Compost Fungi Allow for Effective Dispersal of Putative PGP Bacteria

Abstract

Use of compost is a common agricultural practice. It improves soil fertility by adding nutrients and plant growth promoting (PGP) microorganisms. The role of bacterial-fungal interactions for compost-driven fertilization, however, is still poorly understood. In this study, we investigated whether putative PGP bacteria associate to and disperse along mycelia of fungal isolates. A ‘Fungal highway column system’ was used to isolate and characterize fungal—bacterial couples derived from commercial compost (C), non-composted bulk soil (BS) and rhizosphere soil with compost application (RSC). Bacterial-fungal couples were identified by 16S and 18S rRNA gene sequencing and isolated bacteria were tested for representative PGP traits. Couples of fungi and associated migrator bacteria were isolated from C and RSC only. They included the fungal genera Aspergillus, Mucor, Ulocladium, Rhizopus and Syncephalastrum, and the bacterial genera Rhodococcus, Bacillus, Pseudomonas, Agrobacterium, Glutamicibacter and Microbacterium. Many of migrator bacteria in RSC and C showed PGP traits (e.g., tryptophane—induced auxin synthesis or phytate mineralizing activity) suggesting that fungi contained in C and RSC allow for dispersal of putative PGP bacteria. Next to being provider of nutrients, compost may therefore be source for PGP bacteria and fungal mycelia serving as networks for their efficient dispersal.

Microbial Community in the Composting Process and Its Positive Impact on the Soil Biota in Sustainable Agriculture

“…From each well-colonized compost particle, the microbiota relevant as an ecosystem service provider will proliferate and colonize the neighboring micro-and macro-aggregates, becoming an established soil or rhizospheric population. While the effect of arbuscular mycorrhizal fungal on bacterial transport and organic phosphorus mineralization of organic phosphorus or the colonization of legume roots by symbiotic dinitrogen-fixing bacteria is known [167], the effects of compost-derived fungi on the spread of other microorganisms remains poorly studied. The same applies to the factors affecting the migration of microbial cells from compost particles to soil aggregates.…”

Short- term Influence of Glyphosate on Microorganisms in Backyard Compost

“…All groups of microorganisms need each other in the composting process. The most efficient composting process is achieved with mixed composting, involving both bacteria and fungi [7].…”

Introducing Autochthonous Bacterium and Fungus Composition to Enhance the Phytopathogen-Suppressive Capacity of Composts against Clonostachys rosea, Penicillium solitum and Alternaria alternata In Vitro

“…Interestingly, using bacterial-fungal consortiums can have a prolonged influence, a potential in the environment. González-González et al (2021) [30] showed that Aspergillus fungi present in compost or in rhizosphere soil where compost was previously applied promoted the spread of plant growth stimulating Pseudomonas and Bacillus via mycelia. This can have a positive impact on the growth and development of plants and represents a way to improve their protection against pathogens.…”