Current Microbiology最新文献

Pseudomonas aeruginosa is a human pathogen causing mild skin to life-threatening bloodstream infections. Antibiotic treatment of P. aeruginosa is uneasy because the bacterium possesses intrinsic resistance mechanisms to various antibiotics and can acquire resistance to nearly all available antibiotics. It was reported that some antibiotics can induce oxidative stress that contributes to cellular death, but bacterial cells can detoxify oxidative stress by the oxidative stress-scavenging systems. The relative amount of antibiotic-induced oxidative stress to oxidative stress-scavenging systems may determine the roles of antibiotic-induced oxidative stress in cellular death. Glutathione is one of the oxidative-scavenging systems and is synthesized by glutamyl-cysteine synthetase encoded by gshA and glutathione synthetase encoded by gshB. This study aims to determine the roles of glutathione in oxidative stress and antibiotic susceptibility in P. aeruginosa. Glutathione-encoding genes were knocked out in P. aeruginosa PAO1, and the mutant strains (gshA::Gm, gshB::Gm, and gshA::Gm/gshB::Tc) were used to determine susceptibility to hydrogen peroxide, superoxide-producing paraquat, and antibiotics. The mutant strains were 2- to eightfold more susceptible to hydrogen peroxide and superoxide and 2- to fourfold more susceptible to all tested antibiotics than their parental strain. The susceptibility of hydrogen peroxide, superoxide, and antibiotics was genetically complemented in P. aeruginosa PAO1. Overall results indicate that glutathione is crucial in detoxifying oxidative stress induced internally and by antibiotics in P. aeruginosa. This finding suggests that glutathione is one of the oxidative stress-scavenging systems and one of the intrinsic resistance mechanisms to antibiotics and, thus, a potential drug target for P. aeruginosa.

Bacteriophages are viruses that specifically target bacteria and play a crucial role in influencing bacterial evolution and the transmission of antibiotic resistance. In this study, we explored the genomic profiles of 66 bacteriophages that infect Morganella morganii, an opportunistic pathogen associated with difficult-to-treat nosocomial and urinary tract infections. Our findings highlight the extraordinary diversity within this phage population, reflected in their genomic features, evolutionary relationships, and potential contributions to bacterial pathogenicity. The 66 phage genomes exhibited diversity in size, spanning from 6 to 115 kilobase pairs, reflecting a heterogeneous genetic material and coding potential. Their guanine-cytosine (G+C) content varied widely, from 43.3% to 64.6%, suggesting diverse evolutionary origins and adaptive strategies. Phylogenetic analysis identified ten distinct evolutionary clusters, some classified as singletons, highlighting unique evolutionary pathways. Several clusters included phages capable of infecting multiple M. morganii strains, indicating a broader host range and the potential for horizontal gene transfer. Genomic analysis also determined a substantial number of hypothetical proteins, underscoring the need for further investigation to clarify their functions. Importantly, we identified a wide array of antibiotic resistance and virulence-associated genes within these phage genomes, illuminating their potential to impact the treatment of M. morganii infections and develop new, more virulent strains. These findings highlight the critical role of phage-mediated gene transfer in shaping bacterial evolution and facilitating the transmission of antibiotic resistance.

The marine bacterium Vibrio parahaemolyticus is responsible for the seafood-borne gastroenteritis in humans. Two-component system (TCS) TtrRS plays important roles in host colonization and works as an important regulator in V. parahaemolyticus. However, the mechanisms by which TtrRS regulates the downstream genes, as well as the function of their target genes, remain largely unknown. In this study, we performed a Find Individual Motif Occurrences (FIMO) analysis using the ttrR box to scan the V. parahaemolyticus genome and identified 68 potential binding sites harboring the ttrR box. Thereinto, a ttrR box exists in the promoter region of the 05890-05900 operon. We further demonstrated that TtrR directly regulates the expression of the 05890-05900 operon by binding to the ttrR box. In addition, another TCS, 05905/05910, could assist in the regulation of TtrR to the 05890-05900 operon. Subsequent study showed that the 05890-05900 operon promotes the sulfur metabolism of V. parahaemolyticus at the early growth stage. Our results suggested that TtrRS and their target genes generate a complex regulatory pathway to better control sulfur metabolism in V. parahaemolyticus.Please check and confirm the edit made in the article title and amend if necessary.It's OK.

In recent years, as excellent industrial microorganisms, Halomonas has become a potential chassis cell of the next generation of industrial biotechnology because of its advantages of low complexity, antipollution ability, and rapid fermentation. Therefore, there is an urgent need to study the genome information, synthetic biology, multiomics, and other technologies of Halomonas, and it is also highly important to study its tolerance to extreme environments. Halomonas alkalicola CICC 11012 s is the most alkaliphilic bacterium in the genus Halomonas and is an excellent alkali-resistant bacterium that was independently isolated in our laboratory; this bacterium plays a certain role in industrial pollution control and the application of synthetic biology chassis cells. The H. alkalicola mutant was designed and constructed via CRISPR technology in the early stage of this experiment, which verified that the tonb gene plays an important role in the alkali resistance mechanism of this strain. Therefore, the molecular mechanism of the response of H. alkalicola CICC 11012 s to alkaline stress was explored through combined proteomic and metabolomic analysis. The experimental results revealed that the wild-type and mutant strains evolved multilevel adaptive strategies to regulate pH homeostasis in response to alkaline stress, including increasing their membrane transport activities and synthesizing carbohydrates and amino acids. In summary, the experimental results provide a deep understanding of the alkaline response mechanism of alkalophilic bacteria, thereby further promoting their application in different environments.

The rising resistance to conventional antimicrobial therapies in veterinary contexts poses a formidable challenge. While various innovative treatment strategies for pathogenic infections have emerged, their success still needs to be improved, warranting continued research. Recent investigations into natural products as potential sources for biologically active therapeutics have gained traction. Phytochemicals present a promising alternative in combating a spectrum of pathogens, including bacteria, fungi and parasites. One such class of phytochemicals with mounting potential is the structurally diverse terpenes. These chemicals contribute to plants' characteristic odour and medicinal effects and have been widely investigated in the scientific literature for their exceptional antibacterial activity. Their efficacy is demonstrated through diverse mechanisms, encompassing damage to bacterial membranes, suppression of virulence factors, and interference with enzymes, toxins, and biofilm formation. This review comprehensively examines terpenes' in vitro and in vivo activity and their derivatives against pathogens, elucidating their potential against antimicrobial resistance (AMR) and the underlying mechanisms specific to each terpene class. The findings underscore the burgeoning potential of terpene therapy as a viable alternative or supplementary approach to conventional antibiotics in addressing bacterial and parasitic infections in livestock and companion animals.

Ferroptosis is a unique form of regulated cell death that results from unrestricted lipid peroxidation, and it enhances the production of intracellular oxidative stress molecules. In this study, we investigated the effect of macrophage ferroptosis on the proliferation of Staphylococcus aureus (S. aureus) and sought potential host-directed therapy (HDT) targets for S. aureus. The study findings revealed that erastin concentrations (< 20 μM), which do not have an impact on macrophage proliferation, can effectively impede the proliferation of S. aureus within macrophages. High-throughput sequencing was used to identify DEGs and DEMIs in infected macrophages. Subsequently, the mRNA-miRNA regulatory network was successfully constructed, and two sets of molecules were selected. Experimental findings confirmed that mmu-miR-6935-5p exhibited complementary binding to specific sequences within the GM867 mRNA, and mmu-miR-7082-3p specifically bound to the GPR176 mRNA. Inducing ferroptosis in macrophages can effectively impede the proliferation of drug-resistant S. aureus. Notably, our study has identified GM867, GPR176, mmu-miR-6935-5p, and mmu-miR-7082-3p as key regulators involved in this process. These findings highlight the potential of targeting these four molecules for HDT, offering novel ways to combat drug-resistant S. aureus infection.

The primary objective of this study was to assess the growth-promoting potential of Colletotrichum sp. as a broad-spectrum plant inoculant and to investigate its applicability beyond its natural host range. Out of ten endophytes isolated from Ocimum basilicum, only four were reported for IAA production and among them, Colletotrichum sp. was chosen for further investigation due to its higher IAA production. Highest production of IAA was observed by providing Czapek dox broth with dextrose as carbon source, ammonium sulphate as nitrogen source at pH 7 and 32 °C. The crude fungal extract from Colletotrichum sp. was tested for its impact on rice plants under different application methods (soil drenching, foliar spraying, and seed immersion). Seed immersion treatment showed a notable effect on the growth of rice seedlings in contrast to soil drenching and foliar spraying. Plant growth assay with fungal elicitor treatment of plantlets produced by shoot culture, supplementing with 0.04 mL of culture filtrate per 30 mL media has significant impact on induction of rooting and overall biomass in Ocimum tenuiflorum as compared to untreated control plants. High-resolution liquid chromatography mass spectrometry (HR-LCMS) analysis of the fungal extract revealed the production of 3-indoleacetic acid and related intermediates.

A novel bacterium, designated as strain PR12^T, was isolated from intestine of red swamp crayfish (Procambarus clarkii), which appeared as creamy white colonies on TSA plates. Growth occurred at temperatures of 4-37 °C (28-30 °C optimal), pH of 6.0-9.0 (7.0-8.5 optimal), and with 0-4.0% (w/v) NaCl (0-1.5% optimal). The cells were Gram-stain-negative, rod-shaped, non-motile, aerobic, oxidase- and catalase-positive, and chemoorganotrophic. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain PR12^T was related to members of the genus Comamonas and shared the highest sequence similarities with Comamonas koreensis KCTC 12005^T (99.0%), Comamonas sediminis S3^T (98.8%), and Comamonas piscis CN1^T (98.0%). Whole genome size of PR12^T was 5,111,300 bp and DNA G + C content was 63.5%. The major cellular fatty acids (> 10%) were C_16:0, C_17:0 cyclo, summed features 3 (C_16:1ω6c and/or C_16:1ω7c) and summed features 8 (C_18:1ω6c and/or C_18:1ω7c). The major respiratory quinone was Q-8 and the major polar lipids contained diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). Based on the digital DNA-DNA hybridization, phylogenetic analysis, average nucleotide identity, average aminoacid identity as well as biochemical characteristics, strain PR12^T was clearly distinguishable from all recognized type strains of the genus Comamonas and represents a novel species, for which the name Comamonas squillarum sp. nov. is proposed. The type strain is PR12^T (= MCCC 1K08379^T = JCM 35896^T).

Bacteria of the genus Bacillus are ubiquitous in nature and produce several antimicrobial compounds, being increasingly used in plant biocontrol. The objective of this study was to identify the isolate Bacillus sp. 1.4 at the species level and study its bioactive properties prospecting the potential for agricultural application. The bacterial isolate was identified as belonging to Bacillus altitudinis through genomic metrics. The antimicrobial substance extracted with butanol inhibited Listeria monocytogenes ATCC 7644 and Bradyrhizobium japonicum CT 00345 with inhibition halos of 16 and 13 mm, respectively. In the exopolysaccharide production assay, B. altitudinis 1.4 presented a negative result and in the assessment of motility through the swarming assay, 90 mm halos were observed in both agar concentrations (0.3 and 0.7%) for up to 72 h of incubation. Genomic analysis revealed genes potentially encoding traits that could be beneficial to plants, such as phytohormone and siderophores production, polyamine metabolism, biofilm formation, exopolysaccharide, and motility. These characteristics may be important to improve the competition of B. altitudinis 1.4 in the soil. This bacterium was able to solubilize inorganic phosphate, coexist with B. japonicum CT 00345 and form biofilm. Based on the results found and with new tests to be carried out, it is suggested that the isolate B. altitudinis1.4 could be a candidate for plant growth promoter.

Many phytopathogenic fungi cause a variety of plant diseases which can seriously damage a number of significant crops worldwide. In agricultural and food safety, nanomaterials have become significant for the development of novel antifungal agents that exhibit greater efficacy at lower concentrations than chemical fungicides. In this research, boron/selenium nanoparticles (B/Se NPs) were synthesized via radical polymerization using polyvinyl pyrrolidone (PVP) and tested for their inhibitory effect against two phytopathogenic fungi, Alternaria alternata and Fusarium equiseti, isolated from diseased rice plants and identified morphologically and molecularly. The nanostructure of PVP-loaded B/Se core shell was prepared and confirmed using HRTEM. The size distribution for the nanoparticles ranges between 8.74 and 12.23 nm. The morphology was shown via SEM imaging for the PVP-loaded B/Se sample in cross-section mode. Moreover, their elemental composition analysis was achieved via EDS, and functional structure was confirmed by FTIR spectroscopy. The strong antifungal activity of B/Se NPs was against A. alternata (49 ± 0.57 mm) with MIC of 3.125/0.938 mg mL^-1, followed by F. equiseti (30.6 ± 0.33 mm) with MIC of 12.5/3.75 mg mL^-1, causing severe damage and deformities to hyphae and conidia observed using optical microscopy and SEM. B/Se NPs cytotoxic concentration (CC₅₀) against normal cell line was 0.361/0.109 mg mL^-1. In the future, B/Se NPs are thought to be a useful tool for managing A. alternata and F. equiseti after phytotoxic evaluation in field studies. To our knowledge, this is the first report that investigates the synthesis, characterization, and antifungal activity of B/Se NPs against tested pathogens.