Abstract
BackgroundThe free-living amoeba Naegleria fowleri is the causative agent of the rapidly progressing and typically fatal primary amoebic meningoencephalitis (PAM) in humans. Despite the devastating nature of this disease, which results in > 97% mortality, knowledge of the pathogenic mechanisms of the amoeba is incomplete. This work presents a comparative proteomic approach based on an experimental model in which the pathogenic potential of N. fowleri trophozoites is influenced by the compositions of different media.ResultsAs a scaffold for proteomic analysis, we sequenced the genome and transcriptome of N. fowleri. Since the sequence similarity of the recently published genome of Naegleria gruberi was far lower than the close taxonomic relationship of these species would suggest, a de novo sequencing approach was chosen. After excluding cell regulatory mechanisms originating from different media compositions, we identified 22 proteins with a potential role in the pathogenesis of PAM. Functional annotation of these proteins revealed, that the membrane is the major location where the amoeba exerts its pathogenic potential, possibly involving actin-dependent processes such as intracellular trafficking via vesicles.ConclusionThis study describes for the first time the 30 Mb-genome and the transcriptome sequence of N. fowleri and provides the basis for the further definition of effective intervention strategies against the rare but highly fatal form of amoebic meningoencephalitis.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-496) contains supplementary material, which is available to authorized users.
Highlights
The free-living amoeba Naegleria fowleri is the causative agent of the rapidly progressing and typically fatal primary amoebic meningoencephalitis (PAM) in humans
This model showed that N. fowleri trophozoites maintained in either Nelson’s medium or PYNFH medium supplemented with liver hydrolysate (LH, PYNFH/Liver hydrolysate (LH) medium) are highly pathogenic in mice and demonstrate rapid in vitro proliferation, whereas trophozoites cultured in PYNFH medium are weakly pathogenic with a slower growth
According to the genome similarity network obtained by comparing N. fowleri with N. gruberi, A. castellanii, E. histolytica, T. brucei and T. cruzi based on EST sequences (Figure 2), we found that the extent of the relationship between N. fowleri and N. gruberi is comparable to that between T. brucei and T. cruzi
Summary
Genomic DNA sequencing As a pre-requisite for obtaining insight into the pathogenic mechanism of N. fowleri, the genome of the amoeba was sequenced using both Illumina HiSeq 2000 and Roche 454 GS FLX technology. This observation confirmed the potential of all four proteins to contribute to the pathogenicity of N. fowleri. Clustering of these newly identified potential pathogenicity factors from N. fowleri according to their cellular component GO affiliations suggested localization of the proteins to the cellular membrane, in vesicles and cell projections (Figure 5)
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