Protist and Plant Growth-Promoting Bacterium Interaction Alters GH3-2 Expression and Enhances Nutrient Content in Rice

The present study aimed to assess the interactive effects of four plant growth-promoting bacterium(PGPB)species[Providencia sp.(Pr),Stenotrophomonas sp.(St),Morganella sp.(Mo),and Lysinibacillus sp.(Lb)]and six protist species[two amoebae Vermamoeba vermiformis(A9)and Acanthamoeba genotype T4(A34),and four ciliates Crytolophosis mucicola(C1),Tetrahymena sp.(C2),Colpoda elliotti(C12),and an unidentified genus of the family Kreyellidae(C5)]on the uptake of nutrients and the expression of auxin-responsive gene(GH3-2)in rice.The findings revealed that rice seedlings grew healthily,and a statistically significant difference was observed after 30 d of incubation in pots under greenhouse conditions treated with each PGPB and protist-PGPB consortia,compared with the untreated control plants.However,the protist-PGPB treatments were more significant than PGPB treatment alone.The greatest improvement in rice seedling growth was observed in C.elliotti with Stenotrophomonas sp.(C12St)treatment,showing increased root and shoot length(88.57%and 79.69%).

Role of methylotrophic bacteria in managing abiotic stresses for enhancing agricultural production

Abiotic stresses are a significant factor that considerably limits plant growth and productivity.Methylotrophs are an essential group of bacteria that utilize volatile carbon compounds,are prolific colonizers of different plant parts,and play a vital role in plant growth promotion(PGP)under stress conditions.Numerous rhizospheric and phyllosphere methylotrophs have been reported to exhibit PGP activities with superior stress-tolerating capacity against drought,heavy metal,salinity,high and low temperatures,solar ultraviolet radiation,and other harsh environmental conditions.Methylotrophs promote plant growth through N2 fixation,phosphate solubilization,production of phytohormones(i.e.,auxins,gibberellins,and cytokinins),1-aminocyclopropane-1-carboxylic acid(ACC)deaminase activity,siderophore,ammonia production,and secondary metabolites.The production of these compounds by methylotrophs protects a plant against adverse environmental conditions and influences its productivity.This review discusses the role methylotrophs play in managing various abiotic stresses,how they help mitigate these stresses,and how they improve agricultural productivity.

Soil protists: An untapped microbial resource of agriculture and environmental importance

Protists are essential components of soil biodiversity and ecosystem functioning. They play a vital role in the microbial food web as consumers of bacteria, fungi, and other small eukaryotes and are also involved in maintaining soil fertility and plant productivity. Protists also contribute to regulating and shaping the bacterial community in terrestrial ecosystems via specific prey spectra. They play a role in plant growth promotion and plant health improvement,mostly via nutrient cycling, grazing, and the activation of bacterial genes required for plant growth and phytopathogen suppression. Thus, protists may prove to be a useful inoculant as biofertilizer and biocontrol agent. They can also be applied as model organisms as bioindicators of soil health. Despite their usefulness and essentiality, they are often forgotten and under-researched components of the soil microbiome, as most of our research focuses on bacteria and fungi. In this review, we provide an overview of the role of protists in plant productivity and plant health management and in shifts in soil bacterial community composition, as well as their roles as bioindicator. We also discuss the perspectives of knowledge gaps and future prospects to further improve soil biology.More research in soil protistology will provide insights into sustainable agriculture and environmental health alongside the study of bacteria and fungi.