Department of Veterinary Pathobiology, University of Missourigrid.134936.a, Columbia, Missouri, USA.
Bond Life Sciences Center, University of Missourigrid.134936.a, Columbia, Missouri, USA.
J Bacteriol. 2021 Aug 9;203(17):e0013521. doi: 10.1128/JB.00135-21.
Bis-(3'-5')-cyclic-dimeric GMP (c-di-GMP) is an important bacterial regulatory signaling molecule affecting biofilm formation, toxin production, motility, and virulence. The genome of Bacillus anthracis, the causative agent of anthrax, is predicted to encode ten putative GGDEF/EAL/HD-GYP-domain containing proteins. Heterologous expression in Bacillus subtilis hosts indicated that there are five active GGDEF domain-containing proteins and four active EAL or HD-GYP domain-containing proteins. Using an mCherry gene fusion-Western blotting approach, the expression of the c-di-GMP-associated proteins was observed throughout the life cycle. Of the six c-di-GMP-associated proteins found to be present in sporulating cells, four (CdgA, CdgB, CdgD, and CdgG) contain active GGDEF domains. The six proteins expressed in sporulating cells are retained in spores in a CotE-independent manner and thus are not likely to be localized to the exosporium layer of the spores. Individual deletion mutations involving the nine GGDEF/EAL protein-encoding genes and one HD-GYP protein-encoding gene did not affect sporulation efficiency, the attachment of the exosporium glycoprotein BclA, or biofilm production. Notably, expression of anthrax toxin was not affected by deletion of any of the determinants. Three determinants encoding proteins with active GGDEF domains were found to affect germination kinetics. This study reveals a spore association of cyclic-di-GMP regulatory proteins and a likely role for these proteins in the biology of the B. anthracis spore. The genus is composed of Gram-positive, rod shaped, soil-dwelling bacteria. As a mechanism for survival in the harsh conditions in soil, the organisms undergo sporulation, and the resulting spores permit the organisms to survive harsh environmental conditions. Although most species are saprophytes, Bacillus cereus and Bacillus anthracis are human pathogens and Bacillus thuringiensis is an insect pathogen. The bacterial c-di-GMP regulatory system is an important control system affecting motility, biofilm formation, and toxin production. The role of c-di-GMP has been studied in the spore-forming bacilli Bacillus subtilis, Bacillus amyloliquefaciens, B. cereus, and B. thuringiensis. However, this regulatory system has not heretofore been examined in the high-consequence zoonotic pathogen of this genus, B. anthracis.
双(3'-5')-环二鸟苷酸(c-di-GMP)是一种重要的细菌调节信号分子,影响生物膜形成、毒素产生、运动性和毒力。炭疽杆菌,炭疽的病原体,其基因组预计编码十个假定的 GGDEF/EAL/HD-GYP 结构域含有蛋白。在枯草芽孢杆菌宿主中的异源表达表明,有五个活性 GGDEF 结构域含有蛋白和四个活性 EAL 或 HD-GYP 结构域含有蛋白。使用 mCherry 基因融合-免疫印迹方法,观察到 c-di-GMP 相关蛋白在整个生命周期中的表达。在产孢细胞中发现的六种 c-di-GMP 相关蛋白中,有四种(CdgA、CdgB、CdgD 和 CdgG)含有活性 GGDEF 结构域。在产孢细胞中表达的六种蛋白以 CotE 非依赖性的方式保留在孢子中,因此不太可能定位于孢子的外孢子层。涉及九个 GGDEF/EAL 蛋白编码基因和一个 HD-GYP 蛋白编码基因的单个缺失突变不影响孢子形成效率、外孢子糖蛋白 BclA 的附着或生物膜形成。值得注意的是,炭疽毒素的表达不受任何决定因素缺失的影响。三个编码具有活性 GGDEF 结构域的蛋白的决定因素被发现影响发芽动力学。本研究揭示了环二鸟苷酸调节蛋白与孢子的关联,并可能在炭疽杆菌孢子的生物学中发挥作用。该属由革兰氏阳性、杆状、土壤居住的细菌组成。作为在土壤中恶劣条件下生存的一种机制,这些生物体经历孢子形成,并且产生的孢子使生物体能够耐受恶劣的环境条件。尽管大多数物种是腐生菌,但蜡状芽孢杆菌和炭疽杆菌是人类病原体,苏云金芽孢杆菌是昆虫病原体。细菌 c-di-GMP 调节系统是一种重要的控制系统,影响运动性、生物膜形成和毒素产生。c-di-GMP 的作用已在芽孢形成细菌枯草芽孢杆菌、解淀粉芽孢杆菌、蜡状芽孢杆菌和苏云金芽孢杆菌中进行了研究。然而,该调节系统迄今为止尚未在该属的高后果性人畜共患病病原体炭疽杆菌中进行研究。