Microsporidia: Obligate Intracellular Pathogens Within the Fungal Kingdom

Abstract

Microsporidia are obligate intracellular pathogens related to Fungi. These organisms have a unique invasion organelle, the polar tube, which upon appropriate environmental stimulation rapidly discharges out of the spore, pierces a host cell’s membrane, and serves as a conduit for sporoplasm passage into the host cell. Phylogenetic analysis suggests that microsporidia are related to the Fungi, being either a basal branch or sister group. Despite the description of microsporidia over 150 years ago, we still lack an understanding of the mechanism of invasion, including the role of various polar tube proteins, spore wall proteins, and host cell proteins in the formation and function of the invasion synapse. Recent advances in ultrastructural techniques are helping to better define the formation and functioning of the invasion synapse. Over the past 2 decades, proteomic approaches have helped define polar tube proteins and spore wall proteins as well as the importance of posttranslational modifications such as glycosylation in the functioning of these proteins, but the absence of genetic techniques for the manipulation of microsporidia has hampered research on the function of these various proteins. The study of the mechanism of invasion should provide fundamental insights into the biology of these ubiquitous intracellular pathogens that can be integrated into studies aimed at treating or controlling microsporidiosis.

Detection of the intranuclear microsporidian Enterospora nucleophila in gilthead sea bream by in situ hybridization

“…Scarce spores were found in stomach, gall bladder, peripheral blood or liver samples (Figure c and d and data not shown). Calcofluor white M2R is widely used to detect microsporidian species due to the high affinity of this compound to bind the chitin present at the Microsporidia endospore membrane (Han & Weiss, ). Other chemofluorescent agents, mostly stilbene derivatives typically used as whiteners in detergents and in paper and fabrics manufacture, present similar properties acting as chitin‐specific stains (e.g., Hoch, Galvani, Szarowski, & Turner, ; Rüchel & Schaffrinski, ).…”

“…Over half of the known genera infect aquatic organisms (Stentiford et al, 2016). With a close phylogenetic relationship with fungi, they share biological features such as the presence of chitin in the spores, the use of trehalose as the main sugar reserve or some similarities during mitosis and meiosis (Han & Weiss, 2017). Like in the Rozellomycota, adaption to obligate intracellular parasitism has led to gene loss, genome reduction and dependence upon the host for cell function (Ndikumana et al, 2017;Quandt et al, 2017).…”

Morphology and Transcriptome Analysis of Nosema bombycis Sporoplasm and Insights into the Initial Infection of Microsporidia

“…Microsporidia may invade host cells by a variety of means. The main hypotheses include direct penetration of the host cell through the polar tube, polar tube interaction with the host cell plasma membrane and sporoplasm endocytosis, and spore adher-ence to the host cell and invasion by endocytosis (12,37,38). However, the molecular mechanism of these invasion methods is unknown, and the role that the sporoplasm plays in the infection process has not been widely reported.…”

Prevalence of enteric Protozoa on fresh vegetables and their irrigation water in Giza, Egypt

“…parasites (Adamu et al, 2013). Intestinal protozoan infections were documented among both immunosuppressed and immunocompetent patients (Fletcher et al, 2012;Han and Weiss, 2017). Cryptosporidium, Entamoeba and microsporidia are considered as major intestinal Protozoa of public health importance (Kosek et al, 2001 ;Haque et al, 2003;Han and Weiss, 2017;Daniel et al, 2018;Kimosop et al, 2019;Ögren et al, 2020) due to being responsible for waterborne diseases in human.…”