Advances and Hotspots in Research on Verrucomicrobiota: Focus on Agroecosystems

Abstract

Members of the phylum Verrucomicrobiota are abundant yet relatively understudied soil bacteria that play key roles in biogeochemical cycling and plant-microbe interactions. They participate in the carbon (C) and nitrogen (N) cycles through the degradation of complex organic polymers such as cellulose, pectin, and starch - via the production of hydrolytic enzymes (e.g., cellulases, xylanases, chitinases), and through nitrogen transformations including denitrification, ammonification, and nitrogen fixation. Methanotrophic representatives (Methylacidiphilum, Methylacidimicrobium) oxidise methane under acidic or thermophilic conditions, thereby contributing to greenhouse gas mitigation. The ecological distribution and activity of Verrucomicrobiota are strongly influenced by nutrient availability, particularly of C, N, phosphorus (P), and potassium (K). Their variable responses to these elements reflect diverse life-history strategies, encompassing both copiotrophic (r-strategist) and oligotrophic (K-strategist) taxa. While Spartobacteria (e.g., Ca. Udaeobacter) are typically oligotrophic, classes such as Opitutia and Verrucomicrobiae exhibit mixed strategies. Beyond nutrient cycling, several members of the phylum function as plant growth-promoting and stress mitigating bacteria. They produce phytohormones (e.g., indole-3-acetic acid) and siderophores, increase the availability of nitrogen and solubilise phosphate. Some taxa exhibit antioxidant activity and can suppress phytopathogens such as Fusarium oxysporum through secondary metabolite production. These traits suggest a significant potential in soil health improvement. Overall, Verrucomicrobiota represent a functionally diverse and ecologically significant bacterial phylum whose metabolic versatility, adaptive life strategies, and plant-associated traits underscore their central role in sustainable agricultural ecosystems.

Keywords: Bacterial life strategies; Ecological functions; Microbial ecology; Plant growth promotion; Soil bacteria.

Fig. 1

Verrucomicrobiota isolated from various environments; numbers refer to isolated genera of each class. References: [, , , , –92]

Fig. 2

Descriptive statistical analyses of articles on Verrucomicrobiota published from 1997 to 2024. (A) annual publication numbers and citation times of publications, (B) global geographical distribution of publications, and VOSviewer based network visualisation of keyword co-occurrence: (C) keyword cluster map revealing major research themes, (D) a chronological overview of keywords based on the average publication year (scores were normalised by subtraction of the mean value), blue colour denote oldest while red – newest records)

Fig. 3

PGP properties of soil Verrucomicrobiota, including their contribution to the C and N cycles; PS - polysaccharides, PP - polypeptides released as secondary metabolites. The names of genera in brackets originate from the publication by Bünger et al. [37] and cannot be found in databases such as NCBI and DSMZ. References: [, , , , –, , , , , , –, –, –217]