Biodiversity of Bacteria Associated with Eight Pleurotus ostreatus (Fr.) P. Kumm. Strains from Poland, Japan and the USA

Abstract

Few publications report the occurrence of bacteria associated with fungal cells. The presence of bacteria associated with one strain of Pleurotus ostreatus (Fr.) P. Kumm. was described in the literature. We describe the biodiversity of bacteria associated with eight oyster mushroom strains from Japan, Poland, and the USA. The presence of microorganisms associated with all tested P. ostreatus strains was confirmed using fluorescent microscopy. Among 307 sequences, 233 of clones representing 34 genera and 74 sequences were identified as Bacteria. Most of the bacteria associated with the strain PUSAS were related to E. coli and two clones were related to Cupriavidus genus. The biodiversity of clones isolated from fungal strains originating from Japan and Poland ranged from 15 to 32 different bacterial clones. The most often the bacteria related to genus Curvibacter, Pseudomonas, Bacillus, Cupriavidus, Pelomonas, and Propionibacterium were associated with the strains of fungi mentioned above. Laccase-like (LMCO) genes were identified in whole bacterial DNA isolated from the associated bacteria but β-glucosidase and β-xylanase genes were not detected.

Few publications report the occurrence of bacteria associated with fungal cells. The presence of bacteria associated with one strain of Pleurotus ostreatus (Fr.) P. Kumm. was described in the literature. We describe the biodiversity of bacteria associated with eight oyster mushroom strains from Japan, Poland, and the USA. The presence of microorganisms associated with all tested P. ostreatus strains was confirmed using fluorescent microscopy. Among 307 sequences, 233 of clones representing 34 genera and 74 sequences were identified as Bacteria. Most of the bacteria associated with the strain PUSAS were related to E. coli and two clones were related to Cupriavidus genus. The biodiversity of clones isolated from fungal strains originating from Japan and Poland ranged from 15 to 32 different bacterial clones. The most often the bacteria related to genus Curvibacter, Pseudomonas, Bacillus, Cupriavidus, Pelomonas, and Propionibacterium were associated with the strains of fungi mentioned above. Laccase-like (LMCO) genes were identified in whole bacterial DNA isolated from the associated bacteria but β-glucosidase and β-xylanase genes were not detected.

Fig. 1.

Microscopic picture of analyzed oyster mushroom cells treated with fluorescent dyes under the fluorescent microscope. Strains: a) P234, b) PBo6S, c) PB8, d) P112, e) PB63S, f) PUSAS, g) PB7’96, h) PxS. Bacteria-like organisms, marked with white arrows, are visible as small green or yellow-green rods against fungal cells.

Fig. 2.

Bacteria-like organisms microcolonies growing deeply in TSAt medium after 10 days long cultivation. Strains: a) P234, b) PBo6S, c) PB8, d) P112, e) PB63S, f) PUSAS, g) PB7’96, h) PxS.

Fig. 3.

Agarose gel electrophoresis showing products of PCR with 799f and 1942r primers of analyzed oyster mushroom, maize cv. Cyrkon (Zea mays L.) (line C) and bacterial strain Pseudomonas fluorescens PE16 (line PE16) DNA. The product of 700 bp is characteristic for bacterial 16S rRNA, the product of 1100 bp is characteristic for plant mitochondrial DNA. M – marker; B – blind control.

Fig. 4.

Phylogenetic tree of identified bacteria associated with P. ostreatus strains representatives and most similar to them sequences from NCBI database. As an outgroup sequence Thermosipho sp. MV1063 (AJ419874) was used. The scale bar represents the number of changes per nucleotide position. Accession numbers are given at the end of each sequence.

Fig. 5.

Agarose gel electrophoresis showing products of PCR with Cu1AF and Cu2R primers and analyzed oyster mushroom DNA. Visible 140 bp band represents amplified LMCO genes. M – marker; B – blind control.