The Myxococcota Phylum: An Updated Taxonomy and List of Key Species (2025)
Myxobacteria, conventionally known as Gram-negative, rod-shaped bacteria, represent a unique and crucial group within the microbial world. They are famous for their complex social behaviors, which include coordinated swarming, cooperative predation on other microbes, and the formation of intricate, macroscopic fruiting bodies that house resting myxospores. These characteristics, combined with their prolific capacity to produce secondary metabolites—many of which are potent antibiotics, antifungals, and anticancer agents—make Myxobacteria a focal point in environmental microbiology and natural product drug discovery. Their traditional placement within the Delta-proteobacteria class has been challenged by genomic evidence, leading to a recent and significant taxonomic shift.
The Myxobacteria have been formally reclassified into a novel phylum, the Myxococcota (Waite et al., 2020), which encompasses the classes Myxococcia and Polyangia. This phylum contains four recognized orders: Myxococcales, Polyangiales, Nannocystales, and Haliangiales. Despite their ecological ubiquity in soil, water, and even saline environments, the inherent difficulties in their isolation and cultivation mean that only a small fraction of their immense diversity has been successfully cataloged. As of the most recent updates, the validly published taxa include only seven families and 19 genera, with new species and even new genera still being proposed and validated.
Order Myxococcales: The Primary Social Predators
The order Myxococcales is perhaps the most extensively studied, containing the families Myxococcaceae, Anaeromyxobacteraceae, and Vulgatibacteraceae. The family Myxococcaceae, in particular, hosts numerous well-known genera. The genus Myxococcus is home to the model organism Myxococcus xanthus, renowned for its multicellular development. Currently, Myxococcus is recognized to contain 11 species, including Myxococcus fulvus, Myxococcus virescens, and the newly proposed Myxococcus faecalis sp. nov. (2025). Another key genus in this family is Corallococcus, which has 14 species, such as Corallococcus exiguus and Corallococcus coralloides. Other genera in Myxococcaceae include Aggregicoccus (1 species), Citreicoccus (1 species), Pyxidicoccus (4 species), and Simulacricoccus (1 species).
The Anaeromyxobacteraceae family consists of the single genus Anaeromyxobacter, with 7 known species. The most notable is Anaeromyxobacter dehalogenans, which is a rare exception among Myxobacteria as a facultative anaerobe, capable of utilizing 2-chlorophenol as an electron acceptor. The Vulgatibacteraceae family also contains a single genus, Vulgatibacter, highlighting the phylogenetic distinctness of these groups from the more prolific Myxococcaceae.
Order Polyangiales and Associated Genera
The Order Polyangiales is dominated by the Family Polyangiaceae, which is characterized by a significant number of genera—ten in total—and a history of important natural product discoveries. The genus Sorangium, with 9 species, is particularly noteworthy. One species, Sorangium cellulosum, holds the distinction of possessing one of the largest bacterial genomes known, a trait often correlated with the capacity for complex secondary metabolite production. The genus Polyangium itself has 11 species. Other genera within this group include Chondromyces (6 species), which are known for their spectacular, branched fruiting bodies, Archangium (5 species), Cystobacter (7 species, including Cystobacter fuscus), and Melittangium (3 species). The family Archangiaceae, which is sometimes grouped with Polyangiaceae, includes the genera Archangium, Cystobacter, Hyalangium, Melittangium, Stigmatella, and Vitiosangium, collectively contributing to the morphological and metabolic diversity of the Myxococcales.
Orders Nannocystales and Haliangiales: Specialists and Extremophiles
The Order Nannocystales is primarily represented by the Family Nannocystaceae, which includes the genus Nannocystis (4 species, e.g., Nannocystis exedens) and the genus Minicystis. Minicystis rosea is a remarkable species, as its genome, at over 16 million nucleotides, is the single largest known bacterial genome, underscoring the genetic complexity of these organisms. Other associated genera include Enhygromyxa and Plesiocystis, which have been found predominantly in marine and saline environments, a habitat less typical for Myxobacteria which usually prefer neutral or slightly alkaline terrestrial soils. The Order Haliangiales, including the family Kofleriaceae, features the genus Haliangium (2 species) and Kofleria (1 species). Haliangium tepidum and H. ochraceum are examples of marine Myxobacteria that are adapted to higher salt concentrations, possessing anteiso-branched fatty acids for osmotic stability.
The 2025 Discoveries: New Genera and Human Gut Inhabitants
The year 2025 has brought significant updates to the Myxobacteria list, most notably through studies on previously unexplored niches. One groundbreaking finding reported in July 2025 involved the successful isolation of culturable Myxobacterial strains from human fecal samples of inflammatory bowel disease (IBD) patients. Historically, Myxobacteria have been considered environmental microbes, and their presence in the human gut was only tentatively suggested by metagenomic data. This study validated the existence of these predatory bacteria in a human host, proposing two novel taxa: the new species Myxococcus faecalis sp. nov. and an entirely new genus and species, Pseudomyxococcus flavus gen. nov. The isolation of these species challenges previous assumptions about Myxobacteria habitats and opens new avenues for studying their role, if any, in human health and disease. For instance, their predatory and potent secondary metabolite-producing nature could influence the gut microbiota structure.
Additionally, ongoing genomic analyses continue to refine the classification of existing isolates. For example, recent genomic data from environmental surveys has helped clarify the taxonomic position of candidate novel species, such as Archangium isolate PVMSAZ, which is closely related to Archangium gephyra, and various subspecies of Corallococcus terminator, Cystobacter fuscus, and Myxococcus fulvus. These studies, which rely on Average Nucleotide Identity (ANI) and digital DNA–DNA hybridization (dDDH) values, are essential for differentiating genuine new species from known subspecies, ensuring the accuracy of the updated species list.
Conclusion: Metabolic Diversity and Future Prospects
The updated list of Myxobacteria species, formally placed in the Myxococcota phylum, reveals an organismal group defined by both morphological complexity and profound metabolic diversity. The species list, encompassing genera like Myxococcus, Corallococcus, Anaeromyxobacter, Sorangium, and the newly discovered Pseudomyxococcus, represents a deep and largely untapped reservoir of biological innovation. From the synthesis of vital compounds like carotenoids and geosmin (found in most species except those in Anaeromyxobacter, Labilithrix, and Vulgatibacter) to the production of a wide array of cytotoxic metabolites—including soraphen, epothilone, and myxochromide—Myxobacteria remain one of the most critical bacterial sources for new drug leads. The recent discovery of species in the human gut environment further expands the known ecological range and potential importance of this remarkable phylum, underscoring the ongoing need for isolation and characterization of new species to fully harness their biomedical potential.