Ovotransferrin Plays a Major Role in the Strong Bactericidal Effect of Egg White against the Bacillus cereus Group
Ovotransferrin Plays a Major Role in the Strong Bactericidal Effect of Egg White against the Bacillus cereus Group
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DOI：
10.4315/0362-028x.jfp-13-473
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发表时间：
2014-06-01
影响因子：
2
通讯作者：
Nau, Fracoise
中科院分区：
文献类型：
--
作者：
Baron, Florence;Jan, Sophie;Nau, Fracoise
蜡样芽孢杆菌群细菌是巴氏灭菌食品领域众所周知的机会致病性孢子形成微生物，因为它们参与腐败事件。在蛋制品加工领域，这些细菌可能会导致重大的经济损失。因此，研究它们在蛋清中的行为似乎是相关的，蛋清是一种广泛使用的蛋制品，通常被认为根据环境条件产生不同水平的抗菌活性。 68 个蜡状芽孢杆菌组分离株在 30 摄氏度、pH 9.3（天然蛋清 pH）的蛋清中独立培养，观察到强烈的杀菌作用（细菌数量减少 6.1 +/- 0.2 log CFU/ml）。为了确定哪些成分可以解释如此强大的杀菌作用，我们制定了一种实验策略，基于超滤和阴离子交换液相色谱法分离蛋清。由此证明了蛋白质组分的作用，随后的纳米液相色谱串联质谱分析允许将卵转铁蛋白鉴定为所涉及的主要蛋白质。在商业卵转铁蛋白的存在下证实了强大的杀菌作用。这种杀菌作用（即通过细胞死亡减少细菌数量）从未被描述过，因为卵转铁蛋白因其螯合铁的能力而以其抑菌作用（即抑制生长）而闻名。令人惊讶的是，在碱性条件（pH 9.3）下添加铁并没有逆转卵转铁蛋白的杀菌作用，而在pH 7.3下则完全逆转了这种作用。卵转铁蛋白被证明会引起细胞质膜电化学电位的扰动。因此，可能涉及膜干扰机制，导致在蛋清中孵育的蜡样芽孢杆菌组细菌裂解。
Bacillus cereus group bacteria are opportunistically pathogenic spore-forming microorganisms well known in the sector of pasteurized food products because of their involvement in spoilage events. In the sector of egg product processing, these bacteria may lead to important economic losses. It seemed then relevant to study their behavior in egg white, a widely used egg product usually recognized as developing different levels of antimicrobial activities depending on the environmental conditions. A strong bactericidal effect (decrease in the bacterial population of 6.1 +/- 0.2 log CFU/ml) was observed for 68 B. cereus group isolates, independently incubated at 30 degrees C in egg white at pH 9.3 (natural egg white pH). To determine which components could explain such a strong bactericidal effect, an experimental strategy was mined out, based on egg white fractionation by ultrafiltration and by anion-exchange liquid chromatography. The role of the protein fraction was thus demonstrated, and subsequent nano-liquid chromatography tandem mass spectrometry analyses allowed identification of ovotransferrin as a major protein involved. The strong bactericidal effect was confirmed in the presence of commercial ovotransferrin. Such a bactericidal effect (i.e., a decrease in the bacterial population through cell death) had never been described because ovotransferrin is known for its bacteriostatic effect (i.e., inhibition of growth) due to its ability to chelate iron. Surprisingly, the addition of iron did not reverse the bactericidal effect of ovotransferrin under alkaline conditions (pH 9.3), whereas it completely reversed this effect at pH 7.3. Ovotransferfin was shown to provoke a perturbation of the electrochemical potential of the cytoplasmic membrane. A membrane disturbance mechanism could, hence, be involved, leading to the lysis of B. cereus group bacteria incubated in egg white.