School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, Nevada, USA.
J Bacteriol. 2013 Mar;195(5):1005-11. doi: 10.1128/JB.01958-12. Epub 2012 Dec 21.
Paenibacillus larvae is the causative agent of American foulbrood (AFB), a disease affecting honey bee larvae. First- and second-instar larvae become infected when they ingest food contaminated with P. larvae spores. The spores then germinate into vegetative cells that proliferate in the midgut of the honey bee. Although AFB affects honey bees only in the larval stage, P. larvae spores can be distributed throughout the hive. Because spore germination is critical for AFB establishment, we analyzed the requirements for P. larvae spore germination in vitro. We found that P. larvae spores germinated only in response to l-tyrosine plus uric acid under physiologic pH and temperature conditions. This suggests that the simultaneous presence of these signals is necessary for spore germination in vivo. Furthermore, the germination profiles of environmentally derived spores were identical to those of spores from a biochemically typed strain. Because l-tyrosine and uric acid are the only required germinants in vitro, we screened amino acid and purine analogs for their ability to act as antagonists of P. larvae spore germination. Indole and phenol, the side chains of tyrosine and tryptophan, strongly inhibited P. larvae spore germination. Methylation of the N-1 (but not the C-3) position of indole eliminated its ability to inhibit germination. Identification of the activators and inhibitors of P. larvae spore germination provides a basis for developing new tools to control AFB.
幼虫芽孢杆菌是美洲幼虫腐臭病（AFB）的病原体，这种疾病会影响蜜蜂幼虫。当一龄和二龄幼虫摄入被幼虫芽孢杆菌孢子污染的食物时，就会受到感染。然后，孢子发芽成营养细胞，在蜜蜂的中肠中增殖。尽管 AFB 仅在幼虫阶段影响蜜蜂，但幼虫芽孢杆菌孢子可以分布在整个蜂巢中。由于孢子发芽对于 AFB 的建立至关重要，因此我们分析了幼虫芽孢杆菌孢子在体外发芽的要求。我们发现，幼虫芽孢杆菌孢子仅在生理 pH 值和温度条件下响应 l-酪氨酸加尿酸才发芽。这表明这些信号的同时存在是体内孢子发芽所必需的。此外，环境衍生孢子的发芽曲线与生物化学分型菌株的孢子相同。由于 l-酪氨酸和尿酸是体外唯一必需的发芽剂，因此我们筛选了氨基酸和嘌呤类似物，以研究它们作为幼虫芽孢杆菌孢子发芽拮抗剂的能力。吲哚和苯酚，酪氨酸和色氨酸的侧链，强烈抑制幼虫芽孢杆菌孢子发芽。吲哚 N-1 位（而不是 C-3 位）的甲基化消除了其抑制发芽的能力。鉴定幼虫芽孢杆菌孢子发芽的激活剂和抑制剂为开发控制 AFB 的新工具提供了基础。
