Plasmodium Biology: Scientific Classification

Morphological characterization and genetic techniques allow the description of the phylogenetic diversity of organisms. The Plasmodium genus belongs to the Plasmodiidae family, Haemospororida order, Aconoidasida class, Apicomplexa phylum, Alveolata superphylum, Halvaria infrakingdom, Harosa subkingdom, Chromista kingdom, and Eukaryote domain (Figure 1).

Five species that cause human Malaria are Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium knowlesi. Artemisinin, mosquito nets, and vector control are antimalarial tools in endemic areas. It is crucial to have a good understanding of Plasmodium biology to implement effective control measures. Obtaining information about the structure and evolutionary processes of the Plasmodium can help achieve this understanding (Egwu et al., 2023).

Haemosporida are intracellular parasites that infect vertebrates and are transmitted by blood-sucking insects. Genetic analysis, particularly of the mitochondrial cytochrome b gene, is used to identify haemosporidian species (Bernotiené et al., 2019; Fecchio et al., 2020). Aconoidasida possesses an apical complex, which enables mobility and host cell invasion. This complex includes various organelles such as the polar ring, conoids, rhoptries, dense granules, microtubules, and micronemes (Figure 2). However, the Plasmodium species have a reduced or absent conoid. Recent proteomic and tomography studies have shown conoid structures across all Plasmodium life cycle forms (Koreny et al., 2021; Haase et al., 2022 ).

Apicomplexa are single-celled eukaryotes that parasitize metazoans. They possess apical complexes that secrete enzymes and are involved in host cell invasion. Apicomplexa is a taxonomic group that comprises entirely parasitic organisms (Swapna and Parkinson, 2017; Boisard and Florent, 2020). The Apicomplexa possess apicoplasts containing an additional circular DNA molecule that resembles the plastid DNA found in non-photosynthetic plants. This DNA molecule is approximately 35 kd and contains a palindromic sequence of genes responsible for subunit rRNAs, various tRNAs, proteins, and RNA polymerase subunits. The subunit rRNA genes are similar to those in mitochondrial or plastid sequences (Ng et al., 2018). This plastid-like DNA has been acquired through secondary endosymbiosis and conserved among organellar genomes. Apicomplexan parasites also have highly conserved organellar genomes with DNA similar to that found in mitochondria. This mitochondrial DNA consists of a 6 kb tandem repeat that codes for proteins, such as cytochrome b and cytochrome oxidase, as well as rRNAs (Verhoef et al., 2021).

Alveolata are single-celled organisms that have submembranous alveoli. The identifi cation of Alveolata relies on the ultrastructure and molecular phylogenies of the 18S rRNA gene (Arzul and Carnegie, 2015; Gigeroff et al., 2023). Harosa is a monophyletic lineage with an RAB paralog (Rab1A), and it exhibits ciliary or pseudopodial locomotion with cortical alveoli. The Rab GTPase is a gene family with multiple paralogs that regulate the maintenance of the eukaryotic cell’s compartmentalization system. Rab paralogs are regulators of membrane traffi cking conserved in all eukaryotes (Cavalier-Smith, 2010; Cavalier-Smith et al., 2018; Morse et al., 2016).

The chromalveolates may have emerged from a process of chloroplast endosymbiosis between heterotrophic unicellular eukaryotes and unicellular red algae, based on molecular and morphological data of eukaryotic phylogeny. These organisms have evolved and specialized to thrive in specifi c environments, and establishing a new plastid organelle by secondary endosymbiosis is a highly complex process (Keeling, 2010; Walker et al., 2011; Sierra et al., 2013). Plasmodium, a eukaryotic organism, undergoes schizogonies in recipient vertebrates and sporogonies in vector insects. It possesses specialized organelles, notably the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, ribosomes, peroxisomes, and plastids (Cavalier-Smith, 1998; Simpson et al., 2004).

Understanding the taxonomical position, cellular architecture, and evolutionary history of Plasmodium is essential for advancing malaria research and improving control strategies. The integration of morphological, genetic, and molecular data allows researchers to decipher the complex biology of these parasites and their relationships within the phylogenetic tree of eukaryotes. Insights into organellar genomes, endosymbiotic origins, and technical invasion machinery deepen our knowledge of parasite evolution and provide serious targets for sanative intervention. Continued interdisciplinary research will be essential for developing modern tools to combat malaria and mitigate its orbicular impact (Moumaris et al., 1992 - 2025).

Keywords: Plasmodium, Malaria Parasites, Apicomplexa, Endosymbiosis, Phylogeny, Organellar genomes.

Abbreviations

kb / kb: Kilobase (unit of DNA length)

kd / kDa: Kilodalton (unit of molecular mass)

Rab: Ras-related in brain (GTPase family)