Bacillus subtilis Promotes Cucumber Growth and Quality under Higher Nutrient Solution by Altering the Rhizospheric Microbial Community

Summary

This experimental study evaluated whether Bacillus subtilis K424 inoculation could mitigate the negative effects of high-nutrient hydroponic solutions on cucumber growth and quality in a peat-based soilless system. The bacterium improved growth performance, photosynthetic capacity, and fruit quality parameters (vitamin C, soluble sugars, soluble protein, pectin) under elevated nutrition conditions, whilst also modifying the rhizospheric microbial community structure and enhancing substrate enzyme activities. The results suggest that B. subtilis K424 acts through multiple mechanisms: substrate enzyme enhancement, microbial community regulation, and photosynthetic improvement.

Regional applicability

The study was conducted in a controlled soilless (hydroponic) environment and does not specify the geographic location. The findings are directly applicable to UK horticultural practice, particularly commercial protected cucumber production systems that use soilless media and standard or intensive nutrient regimes. The use of beneficial bacteria to optimise quality under high-nutrient conditions is relevant to UK glasshouse horticulture, although field-scale validation in UK climatic conditions would strengthen applicability.

Key measures

Cucumber biomass and growth; photosynthetic capacity; fruit vitamin C content; soluble sugars; soluble protein; total pectin; volatile flavour compounds ((E,Z)-2,6-nonadienal and (E)-2-Nonenal); bacterial and fungal diversity (16S rRNA, ITS sequencing); relative abundance of bacterial genera; substrate enzyme activities (sucrase, catalase, urease)

Outcomes reported

The study measured the effects of Bacillus subtilis K424 inoculation on cucumber growth performance, photosynthetic capacity, fruit quality (vitamin C, soluble sugars, soluble protein, total pectin, and volatile flavour compounds), and rhizospheric microbial community composition under standard and elevated nutrient solution regimes in peat-based soilless cultivation.

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