Jun 2026· Frontiers in Microbiology· Vol 17· 0 citations· 89 references
Medicine
Abstract
A polyphasic taxonomic approach was used to characterize strain B38T, isolated from the phyllosphere of Salicornia hispanica. The strain is an aerobic, Gram-negative, halotolerant coccus–rod-shaped bacterium exhibiting optimal growth at 28 °C, pH 6–9, and up to 12% (w/v) NaCl. The genome of strain B38T is 3.2 Mbp with a DNA G+C content of 43.81 mol%. Phylogenetic analysis based on the 16S rRNA gene sequences placed B38T within the genus Psychrobacter. Although 16S rRNA gene sequencing showed high similarity to P. alimentarius (99.73%), genomic indices (ANI, AAI, and dDDH) remained below species delimitation thresholds. Chemotaxonomic features included C18:1 ω9c as the major fatty acid, Q-8 as the main quinone, and diphosphatidylglycerol as the major polar lipid. Consequently, strain B38T (=CECT 31210; =LMG 33901) is proposed as Psychrobacter halotolerans sp. nov. Additionally, the plant growth-promoting (PGP) potential of the halotolerant strain B38T was evaluated in lettuce under salt stress, alongside the salt-tolerance mechanisms induced by inoculation. Strain B38ᵀ significantly enhanced lettuce biomass, leaf area, and PSII quantum efficiency compared to non-inoculated controls. These benefits were linked to increased soluble sugars and phenolic compounds, modulation polyamine homeostasis, and reduced oxidative damage. Our results demonstrate that P. halotolerans B38ᵀ effectively mitigates salt stress in plants, representing a promising biotechnological tool for enhancing salinity tolerance in agricultural systems.
A novel Gram-stain-positive, rod-shaped bacterium with peritrichous flagella, designated C159T, was isolated from tomato rhizosphere soil. Growth of strain C159T occurred at 4-45 °C, pH 6.0-10.0 and in the presence of 0-5% NaCl. Based on 16S rRNA gene sequence analysis, strain C159T belongs to the genus Pseudoneobacillus and has a sequence similarity of 98.70% with Pseudoneobacillus rhizosphaerae JJ-79T. The whole genome of strain C159T was 4.65 Mb, with a DNA G+C content of 38.65 mol%. The average nucleotide identity between strain C159T and P. rhizosphaerae JJ-79T was 75.31%, and the digital DNA-DNA hybridization value was 19.6%, supporting its designation as a novel species of the genus Pseudoneobacillus. The major respiratory quinone of strain C159T was menaquinone 7; the major fatty acids were iso-C14:0, iso-C15:0 and anteiso-C15:0; and the major polar lipids are diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. Based on its phenotypic, chemotaxonomic, phylogenetic and genomic characteristics, strain C159T represents a novel species in the genus Pseudoneobacillus, for which the name Pseudoneobacillus rhizolycopersici sp. nov. is proposed. The type strain is C159T (=GDMCC 1.5552T=KCTC 43820T). In addition, strain C159T possesses the ability to produce indole-3-acetic acid (33.72 mg·l-1) and to mineralize insoluble organic phosphorus. In a pot experiment, this strain demonstrated a plant growth-promoting effect of 22.68-44.49% and a disease suppression efficacy of 89.29% against bacterial wilt of tomato caused by Ralstonia solanacearum. The above results confirm that strain C159T is a novel multifunctional rhizobacterium for the biocontrol of tomato bacterial wilt.
Shengfeng Pan, Zengwei Feng, Meng Chen et al.· International Journal of Sys...· 0 citations
A novel slow-growing bacterium, designated strain ag2_l2_5AT, was isolated from pine forest soil at Kagamiyama, Hiroshima, Japan, by using a gel microdroplet cultivation approach. The strain was characterized as a Gram-negative, non-motile bacterium with a short rod-shaped morphology. The strain formed small, circular, smooth and umbonate colonies after prolonged incubation on agar plates. Cells accumulated intracellular polyphosphate and produced membrane vesicles during the exponential growth phase. The strain grew optimally at 20-30 °C and pH 6.0-7.5, utilizing various sugars, amino acids and organic acids as carbon sources. The genomic G+C content was 62.8%. The major fatty acids were iso-C15 : 0, C16 : 1 ω7c, iso-C16 : 0, iso-C17 : 0 and C16 : 0. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain ag2_l2_5AT belongs to the class Gemmatimonadetes within the phylum Gemmatimonadota. Its closest relatives were Gemmatimonas phototrophica AP64T (91.3% gene sequence similarity), Gemmatimonas aurantiaca T-27T and Pseudogemmatithrix spongiicola 318T. Based on polyphasic characterization, the strain ag2_l2_5AT represents a novel genus and species of the class Gemmatimonadetes, for which the name Leucogemmata humicola gen. nov., sp. nov. is proposed. The type strain is ag2_l2_5AT (=NBRC 117234T=DSM120521T).
Rikuta Suzuki, Yumi Shimomura, T. Iwashita et al.· International Journal of Sys...· 0 citations
A Gram-stain-negative, facultative anaerobic, short rod-shaped, non-spore-forming, mesotrione-resistant bacterium, designated strain A39T, was isolated from activated sludge treating pesticide-manufacturing wastewater. Strain A39T grew at 15-42 ℃, pH 6-10 and 0-1.0% NaCl (w/v), tolerated up to 2 mM mesotrione and could fix nitrogen. Strain A39T showed the highest 16S rRNA gene sequence similarity to Azospirillum halopraeferens Au 4T (98.1%) and less than 97% sequence similarity with other species of the genus Azospirillum. Phylogenetic analysis based on 16S rRNA gene and genome sequences placed strain A39T within genus Azospirillum, forming a subclade with A. halopraeferens Au 4T. The values of digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) between strain A39T and A. halopraeferens Au 4T were 25.5% and 82.7%, respectively, which were significantly below the recommended thresholds for species delineation (dDDH <70% and ANI <95-96%). The major fatty acids were summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), C16 : 0 and C18 : 0. Strain A39T comprised phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, glycolipid and two aminolipids as the predominant polar lipids; and ubiquinone 10 as the major respiratory quinone. The genome size was 8.1 Mb with a DNA G+C content of 72.1%. Based on the phylogenetic, phenotypic and chemotaxonomic characteristics, strain A39T represented a novel species of the genus Azospirillum, for which the name Azospirillum caeni sp. nov. is proposed. The type strain is A39T (=MCCC 1K09771T=KCTC 18385T). Additionally, a gene encoding 4-hydroxyphenylpyruvate dioxygenase (HPPD), named AzhppD, was identified in strain A39T. AzHPPD showed less than 61% similarity to previously reported HPPDs and was able to tolerate 30 µM of mesotrione, which is an inhibitor of HPPD.
Minglai Wan, Chenghui Li, Le Chen et al.· International Journal of Sys...· 0 citations