Czolkoss Simon, Fritz Christiane, Hölzl Georg, Aktas Meriyem
Microbial Biology, Ruhr University Bochum, Bochum, Germany.
Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, Germany.
PLoS One. 2016 Jul 29;11(7):e0160373. doi: 10.1371/journal.pone.0160373. eCollection 2016.
Cardiolipin (CL) is a universal component of energy generating membranes. In most bacteria, it is synthesized via the condensation of two molecules phosphatidylglycerol (PG) by phospholipase D-type cardiolipin synthases (PLD-type Cls). In the plant pathogen and natural genetic engineer Agrobacterium tumefaciens CL comprises up to 15% of all phospholipids in late stationary growth phase. A. tumefaciens harbors two genes, atu1630 (cls1) and atu2486 (cls2), coding for PLD-type Cls. Heterologous expression of either cls1 or cls2 in Escherichia coli resulted in accumulation of CL supporting involvement of their products in CL synthesis. Expression of cls1 and cls2 in A. tumefaciens is constitutive and irrespective of the growth phase. Membrane lipid profiling of A. tumefaciens mutants suggested that Cls2 is required for CL synthesis at early exponential growth whereas both Cls equally contribute to CL production at later growth stages. Contrary to many bacteria, which suffer from CL depletion, A. tumefaciens tolerates large changes in CL content since the CL-deficient cls1/cls2 double mutant showed no apparent defects in growth, stress tolerance, motility, biofilm formation, UV-stress and tumor formation on plants.
心磷脂（CL）是能量产生膜的普遍组成成分。在大多数细菌中，它是由磷脂酶D型心磷脂合酶（PLD型Cls）通过两个磷脂酰甘油（PG）分子缩合而成。在植物病原体和天然基因工程菌根癌土壤杆菌中，CL在稳定生长期后期占所有磷脂的比例高达15%。根癌土壤杆菌含有两个编码PLD型Cls的基因，atu1630（cls1）和atu2486（cls2）。在大肠杆菌中对cls1或cls2进行异源表达会导致CL积累，这表明它们的产物参与了CL的合成。cls1和cls2在根癌土壤杆菌中的表达是组成型的，与生长阶段无关。根癌土壤杆菌突变体的膜脂分析表明，在指数生长早期，Cls2是CL合成所必需的，而在生长后期，两种Cls对CL的产生贡献相同。与许多因CL消耗而受影响的细菌不同，根癌土壤杆菌能够耐受CL含量的大幅变化，因为CL缺陷型cls1/cls2双突变体在生长、胁迫耐受性、运动性、生物膜形成、紫外线胁迫和植物肿瘤形成方面没有明显缺陷。
