Journal of Basic Microbiology最新文献

Rac-metalaxyl is a widely used fungicide for managing plant diseases; however, its environmental persistence and potential toxicity to aquatic microorganisms raise significant ecological concerns. Despite its widespread application, there is limited understanding of how cyanobacteria, which play vital ecological roles in aquatic systems, respond to such chemical stressors. This study addresses this gap by investigating the physiological and metabolic responses of the cyanobacterium Anabaena laxa to rac-metalaxyl exposure. Cultures were treated with 100 mg/L and 200 mg/L concentrations of the fungicide. Results showed increased intracellular accumulation of rac-metalaxyl at 200 mg/L, leading to significant reductions in cell growth, photosynthetic pigments, and the activities of key enzymes such as phosphoenolpyruvate carboxylase and ribulose-1,5-bisphosphate carboxylase/oxygenase. Further elevated lipid peroxidation levels indicated oxidative damage. Consequently, rac-metalaxyl triggered substantial metabolic shifts, total soluble sugars increased by 7.66% at 100 mg/L and 67.48% at 200 mg/L; malic acid rose to 76.23% at 200 mg/L; amino acids increased by 27.14% at 100 mg/L and 48.8% at 200 mg/L; total fatty acids rose by 10.11% at 100 mg/L and 35.06% at 200 mg/L. These findings suggest that Anabaena laxa exhibits coordinated oxidative and metabolic responses to mitigate rac-metalaxyl toxicity, highlighting its potential resilience and role in the bioremediation of contaminated aquatic environments.

The rise of carbapenem resistance in Escherichia coli is mainly due to the rapid spread of carbapenemase-encoding genes through horizontal gene transfer, particularly via bacterial conjugation. Recent research has highlighted the role of a small RNA molecule known as RydB in bacterial conjugation, specifically through its interaction with the protein SdiA. This study investigated the effects of sub-inhibitory concentrations of imipenem and N-acyl homoserine lactones (AHLs) on the expression of rydB in E. coli strains that overexpress sdiA. Additionally, we examined how AHLs influence the bacterial conjugation of plasmids that contain carbapenem resistance genes. We selected a carbapenem-resistant isolate of E. coli harbouring the bla_NDM gene and its corresponding plasmid-cured derivative, based on the overexpression of the sdiA gene in response to AHLs. Conjugation experiments were conducted, both without AHL treatment and with AHL treatments, to assess the transferability of the bla_NDM plasmid. The transcriptional response of rydB gene was evaluated in the plasmid-cured derivative, the native type, the transconjugant, and E. coli J53. Our findings indicated that AHLs and imipenem inhibit the expression of the rydB gene. Interestingly, while RydB does not seem to impact bacterial conjugation when suppressed by these agents, the combination of AHLs enhances the conjugation of plasmid that carry the bla_NDM gene. This study enhances our understanding of the regulatory roles that quorum sensing signal molecules, including C4 AHL and C12AHL, as well as imipenem, play in bacterial conjugation and sRNA expression.

Actinobacteria have shown significant potential in promoting the growth of various plant species, especially those that inhabit in association with plants. However, previous research has mainly focused on higher plant species. Bryophytes are a large group of non-vascular, non-flowering land plants without true vascular bundles, roots, stems, and leaves. Despite the extensive diversity of bryophytes in Thailand, research on the diversity of actinobacteria associated with bryophytes remains scarce. This study aimed to isolate actinobacteria from three bryophyte species in northern Thailand: Koponobryum papillosum Printarakul & Chantanaorr, Pseudotrismegistia undulata, and Sphagnum cuspidatulum C. Müll. A total of 52 isolates were identified, including 6 endophytic and 46 epiphytic isolates. These isolates were assigned to four genera: Brevibacterium (1 isolate), Microbacterium (1 isolate), Rhodococcus (6 isolates), and Streptomyces (44 isolates). All isolates were assessed for their plant-growth promoting abilities both in vitro and in planta. Most actinobacteria exhibited the in vitro ability to produce indole-3-acetic acid (IAA), siderophores, and solubilize tricalcium phosphate. Three isolates—Streptomyces brevispora RHP2, S. halstedii WS1, and Rhodococcus triatomae RHK22—were selected to evaluate their potential to enhance the growth of S. cuspidatulum C. Müll in soil. R. triatomae RHK22 was highly effective in promoting the regeneration of new shoots and significantly enhancing thallus height, fresh weight, dry weight, total chlorophyll content, and total carotenoid content (p < 0.05) of S. cuspidatulum C. Müll when applied as cell suspension and cell free supernatant.

The emergence of multidrug-resistant pathogens has significantly reduced the efficacy of current antimicrobial treatments against bacterial and fungal infections. To combat this challenge, the exploration of novel antimicrobial sources or the development of synthetic antibiotics is imperative. Microbes have emerged as promising natural reservoirs for antimicrobial compounds, with slime molds garnering attention due to their unique bioactive metabolites in recent years. Some of these metabolites demonstrate potent antibiotic properties. This study investigates the inhibitory effects of slime mold extracts on pathogenic bacteria, attributing this activity primarily to symbiotic bacteria associated with the slime molds rather than to the slime mold cells themselves. Furthermore, we demonstrate that this antibacterial effect can be horizontally transferred through bacterial ingestion, enabling recipient slime molds to exhibit antibacterial properties upon extraction. Importantly, slime molds selectively acquire bacteria from their environment to enhance their antibacterial characteristics, a process that appears non-random and persists through sexual cycles. These findings underscore slime molds as valuable reservoirs of antimicrobial agents. Nevertheless, it remains critical to ascertain whether these antimicrobial agents originate solely from symbiotic bacteria or result from complex interactions between these bacteria and their slime mold hosts. Understanding the mechanisms behind this antimicrobial activity not only expands our knowledge of host-microbe interactions but also provides new avenues for bioprospecting novel antibiotics. Investigating how slime molds selectively acquire and retain beneficial bacteria may offer insights into microbial symbiosis that could be leveraged for antimicrobial discovery, potentially addressing the urgent need for alternative treatments against resistant pathogens.

Drought-tolerant multifunctional soil bacteria can increase drought tolerance mechanisms in plants. Here, rhizobacteria CRB-4 and SPGPR-11 were isolated and their single and co-inoculation effect was evaluated in drought-stressed tomato plants. Isolates were selected based on their preliminary polyethylene glycol (PEG) screening, and plant growth-promoting properties. Increasing water stress adversely affected growth and physiological attributes of tomato plant. However, plant growth-promoting bacteria (PGPB), particularly their combined inoculation, alleviated drought stress. For instance, CRB-4, SPGPR-11 and their co-inoculation significantly increased root biomass (33.3, 37.5% and 45.4%), total chlorophyll (17.5, 15.6% and 19.2%) and carotenoid content (20, 30.4% and 48.3%) in 3%-PEG-stressed tomatoes. Similarly, co-inoculation of 3%-PEG-treated plants with PGP isolates resulted in a significant increase in Fv/Fm (50%), Fv'/Fm' (29.4%), PS-II (44.4%), Pq (40%), NPQ (40%), and effective electron transfer rate (37.5%). Furthermore, under 5%-PEG stress, CRB-4, SPGPR-11, and their co-inoculation enhanced drought stress resilience in tomato by improving leaf gas exchange attributes. Combined inoculation significantly enhanced gs (19%), Ci (31.2%), transpiration rate (41%), water vapor deficit (38.7%), iWUE (33.7%), and photosynthetic rate (33.3%) in 5%-PEG-stressed tomatoes. Among the treatments, co-inoculations significantly enhanced the antioxidant defense responses in drought-stressed tomatoes. Concurrently, qRT-PCR analysis revealed a significant upregulation in ROS scavenging genes, SOD, CAT, APX, GR, and POD, by 6.53, 14.08, 11.72, 10.12, and 5.95-fold, respectively, in drought-stressed plants co-inoculated with bacterial strains. This study concludes that PGP isolates CRB-4 and SPGPR-11, alone or in combination, offer an effective, eco-friendly solution for improving drought resilience in tomatoes.

Metal contamination represents a critical environmental challenge, adversely impacting ecosystems and human health. Microorganisms, including fungi, have developed diverse mechanisms to tolerate and resist metal-induced stress, making them valuables for bioremediation. This study evaluates the metal tolerance of Absidia glauca, Penicillium bilaiae, and Trichoderma viridescens using minimum inhibitory concentration (MIC) assay and the alternative minimum profile change concentration (MPCC) approach via MALDI-TOF MS. MIC assay revealed species-specific tolerances to copper, zinc, and cadmium. A. glauca showed the highest tolerance to copper and cadmium (75 and 9 mg L⁻¹), producing a dry biomass of 0.03 and 0.04 g, respectively. While P. bilaiae exhibited the highest tolerance to zinc (75 mg L⁻¹) producing a dry biomass of 0.06 g. MALDI-TOF MS provided rapid proteomic information on fungal responses to metals, showing changes in the protein profile as the metal concentration increased. We performed a comparative analysis between the values obtained in the MIC and MPCC, giving a positive correlation in the results of both techniques for Cu, Zn, and Cd (r = 1.00; 0.87 and 0.99 respectively, p < 0.05). In conclusion, MALDI-TOF MS has proven to be an effective method for analyzing fungal proteomic responses to metal exposure, providing more detailed molecular insights than traditional MIC assays. Future studies should investigate the mechanisms underlying metal resistance, particularly focus on the regulation of specific proteins.