Cooperation among phosphate-solubilizing bacteria, humic acids and arbuscular mycorrhizal fungi induces soil microbiome shifts and enhances plant nutrient uptake

Abstract

Background Increasing the presence of beneficial soil microorganisms is a promising sustainable alternative to support conventional and organic fertilization and may help to improve crop health and productivity. If the application of single bioeffectors has shown satisfactory results, further improvements may arise by combining multiple beneficial soil microorganisms with natural bioactive molecules. Methods In the present work, we investigated in a pot experiment under greenhouse conditions whether inoculation of two phosphate-solubilizing bacteria, Pseudomonas spp. (B2) and Bacillus amyloliquefaciens (B3), alone or in combination with a humic acids (HA) extracted from green compost and/or a commercial inoculum (M) of arbuscular mycorrhizal fungi (AMF), may affect maize growth and soil microbial community. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) fingerprinting analysis were performed to detect changes in the microbial community composition. Results Plant growth, N and P uptake, and mycorrhizal root colonization were found to be larger in all inoculated treatments than in the uninoculated control. The greatest P uptake was found when B. amyloliquefaciens was applied in combination with both HA and arbuscular mycorrhizal fungi (B3HAM), and when Pseudomonas was combined with HA (B2HA). The PLFA-based community profile revealed that inoculation changed the microbial community composition. Gram+/Gram− bacteria, AMF/saprotrophic fungi and bacteria/fungi ratios increased in all inoculated treatments. The greatest values for the AMF PLFA marker (C16:1ω5) and AMF/saprotrophic fungi ratio were found for the B3HAM treatment. Permutation test based on DGGE data confirmed a similar trend, with most significant variations in both bacterial and fungal community structures induced by inoculation of B2 or B3 in combination with HA and M, especially in B3HAM. Conclusions The two community-based datasets indicated changes in the soil microbiome of maize induced by inoculation of B2 or B3 alone or when combined with humic acids and mycorrhizal inoculum, leading to positive effects on plant growth and improved nutrient uptake. Our study implies that appropriate and innovative agricultural management, enhancing the potential contribution of beneficial soil microorganisms as AMF, may result in an improved nutrient use efficiency in plants.

Impacts of humic-based products on the microbial community structure and functions toward sustainable agriculture

“…with HA were applied to soil. This work also noted significant changes in bacterial and fungal diversity with HA application (Cozzolino et al, 2021). Selected studies showing combined effects of HPs with other inputs on microbial community structure and functions are presented in Table 2.…”

Antiflammatory activity and potential dermatological applications of characterized humic acids from a lignite and a green compost

“…Several studies pointed out the occurrence of beneficial effects of humic matter, also from composted biomasses, on either plants or microorganisms at molecular, physiological and transcriptional levels 56 . A working hypothesis of the bioactive effects of humic matter relies on the concomitant combination of conformational structure and molecular composition on the interaction with a different type of cells 57 .…”

PLaBAse: A comprehensive web resource for analyzing the plant growth-promoting potential of plant-associated bacteria

“…Comparable PGPT annotation results will facilitate the selection of plant-beneficial inoculant strains for a sustainable plant production and protection, by determination of (i) best site adapted pathways (e.g., for salinity tolerance) and of (ii) overlapping traits with antagonizing functions of pathogens (e.g., bactericidal compounds), the latter important for exclusion of dysbiosis by competition and assertiveness in an established environment. Those interspecies-interactions, whether symbiotic or not, have to be further elucidated, for example by co-cultivation studies on plant-based media or germ-free plants to determine the best plant-simulating environments 23,[97][98][99] . Here the cultivability of yet uncultured PA strains will enable a better understanding of genetic traits or genome organization (e.g., biosynthetic gene clusters) related to niche adaption 100,101 .…”