The dlt Operon of Bacillus cereus Is Required for Resistance to Cationic Antimicrobial Peptides and for Virulence in Insects
The dlt Operon of Bacillus cereus Is Required for Resistance to Cationic Antimicrobial Peptides and for Virulence in Insects
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DOI：
10.1128/jb.00892-09
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发表时间：
2009-11-15
影响因子：
3.2
通讯作者：
Gaudriault, S.
中科院分区：
文献类型：
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作者：
Khattar, Z. Abi;Rejasse, A.;Gaudriault, S.
dlt 操纵子编码丙氨酰磷壁酸的蛋白质，磷壁酸是革兰氏阳性细菌细胞壁的主要成分。这会在细菌细胞壁上产生净正电荷，排斥带正电荷的分子，并赋予革兰氏阳性病原菌对动物和人类阳离子抗菌肽（AMP）的抗性。 AMP 会破坏细菌膜，是针对细菌的体液免疫反应中最有效的成分。我们通过灭活蜡状芽孢杆菌中的 dlt 操纵子来研究 dlt 操纵子在昆虫毒力中的作用，蜡状芽孢杆菌既是机会性人类病原体，也是昆虫病原体。 Delta dlt(Bc) 突变体表现出几种形态变化，但生长速度与野生型菌株相似。在体外，该突变体对鱼精蛋白和几种细菌阳离子 AMP（例如乳链菌肽、多粘菌素 B 和粘菌素）的抵抗力较低。它对昆虫体液免疫系统分子、溶菌酶和草地贪夜蛾的阳离子 AMP 天蚕素 B 的抵抗力也较低。 Delta dlt(Bc) 在大蜡螟口腔感染中的致病性与野生型菌株相同，但当注射到大蜡螟和斜纹夜蛾的血腔中时，其毒性要低得多。我们在三个革兰氏阴性菌属中检测到了 dlt 操纵子：欧文氏菌 (Erwinia carotovora)、博德特氏菌 (Bordetella pertussis、Bordetella parapertussis 和 Bordetella bronchiseptica) 和 Photorhabdus (昆虫病原细菌 Photorhabdus luminescens TT01，其 dlt 操纵子在德尔塔 dlt(Bc))。我们认为，dlt 操纵子可以保护蜡样芽孢杆菌免受昆虫体液免疫介质（包括血淋巴阳离子 AMP）的侵害，并且可能对于昆虫中致命败血症和人类医院感染的建立至关重要。
The dlt operon encodes proteins that alanylate teichoic acids, the major components of cell walls of gram-positive bacteria. This generates a net positive charge on bacterial cell walls, repulsing positively charged molecules and conferring resistance to animal and human cationic antimicrobial peptides (AMPs) in gram-positive pathogenic bacteria. AMPs damage the bacterial membrane and are the most effective components of the humoral immune response against bacteria. We investigated the role of the dlt operon in insect virulence by inactivating this operon in Bacillus cereus, which is both an opportunistic human pathogen and an insect pathogen. The Delta dlt(Bc) mutant displayed several morphological alterations but grew at a rate similar to that for the wild-type strain. This mutant was less resistant to protamine and several bacterial cationic AMPs, such as nisin, polymyxin B, and colistin, in vitro. It was also less resistant to molecules from the insect humoral immune system, lysozyme, and cationic AMP cecropin B from Spodoptera frugiperda. Delta dlt(Bc) was as pathogenic as the wild-type strain in oral infections of Galleria mellonella but much less virulent when injected into the hemocoels of G. mellonella and Spodoptera littoralis. We detected the dlt operon in three gram-negative genera: Erwinia (Erwinia carotovora), Bordetella (Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica), and Photorhabdus (the entomopathogenic bacterium Photorhabdus luminescens TT01, the dlt operon of which did not restore cationic AMP resistance in Delta dlt(Bc)). We suggest that the dlt operon protects B. cereus against insect humoral immune mediators, including hemolymph cationic AMPs, and may be critical for the establishment of lethal septicemia in insects and in nosocomial infections in humans.