From Lab to Field: Context-Dependent Impacts of Pseudomonas-Produced 2,4-Diacetylphloroglucinol on Soil Microbial Ecology

TL;DR

This study shows that the antimicrobial compound 2,4-DAPG from Pseudomonas bacteria affects soil microbes differently in labs versus real-world fields, highlighting the importance of context in ecological research.

Contribution

The study reveals context-dependent microbial responses to 2,4-DAPG in lab and field settings, emphasizing the limitations of extrapolating lab results to natural ecosystems.

Findings

2,4-DAPG altered bacterial and fungal diversity in lab experiments but had smaller effects in field conditions.

Fungal groups like Mucoromycota were consistently suppressed, while bacteria like Bacillota were enriched in the lab but not in the field.

Enzymatic activity showed dose-dependent changes, with stronger responses observed in field conditions compared to the lab.

Abstract

The secondary metabolite 2,4-diacetylphloroglucinol (2,4-DAPG), which is produced by Pseudomonas bacteria, is a potent antimicrobial agent with well-documented properties that suppress phytopathogens. However, its broader ecological impact on soil microbial communities is not understood. Through a combination of controlled microcosm and field trials, we have demonstrated that the effects of 2,4-DAPG are highly context-dependent. Laboratory exposure (10 mg kg−1) altered the abundance of 8.53% of bacterial and 6.91% of fungal amplicon sequence variants, and simplified the bacterial co-occurrence networks (reduced number of nodes and links). In contrast, field conditions amplified bacterial sensitivity (the Shannon index decreased from 4.77 to 4.17, p < 0.05) but maintained fungal stability (Shannon index varied from 3.93 to 3.97, p > 0.05); these conditions affected a smaller proportion of fungal ASVs (4.23%). Taxonomic analysis revealed consistent suppression of fungi of the Mucoromycota (e.g., Mortierella) and context-dependent shifts in bacteria, with an enrichment of Bacillota (e.g., Bacillus, Paenibacillus) in the laboratory but not in the field. Enzymatic responses revealed a dose-dependent activation of the C-cycle, with up to 7.4-fold increases in the laboratory and up to a 10.5-fold increase in the field. P- and N- cycles showed more complex dynamics, with acid phosphatase activity increasing 3.8-fold in laboratory conditions and recovering from initial suppression to an increase of 144% in field conditions, while N-acetylglucosaminidase activity increased and L-leucine aminopeptidase decreased under laboratory conditions. Our results suggest that the response of microorganisms to 2,4-DAPG in natural soils is reduced, probably due to functional redundancy and pre-adaptation to abiotic stresses. This difference between laboratory and field studies warns against extrapolating data from controlled experiments to predict outcomes in agricultural ecosystems, and emphasizes the need for a context-specific evaluation of biocontrol agents.

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