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Abstract：
This work aimed to isolate, and identify Lactic Acid Bacteria LAB from Egyptian immature citrus honey, and characterize their secondary metabolites, as well as determine the antibacterial activities and transcription of virulence genes (stx1, stx2, and eae) influenced by these bacterial secondary metabolites. From twenty hives, twenty immature citrus bee honey samples were taken. Traditional cultural and biochemical testing were used, followed by molecular confirmation. Further, LAB isolates\' antibacterial and cytotoxic properties were investigated. 16S rRNA gene sequencing were assessed and, two lactic acid bacterial isolates were identified as Lactobacillus acidophilus Ch2 and Levilactobacillus brevis Ch1. Both isolates have good antagonistic action against clinical pathogens, with Levilactobacillus brevis Ch1 exhibiting the best antibacterial activity against all indicator pathogens examined. When compared to untreated cancer cells, the isolates demonstrated significant cytotoxic activity. Ch1 and Ch2 cell viability percentages were 39.5% and 18.76%, respectively. Furthermore, when exposed to Levilactobacillus brevis Ch1 metabolites, Shiga-producing Escherichia coli (STEC) virulence gene expression was suppressed. To identify bacterial secondary metabolites, a high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTOF) approach was developed. Twenty-seven metabolites from diverse chemical classes were discovered in the crude extracts with antibacterial and anticancer characteristics. This is the first thorough investigation on the metabolic profile of LAB isolated from immature Egyptian honey and the findings suggested that isolates or their secondary metabolites could be used in the food sector as medicinal alternatives or as a biocontrol agent.
摘要：
这项工作旨在隔离，并从埃及未成熟柑橘蜂蜜中鉴定乳酸菌LAB，并表征它们的次级代谢产物，以及确定受这些细菌次级代谢产物影响的抗菌活性和毒力基因（stx1，stx2和eae）的转录。从二十个荨麻疹中，采集了二十个未成熟的柑橘蜜蜂蜂蜜样本。使用传统的文化和生化测试，其次是分子确认。Further,研究了LAB分离株的抗菌和细胞毒性。16SrRNA基因测序进行了评估，2株乳酸菌分离株分别为嗜酸乳杆菌Ch2和短小杆菌Ch1。两种分离株对临床病原菌均有良好的拮抗作用,短左芽孢杆菌Ch1对所检查的所有指示病原体表现出最佳的抗菌活性。与未经治疗的癌细胞相比，分离株表现出显著的细胞毒活性。Ch1和Ch2细胞存活率分别为39.5%和18.76%,分别。此外，当暴露于短小杆菌Ch1代谢物时，产志贺大肠杆菌（STEC）毒力基因表达受到抑制。为了鉴定细菌次生代谢产物，开发了一种高效液相色谱-四极杆飞行时间质谱（HPLC-QTOF）方法。在具有抗菌和抗癌特性的粗提物中发现了来自不同化学类别的27种代谢物。这是对从未成熟的埃及蜂蜜中分离出的LAB的代谢谱进行的首次彻底调查，结果表明，分离株或其次级代谢产物可以在食品领域用作药用替代品或用作生物防治剂。
