Untersuchungen zum Einfluss von pH-Variation und erhöhter CO2 Konzentration auf Stoffwechsel und Aminosäureproduktion mit Corynebacterium glutamicum

Das grampositive Bodenbakterium Corynebacterium glutamicum wird in großem Umfang zur biotechnologischen Produktion von L-Lysin eingesetzt. In dieser Arbeit wurden die Auswirkungen einer Variation des pH-Wertes sowie von erhöhter CO2 Konzentration - zwei während der industriellen L-Lysinproduktion häufig auftretende Stressfaktoren - analysiert. Es wurde gezeigt, dass C. glutamicum bei externen pH-Werten zwischen pH 6,0 und 9,5 einen relativ stabilen cytoplasmatischen pH-Wert und bei pH-Werten zwischen pH 4,5 und 10 ein relativ konstantes elektrochemisches Protonenpotential aufrechterhält. Die höchsten Wachstumsraten wurden im Bereich der effektiven pH-Homöostase zwischen pH 6,0 und 9,5 mit einem Optimum bei pH 8,0 bis 8,5 beobachtet. Erhöhte CO2 Konzentrationen hatten bei neutralem pH keinen Einfluss, weder auf das Wachstum, noch auf bioenergetische Parameter oder die Lysinbildung. Bei erniedrigtem pH führte eine Erhöhung der CO2 Konzentration zu einer massiven Beeinträchtigung des Zellwachstums und der Lysinbildung. Dabei wurde gezeigt, dass eine Erhöhung der CO2 Konzentration direkt eine Absenkung des cytoplasmatischen pH-Wertes nach sich zieht und die Mechanismen der pH-Homöostase bei gleichzeitig erniedrigtem pH und erhöhter CO2 Konzentration überfordert sind. Es wurden zwei putative Mrp Na+/H+ Antiporter identifiziert, welche bei erhöhten Na+ Konzentrationen essentiel sind und deren Aktivität vermutlich zudem für die pH-Homöostase bei gleichzeitig vorliegendem alkalischem pH und erhöhter Na+ Konzentration wichtig ist. Des Weiteren wurde gezeigt, dass bei erniedrigtem externen pH die Anwesenheit von K+ zur Aufrechterhaltung eines neutralen cytoplasmatischen pH-Wertes sowie zum Wachstum notwendig ist. Dabei sind sowohl der interne Kaliumgehalt als auch der Vorgang des Kaliumtransportes, welcher über den putativen Kaliumkanal CglK erfolgt, ausschlaggebend. Es wurde ein direkter Zusammenhang zwischen der Einstellung des internen pH-Wertes und der Einstellung des Membranpotentials beobachtet und als Modell für die K+ abhängige pH-Homöostase vorgeschlagen, dass eine durch K+ vermittelte Absenkung des Membranpotentials zu einer Stimulierung von Protonen exportierenden Komponenten und damit zur Anhebung des cytoplasmatischen pH-Wertes führt

Functional genomics of pH homeostasis in Corynebacterium glutamicum revealed novel links between pH response, oxidative stress, iron homeostasis and methionine synthesis

Follmann M, Ochrombel I, Kraemer R, et al. Functional genomics of pH homeostasis in Corynebacterium glutamicum revealed novel links between pH response, oxidative stress, iron homeostasis and methionine synthesis. BMC Genomics. 2009;10(1):621.Background: The maintenance of internal pH in bacterial cells is challenged by natural stress conditions, during host infection or in biotechnological production processes. Comprehensive transcriptomic and proteomic analyses has been conducted in several bacterial model systems, yet questions remain as to the mechanisms of pH homeostasis. Results: Here we present the comprehensive analysis of pH homeostasis in C. glutamicum, a bacterium of industrial importance. At pH values between 6 and 9 effective maintenance of the internal pH at 7.5 +/- 0.5 pH units was found. By DNA microarray analyses differential mRNA patterns were identified. The expression profiles were validated and extended by 1D-LC-ESI-MS/MS based quantification of soluble and membrane proteins. Regulators involved were identified and thereby participation of numerous signaling modules in pH response was found. The functional analysis revealed for the first time the occurrence of oxidative stress in C. glutamicum cells at neutral and low pH conditions accompanied by activation of the iron starvation response. Intracellular metabolite pool analysis unraveled inhibition of the TCA and other pathways at low pH. Methionine and cysteine synthesis were found to be activated via the McbR regulator, cysteine accumulation was observed and addition of cysteine was shown to be toxic under acidic conditions. Conclusions: Novel limitations for C. glutamicum at non-optimal pH values were identified by a comprehensive analysis on the level of the transcriptome, proteome, and metabolome indicating a functional link between pH acclimatization, oxidative stress, iron homeostasis, and metabolic alterations. The results offer new insights into bacterial stress physiology and new starting points for bacterial strain design or pathogen defense

A Chlamydia trachomatis VD1-MOMP vaccine elicits cross-neutralizing and protective antibodies against C/C-related complex serovars.

Ocular and urogenital infections with Chlamydia trachomatis (C.t.) are caused by a range of different serovars. The first C.t. vaccine in clinical development (CTH522/CAF®01) induced neutralizing antibodies directed to the variable domain 4 (VD4) region of major outer membrane protein (MOMP), covering predominantly B and intermediate groups of serovars. The VD1 region of MOMP contains neutralizing B-cell epitopes targeting serovars of the C and C-related complex. Using an immuno-repeat strategy, we extended the VD1 region of SvA and SvJ to include surrounding conserved segments, extVD1A and extVD1J, and repeated this region four times. The extVD1A*4 was most immunogenic with broad cross-surface and neutralizing reactivity against representative members of the C and C-related complex serovars. Importantly, in vitro results for extVD1A*4 translated into in vivo biological effects, demonstrated by in vivo neutralization of SvA and protection/cross-protection against intravaginal challenge with both SvA and the heterologous SvIa strain

Publisher Correction: A Chlamydia trachomatis VD1-MOMP vaccine elicits cross-neutralizing and protective antibodies against C/C-related complex serovars.

In the original version of this article, Table 2 was missing from the PDF version. The PDF version has now been corrected. The HTML version of this article did not need correcting

Agronomic performance of canola hybrids cultivated in a low altitude region in Southern Brazil

The area occupied by crops has expanded in recent years in the central region of Rio Grande do Sul, Brazil and the search for alternative winter crops to integrate the productive system is relevant given the idleness of the areas at this time and the lower risk of frost losses that occur in most grain-producing regions. In this sense, the objective of this research was to evaluate the agronomic performance of eight canola hybrids (Hyola 61, Hyola 50, Hyola 433, Hyola 571CL, Hyola 575CL, Diamond, ALHT B4, and ALHT M6), cultivated in low altitude areas, in the Central region of Rio Grande do Sul (RS). The experiment was conducted in 2017, in Santa Maria, RS, using a randomized block design with four replicates. Canola hybrids show variability regarding the morphological components and grain production. The environmental condition and low altitude of the region of Santa Maria do not compromise the productive potential of the canola crop, obtaining grain productivity superior to the state and national averages. Therefore, canola crop can be inserted in the central region of Rio Grande do Sul if adequate agronomic management is performed. The cultivars Hyola 50, Hyola 571CL, Hyola 433, Hyola 575CL, Diamond, and Hyola 61 present the highest grain productivity

Ambulance location for maximum survival

This article proposes new location models for emergency medical service stations. The models are generated by incorporating a survival function into existing covering models. A survival function is a monotonically decreasing function of the response time of an emergency medical service (EMS) vehicle to a patient that returns the probability of survival for the patient. The survival function allows for the calculation of tangible outcome measures—the expected number of survivors in case of cardiac arrests. The survival-maximizing location models are better suited for EMS location than the covering models which do not adequately differentiate between consequences of different response times. We demonstrate empirically the superiority of the survival-maximizing models using data from the Edmonton EMS system.NSERCpre-prin

A systems serology approach to the investigation of infection-induced antibody responses and protection in trachoma.

BACKGROUND: Ocular infections with Chlamydia trachomatis serovars A-C cause the neglected tropical disease trachoma. As infection does not confer complete immunity, repeated infections are common, leading to long-term sequelae such as scarring and blindness. Here, we apply a systems serology approach to investigate whether systemic antibody features are associated with susceptibility to infection. METHODS: Sera from children in five trachoma endemic villages in the Gambia were assayed for 23 antibody features: IgG responses towards two C. trachomatis antigens and three serovars [elementary bodies and major outer membrane protein (MOMP), serovars A-C], IgG responses towards five MOMP peptides (serovars A-C), neutralization, and antibody-dependent phagocytosis. Participants were considered resistant if they subsequently developed infection only when over 70% of other children in the same compound were infected. RESULTS: The antibody features assayed were not associated with resistance to infection (false discovery rate < 0.05). Anti-MOMP SvA IgG and neutralization titer were higher in susceptible individuals (p < 0.05 before multiple testing adjustment). Classification using partial least squares performed only slightly better than chance in distinguishing between susceptible and resistant participants based on systemic antibody profile (specificity 71%, sensitivity 36%). CONCLUSIONS: Systemic infection-induced IgG and functional antibody responses do not appear to be protective against subsequent infection. Ocular responses, IgA, avidity, or cell-mediated responses may play a greater role in protective immunity than systemic IgG