Practice question

Microsporidia represent highly reduced parasitic fungi-related lineage lacking canonical mitochondria with oxidative phosphorylation and citric acid cycle. Instead contain tiny double-membrane organelles called mitosomes remnants of mitochondria retaining iron-sulfur cluster assembly machinery but lacking respiratory chain, mitochondrial genome and cristae. Hydrogenosomes occur in parabasalids producing hydrogen via fermentation, peroxisomes and glyoxysomes distinct peroxisome family with catalase. Discovery of mitosomes in Encephalitozoon cuniculi via Hsp70 immunolocalization confirmed mitochondrial ancestry and reductive evolution. Hence microsporidia possess mitosomes as mitochondrial derivative. Genomic reduction includes loss of de novo nucleotide synthesis pathways making them hypersensitive to drugs targeting polar tube extrusion mechanisms.