The Central Highlands region contains most of the national parks in Vietnam with different ecosystems, including the national parks of Kon Ka Kinh, Chu Mon Ray, Chu Yang Sin, Yok Don, Bidoup-Nui Ba, and Ta Dung. Thus, this region is considered a center with the highest biodiversity in Vietnam
[1]
. Among the national parks, Yok Don is unique in its conservation of the dry deciduous dipterocarp forest. Furthermore, Yok Don is the second-largest park in Vietnam; it has the most different ecosystem compared with other national parks in this region
[2]
. Although some studies have investigated biodiversity preservation in the region, some other studies have only dealt with medicinal plants, lichens, and the rhizospheric bacteria of cultivated black pepper
[1
,
[3]
,
[4]
,
[5]
. To the best of our knowledge, no research on the microbial communities in Yok Don national park and in the Central Highlands has been reported. At present, global warming and a decrease in the forest area in the Central Highlands have led to the ongoing reduction in biodiversity and microbial resources.
The current study reports the microbiome dataset from the soil sample collected in Yok Don national park. Metagenomic next-generation sequencing was used to characterize the microbial communities in the sample. The metagenome dataset generated provides information on microbial diversity and its functionality and can be useful for further studies on the conservation and use of microbial genetic resources in this region.
Bacillus velezensis RB.IBE29 is a potent biocontrol agent with high chitinase activity isolated from the rhizosphere of black pepper cultivated in the Central Highlands, Vietnam. Genome sequences revealed that this species possesses some GH18 chitinases and AA10 protein(s); however, these enzymes have not been experimentally characterized. In this work, three genes were identi ed from the genomic DNA of this bacterium and cloned in Escherichia coli. Sequence analysis exhibited that the ORF of chiA consists of 1,203 bp and encodes deduced 45.46 kDa-chitinase A of 400 aa. The domain structure of chitinase A is composed of a CBM 50 domain at the N-terminus and a catalytic domain at the C-terminus. The ORF of chiB includes 1,263 bp and encodes deduced 47.59 kDa-chitinase B of 420 aa. Chitinase B consists of two CBM50 domains at the N-terminus and a catalytic domain at the C-terminus. The ORF of lpmo10 is 621 bp and encodes a deduced 22.44 kDa-AA10 protein, BvLPMO10 of 206 aa. BvLPMO10 contains a signal peptide and an AA10 catalytic domain. Chitinases A and B were grouped into subfamily A of family 18 chitinases. Amino acid sequences in their catalytic domains lack aromatic residues (Trp, Phe, Tyr) probably involved in processivity and substrate binding compared with well-known bacterial GH18 chitinases. chiB was successfully expressed in E. coli. Puri ed rBvChiB degraded insoluble chitin and was responsible for inhibition of fungal spore-germination and egg hatching of plant-parasitic nematode. This is the rst report describing the analysis of the chitinase system from B. velezensis.
Aims
This study focused on the isolation and characterization of chitinolytic bacteria from Yok Don National Park, Vietnam for future studies regarding biofertilizers and biocontrol agents.
Methods and results
Chitinolytic bacteria were isolated from soils and chitin flakes soaked in river water at the National Park. On the basis of the halo zones caused by colloidal chitin degradation and colony morphologies, 12 chitinolytic strains were chosen from 15 700 isolates for various examinations. Findings from 16S rDNA analysis indicated that among these strains, 10 could be identified as different species and the remaining 2 showed less identity to known species and genera. The 12 bacteria possess numerous properties concerning plant growth promotion and/or phytopathogenic biocontrol. Paenibacillus chitinolyticus YSY-3.1, which exhibited the highest chitinase activity and remarkable properties for plant growth, was chosen for sequencing and draft genome analysis. The results showed that the genome is 6571 781 bp in length with 6194 coding sequences, 52.2% G + C, and 96.53% ANI value. It harbors the chitinolytic system comprising 22 enzymes. Among these enzymes, PcChiQ has a loop structure different from that of known family 19 chitinases, PcChiA contains two GH18 catalytic domains rarely found in microorganisms, and PcChiF contains three GH18 catalytic domains that have never been reported.
Conclusions
The 12 identified chitinolytic bacteria exhibit great potential for further studies on plant growth-promoting and/or biocontrol properties. Among these bacteria, two strains might be good candidates for next examinations concerning novel species and/or genera, and strain YSY-3.1 could possess a novel chitinolytic system.
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