Analyzing Microsporidia sp. MB from sequence to biology: comprehensive exploration of the genome, protein structures, and functions through extensive bioinformatics analysis
Authors:   , Ang'ang'o Lilian Mbaisi 
Published: December 2024

Microsporidia are spore-forming intracellular organisms classified as the earliest divergent group within the Fungi kingdom. Microsporidia have been found widely affecting different hosts, including both vertebrates and invertebrates. The pathogenicity of microsporidia depends on their species and the host species they infect. Due to their obligate intracellular nature, microsporidia have extensively evolved. This is illustrated by their highly variable genome sizes and gene content. Being minimalist eukaryotes, the microsporidia genome is often associated with extreme gene reduction and compaction. However, these interesting microorganisms retain particular genes that help them acquire specific host nutrients, thereby relying heavily on their host for survival and proliferation. The mode of sexual reproduction of microsporidia has not been well-studied. Harnessing microsporidia in the laboratory is often a challenge, however, the advances in computational tools have made it cheaper and quicker to accurately predict and annotate these organisms to understand their mechanism of infection. Understanding the protein structure and function of these unique organisms is the baseline for providing insights into their biology and survival in their respective hosts. Microsporidia genomes contain a large proportion of hypothetical proteins of which their functions are not described. Vittaforma corneae ATCC 50505 was used as a model to highlight the functions and structure of these otherwise unknown proteins. A systematic annotation pipeline employing exhaustive computational tools was devised to carefully annotate the hypothetical proteins of V. corneae, aiming to characterize their structure and function.The genome of the novel microsporidian, Microsporidia sp. MB, a Plasmodium-transmission-blocking symbiont isolated from Anopheles mosquitoes in Sub-Saharan Africa, was sequenced, assembled, and annotated. The genome was found to contain over 2000 putative genes spanning its 5.9 Mb size and contained minimal repeats. Comparative phylogenomic analysis of Microsporidia sp. MB grouped this symbiont within the Enterocytozoonida (clade IV) microsporidia, clustering with its closest relative – V. corneae. Using robust computational techniques, prediction and characterization of the putative proteins of Microsporidia sp. MB was conducted. The decay of several proteins in the glycolytic pathway is one unique characteristic associated with microsporidia. The proteins retained or lost often vary across the microsporidian taxon. This study highlights the retention of most of the proteins involved in the glycolytic pathway in Microsporidia sp. MB. The available genome dataset of Microsporidia sp. MB was further used to infer its mode of sexual reproduction. The symbiont appears to have several meiotic-related gene orthologs, suggesting that it is capable of sexual reproduction. These findings describe the basic biology of Microsporidia sp. MB and provide a basis for future Next-Generation Sequencing, RNA sequencing experiments ultimately informing the application of this microorganism as a biological malaria control tool.