AUTHOR=Hua Zhongyi , Liu Tianrui , Han Pengjie , Zhou Junhui , Zhao Yuyang , Huang Luqi , Yuan Yuan 

TITLE=Isolation, genomic characterization, and mushroom growth-promoting effect of the first fungus-derived Rhizobium

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.947687

DOI=10.3389/fmicb.2022.947687

ISSN=1664-302X

ABSTRACT=<p><italic>Polyporus umbellatus</italic> is a well-known edible and medicinal mushroom, and some bacteria isolated from mushroom sclerotia may have beneficial effects on their host. These mushroom growth-promoting bacteria (MGPBs) are of great significance in the mushroom production. In this work, we aimed to isolate and identify MGPBs from <italic>P. umbellatus</italic> sclerotia. Using the agar plate dilution method, strain CACMS001 was isolated from <italic>P. umbellatus</italic> sclerotia. The genome of CACMS001 was sequenced using PacBio platform, and the phylogenomic analysis indicated that CACMS001 could not be assigned to known <italic>Rhizobium</italic> species. In co-culture experiments, CACMS001 increased the mycelial growth of <italic>P. umbellatus</italic> and <italic>Armillaria gallica</italic> and increased xylanase activity in <italic>A. gallica</italic>. Comparative genomic analysis showed that CACMS001 lost almost all nitrogen fixation genes but specially acquired one redox cofactor cluster with <italic>pqqE</italic>, <italic>pqqD</italic>, <italic>pqqC</italic>, and <italic>pqqB</italic> involved in the synthesis of pyrroloquinoline quinone, a peptide-derived redox participating in phosphate solubilization activity. Strain CACMS001 has the capacity to solubilize phosphate using Pikovskaya medium, and <italic>phnA</italic> and <italic>phoU</italic> involved in this process in CACMS001 were revealed by quantitative real-time PCR. CACMS001 is a new potential <italic>Rhizobium</italic> species and is the first identified MGPB belonging to <italic>Rhizobium.</italic> This novel bacterium would play a vital part in <italic>P. umbellatus</italic>, <italic>A. gallica</italic>, and other mushroom cultivation.</p>