Age-related macular degeneration (AMD) is the most frequent cause of blindness in the elderly. There is evidence that nutrition, inflammation and genetic risk factors play an important role in the development of AMD. Recent studies suggest that the composition of the intestinal microbiome is associated with metabolic diseases through modulation of inflammation and host metabolism. To investigate whether compositional and functional alterations of the intestinal microbiome are associated with AMD, we sequenced the gut metagenomes of patients with AMD and controls. The genera Anaerotruncus and Oscillibacter as well as Ruminococcus torques and Eubacterium ventriosum were relatively enriched in patients with AMD, whereas Bacteroides eggerthii was enriched in controls. Patient’s intestinal microbiomes were enriched in genes of the L-alanine fermentation, glutamate degradation and arginine biosynthesis pathways and decreased in genes of the fatty acid elongation pathway. These findings suggest that modifications in the intestinal microbiome are associated with AMD, inferring that this common sight threatening disease may be targeted by microbiome-altering interventions.

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.

Age-related macular degeneration (AMD) is a leading cause of severe vision loss in the aged population. The etiology of AMD is multifactorial including nutritional factors, genetic variants mainly in the complement pathway, environmental risk factors and alterations in the intestinal microbiome. However, it remains unexplored whether there is an interdependency of these factors leading to the development of AMD. To investigate this issue, a shotgun metagenomics analysis of 57 neovascular AMD and 58 healthy controls as well as of 16 complement C3-deficient mice and 16 wildtypes was performed. Whereas the class Negativicutes was more abundant in patients, the genus Oscillibacter and species Bacteroides had a significantly higher prevalence in persons without AMD. Similar taxonomic features were identified that distinguished wildtype mice from C3-deficient mice. Moreover, several purine signaling pathways were associated with both, neovascular AMD and C3 deficiency. While SNPs within the complement factor B gene were more abundant in controls, SNPs within the high temperature requirement A serine peptidase 1 and complement factor H (CFH) genes were associated with neovascular AMD. Using a classification model, Negativicutes was identified as a potential biomarker for AMD and furthermore, it positively correlated with CFH. This study suggests an association between the intestinal microbiome and the complement system in neovascular AMD.