The phylum Minisyncoccota (formerly known as “Candidatus Patescibacteria”/candidate phyla radiation [CPR] and designated under SeqCode as Patescibacteriota) represents one of the major bacterial phyla; however, its physiological and ecological characteristics remain unclear. This review summarizes relevant studies on currently available isolate and genomic/metagenomic data, outlining the phylogenetic placement, metabolic features, host interactions, and unique genetic code usage of Minisyncoccota. Minisyncoccota play complementary and interdependent roles within microbial communities, while being restricted by incomplete metabolic capabilities that prevent independent survival. Studies on Minisyncoccota offer important insights into the diversity and evolution of uncultivated bacteria, as well as the hidden interaction networks that shape microbial ecosystems.

Bacterial communities often originate from physical encounters between distinct species on solid surfaces; however, the mechanisms underlying these initial interactions remain unclear. The γ-hexachlorocyclohexane (γ-HCH; a toxic recalcitrant insecticide)-degrading consortium includes the surface-motile bacterium Cupriavidus sp. strain TKC and the γ-HCH-degrading Sphingobium sp. strain TKS. During a co-culture on R2A agar, TKC colonies exhibited directional colony growth (DCG), characterized by asymmetric expansion toward neighboring TKS colonies. When TKC colonies eventually overgrew TKS colonies, non-motile TKS cells were passively carried along the expanding TKC front, indicating that DCG facilitates the physical association and surface dispersal of Sphingobium cells. DCG activity was also observed against various strains of Sphingobium, Sphingomonas, and Novosphingobium, whereas extremely weak or no DCG activity was observed toward other bacterial groups, including representatives of α-, β-, and γ-proteobacteria as well as actinobacteria. These results indicate that TKC exhibits DCG selectively toward sphingomonads, recognizing taxon-specific cues rather than responding indiscriminately to neighboring colonies. Among the components tested, sphingosine reproducibly triggered DCG in a dose-dependent manner, and the inhibition of sphingolipid biosynthesis in Sphingobium with myriocin markedly suppressed the inducing effect. These results highlight the sphingosine-mediated induction of DCG as a molecular mechanism underlying the initial step in the spatial organization of bacterial communities on solid surfaces.

Horizontal chromosome transfer (HCT) has been demonstrated in Fusarium oxysporum. Several pathogenic F. oxysporum strains have been used as donors in HCT experiments, while the non-pathogenic strain Fo47 has mainly been employed as a recipient. It currently remains unknown whether other non-pathogenic F. oxysporum strains are recipients of mobile chromosomes. In the present study, we investigated whether the non-pathogenic strain 08C-3B, obtained from cabbage, acquired the mobile chromosomes of F. oxysporum f. sp. conglutinans strain Cong:1-1, which infects cabbage. We detected HCT between Cong:1-1 and 08C-3B in a conidial anastomosis tube (CAT) fusion-inductive medium, yielding HCT progeny strains that carried scaffolds (SCs) 8 and 9 of Cong:1-1. These progeny strains exhibited reduced colony growth on potato dextrose agar plates and produced no symptoms on cabbage. These results suggest that SC8 and/or SC9 hinder vegetative growth, but do not confer virulence to 08C-3B. We then conducted HCT experiments to assess whether the HCT progeny strain transfers the acquired chromosomes to other strains. However, no progeny strains were obtained, suggesting that 08C-3B does not function as a donor for mobile chromosomes.