Damrow Ramon, Maldener Iris, Zilliges Yvonne
Section of Plant Biochemistry, Institute of Biology, Humboldt-Universität zu Berlin Berlin, Germany.
Section of Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls Universität Tübingen Tübingen, Germany.
Front Microbiol. 2016 Jun 21;7:966. doi: 10.3389/fmicb.2016.00966. eCollection 2016.
Classical microbial carbon polymers such as glycogen and polyhydroxybutyrate (PHB) have a crucial impact as both a sink and a reserve under macronutrient stress conditions. Most microbial species exclusively synthesize and degrade either glycogen or PHB. A few bacteria such as the phototrophic model organism Synechocystis sp. PCC 6803 surprisingly produce both physico-chemically different polymers under conditions of high C to N ratios. For the first time, the function and interrelation of both carbon polymers in non-diazotrophic cyanobacteria are analyzed in a comparative physiological study of single- and double-knockout mutants (ΔglgC; ΔphaC; ΔglgC/ΔphaC), respectively. Most of the observed phenotypes are explicitly related to the knockout of glycogen synthesis, highlighting the metabolic, energetic, and structural impact of this process whenever cells switch from an active, photosynthetic 'protein status' to a dormant 'glycogen status'. The carbon flux regulation into glycogen granules is apparently crucial for both phycobilisome degradation and thylakoid layer disassembly in the presence of light. In contrast, PHB synthesis is definitely not involved in this primary acclimation response. Moreover, the very weak interrelations between the two carbon-polymer syntheses indicate that the regulation and role of PHB synthesis in Synechocystis sp. PCC 6803 is different from glycogen synthesis.
经典的微生物碳聚合物,如糖原和聚羟基丁酸酯(PHB),在大量营养素胁迫条件下作为碳汇和储备具有至关重要的影响。大多数微生物物种仅合成和降解糖原或PHB。少数细菌,如光合模式生物集胞藻PCC 6803,令人惊讶地在高碳氮比条件下产生两种物理化学性质不同的聚合物。首次在单基因敲除和双基因敲除突变体(ΔglgC;ΔphaC;ΔglgC/ΔphaC)的比较生理学研究中分析了这两种碳聚合物在非固氮蓝细菌中的功能和相互关系。观察到的大多数表型都与糖原合成的敲除直接相关,突出了每当细胞从活跃的光合“蛋白质状态”转变为休眠的“糖原状态”时,这一过程对代谢、能量和结构的影响。在有光的情况下,进入糖原颗粒的碳通量调节显然对藻胆体降解和类囊体层解体都至关重要。相比之下,PHB合成肯定不参与这种初级适应反应。此外,两种碳聚合物合成之间非常微弱的相互关系表明,集胞藻PCC 6803中PHB合成的调节和作用与糖原合成不同。