Current Microbiology最新文献

This study aimed to investigate the antibacterial activity of essential oils from Cupressus sempervirens (CSEO) and Eucalyptus globulus (EGEO) against clinical isolates of colistin-resistant E. coli and methicillin-resistant M. sciuri recovered from diseased food-producing animals in Tunisia. The chemical compositions of both essential oils were analyzed using Gas chromatography-mass spectrometry (GC-MS). Antibacterial activity was determined through disk diffusion and microdilution assays, while the fractional inhibitory concentration index (FICI) was used to measure the synergistic effect of CSEO and colistin. The major constituents of CSEO were α-pinene (59.03%), δ-3 Carene (21.48%), D-limonene (5.62%) and α-thujene (3.08%), while EGEO contained eucalyptol (52.1%), α-pinene (26.51%), γ-terpinene (4.81%) and D-limonene (3.54%). The inhibition zone diameters (IZDs) against E. coli and M. sciuri ranged from 6 to 29 mm for CSEO and 9.3 to 28.6 mm for EGEO. Minimum inhibitory concentrations (MICs) showed a range of 4 to 512 µg/mL for CSEO against M. sciuri and 2 to 426.66 µg/mL for EGEO. For E. coli, MICs ranged from 170.66 to 512 µg/mL for CSEO and 53.33 to 512 µg/mL for EGEO. The checkerboard test demonstrated a synergistic effect between CSEO and colistin against two colistin-resistant E. coli isolates, with FICI 3- to 32-fold lower than the MICs of the individual compounds. This study highlights the potency of essential oils from CSEO and EGEO against antibiotic-resistant M. sciuri and E. coli strains from animals in Tunisia and provides evidence of the synergistic effect between CSEO and colistin against clinically relevant colistin-resistant E. coli isolates.

The emergence of pathogenic bacteria resistant to conventional antibiotics is becoming increasingly challenging. Plant-derived flavonoids are potential alternatives to antibiotics, owing to their antimicrobial properties. However, the molecular mechanisms through which they inhibit the growth of pathogenic microorganisms remain unclear. Therefore, Klebsiella pneumoniae ATCC700603 was separately incubated in two flavonoids to elucidate their inhibitory mechanism. Metabolomic and transcriptomic analyses were performed after 4-h incubation. In total, 5483 genes and 882 metabolites were identified. Compared to the untreated control, rutin and luteolin activated 507 and 374 differentially expressed genes (DEGs), respectively. However, the number of differential abundant metabolites (DAMs) remained the same. The top 10 correlated DEGs and DAMs were identified within each comparative group after a correlation analysis. Rutin induced the accumulation of unique metabolites and suppressed gene expression whereas luteolin did not. Our results explain the disparate effects of these two flavonoids and demonstrate the inhibitory mechanism of rutin on strain growth.

Infections and antimicrobial resistance are becoming serious global public health crises. Multidrug-resistant Staphylococcus aureus (S. aureus) infections necessitate novel antimicrobial development. In this study, we demonstrated TAK-285, a novel dual HER2/EGFR inhibitor, exerted antibacterial activity against 17 clinical methicillin-resistant S. aureus (MRSA) and 15 methicillin sensitive S. aureus (MSSA) isolates in vitro, with a minimum inhibitory concentration (MIC) of 13.7 μg/mL. At 1 × MIC, TAK-285 completely inhibited the growth of S. aureus bacterial planktonic cells, and at 2 × MIC, it exhibited a superior inhibitory effect on intracellular S. aureus SA113-GFP compared to linezolid. Moreover, TAK-285 effectively inhibited biofilm formation at sub-MIC, eradicated mature biofilm and eliminated bacteria within biofilms, as confirmed by CLSM. Furthermore, the disruption of cell membrane permeability and potential was found by TAK-285 on S. aureus, suggesting its targeting of cell membrane integrity. Global proteomic analysis demonstrated that TAK-285 disturbed the metabolic processes of S. aureus, interfered with biofilm-related gene expression, and disrupted membrane-associated proteins. Conclusively, we repurposed TAK-285 as an antimicrobial with anti-biofilm properties against S. aureus by targeting cell membrane. This study provided strong evidence for the potential of TAK-285 as a promising antimicrobial agent against S. aureus.

In the summer of 2019, a severe stem canker disease affected potato (Solanum tuberosum) plants in a 10-hectare commercial field in Kermanshah province, Iran. Approximately 10% of the plants exhibited wilting, leaf yellowing and brown stem lesions with black sporodochia. Infected plants produced small tubers with no visible lesions. Ten fungal isolates from diseased plants were identified as Paramyrothecium roridum based on colony culture, microscopic characteristics, and analysis of the internal transcribed spacer (ITS) region and part of the β-tubulin gene. The pathogenicity of P. roridum on seedlings was confirmed by fulfilling Koch's postulates. Host range studies revealed a broad pathogenicity of the P. roridum isolate, successfully infecting various plant species with varying disease severities. Cucumis melo (melon) and Nicotiana rustica (wild tobacco) displayed susceptibility, while Triticum aestivum (wheat) and Avena sativa (oat) from the Poaceae family exhibited resistance. This study identifies P. roridum as a novel cause of potato stem canker disease in Iran.

Vibrio parahaemolyticus is equipped with two distinct flagellar systems: a polar flagellum and numerous lateral flagella. The polar flagellum plays a role in propelling swimming in liquids, while the lateral flagella serve to enhance swarming on surfaces or in viscous environments. H-NS is a histone-like nucleoid structuring protein that plays a regulatory role in both the swimming and swarming motility of V. parahaemolyticus. However, the detailed mechanisms have not been fully understood. In this study, we have demonstrated that the deletion of hns hindered the growth rate of V. parahaemolyticus during the logarithmic growth phase and significantly decreased the swimming motility. H-NS directly activated the transcription of flgMN, flgAMN, flgBCDEFGHIJ, and flgKL-flaC located within the polar flagellar gene clusters. The expression of H-NS in Escherichia coli led to a marked elevation in the expression levels of flgM, flgA, flgB, and flgK, suggesting the positive effect of H-NS on the expression of polar flagellar genes in E. coli. This work demonstrates that the positive regulation of H-NS on the swimming motility in V. parahaemolyticus may be achieved through its regulation of polar flagellar gene expression and bacterial growth.

Antimicrobial resistance (AMR) is a growing public health threat caused by the widespread overuse of antibiotics. Bacteria with antibiotic resistance may acquire resistance genes from soil or water. Endogenous hydrogen sulfide (H₂S) production in bacteria confers antibiotic tolerance in many, suggesting a universal defense mechanism against antibiotics. In this study, we isolated and identified soil-based antibiotic-resistant bacteria collected from contaminated areas. An antibiotic-resistant bacterium was identified as non-endogenous-H₂S-producing, allowing us to examine the effect of exogenous H₂S on its resistance mechanism. Therefore, we demonstrated that different classes of antibiotic resistance can be reverted by employing H₂S with antibiotics like ampicillin and gentamicin. Methods like Kirby-Bauer Disk-Diffusion, Scanning Electron Microscopy, and Flow Cytometer analysis were performed to assess the antibacterial activity of H₂S with ampicillin and gentamicin. The antioxidative efficiency of H₂S was evaluated using the DCFH-DA (ROS) test, as well as lipid peroxidation, and LDH activity. These were further confirmed with enzymatic and non-enzymatic (SOD, CAT, GST, and GSH) antioxidant studies. These findings support H₂S as an antibiotic-potentiator, causing bacterial membrane damage, oxidative stress, and disrupting DNA and proteins. Thus, supplying exogenous H₂S can be a good agent for the reversal of Antibiotic resistance.

Providencia stuartii is an emerging pathogen that causes nosocomial infections. In this study, a multidrug-resistant strain P. stuartii MF1 was isolated from swine wastewater. Comprehensive analysis of whole genome sequencing revealed that dozens of antibiotic resistance genes were found in MF1. A novel transposon Tn6450M which has high sequence identity to Tn6450 and the plasmid-borne Tn6765 from Proteus mirabilis was identified in the genome of MF1. Tn6450M was determined to be stably inserted into a new attTn7 site in the P. stuartii MF1 genome and contains the third-generation cephalosporins resistance-associated genes blaDHA-1. Intergeneric transmission of Tn6450 variants poses risks for the spread of antibiotic resistance genes.

The pyrimidine biosynthetic pathway regulation in the bacterium Pseudomonas lemonnieri ATCC 12983 was investigated since this strain synthesizes a blue aromatic pigment that could have a commercial application as a dye. The effect of the pyrimidine bases, orotic acid and uracil metabolites, on the enzymes unique to the pyrimidine biosynthetic pathway was studied. It was found that pyrimidine addition to the medium affected the biosynthetic enzymes differently depending on the carbon source present. Using chemical mutagenesis and 5-fluoroorotic acid resistance, a mutant strain deficient for OMP decarboxylase activity was isolated. The uracil-requiring mutant strain could also utilize cytosine, uridine, or uridine monophosphate as a pyrimidine source. When the mutant strain was limited for pyrimidines for 1 or 2 h, derepression of pyrimidine biosynthetic enzyme activities was observed in the glucose-grown cells but not in the succinate-grown cells. Clearly, carbon source was a factor in the regulation of pyrimidine biosynthesis in P. lemonierri. The regulation of the known regulatory pyrimidine biosynthetic enzyme aspartate transcarbamoylase activity was examined in succinate-grown ATCC 12983 cells, and its activity was controlled by AMP, ADP, GTP, and CTP under saturating substrate concentrations. This study also provides new information as to the taxonomic relatedness of P. lemonnieri to other species classified within the Pseudomonas fluorescens homology group relative to regulation of pyrimidine biosynthesis.

The rhizosphere bacterial community of plants has a crucial effect on healthy plant growth, and each rhizosphere has a specific microbial community. Camellia sinensis cv. Shifocui (C. sinensis cv. Shifocui) is a tea plant distributed in the Dabie Mountains of Anhui Province. It has the characteristics of high yield, good quality, strong cold resistance, and a high amino acid content. This study was the first to use 16S rRNA high-throughput sequencing technology and bioinformatics methods to explore the characteristics and functions of the rhizosphere bacterial community of the cold-tolerant tea tree C. sinensis cv. Shifocui, providing an important basis for the development and utilization of rhizosphere microbial resources. The dominant phylum in the rhizosphere microbes of the C. sinensis cv. Shifocui rhizosphere microorganisms were Proteobacteria, Chloroflexi, Acidobacteriota, and Actinobacteria. Network analysis showed significant positive and negative correlations among the rhizosphere bacterial groups of C. sinensis cv. Shifocui, among which Candidatus _ Xiphinematobacter, Acidobacteriale, Bradyrhizobium, Subgroup _ 2, Candidatus_Udaeobacter, Gemmataceae, and Gaiellales were notable nodes in the interaction networks. Functional prediction of FAPROTAX indicated that C. sinensis cv. Shifocui was rich in chemoheterotrophic, cellulose hydrolysis, and oxidative heterotrophic conditions, indicating that the dominant bacterial flora was enriched in its rhizosphere microbes and played an important role in plant growth and development. These results lay a foundation for exploring the mechanism of interaction between C. sinensis cv. Shifocui and rhizosphere microorganisms and provide a research basis for the development and utilization of tea plant microbial resources.