Journal of Basic Microbiology最新文献

Malate synthase (MS), the second key enzyme in the glyoxylate cycle, catalyzes the condensation of acetyl-CoA and glyoxylate to produce malate and CoA. Phylogenetic analysis reveals four MS subgroups: MSA, MST, MSG, and MSH. Sequence alignment shows that MSA, MSG, and MSH share similar structures and active sites, while MST exhibits extremely low identity with the other three subtypes. Herein, we report the cloning, expression, and detailed characterization of MS isoforms from Acinetobacter baumannii (AbMSG), Pseudomonas aeruginosa (PaMSG), Escherichia coli (EcMSA), and Sulfolobus acidocaldarius (SaMST). AbMSG, PaMSG, and EcMSA are mesophilic, with optimum temperatures of 40°C, 32°C, and 32°C, respectively. SaMST is thermophilic, with maximal activity at 60°C, and uniquely prefers Mn²⁺, in contrast to the Mg²⁺ dependence of AbMSG, PaMSG, and EcMSA. Despite similar catalytic efficiencies for acetyl-CoA, the isoforms show pronounced differences in glyoxylate turnover. Strikingly, cis-aconitate completely inhibits MS activity, indicating this metabolite and its analogs as potential scaffolds for MS-targeted antibacterial strategies, given the pivotal role of the glyoxylate cycle in bacterial virulence.

Cucumis sativus (L.) is a high-value crop renowned for its nutritional content, including vitamins, minerals, and antioxidants. However, its productivity is severely hindered by Fusarium wilt, a soil-borne disease caused by Fusarium oxysporum f. sp. cucumerinum. This study investigated the biocontrol potential of two plant growth-promoting rhizobacteria (PGPRs), Bacillus aryabhattai Z-48 and Bacillus cereus Z-53, in managing Fusarium wilt under controlled pot conditions. Treatment with PGPRs significantly enhanced C. sativus growth, including root and shoot length, and fresh and dry biomass, compared to both pathogen-inoculated and uninoculated controls. Disease severity was reduced by 34% and 27% in C. sativus plants when treated with B. aryabhattai Z-48 and B. cereus Z-53, respectively. B. aryabhattai Z-48-treated plants exhibited significant increases in defense-related enzyme activities, including polyphenol oxidase (78%), phenylalanine ammonia lyase (3.1-fold), and peroxidase (89%). Physiological parameters were also improved in PGPRs inoculated plants, such as total chlorophyll (29%), carotenoids (36%), phenolics (14%), flavonoids (91%), and protein content (10%) compared to pathogen-infested plants. LC–MS-based metabolomic profiling revealed significant metabolic reprogramming, with upregulation of key stress tolerance, antioxidant, and defense-related compounds, including quercetin, DL-phenylalanine, gluconic acid, xanthophyll, guanosine, and benzoic acid in the PGPR-treated plants. These metabolic shifts corroborated the physiological improvements, indicating enhanced systemic resistance and improved plant vigor. Overall, the results demonstrated that B. aryabhattai Z-48 not only suppressed Fusarium wilt but also promoted C. sativus growth through physiological, biochemical, and metabolic modulation. Further research should explore the practical field application of these strains in pathogen-contaminated soils for sustainable crop production.

Palomero Toluqueño maize (PTM, Zea mays L. var. everta) is an ancient landrace cultivated in the highlands of central Mexico (2200–2800 masl) under traditional agroecosystems considered suboptimal by conventional agronomic standards, suggesting that its adaptation may be partially mediated by its associated microbiome. This study characterized the cultivable rhizobacteria associated with PTM, focusing on their functional traits and potential agronomic applications. Acidic soils with nitrogen and site-specific phosphorus deficiencies yielded 73 bacterial isolates from three conservation plots, spanning 35 genera across the phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. Functional screening of 60 strains revealed convergence across sites, with the Proteobacteria phylum being the most abundant and functionally diverse. Overall, 80% of the strains exhibited plant growth-promoting activities (PGPA), with 70% producing IAA, 32% solubilizing phosphate, and 43% producing siderophores. Phosphate solubilization ranged from 660 to 830 µg mL⁻¹ (e.g., Acinetobacter, Advenella, Pseudomonas); the siderophore production index ranged from 3.2 to 3.9 in 24 h (Enterobacter, Pseudomonas, Serratia); and IAA synthesis was notable in Achromobacter and Curtobacterium. Two relevant functional clusters were identified, comprising generalist and specialist strains. Greenhouse assays validated nine strains, particularly Pseudomonas alvandae RSPTM-03 20, Achromobacter deleyi RSPTM-01 34, and Enterobacter sp. RSPTM-03 05, which enhanced shoot growth. Pseudomonas emerged as a key functional genus, reinforcing the potential of PTM-associated bacteria as PGPR.

Oryza sativa L. is vulnerable to over 76 diseases, with Bacterial Leaf Blight (BLB) being one of the most prevalent and destructive disease. BLB caused by the pathogen Xanthomonas oryzae pv. oryzae (Xoo), poses a significant threat to rice cultivation globally. The study aims to isolate and characterize potential natural biocontrol agents capable of inhibiting Xoo. Among 115 bacterial isolates, AJS36 showed the highest antagonistic activity, followed by ACS17 and ACS48. Based on 16S rRNA gene sequencing, the isolates were identified as close relatives of Alcaligenes faecalis AJS36 (PQ151613), Enterobacter hormaechei ACS17 (PP998655) and Enterobacter asburiae ACS48 (PP998620). MIC value against Xoo was determined as 2, 4, and 5 µg/mL against AJS36, ACS17, ACS48 respectively. Further, it was observed that the isolates AJS36 and ACS17 significantly reduced biofilm formation, xanthomonadin production, extracellular polymeric substance (EPS) synthesis while inducing cellular protein leakage and enhancing scavenging activity in Xoo in comparison to the isolate ACS48. The potent isolates were sensitive towards various antibiotics like amikacin, levofloxacin, ticarcillin, norfloxacin, ciprofloxacin, tobramycin. Greenhouse trials demonstrated that foliar application of these isolates before Xoo infection significantly reduced lesion length and disease severity under natural conditions, with AJS36 showing the most prominent effect. This is the first report in use of A. faecalis AJS36, E. hormaechei ACS17 and E. asburaei ACS48 as promising candidates to be developed as biocontrol agents for sustainable management of BLB in rice plants and offering alternatives to chemical pesticides.

Microbial contamination and plastic packaging pose significant health and environmental risks and are nonrecyclable. Biomaterials are gaining popularity in food packaging due to their biodegradability, renewability, and eco-friendly nature. Therefore, zinc oxide-chitosan-based nanocomposite (ZnOCh) films were synthesised in this study as a biodegradable food packaging material. Three composite films were prepared, containing different concentrations of nanoparticles (1%, 2%, and 3% wt) and pure chitosan. Ultraviolet-visible and Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, energy-dispersive X-ray, and scanning electron microscopy were used for characterisation. The films were also characterised for their biodegradability and ability to enhance the shelf life of chicken meat. Two bacterial strains were isolated from chicken meat and identified: SHA as Klebsiella pneumoniae (PQ313102) and SHC as Serratia marcescens (PQ312920). The appearance of a peak at 370 nm in UV-visible spectra confirms the formation of zinc oxide nanoparticles. The SEM revealed a smooth surface of ZnOCh film with scattered nanoparticles, while degraded film showed less scattering and a rougher surface. The formation of peaks at 432 and 471 cm^-1 in FTIR spectra confirmed the incorporation of ZnO, attributed to Zn–O stretching vibrations. ZnOCh 1% showed statistically significant degradation (96.50% ± 0.56%) after 14 days, and these films also showed promising results in increasing the shelf life of meat after 12 days of storage at 4°C. ZnOCh films showed significantly high (p ≤ 0.000) antibacterial activity (upto 19.6 ± 0.4 mm inhibition zone) against both erythromycin-resistant bacterial strains. Based on these results, this study suggests that ZnOCh films could be an alternative to plastic food packaging materials.

The textile industry releases large volumes of harmful chemicals, including residual dyes and xenobiotics—synthetic or foreign compounds not naturally produced or expected in living systems, such as dyes, surfactants, and pesticides. These pollutants contribute to environmental toxicity, mutagenicity, and carcinogenicity. While physicochemical treatments are commonly employed for dye and heavy metal removal, bioremediation using microorganisms offers a sustainable and eco-friendly alternative. Diverse microbial groups, including bacteria, fungi, and microalgae, can degrade textile pollutants through specialized metabolic pathways. However, biodegradation efficiency is often influenced by dye toxicity, environmental stress, and microbial diversity. Sulfate-reducing bacteria (SRBs) have emerged as promising agents for bioremediation due to their metabolic versatility. SRBs reduce sulfate to hydrogen sulfide (H₂S), which reacts with heavy metals to form insoluble metal sulfides, enabling their effective removal from wastewater. SRBs are also capable of decolourizing textile dyes—particularly azo dyes and, to a lesser extent, anthraquinone, triphenylmethane, and sulfur dyes—thereby enhancing their capacity for pollutant degradation and heavy metal removal. Understanding the role of SRBs requires a thorough knowledge of the sulfur cycle, including biogeochemical pathways, reduction mechanisms, and the genes and enzymes involved. Sulfur itself holds significant importance in agriculture and industry, further emphasizing the relevance of SRBs in environmental remediation. This review underscores the significance of sulfur, key features of the sulfur cycle, and the physiological roles of SRBs in degrading textile pollutants, positioning them as vital contributors to sustainable wastewater treatment strategies.

Successful colonization of plant roots is vital for optimizing rhizobacterial benefits, but osmotic stress can significantly impact bacterial colonization. In this study, mustard seedlings were grown under no stress and osmotic stress (20% PEG 6000) conditions, and root exudates (RE_C and RE_OS, respectively) were collected. We analyzed how osmotic stress alters root exudate metabolites, and their impact on motility, biofilm formation, hydrolytic enzyme production and changes in cell surface components of rhizobacteria Bacillus sp. MRD-17 and B. casamancensis MKS-6. Chemical analysis revealed that RE_OS contained higher levels of sugars, organic acids (salicylic and succinic), fatty acids (octadecanoic), and phenolics/flavonoids (quercetin, genistein, dihydrodaidzein). MKS-6 exhibited higher motility in medium supplemented with root exudates from osmotic-stressed plants (RE_OS) compared to control exudates (RE_C), whereas MRD-17 showed no significant motility towards root exudates but exhibited a larger colony diameter in RE_OS than RE_C. Both rhizobacteria formed biofilms and moved toward root exudates with higher cfu/mL in RE_OS. Osmotic stress and root exudates altered rhizobacterial cell surface components and significantly affected cell wall protein expression. Osmotic stress influenced the rhizobacterial production of cell-wall hydrolytic enzymes. Seedlings inoculated with the rhizobacteria showed increased defense enzyme activities (peroxidase and polyphenol oxidase). The changes in root exudate components were positively correlated with colonization parameters. These findings indicate that osmotic stress-induced modifications in mustard root exudates enhance colonization traits of the rhizobacteria, highlighting their potential for drought stress mitigation through bioformulation development.