Abstract
The growth rate (μ) of industrially relevant microbes, such as Corynebacterium glutamicum, is a fundamental property that indicates its production capacity. Therefore, understanding the mechanism underlying the growth rate is imperative for improving productivity and performance through metabolic engineering. Despite recent progress in the understanding of global regulatory interactions, knowledge of mechanisms directing cell growth remains fragmented and incomplete. The current study investigated RNA-Seq data of three growth rate transitions, induced by different pre-culture conditions, in order to identify transcriptomic changes corresponding to increasing growth rates. These transitions took place in minimal medium and ranged from 0.02 to 0.4 h-1 μ. This study enabled the identification of 447 genes as components of the growth modulon. Enrichment of genes within the growth modulon revealed 10 regulons exhibiting a significant effect over growth rate transition. In summary, central metabolism was observed to be regulated by a combination of metabolic and transcriptional activities orchestrating control over glycolysis, pentose phosphate pathway, and the tricarboxylic acid cycle. Additionally, major responses to changes in the growth rate were linked to iron uptake and carbon metabolism. In particular, genes encoding glycolytic enzymes and the glucose uptake system showed a positive correlation with the growth rate.
Highlights
The industrial potential of Corynebacterium glutamicum has attracted the attention of both researchers as well as industry experts, who are engaged in an attempt to clarify and improve its characteristics
The content of one glass reaction tube was used to inoculate 300 mL of modified CGXII minimal medium without urea in a 3 L baffled shaking flask. 3-Morpholinopropane-1-sulfonic acid (MOPS) buffer concentration was doubled to 42 g L−1, and (NH4)2SO4 concentration was reduced to 0.1 g L−1
In order to prevent biased growth rate measurements, differential growth rates were adjusted by only considering viable cell populations
Summary
The industrial potential of Corynebacterium glutamicum has attracted the attention of both researchers as well as industry experts, who are engaged in an attempt to clarify and improve its characteristics. C. glutamicum, a non-pathogenic, small rod-shaped, Gram-positive, soil bacterium, was discovered in 1957 (Kinoshita et al, 1957) and quickly utilized as a natural producer of L-glutamate (Hermann, 2003) and L-lysine (Becker et al, 2007; Takeno et al, 2010) Since it has been established as a prime producer of amino acids, including L-ornithine (Hadiati et al, 2014), L-arginine (Ikeda et al, 2009; Lubitz et al, 2016), L-valine (Oldiges et al, 2014), and L-histidine (Cheng et al, 2013; Kulis-Horn et al, 2014). C. glutamicum has several advantages as a production host, including great robustness to process deviations, excellent culture characteristics that are stable up to high cell densities, genetic stability, and broad utilization of carbon sources (Lee et al, 2016). C. glutamicum has gained recognition for its potential to host recombinant protein expression, largely due to advantages such as a lack of endotoxins, ability to secrete heterologous proteins, and high efficacy as a production host (Liu et al, 2016; Freudl, 2017)
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