Mechanisms of Cation Exchange by Pseudomonas aeruginosa PAO1 and PAO1 wbpL, a Strain with a Truncated Lipopolysaccharide
Mechanisms of Cation Exchange by Pseudomonas aeruginosa PAO1 and PAO1 wbpL, a Strain with a Truncated Lipopolysaccharide
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DOI：
10.1128/aem.01117-08
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发表时间：
2008-11-01
影响因子：
4.4
通讯作者：
Bremer, P. J.
中科院分区：
文献类型：
--
作者：
Shephard, J.;McQuillan, A. J.;Bremer, P. J.
细菌细胞螯合阳离子的能力已得到广泛认可，尽管该过程的具体结合位点和机制细节尚不清楚。为了解决这些问题，将带有截短脂多糖 (LPS) (PAO1 wbpL) 的铜绿假单胞菌 PAO1 细胞和通过在缺镁培养基中生长进一步修饰的细胞 (PAO1 wbpL - Mg2+) 与野生型铜绿假单胞菌 PAO1 细胞的阳离子交换行为进行了比较。由于 B 波段 LPS 中存在羧酸根基团，铜绿假单胞菌 PAO1 细胞在 pH 11 和 2.2 之间具有负表面电荷（zeta 电位）。由于核心 LPS 中 NH3+ 基团的影响，PAO1 wbpL 细胞上的净电荷在 pH 3.5 以下逐渐呈正电。还在 Na+、Ca2+ 和 La3+ 电解质中测量了这些电池的 zeta 电位。 La3+ 电解质中的细胞在所有测试的 pH 值下均具有正 zeta 电位。在缺镁培养基 (PAO1 wbpL - Mg2+) 中生长铜绿假单胞菌 PAO1 wbpL 会导致其 zeta 电位在 pH 值 3.0 至 6.5 范围内增加。在中性 pH 值下使用铜绿假单胞菌 PAO1 或 PAO1 wbpL 进行的阳离子交换实验中，发现随着 pH 从 7.0 降低至 3.5，结合的 Ca2+ 浓度降低。在 pH 3.5 时，结合的 Mg2+ 浓度急剧下降，揭示了阳离子交换表面位点的活性及其 pH 依赖性。附着生物膜的红外光谱表明核心 LPS 内的羧酸根和磷酸单酯官能团参与阳离子交换。
The ability of bacterial cells to sequester cations is well recognized, despite the fact that the specific binding sites and mechanistic details of the process are not well understood. To address these questions, the cation-exchange behavior of Pseudomonas aeruginosa PAO1 cells with a truncated lipopolysaccharide (LPS) (PAO1 wbpL) and cells further modified by growth in a magnesium-deficient medium (PAO1 wbpL - Mg2+) were compared with that of wild-type P. aeruginosa PAO1 cells. P. aeruginosa PAO1 cells had a negative surface charge (zeta potential) between pH 11 and 2.2, due to carboxylate groups present in the B-band LPS. The net charge on PAO1 wbpL cells was increasingly positive below pH 3.5, due to the influence of NH3+ groups in the core LPS. The zeta potentials of these cells were also measured in Na+, Ca2+, and La3+ electrolytes. Cells in the La3+ electrolyte had a positive zeta potential at all pH values tested. Growing P. aeruginosa PAO1 wbpL in magnesium-deficient medium (PAO1 wbpL - Mg2+) resulted in an increase in its zeta potential in the pH range from 3.0 to 6.5. In cation-exchange experiments carried out at neutral pH with either P. aeruginosa PAO1 or PAO1 wbpL, the concentration of bound Ca2+ was found to decrease as the pH was reduced from 7.0 to 3.5. At pH 3.5, the bound Mg2+ concentration decreased sharply, revealing the activity of surface sites for cation exchange and their pH dependence. Infrared spectroscopy of attached biofilms suggested that carboxylate and phosphomonoester functional groups within the core LPS are involved in cation exchange.