Electron microscopic evidence that expression of capsular polysaccharide by Photobacterium damselae subsp. piscicidais dependent on iron availability and growth phase

Diseases of Aquatic Organisms

Manuel T. Silva¹  Ana do Vale¹  Anthony E. Ellis¹ 

关键词: Photobacterium damselae;    Bacterial capsule;    Capsule regulation;    Iron and capsular expression;   

DOI  :  10.3354/dao044237

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: The expression of capsular polysaccharide (CPS) by the fish pathogen Photobacterium damselae subsp. piscicida was analysed in the virulent strain DI 21 in relation to the growth phase and presence or absence of available iron inthe culture medium. Bacterial cells were processed for electron microscopy by a procedure that improves visualisation of the capsule through stabilisation with polycationic ferritin, and electron micrographs of ultrathin sections were scanned with anacquired computerised image analyser to measure capsular area. Cells grown under iron-limited conditions always had a significantly lower amount of capsular material on their surfaces than iron-supplemented cells, even when cells from different culturephases were compared. Irrespective of the presence or absence of iron in the culture medium the amount of CPS decreased with the age of the culture, i.e., from early log phase to late log phase to stationary phase. The in vivo significance of thisregulatory role of iron remains to be investigated.

【 授权许可】

Unknown