• Journal of Mushroom
• /
• v.22 no.2
• /
• pp.60-66
• /
• 2024

This study was conducted to selection and investigate appropriate conditions for mass production of antagonistic microbes to control cobweb disease caused by Cladobotryum mycophilum. A grampositive bacterium was isolated from spent substrate of Agaricus bisporus and showed significant antagonistic activity against Cladobotryum mycophilum. The bacterium was identified as Bacillus altitudinis. based on the cultural, biochemical and physiological characteristics, and 16S rRNA sequence. The isolate is saprophytic, but not parasitic nor pathogenic to cultivated mushroom whereas it showed strong inhibitory effects against C. mycophilum cells in vitro. The control efficacy of B. altitudinis HC7 against cobweb disease of C. mycophilum was up to 78.2% on Agaricus bisporus. The suppressive bacterium may be useful for the development of biocontrol system. To define the appropriate conditions for the mass production of the Bacillus altitudinis HC7, we have investigated appropriate culture conditions and effects of various nutrient source on the bacterial growth. The appropriate initial pH and temperature were determined as pH 6.0 and 30℃, respectively. The appropriate concentration of medium elements for the growth of pathogen inhibitor bacterium(Bacillus altitudinis HC7) was determined as follows: 3.0% soluble startch, 10% soytone, 1.0% (NH₄)₂HPO₄, 1.0 mmol KCl, and 0.5% L-asparagine.

• Microbiology and Biotechnology Letters
• /
• v.39 no.2
• /
• pp.97-103
• /
• 2011

Two Gram positive bacterial strains, designated strain GC-1 and GC-4, were isolated from coastal seawater near Jeju Island in the Republic of Korea. The two strains were identified as members of the genus Bacillus, based on 16S rRNA gene sequencing and data for physiological characteristics analyses. A subtle difference in physiological and genotypical characteristics has led us to designate the strains GC-1 and GC-4. The strain GC-1 showed a 99.91% similarity in 16S rRNA gene sequencing with B. tequiliensis and B. subtilis subsp. inaquosorum and the strain GC-4 showed a 100% similarity in 16S rRNA gene sequencing with those of B. altitudinis, B. stratosphericus, and B. aerophilus. However, both strains exhibited different physiological and genotypical characteristics in many aspects from those of their phylogenetically closest neighbors listed above, which implies that genus Bacillus has diversified into various species during its evolutionary process.

• The Korean Journal of Mycology
• /
• v.44 no.1
• /
• pp.36-47
• /
• 2016

This study was conducted to evaluate five different strains of rhizobacterial isolates viz. PA1, PA2, PA4, PA5 and PA12 for biological control against Colletotrichum acutatum, C. coccodes, C. gloeosporioides, C. dematium, Botrytis cinerea, Rhizoctonia solani, Sclerotinia minor and Fusarium sp. In vitro inhibition assay was performed on three different growth mediums, potato dextrose agar (PDA), tryptic soy agar (TSA), and PDA-TSA (1:1 v/v) for the selection of potential antagonistic isolates. According to the result, isolate PA2 showed the highest inhibitory effect with 65.5% against C. coccodes on PDA and with 96.5% against S. minor on TSA. However, the same isolate showed the highest inhibition with 58.5% against C. acutatum on PDA-TSA. In addition, an in vivo experiment was performed to evaluate these bacterial isolates for biological control against fungal pathogens. Plants treated with bacteria were analyzed with phytopathogens and plants inoculated with phytopathogens were treated with isolates to determine the biological control effect against fungi. According to the result, all five isolates tested showed inhibitory effects against phytopathogens at various levels. Mode of action of these rhizobacterial isolates was evaluated with siderophore production, protease assay, chitinase assay and phosphate solubilizing assay. Bacterial isolates were identified by 16S rDNA sequencing, which showed that isolates PA1 and PA2 belong to Bacillus subtilis, whereas, PA4, PA5, and PA12 were identified as Bacilus altitudinis, Paenibacillus polymyxa and Bacillus amyloliquefaciens, respectively. Results of the current study suggest that rhizobacterial isolates can be used for the plant growth promoting rhizobacteria (PGPR) effect as well as for biological control of various phytopathogens.

• The Plant Pathology Journal
• /
• v.37 no.3
• /
• pp.243-257
• /
• 2021

Bacillus pumilus is the causal agent of trunk bulges disease affecting rubber and rubberwood quality and yield production. In this study, B. pumilus and other closely related species were included in B. pumilus group, as they shared over 99.5% similarity from 16S rRNA analysis. Multilocus sequence analysis (MLSA) of five housekeeping genes and repetitive elements-based polymerase chain reaction (rep-PCR) using REP, ERIC, and BOX primers conducted to analyze the diversity and systematic relationships of 20 isolates of B. pumilus group from four rubber tree plantations in Peninsular Malaysia (Serdang, Tanah Merah, Baling, and Rawang). Multi rep-PCR results revealed the genetic profiling among the B. pumilus group isolates, while MLSA results showed 98-100% similarity across the 20 isolates of B. pumilus group species. These 20 isolates, formerly established as B. pumilus, were found not to be grouped with B. pumilus. However, being distributed within distinctive groups of the B. pumilus group comprising of two clusters, A and B. Cluster A contained of 17 isolates close to B. altitudinis, whereas Cluster B consisted of three isolates attributed to B. safensis. This is the first MLSA and rep-PCR study on B. pumilus group, which provides an in-depth understanding of the diversity of these rubber-pathogenic isolates in Malaysia.

• Research in Plant Disease
• /
• v.28 no.3
• /
• pp.152-161
• /
• 2022

Several types of chemical bactericides have been used to control fire blight. However, their excessive usage leads to environmental deterioration. Therefore, several researchers have analyzed antagonistic microorganisms as promising, effective, and safe biological control agents (BCAs). The primary aim of this study was to screen for potential antagonistic bacteria that suppress Erwinia amylovora. Among the 45 isolates studied, 5 strains showed the largest inhibition zone against E. amylovora. 16S rRNA gene sequencing identified them as Bacillus amyloliquefaciens (KPB 15), B. stratosphericus (KPB 21), B. altitudinis (KPB 25), B. safensis (KPB 31), and B. subtilis (KPB 39). KPB 25 and 31 reduced the lesion size of fire blight by 50% in immature apple fruits, and did not show antagonism against each other. Therefore, KPB 25 and 31 were selected to develop an antagonistic mixture against fire blight. Although the mixture with KPB 25 and 31 showed a slightly increased ability to reduce lesion size on immature fruits, they did not exhibit a synergistic effect in reducing E. amylovora population compared to each strain alone. Nevertheless, we have identified these two strains as useful and novel BCAs against fire blight with additional benefits safety and potential in developing a mixture without loss of their activity, owing to the absence of antagonism against each other.

• Korean Journal of Microbiology
• /
• v.54 no.4
• /
• pp.410-419
• /
• 2018

It is urgently required to construct safety data on agricultural by-products imported for use as medium materials for domestic mushroom production. However, research on microorganisms is insufficient. This study was conducted to investigate the presence of bacteria that have the possibility of harmful effects on human, plants and mushroom in wheat straw, peatmoss, cottonseed hull, cottonseed meal, and beet pulp imported from Australia, Canada, China, Egypt, Germany. Bacteria were found in the range of $1.35{\times}10^2$ to $8.34{\times}10^6CFU/g$. As a result of 16S rDNA sequence analysis, total of 19 genera and 45 species of bacteria were identified. Bacillus genus was dominant, followed by Paenibacillus genus. At the species level, diverse species was in the order of Firmicute, Proteobacteria and Actinobacteria. Regarding the agricultural by-products, straw and peat moss had more diverse bacteria than other agricultural by-products. Among the indentified bacteria, 6 species of 5 genera (Enterobacter asburiae, Enterobacter ludwigii, Stenotrophomonas maltophilia, Pseudomonas monteilii, Bacillus anthracis, and Cellulosimicrobium funkei) were present as potent harmful bacteria to human. Surprisingly, both the human and plant pathogenic Klebsiella pneumoniae subsp. pneumonia was present. Bacillus altitudinis was present as a plant pathogen. Lysinibacillus sphaericus, an insect pathogen, and Ochrobactrum pseudogrignonense, a mushroom pathogen, were also present. The results of this study confirmed that several kinds of pathogenic bacteria were present in the agricultural by-products for the mushroom cultivation medium imported into Korea. Our work suggests that hygiene inspection and management is urgently needed for imported agricultural by-products to be safely used for mushroom production.