An Antifungal Chitosanase from Bacillus subtilis SH21

Characterization of Bacillus velezensis TJS119 and its biocontrol potential against insect pathogens

Introduction

The white-spotted flower chafer (Protaetia brevitarsis seulensis), which is widely distributed in Asian countries, is traditionally used in oriental medicine. However, its larvae are prone to severe damage by green muscardine disease (caused by Metarhizium anisopliae) during breeding. The aim of this study was to characterize Bacillus velezensis TJS119, which has been isolated from freshwater, and investigate its potential as a biocontrol agent against M. anisopliae in insects.

Methods

TJS119 was obtained from freshwater samples in the Republic of Korea and was classified as B. velezensis. We evaluated its in vitro antifungal effect, sequenced the bacterial whole genome, mined genes responsible for the synthesis of secondary metabolites, performed secondary metabolite analysis Ultra performance liquid chromatography-mass spectrometry (UPLC-MS/MS), and conducted bioassays for determining green muscardine disease control ability.

Results

Bacillus velezensis TJS119 inhibited the mycelial growth of M. anisopliae in vitro. The size of the B. velezensis TJS119 genome was estimated to be 3,890,913 bp with a GC content of 46.67% and 3,750 coding sequences. Biosynthetic gene clusters for secondary metabolites with antifungal activity were identified in the genome. Lipopeptides, including fengycin secreted by TJS119 exhibit antifungal activity. Application of TJS119 for the biocontrol against green muscardine disease increased the viability of white-spotted flower chafer by 94.7% compared to the control.

Discussion

These results indicate that B. velezensis TJS119 is a potential biocontrol agent for insect pathogens.

Chitosanase Production from the Liquid Fermentation of Squid Pens Waste by Paenibacillus elgii

Chitosanases play a significant part in the hydrolysis of chitosan to form chitooligosaccharides (COS) that possess diverse biological activities. This study aimed to enhance the productivity of Paenibacillus elgii TKU051 chitosanase by fermentation from chitinous fishery wastes. The ideal parameters for achieving maximum chitosanase activity were determined: a squid pens powder amount of 5.278% (w/v), an initial pH value of 8.93, an incubation temperature of 38 °C, and an incubation duration of 5.73 days. The resulting chitosanase activity of the culture medium was 2.023 U/mL. A chitosanase with a molecular weight of 25 kDa was isolated from the culture medium of P. elgii TKU051 and was biochemically characterized. Liquid chromatography with tandem mass spectrometry analysis revealed that P. elgii TKU051 chitosanase exhibited a maximum amino acid identity of 43% with a chitosanase of Bacillus circulans belonging to the glycoside hydrolase (GH) family 46. P. elgii TKU051 chitosanase demonstrated optimal activity at pH 5.5 while displaying remarkable stability within the pH range of 5.0 to 9.0. The enzyme displayed maximum efficiency at 60 °C and demonstrated considerable stability at temperatures ≤40 °C. The presence of Mn2+ positively affected the activity of the enzyme, while the presence of Cu2+ had a negative effect. Thin-layer chromatography analysis demonstrated that P. elgii TKU051 chitosanase exhibited an endo-type cleavage pattern and hydrolyzed chitosan with 98% degree of deacetylation to yield (GlcN)2 and (GlcN)3. The enzymatic properties of P. elgii TKU051 chitosanase render it a promising candidate for application in the production of COS.

Complete genome sequence of biocontrol strain Bacillus velezensis YC89 and its biocontrol potential against sugarcane red rot

Introduction

Sugarcane is one of the most important sugar crops worldwide, however, sugarcane production is seriously limited by sugarcane red rot, a soil-borne disease caused by Colletotrichum falcatum. Bacillus velezensis YC89 was isolated from sugarcane leaves and can significantly inhibited red rot disease caused by C. falcatum.

Methods

In this study, the genome of YC89 strain was sequenced, its genome structure and function were analyzed using various bioinformatics software, and its genome was compared with those of other homologous strains. In addition, the effectiveness of YC89 against sugarcane red rot and the evaluation of sugarcane plant growth promotion were also investigated by pot experiments.

Results

Here, we present the complete genome sequence of YC89, which consists of a 3.95 Mb circular chromosome with an average GC content of 46.62%. The phylogenetic tree indicated that YC89 is closely related to B. velezensis GS-1. Comparative genome analysis of YC89 with other published strains (B. velezensis FZB42, B. velezensis CC09, B. velezensis SQR9, B. velezensis GS-1, and B. amyloliquefaciens DSM7) revealed that the strains had a part common coding sequences (CDS) in whereas 42 coding were unique of strain YC89. Whole-genome sequencing revealed 547 carbohydrate-active enzymes and identified 12 gene clusters encoding secondary metabolites. Additionally, functional analysis of the genome revealed numerous gene/gene clusters involved in plant growth promotion, antibiotic resistance, and resistance inducer synthesis. In vitro pot tests indicated that YC89 strain controlled sugarcane red rot and promoted the growth of sugarcane plants. Additionally, it increased the activity of enzymes involved in plant defense, such as superoxide dismutase, peroxidase, polyphenol oxidase, chitinase, and β-1,3-glucanase.

Discussion

These findings will be helpful for further studies on the mechanisms of plant growth promotion and biocontrol by B. velezensis and provide an effective strategy for controlling red rot in sugarcane plants.

Isolation, purification, and identification of antifungal protein produced by Bacillus subtilis SL-44 and anti-fungal resistance in apple

Apple anthracnose is a fruit fungal disease that is currently recognized as one of the most severe threats to apples worldwide. In this study, antifungal protein from Bacillus subtilis SL-44 was isolated, purified, identified, and applied for Colletotrichum gloeosporioides control. The antagonistic experiment showed that SL-44 had an excellent broad spectrum against plant pathogenic fungi. The optimal fermentation conditions were as follows: initial pH was 7, inoculum volume was 2%, and rotational speed was 180 r/min. The optimized yield of antifungal protein increased by 45.83% compared with that before. The crude protein was isolated and purified by (NH₄)₂SO₄ precipitation, DEAE-Sepharose Fast Flow, and Sephadex G-100 column chromatography. LC-MS analyzed that antifungal protein was likely to be a novel protein with a molecular weight of 42 kDa. The mechanism revealed that the antifungal protein may disrupt the cell wall structure of C. gloeosporioides and function as its antifungal action. Additionally, antifungal protein significantly alleviated the size of the lesion to more than 70% in the apple infection protection test. In conclusion, antifungal protein has remarkable potential in developing fungicides for the biological control of apple anthracnose. HIGHLIGHTS: 1. B. subtilis SL-44 had broad-spectrum antagonism against plant pathogenic fungi. 2. The optimal fermentation conditions for extracting antifungal protein were optimized. 3. The antifungal protein is a novel protein with a molecular weight of 42 kDa. 4. The mechanism of antifungal protein may disrupt the cell wall structure of C. gloeosporioides.

Antimicrobial Properties of Bacillus Probiotics as Animal Growth Promoters

Antibiotic growth promoters (AGPs) suppress the growth of infectious pathogens. These pathogens negatively impact agricultural production worldwide and often cause health problems if left untreated. Here, we evaluate six Bacillus strains (BPR-11, BPR-12, BPR-13, BPR-14, BPR-16 and BPR-17), which are known for their ability to survive harsh environmental conditions, as AGP replacements in animal feed. Four of these Bacillus strains (BPR-11, BPR-14, BPR-16 and BPR-17) showed antimicrobial activity against the pathogenic strains Clostridium perfringens, Escherichia coli and Staphylococcus aureus at 25 μg/mL, with BPR-16 and BPR-17 also able to inhibit Pseudomonas aeruginosa and Salmonella enterica at 100 μg/mL. Further chemical investigation of BPR-17 led to the identification of eight metabolites, namely C16, C15, C14 and C13 surfactin C (1-4), maculosin (5), maculosine 2 (6), genistein (7) and daidzein (8). Purified compounds (1-4) were able to inhibit all the tested pathogens with MIC values ranging from 6.25 to 50 μg/mL. Maculosin (5) and maculosine 2 (6) inhibited C. perfringens, E. coli and S. aureus with an MIC of 25 μg/mL while genistein (7) and daidzein (8) showed no activity. An animal trial involving feeding BPR-11, BPR-16 and BPR-17 to a laboratory poultry model led to an increase in animal growth, and a decrease in feed conversion ratio and mortality. The presence of surfactin C analogues (3-4) in the gut following feeding with probiotics was confirmed using an LC-MS analysis. The investigation of these Bacillus probiotics, their metabolites, their impacts on animal performance indicators and their presence in the gastrointestinal system illustrates that these probiotics are effective alternatives to AGPs.

Gene cloning and molecular characterization of a thermostable chitosanase from Bacillus cereus TY24

Background

An important conceptual advance in health and the environment has been recognized that enzymes play a key role in the green processing industries. Of particular interest, chitosanase is beneficial for recycling the chitosan resource and producing chitosan oligosaccharides. Also, chitosan gene expression and molecular characterization will promote understanding of the biological function of bacterial chitosanase as well as explore chitosanase for utilizing chitosan resources.

Results

A chitosanase-producing bacterium TY24 was isolated and identified as Bacillus cereus. Moreover, the chitosanase gene was cloned and expressed in Escherichia coli. Sequence analysis reveals that the recombinant chitosanase (CHOE) belongs to the glycoside hydrolases 8 family. The purified CHOE has a molecular weight of about 48 kDa and the specific activity of 1150 U/mg. The optimal pH and temperature of CHOE were 5.5 and 65 °C, respectively. The enzyme was observed stable at the pH range of 4.5–7.5 and the temperature range of 30–65 °C. Especially, the half-life of CHOE at 65 °C was 161 min. Additionally, the activity of CHOE was remarkably enhanced in the presence of Mn²⁺, Cu²⁺, Mg²⁺ and K⁺, beside Ca²⁺ at 5 mM. Especially, the activity of CHOE was enhanced to more than 120% in the presence of 1% of various surfactants. CHOE exhibited the highest substrate specificity toward colloid chitosan.

Conclusion

A bacterial chitosanase was cloned from B. cereus and successfully expressed in E. coli (BL21) DE3. The recombinant enzyme displayed good stability under acid pH and high-temperature conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-022-00762-6.

The antifungal activity of a serine protease and the enzyme production of characteristics of Bacillus licheniformis TG116

The growth of Phytophthora capsica, Rhizoctonia solani, Fusarium graminearum, Fusarium oxysporum and Botrytis cinerea were all inhibited by the fermentation supernatant of Bacillus licheniformis TG116, a biocontrol strain isolated from Typhonium giganteum Engl. previously with broad-spectrum resistance to plant pathogens. The fermentation supernatant of the TG116 has a great stability on temperature and UV, and shows the biological activity of protease and cellulase. The antifungal protease produced by B. licheniformis TG116 was purified to homogeneity by ammonium sulfate precipitation, DEAE Sepharose Fast Flow column chromatography and Sephadex G-50 column chromatography. The inhibition of protease by the three surfactants increased with increasing concentration inhibition. Among these surfactants, EDTA showed the strongest inhibition, with only 25% protein activity at a concentration of 1.1 mmol·L^-1. Gene amplification verified the presence of a gene fragment of serine protease in the strain TG116. The antimicrobial substance isolated from the fermentation broth of TG116 is a serine protease component.

Multi-Omics Techniques for Analysis Antifungal Mechanisms of Lipopeptides Produced by Bacillus velezensis GS-1 against Magnaporthe oryzae In Vitro

Magnaporthe oryzae is a fungal pathogen that causes rice blast, a highly destructive disease. In the present study, the bacteria strain GS-1 was isolated from the rhizosphere soil of ginseng and identified as Bacillus velezensis through 16S rRNA gene sequencing, whole genome assembly, and average nucleotide identity analysis. B. velezensis strain GS-1 exhibited significant antagonistic activity to several plant fungal pathogens. Through whole genome sequencing, 92 Carbohydrate-Active Enzymes and 13 gene clusters that encoded for secondary metabolites were identified. In addition, strain GS-1 was able to produce the lipopeptide compounds, surfactin, fengycin, and plantazolicin. The inhibitory effects of lipopeptide compounds on M. oryzae were confirmed, and the antagonistic mechanism was explored using transcriptomics and metabolomics analysis. Differential expressed genes (DEGs) and differential accumulated metabolites (DAMs) revealed that the inhibition of M. oryzae by lipopeptide produced by GS-1 downregulated the expression of genes involved in amino acid metabolism, sugar metabolism, oxidative phosphorylation, and autophagy. These results may explain why GS-1 has antagonistic activity to fungal pathogens and revealed the mechanisms underlying the inhibitory effects of lipopeptides produced by GS-1 on fungal growth, which may provide a theoretical basis for the potential application of B. velezensis GS-1 in future plant protection.