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Members of the Cytophaga–Flavobacterium–Bacteroides phylum as intracellular bacteria of acanthamoebae: proposal of ‘ Candidatus Amoebophilus asiaticus’
Author(s) -
Horn Matthias,
Harzenetter Marit D.,
Linner Tanja,
Schmid Ernst N.,
Müller KarlDieter,
Michel Rolf,
Wagner Michael
Publication year - 2001
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1046/j.1462-2920.2001.00210.x
Subject(s) - biology , cytophaga , microbiology and biotechnology , acanthamoeba , flavobacterium , 16s ribosomal rna , candidatus , ribosomal rna , bacteria , genetics , gene , pseudomonas
Three Gram‐negative, rod‐shaped bacteria that were found intracellularly in two environmental and one clinical Acanthamoeba sp. isolates were analysed. Two endocytobionts showing a parasitic behaviour were propagated successfully outside their amoebal host cells and were identified subsequently by comparative 16S rRNA sequence analysis as being most closely affiliated with Flavobacterium succinicans (99% 16S rRNA sequence similarity) or Flavobacterium johnsoniae (98% 16S rRNA sequence similarity). One endocytobiont could neither be cultivated outside its original Acanthamoeba host ( Acanthamoeba sp. TUMSJ‐321) nor transferred into other amoebae. Electron microscopy revealed that the amoebal trophozoites and cysts were almost completely filled with cells of this endosymbiont which are surrounded by a host‐derived membrane. According to 16S rRNA sequence analysis, this endosymbiont could also be assigned to the Cytophaga – Flavobacterium – Bacteroides (CFB) phylum, but was not closely affiliated to any recognized species within this phylogenetic group (less than 82% 16S rRNA sequence similarity). Identity and intracellular localization of this endosymbiont were confirmed by application of a specific fluorescently labelled 16S rRNA‐targeted probe. Based on these findings, we propose classification of this obligate Acanthamoeba endosymbiont as ‘ Candidatus Amoebophilus asiaticus’. Comparative 18S rRNA sequence analysis of the host of ‘ Candidatus Amoebophilus asiaticus’ revealed its membership with Acanthamoeba 18S rDNA sequence type T4 that comprises the majority of all Acanthamoeba isolates.