Buchholz J.,University of Stuttgart |
Graf M.,University of Stuttgart |
Freund A.,University of Stuttgart |
Busche T.,Universitatsstr 27 |
And 3 more authors.
Applied Microbiology and Biotechnology | Year: 2014
The exploration of scale-down models to imitate the influence of large scale bioreactor inhomogeneities on cellular metabolism is a topic with increasing relevance. While gradients of substrates, pH, or dissolved oxygen are often investigated, oscillating CO2/HCO3 − levels, a typical scenario in large industrial bioreactors, is rarely addressed. Hereby, we investigate the metabolic and transcriptional response in Corynebacterium glutamicum wild type as well as the impact on l-lysine production in a model strain exposed to pCO2 gradients of (75–315) mbar. A three-compartment cascade bioreactor system was developed and characterized that offers high flexibility for installing gradients and residence times to mimic industrial-relevant conditions and provides the potential of accurate carbon balancing. The phenomenological analysis of cascade fermentations imposed to the pCO2 gradients at industry-relevant residence times of about 3.6 min did not significantly impair the process performance, with growth and product formation being similar to control conditions. However, transcriptional analysis disclosed up to 66 differentially expressed genes already after 3.6 min under stimulus exposure, with the overall change in gene expression directly correlateable to the pCO2 gradient intensity and the residence time of the cells. © 2014, Springer-Verlag Berlin Heidelberg.
Blombach B.,University of Stuttgart |
Buchholz J.,University of Stuttgart |
Busche T.,Universitatsstr 27 |
Kalinowski J.,Universitatsstr 27 |
Takors R.,University of Stuttgart
Journal of Biotechnology | Year: 2013
We investigated the growth kinetics and transcriptional responses of Corynebacterium glutamicum in environments with low (pCO2<40mbar) and high (pCO2≥300mbar) CO2/HCO3 - levels compared to standard conditions. When cultivated at high CO2/HCO3 --levels, C. glutamicum showed increased (63%) biomass to substrate yields during the initial growth phase. Other kinetic parameters such as growth rate (μ), specific glucose consumption rate (qS), and selected enzymatic activities of anaplerotic reactions, the pentose phosphate pathway and the tricarboxylic acid cycle were similar to standard conditions. However, microarray hybridization disclosed a complex transcriptional response involving 117 differentially expressed genes. Among those, 60 genes were assigned to the complete DtxR/RipA regulon controlling iron homeostasis in C. glutamicum. Impaired growth of a δdtxR mutant at high CO2/HCO3 - levels validated the relevance of this master regulator to cope with excessive CO2/HCO3 - availability. At low CO2/HCO3 - levels, C. glutamicum grew in a bi-level manner with three distinct growth phases. Differential analyses revealed approximately doubled activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase accompanied by the formation of l-alanine and l-valine during the lowest μ occurring in mid-phase of the cultivation. DNA microarray analysis revealed more than 100 differentially expressed genes in growth phase II compared to phase I including almost all thiamin pyrophosphate (TPP) biosynthesis genes, which were significantly up regulated. Concluding, we hypothesize that C. glutamicum counteracts the lack of CO2/HCO3 - by triggering TPP biosynthesis for increasing the activities of TPP-dependent enzymes involved in CO2 formation. © 2013 Elsevier B.V.
Kutyniok M.,Bielefeld University |
Kutyniok M.,Universitatsstr 27 |
Persicke M.,Universitatsstr 27 |
Muller C.,Bielefeld University |
Muller C.,Universitatsstr 27
Journal of Chemical Ecology | Year: 2014
The performance and behavior of herbivores is strongly affected by the quality of their host plants, which is determined by various environmental conditions. We investigated the performance and preference of the polyphagous shoot-infesting aphid Myzus persicae on the host-plant Arabidopsis thaliana in a two-factorial design in which nitrate fertilization was varied by 33 %, and the root-infesting cyst-nematode Heterodera schachtii was present or absent. Aphid performance was influenced by these abiotic and biotic factors in an interactive way. Nematode presence decreased aphid performance when nitrate levels were low, whereas nematode infestation did not influence aphid performance under higher nitrate fertilization. Aphids followed the "mother knows best" principle when given a choice, settling preferentially on those plants on which they performed best. Hence, they preferred nematode-free over nematode-infested plants in the low fertilization treatment but host choice was not affected by nematodes under higher nitrate fertilization. The amino acid composition of the phloem exudates was significantly influenced by fertilization but also by the interaction of the two treatments. Various glucosinolates in the leaves, which provide an estimate of phloem glucosinolates, were not affected by the individual treatments but by the combination of fertilization and herbivory. These changes in primary and secondary metabolites may be decisive for the herbivore responses. Our data demonstrate that abiotic and biotic factors can interactively affect herbivores, adding a layer of complexity to plant-mediated herbivore interactions. © 2014 Springer Science+Business Media New York.
Luque-Almagro V.M.,University of Cordoba, Spain |
Acera F.,University of Extremadura |
Igeno M.I.,University of Extremadura |
Wibberg D.,Universitatsstr 27 |
And 24 more authors.
Environmental Microbiology | Year: 2013
Pseudomonas pseudoalcaligenes CECT5344 is a Gram-negative bacterium able to tolerate cyanide and to use it as the sole nitrogen source. We report here the first draft of the whole genome sequence of a P.pseudoalcaligenes strain that assimilates cyanide. Three aspects are specially emphasized in this manuscript. First, some generalities of the genome are shown and discussed in the context of other Pseudomonadaceae genomes, including genome size, G+C content, core genome and singletons among other features. Second, the genome is analysed in the context of cyanide metabolism, describing genes probably involved in cyanide assimilation, like those encoding nitrilases, and genes related to cyanide resistance, like the cio genes encoding the cyanide insensitive oxidases. Finally, the presence of genes probably involved in other processes with a great biotechnological potential like production of bioplastics and biodegradation of pollutants also is discussed. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.