only sources of hydrogen bond donors and acceptors in the BpML1 active site, i.e., Asp 44 and Tyr 89 , are also conserved in FkpA from C. glutamicum (Asp 52 and Tyr 95 ) ( Fig. 2A).…”

“…Custom-made DNA microarrays for C. glutamicum ATCC 13032 printed with 70mer oligonucleotides were obtained from Operon (Cologne, Germany). Hybridization, stringent washing, and scanning of the microarrays as well as data analysis were performed as described previously (44). Two biological replicates were performed to compare the RNA levels of the ⌬fkpA and reference strains.…”