Dataset Information

Production of ?-1,3-glucanase and chitosanase from clostridial strains isolated from the soil subjected to biological disinfestation.

ABSTRACT: Biological soil disinfestation (BSD) or anaerobic (reductive) soil disinfestation (ASD/RSD) is a bioremediation method used to eliminate soil-borne plant pathogens by exploiting the activities of anaerobic bacteria in soil. In this study, two obligate anaerobic bacterial strains isolated from BSD-treated soil and identified as Clostridium beijerinckii were examined for their abilities to suppress the spinach wilt disease pathogen (Fusarium oxysporum f. sp. spinaciae) as a representative soil-borne fungal plant pathogen. Both strains degraded ?-1,3-glucan and chitosan, two major polysaccharide components of ascomycetes fungal cell wall, supplemented in the medium. ?-1,3-Glucanase was detected in the supernatants of cultures supplemented with different types of glucan. Similarly, chitosanase was detected in cultures supplemented with chitosan. Both the enzyme activities were also detected in cultures containing glucose as a substrate. Live cells of F. oxysporum f. sp. spinaciae that were co-incubated with each anaerobic strain under anaerobic conditions using glucose as a substrate died during incubation. Freeze-dried dead fungal biomass of the pathogen, when added to the culture, supported good growth of both anaerobes and production of both enzymes. Severe and nearly complete degradation of both live and dead fungal cells during incubation with anaerobic bacteria was observed by fluorescence microscopy. When individual anaerobic bacterial strain was co-incubated with live pathogenic fungal cells in wheat bran, a popular material for BSD-treatment, both the strains grew well and killed the fungal pathogen promptly by producing both enzymes. These results indicate that both the bacterial strains attack the fungal cells by releasing extracellular fungal cell wall-degrading enzymes, thereby eliminating the pathogen.

SUBMITTER: Ueki A

PROVIDER: S-EPMC6650511 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Production of β-1,3-glucanase and chitosanase from clostridial strains isolated from the soil subjected to biological disinfestation.

Ueki Atsuko A Takehara Toshiaki T Ishioka Gen G Kaku Nobuo N Ueki Katsuji K

AMB Express 20190723 1

Biological soil disinfestation (BSD) or anaerobic (reductive) soil disinfestation (ASD/RSD) is a bioremediation method used to eliminate soil-borne plant pathogens by exploiting the activities of anaerobic bacteria in soil. In this study, two obligate anaerobic bacterial strains isolated from BSD-treated soil and identified as Clostridium beijerinckii were examined for their abilities to suppress the spinach wilt disease pathogen (Fusarium oxysporum f. sp. spinaciae) as a representative soil-bor ...[more]

PMID: 31338622

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Project description:Biological (or reductive) soil disinfestation (BSD or RSD) is a bioremediation process to control soil-borne plant pathogens using activities of indigenous bacteria in the soil. Three obligate anaerobic bacterial strains (TW1, TW10, and TB10), which were isolated from anoxic soil subjected to BSD treatments, were examined for their abilities to produce anti-fungal enzymes. All strains were affiliated with the different lineages of the genus Clostridium. The three strains decomposed β-1,3-glucans (curdlan and laminarin), and β-1,3-glucanase activities were detected from their culture supernatants with these glucans. The three strains also produced the enzyme with wheat bran as a growth substrate and killed the Fusarium pathogen (Fusarium oxysporum f. sp. spinaciae) in the anaerobic co-incubation conditions. Observation by fluorescence microscopy of the pathogen cells showed that the three strains had degraded the fungal cells in different manners upon co-incubation with wheat bran. When the three strains were cultivated with the dead cells or the cell wall samples prepared from the Fusarium pathogen, strain TW1 utilized these materials as easily decomposable substrates by releasing β-1,3-glucanase. When observed by fluorescence microscopy, it appeared that strain TW1 degraded the mycelial cell wall nearly thoroughly, with the septa remaining as undecomposed luminous rings. In contrast, the other two strains decomposed neither the dead cells nor the cell wall samples directly. The results indicate that the various anaerobic bacteria proliferated in the soil under the BSD treatments should play key roles as an organized bacterial community to eliminate fungal pathogens, namely by release of anti-fungal enzymes with different properties.Key points•Three clostridial strains isolated from BSD-treated soils produced β-1,3-glucanase.•All strains killed the Fusarium pathogen in the anaerobic co-incubation conditions.•One of the strains produced β-1,3-glucanase with the fungal cell wall as a substrate.•The strain degraded the cell wall almost completely, except for the mycelial septa.

Project description:In agricultural practice, reductive soil disinfestation (RSD) is an effective method for eliminating soil-borne pathogens that depends heavily on carbon source. However, knowledge regarding the assembly of soil microbial communities in RDS-treated soils amended with different carbon sources after continuous crop cultivation is still not well-characterized. RSD treatments were performed on greenhouse soil with six different carbon sources (ethanol, glucose, alfalfa, wheat bran, rice bran, and sugarcane residue), which have different C:N ratios (Org C/N) and easily oxidized carbon contents (Org EOC). After RSD, two consecutive seasons of pepper pot experiments were conducted. Then, the effects of carbon source property, crop cultivation, and soil chemical property on soil microbial community reestablishment, pathogen reproduction, and crop performance were investigated in the RSD-cropping system. Variation partition analysis indicated that carbon source property, crop cultivation, and soil chemical property explained 66.2 and 39.0% of bacterial and fungal community variation, respectively. Specifically, Mantel tests showed that Org C/N, crop cultivation, soil available phosphorus and potassium were the most important factors shaping bacterial community composition, while Org C/N, Org EOC, and crop cultivation were the most important factors shaping fungal community composition. After two planting seasons, the number of cultivable Fusarium was positively correlated with Org EOC, and negatively correlated with soil total organic carbon, Fungal Chao1, and Fungal PC1. Crop yield of complex-carbon soils (Al, Wh, Ri and Su) was negatively affected by Org C/N after the first season, and it was highest in Al, and lower in Et and Su after the second season. Overall, Org EOC and Org C/N of carbon source were vitally important for soil microbe reestablishment, Fusarium reproduction and crop performance. Our findings further broaden the important role of carbon source in the RSD-cropping system, and provide a theoretical basis for organic carbon selection in RSD practice.

Project description:Many agricultural soil management strategies have been shown to be effective in preventing soilborne diseases. However, their underlying mechanisms of action remain unknown. In this study, we used reductive soil disinfestation (RSD), also named anaerobic soil disinfestation (ASD) and biological soil disinfestation (BSD), as a representative method for disease management and cucumber damping-off diseased soil as a model system to identify the disease-suppressive agents in artificially managed soil. The results showed that RSD created a soil environment that was different from that of the diseased soil, where the pH level and the carbon content were greater. Heat treatment and pathogen or soil microbiota self- and cross-reinoculations resulted in the expansion of various soil microbial communities harbored by the two soil environments, as well as various disease incidences. Environmental factors were the primary determinant of the reassembled bacterial community, followed by initial microbiota, whereas initial microbiota was the key driver of the reassembled fungal community. The relative abundances of the bacterial order Sphingobacteriales and fungal order Sordariales, as well as their affiliated genera Sphingobacterium, unclassified genus within Sphingobacteriaceae, Zopfiella, and unclassified genera within Lasiosphaeriaceae and Chaetomiaceae, were negatively correlated with disease incidence and positively associated with RSD-conditioned soil environment. Furthermore, we validated that both the microbial disease-suppressive agent and its adapted abiotic environment contributed to disease suppression. Our results elucidate the abiotic and biotic foundations of soilborne disease suppression under artificial management and highlight that the abiotic environment is as important as the microbial agents in disease suppression.IMPORTANCE Most defined systems have identified microbial elements as the primary factors determining disease suppression, but the involvement of the soil abiotic environment is less defined. The significance of this work is that the soil abiotic environment plays a critical role in the establishment of the soil microbial community and key microbial agents that directly contribute to the prevention of soilborne diseases. We highlight the importance of the soil abiotic environment in disease suppression. Furthermore, we provide a framework for the characterization of disease-suppressing agents in artificially managed soil. These results will gradually close the gap in knowledge on soil environment-microbe interactions.

Dataset Information

Production of ?-1,3-glucanase and chitosanase from clostridial strains isolated from the soil subjected to biological disinfestation.

Publications

Production of β-1,3-glucanase and chitosanase from clostridial strains isolated from the soil subjected to biological disinfestation.

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