Native Bacteria Associated with Mushroom Cultivation Promote Mushroom Growth Through Multiple Mechanisms

Some microorganisms present in the cultivation environment serve as biocontrol agents and contribute to enhanced mushroom production. However, the native bacteria naturally associated with commercial cultivation bags of Pleurotus ostreatus, as well as their growth-promoting roles and underlying mechanisms, remain poorly understood. This study aimed to identify native bacteria that promote Pleurotus ostreatus development and to investigate the underlying mechanisms. Four native bacteria, including Brevibacterium epidermidis (P6), Acinetobacter soli (A7), Pseudomonas parafulva (A8), and Pseudomonas hunanensis (A12), were isolated based on their ability to promote mycelial growth of P. ostreatus. B. epidermidis P6 shortened complete mycelial colonization time from ~30 d to 14 d in dual cultivation bags. All four strains increased fresh mushroom yield, with B. epidermidis P6, A. soli A7, and P. parafulva A8 increasing the number of basidiomata, while P. hunanensis A12 enhanced their size. These strains produced exopolysaccharides that enhanced mycelial growth. Additionally, B. epidermidis P6, A. soli A7, and P. parafulva A8 also secreted extracellular crude proteins that also promoted mycelial growth. Bi-plates and further gas chromatography–mass spectrometry analysis demonstrated that volatile organic compounds from P. hunanensis A12, including acetone, 2-butanone, benzaldehyde, and 1-undecene, enhanced fungal mycelial growth. The mycelial growth rates of Ganoderma lucidum and Pleurotus pulmonarius were also enhanced by these four strains. These results reveal that four native bacterial strains promote mushroom development through complex mechanisms.