Biogenesis, inheritance, and 3D ultrastructure of the microsporidian mitosome

Abstract

During the reductive evolution of obligate intracellular parasites called microsporidia, a tiny remnant mitochondrion (mitosome) lost its typical cristae, organellar genome, and most canonical functions. Here, we combine electron tomography, stereology, immunofluorescence microscopy, and bioinformatics to characterise mechanisms of growth, division, and inheritance of this minimal mitochondrion in two microsporidia species (grown within a mammalian RK13 culture-cell host). Mitosomes ofEncephalitozoon cuniculi(2–12/cell) andTrachipleistophora hominis(14–18/nucleus) displayed incremental/non-phasic growth and division and were closely associated with an organelle identified as equivalent to the fungal microtubule-organising centre (microsporidian spindle pole body; mSPB). The mitosome–mSPB association was resistant to treatment with microtubule-depolymerising drugs nocodazole and albendazole. Dynamin inhibitors (dynasore and Mdivi-1) arrested mitosome division but not growth, whereas bioinformatics revealed putative dynamins Drp-1 and Vps-1, of which, Vps-1 rescued mitochondrial constriction in dynamin-deficient yeast (Schizosaccharomyces pombe). Thus, microsporidian mitosomes undergo incremental growth and dynamin-mediated division and are maintained through ordered inheritance, likely mediated via binding to the microsporidian centrosome (mSPB).

Treatment of Microsporidium Nosema bombycis Spores with the New Antiseptic M250 Helps to Avoid Bacterial and Fungal Contamination of Infected Cultures without Affecting Parasite Polar Tube Extrusion

“…Microsporidia secrete a number of enzymes and regulatory proteins into infected cells to manipulate host metabolic and regulatory pathways [ 7 , 8 , 9 , 10 ]. In adapting to their intracellular lifestyle, microsporidia have lost some typical eukaryotic cellular components, such as canonical mitochondria with tricarboxylic acid cycles and respiratory chains [ 11 , 12 , 13 , 14 ] and coated vesicles in the Golgi apparatus [ 15 ]. Furthermore, these microorganisms have highly reduced genomes [ 16 , 17 , 18 ], and their ribosomes differ from the common eukaryotic type but resemble prokaryotic ones [ 19 ].…”