Chitinophaga aurantiaca sp. nov., isolated from a soil sample from a tangerine field

QpmH esterase from cotton rhizosphere bacteria: A novel approach for degrading quizalofop-p-ethyl herbicide

Within the rhizosphere, a rich population of biocontrol bacteria serves as a valuable resource for the biodegradation of environmental herbicides. This study aimed to evaluate rhizospheric microorganisms for their potential to degrade Quizalofop-p-ethyl, a widely used herbicide to control annual and perennial weeds in a variety of crops. A bacterial strain, MJ-8, isolated from cotton rhizosphere soil, demonstrated significant degradation activity. Based on morphological characteristics and 16S rRNA sequencing, the strain was identified as Priestia megaterium. Strain MJ-8 achieved a degradation rate of 90.65 % for Quizalofop-p-ethyl. Genomic analysis and amino acid sequence alignment revealed a key gene, designated QpmH, encoding a 30 kDa protein with strong biodegradation activity. Heterologous expression of the QpmH gene confirmed its role in Quizalofop-p-ethyl degradation. Molecular docking studies and structural modeling further elucidated the enzymatic mechanisms, supported by the analysis of their degradation products. Additionally, when QpmH gene was introduced into rice plants through Agrobacterium-mediated transformation, the resultant transformant conferred resistance to Quizalofop-p-ethyl at the recommended application dose. These findings highlight Priestia megaterium strain MJ-8 as a promising biological agent for sustainable herbicide management and position the QpmH gene as a potential new target for developing herbicide-resistant crops.

Complete genome sequences of Chitinophaga sp. strain MM2321 and Microbacterium sp. strain MM2322, isolated from a sand sample in Harsewinkel, Germany

We cultivated bacteria contained in a sandy soil sample, isolated DNA from a single bacterial colony, and assembled from genomic reads the full genome sequence of Chitinophaga and Microbacterium strains, termed MM2321 and MM2322. Besides the genome sequences, the phylogenetic classifications of both strains are reported.

Description of desferrioxamine-producing bacterium Chitinophaga agrisoli sp. nov., isolated from soil

A Gram-stain-negative, non-motile, yellow-pigmented and non-spore forming rod-shaped bacterium, designated strain BN140078^T, was isolated from farmland soil, Chungbuk, Republic of Korea. It was able to grow aerobically at 10-40 °C (optimum 28 °C), pH 5.5-7.5 (optimum pH 7.0) and with 0-2.0% (w/v) NaCl concentration (optimum 1.0%) on Reasoner's 2A (R2A) agar medium. Comparative 16S rRNA gene sequence analysis showed that the strain BN140078^T had 96.9%, 96.5% and 96.1% 16S rRNA gene similarities with Chitinophaga ginsengihumi KACC 17604^T, Chitinophaga rupis KACC 14521^T and Chitinophaga japonensis KACC 12057^T, respectively. The predominant respiratory quinone was menaquinone MK-7 and the major fatty acids (≥ 5%) were C_16:1 ω5c, iso-C_15:0, iso-C_17:0 3-OH and Summed Feature 3 (C_16:1 ω7c and/or C_16:1 ω6c). The polar lipids were composed of phosphatidylethanolamine, four unidentified amino lipids and six unidentified lipids. The genomic DNA G+C content was 49.5 mol%. The genome of strain BN140078^T comprises a number of biosynthetic gene clusters for secondary metabolites, in particular those for non-ribosomal peptide products. The polyphasic taxonomic study clearly distinguished this strain from its closest phylogenetic neighbors. Thus, we propose that the BN140078^T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga agrisoli sp. nov. was proposed. The type strain is BN140078^T (=KCTC 62555^T = CCTCC AB 2018162^T).

Biocontrol potential of chitinases produced by newly isolated Chitinophaga sp. S167

A chitinolytic bacterium Chitinophaga sp. S167 producing extracellular chitinases was isolated from a soil sample in India. The extracellular chitinases produced by S167 were concentrated by ammonium sulphate precipitation (AS70) and seven bands corresponding to chitinases were observed by zymography. Optimum temperature and pH of AS70 were between 40 and 45 °C and pH 6.0 respectively with high stability at 20-40 °C and pH 5-7. AS70 inhibited the growth of Fusarium oxysporum, Alternaria alternata and Cladosporium sp. in vitro. The culture conditions for the high level production of extracellular chitinases were optimized resulting in 48-folds higher chitinase production. As the combination of chitinases could be more potent in biocontrol of plant diseases, it was checked if AS70 could control postharvest fungal infection caused by Fusarium oxysporum on tomatoes. AS70 treated tomatoes showed significant lower incidence of infection (11%) by F. oxysporum as compared with 100% in the control at 5 days post inoculation. Further, AS70 caused significant mortality in second stage juveniles of root knot nematode, Meloidogyne incognita, a major agriculture pest responsible for economic losses in agriculture. This study highlights the antifungal and nematicidal activity of chitinases produced by Chitinophaga sp. S167. To the best of our knowledge, this is the first report of the biocontrol potential of the chitinases produced by Chitinophaga sp.