Isolation of bacteria at different points of Pleurotus ostreatus cultivation and their influence in mycelial growth

Isolation of bacteria from Grifola frondosa cultivation on wood logs to find mycelial growth-promoting bacteria

This study aimed to isolate bacteria that coexist with the edible mushroom Grifola frondosa when it is cultured on wood, and to determine their interactions; in turn, the aim was to find bacteria that stimulate mycelial growth so as to decrease the time required for spawn preparation on potato dextrose agar (PDA). Some Pseudomonas, Dyella, Bacillus, and Priestia spp. isolated from the cultivation surroundings of G. frondosa had a positive effect on the mycelial growth of the fungus in PDA. However, some isolated bacteria had a severe negative effect on the mycelial growth, especially Burkholderia spp. Thus, both mycelial-promoting bacteria and potentially pathogenic bacteria coexist with G. frondosa in cultivation. Enzyme activity assays indicated that some wood-degrading bacteria inhabit the cultivation surroundings of G. frondosa, and these bacteria probably help the fungus to degrade wood (especially cellulose).

Identification of Growth-Promoting Bacterial Resources by Investigating the Microbial Community Composition of Polyporus umbellatus Sclerotia

The sclerotium of the edible mushroom Polyporus umbellatus (Zhuling) exhibits various medicinal properties. However, given its long growth cycle and overexploitation, wild resources are facing depletion. Macrofungal growth depends on diverse microbial communities; however, the impact of soil bacteria on P. umbellatus development is unknown. Here, we combined high-throughput sequencing and pure culturing to characterize the diversity and potential function of bacteria and fungi inhabiting the P. umbellatus sclerotium and tested the bioactivities of their isolates. Fungal operational taxonomic units (OTUs) were clustered and classified, revealing 1275 genera. Bacterial OTUs yielded 891 genera. Additionally, 81 bacterial and 15 fungal strains were isolated from P. umbellatus sclerotia. Antagonism assays revealed three bacterial strains (FN2, FL19, and CL15) promoting mycelial growth by producing indole-3-acetic acid, solubilizing phosphate, and producing siderophores, suggesting their role in regulating growth, development, and production of active compounds in P. umbellatus. FN2-CL15 combined with bacterial liquid promoted growth and increased the polysaccharide content of P. umbellatus mycelia. This study reports new bioactive microbial resources for fertilizers or pesticides to enhance the growth and polysaccharide accumulation of P. umbellatus mycelia and offers guidance for exploring the correlation between medicinal macrofungi and associated microbial communities.

Study of growth-improving and sporophore-inducing endobacteria isolated from Pleurotus pulmonarius

Several Pleurotus species (oyster mushrooms) are commercially cultivated in India owing to the favorable tropical agro-climatic conditions. However, there are only a few studies on the microbiome of mushrooms, especially oyster mushrooms. The aim of this study was to assess the effect of endobacteria on mycelial growth, spawning, sporophore development, and proximate composition of P. pulmonarius. We isolated several bacterial strains from the sporophores of P. pulmonarius and assessed the in vitro production of indole acetic acid, ammonia, and siderophores. The selected bacteria were individually supplemented with spawn, substrate, or both for sporophore production. Three of 130 isolates were selected as mycelial growth-promoting bacteria in both solid and submerged fermentation. These bacterial isolates were identified through Gram staining, biochemical characterization, and 16S rRNA sequencing. Isolate PP showed 99.24% similarity with Priestia paraflexa, whereas isolates PJ1 and PJ2 showed 99.78% and 99.65% similarities, respectively, with Rossellomorea marisflavi. The bacterial supplementation with spawn, substrate, or both, increased the biological efficiency (BE) and nutrient content of the mushrooms. The bacterial supplementation with substrate augmented BE by 64.84%, 13.73%, and 27.13% using PJ2, PP, and PJ1, respectively; under similar conditions of spawn supplementation, BE was increased by 15.24%, 47.30%, 48.10%, respectively. Overall, the supplementation of endobacteria to improve oyster mushroom cultivation may open a new avenue for sustainable agricultural practices in the mushroom industry.

Identification and profiling of the community structure and potential function of bacteria from the fruiting bodies of Sanghuangporus vaninii

Sanghuangporus sp., a medicinal and edible homologous macrofungus known as 'forest gold', which has good effects on antitumor, hypolipidemia and the treatment of gynecological diseases. However, the natural resources of fruiting body are on the verge of depletion due to its long growth cycle and over exploitation. The growth and metabolism of macrofungi are known to depend on the diverse bacterial community. Here, we characterized the diversity and potential function of bacteria inhabiting in the fruiting body of the most widely applied S. vaninii using a combination method of high-throughput sequencing with pure culturing for the first time, and tested the biological activities of bacterial isolates, of which Illumina NovaSeq provided a more comprehensive results on the bacterial community structure. Total 33 phyla, 82 classes, 195 orders, 355 families, 601 genera and 679 species were identified in the fruiting body, and our results revealed that the community was predominated by the common Proteobacteria, Gammaproteobacteria, Burkholderiales, Methylophilaceae (partly consistent with pure-culturing findings), and was dominated by the genera of distinctive Methylotenera and Methylomonas (yet-uncultured taxa). Simultaneously, the functional analysis showed that companion bacteria were involved in the pathways of carbohydrate transport and metabolism, metabolism of terpenoids and polyketides, cell wall/membrane/envelope biogenesis, etc. Hence, it was inferred that bacteria associated with fruiting body may have the potential to adjust the growth, development and active metabolite production of host S. vaninii combined with the tested results of indole-3-acetic acid and total antioxidant capacity. Altogether, this report first provided new findings which can be inspiring for further in-depth studies to exploit bioactive microbial resources for increased production of Sanghuangporus, as well as to explore the relationship between medicinal macrofungi and their associated endophytes.

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

Polyporus umbellatus 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 P. umbellatus sclerotia. Using the agar plate dilution method, strain CACMS001 was isolated from P. umbellatus sclerotia. The genome of CACMS001 was sequenced using PacBio platform, and the phylogenomic analysis indicated that CACMS001 could not be assigned to known Rhizobium species. In co-culture experiments, CACMS001 increased the mycelial growth of P. umbellatus and Armillaria gallica and increased xylanase activity in A. gallica. Comparative genomic analysis showed that CACMS001 lost almost all nitrogen fixation genes but specially acquired one redox cofactor cluster with pqqE, pqqD, pqqC, and pqqB 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 phnA and phoU involved in this process in CACMS001 were revealed by quantitative real-time PCR. CACMS001 is a new potential Rhizobium species and is the first identified MGPB belonging to Rhizobium. This novel bacterium would play a vital part in P. umbellatus, A. gallica, and other mushroom cultivation.

Impact of Cultivation Substrate and Microbial Community on Improving Mushroom Productivity: A Review

Simple Summary

Lignocellulosic material and substrate formulations affect mushroom productivity. The microbial community in cultivation substrates affects the quality of the substrates and the efficiency of mushroom production. The elucidation of the key microbes and their biochemical function can serve as a useful guide in the development of a more effective system for mushroom cultivation.

Abstract

Lignocellulosic materials commonly serve as base substrates for mushroom production. Cellulose, hemicellulose, and lignin are the major components of lignocellulose materials. The composition of these components depends upon the plant species. Currently, composted and non-composted lignocellulosic materials are used as substrates in mushroom cultivation depending on the mushroom species. Different substrate compositions can directly affect the quality and quantity of mushroom production yields. Consequently, the microbial dynamics and communities of the composting substrates can significantly affect mushroom production. Therefore, changes in both substrate composition and microbial diversity during the cultivation process can impact the production of high-quality substrates and result in a high degree of biological efficiency. A brief review of the current findings on substrate composition and microbial diversity for mushroom cultivation is provided in this paper. We also summarize the advantages and disadvantages of various methods of mushroom cultivation by analyzing the microbial diversity of the composting substrates during mushroom cultivation. The resulting information will serve as a useful guide for future researchers in their attempts to increase mushroom productivity through the selection of suitable substrate compositions and their relation to the microbial community.

Succession and potential role of bacterial communities during Pleurotus ostreatus production

There is an increasing interest in studying bacterial-fungal interactions (BFIs), also the interactions of Pleurotus ostreatus, a model white-rot fungus and important cultivated mushroom. In Europe, P. ostreatus is produced on a wheat straw-based substrate with a characteristic bacterial community, where P. ostreatus is exposed to the microbiome during substrate colonisation. This study investigated how the bacterial community structure was affected by the introduction of P. ostreatus into the mature substrate. Based on the results obtained, the effect of the presence and absence of this microbiome on P. ostreatus production in an experimental cultivation setup was determined. 16S rRNA gene-based terminal restriction fragment length polymorphism (T-RFLP) and amplicon sequencing revealed a definite succession of the microbiome during substrate colonisation and fruiting body production: a sharp decrease in relative abundance of Thermus spp. and Actinobacteria, and the increasing dominance of Bacillales and Halomonas spp. The introduced experimental cultivation setup proved the protective role of the microbial community against competing fungi without affecting P. ostreatus growth. We could also demonstrate that this effect could be attributed to both living microbes and their secreted metabolites. These findings highlight the importance of bacterial-fungal interactions during mushroom production.

Culinary and Medicinal Mushrooms: Insight into Growing Technologies

Humans have used mushrooms from the beginning of their history. However, during the last few decades, the market demand for these fruiting bodies has increased significantly owing to the spread in the capabilities of culinary and pharmacological exploitation. Natural mushroom resources have become insufficient to meet the support needs. Therefore, traditional methods of extensive cultivation as well as modern technologies have been exploited to develop effective growing recommendations for dozens of economically important mushroom species. Mushrooms can decompose a wide range of organic materials, including organic waste. They play a fundamental role in nutrient cycling and exchange in the environment. The challenge is a proper substrate composition, including bio-fortified essential elements, and the application of growing conditions to enable a continuous supply of fruiting bodies of market quality and stabilized chemical composition. Many mushroom species are used for food preparation. Moreover, they are treated as functional foods, because they have health benefits beyond their nutritional value, and are used as natural medicines in many countries. Owing to the rapid development of mushroom farming, we reviewed the growing technologies used worldwide for mushroom species developed for food, processing, and pharmacological industries.