Letters in Applied Microbiology最新文献

Brown seaweeds are known for their bioactive compounds, particularly sulfated polysaccharides such as fucoidans, which have demonstrated antiviral properties. However, limited studies have focused on the antiviral potential of fucoidans extracted from Mediterranean brown seaweeds. In this study, two brown seaweeds Padina pavonica and Dictyopteris membranacea (Fuc-Pad and Fuc-Dic, respectively) were collected from monastir coasts, Tunisia, and a specific extraction protocol was employed to obtain fucoidans. The main objective of this study was to evaluate their antiviral activity against Herpes simplex virus type 2 (HSV-2) and coxsackievirus B3 (CVB-3). Fuc-Pad and Fuc-Dic exhibited potent antiviral activity with high selectivity indexes (>158 780 and 3125 for Fuc-Pad and 6101 and 84 for Fuc-Dic against HSV-2 and CVB-3, respectively). On the other hand, the two brown algae demonstrated different mechanisms of antiviral action according to virus type since they inhibited HSV-2 during the adsorption and penetration stages likely through interaction with cellular receptors that block viral binding while directly inhibiting CVB-3 by blocking specific viral ligands, preventing their attachment to host cell receptors. This antiviral activity seems to be associated with the high degree of sulfating of the fucoidans. These results may suggest the possibility of developing new antiviral drugs.

Methicillin-resistant Staphylococcus aureus's (MRSA) resistance poses a global health challenge. This study investigates lysine succinylation in MRSA using proteomics and bioinformatics approaches to uncover metabolic and virulence mechanisms, with the goal of identifying novel therapeutic targets. Mass spectrometry and bioinformatics analyses mapped the MRSA succinylome, identifying 8048 succinylation sites on 1210 proteins. These analyses included Gene Ontology annotation, Kyoto Encyclopedia of Genes and Genomes pathway enrichment, and protein-protein interaction (PPI) network construction (e.g. using the STRING database, a widely used online tool for analyzing protein-protein interactions), providing a comprehensive functional and interactive landscape of succinylated proteins. The succinylated proteins were predominantly involved in cytoplasmic metabolic processes, with enrichment in glycolysis/gluconeogenesis and the tricarboxylic acid cycle. Both of these pathways are critical for MRSA's energy production, growth, and virulence, supplying the necessary metabolic intermediates and energy to support bacterial survival and pathogenicity. Motif analysis revealed 13 conserved motifs, while PPI analysis highlighted fibronectin-binding protein A (FnbA) as a central virulence factor. Succinylation significantly influences MRSA's metabolism and virulence, potentially impacting biofilm by modifying key proteins such as FnbA, bifunctional autolysin, and S-ribosylhomocysteine lyase(LuxS). These findings provide new avenues for developing antibiofilm strategies and therapeutic interventions against MRSA.

This research explored various concentrations of sodium dodecyl sulfate (SDS) and citric acid (CA), both individually and in combination, to assess their effectiveness against Salmonella biofilms in hydroponic agriculture systems. Results demonstrated that a combined sanitizer of 0.1% SDS (1.0 ± 0.1 log reduction when used alone) and 1% CA (1.4 ± 0.3 log reduction when used alone) was highly effective in eliminating Salmonella biofilms from polyvinyl chloride pipes in hydroponic systems, reducing biofilm levels to below detectable limits (>5.6 log reduction when used in combination). Confocal laser scanning microscopy showed significantly greater proportions of damaged/dead cells in the 0.1% SDS- and 1% CA-treated samples (82.6 ± 2.6%) than in the single treatment with 0.1% SDS (26.1 ± 3.0%) and 1% CA (31.6 ± 2.5%) (P < 0.05). Fourier transform infrared spectroscopy together with analysis of proteins and polysaccharides in the extracellular polymeric substances of the biofilm matrices showed that the treatment not only affected bacterial viability but also significantly reduced the biomass of the biofilm. In summary, this research provides a foundation for the development of improved cleaning protocols in hydroponic systems, promoting safer and more sustainable farming practices.

Exploring effective combination antibacterial therapies has become a research focus. This study selected seven common antibiotics to perform a series of tests on different Gram-negative bacteria isolated from clinical samples of chronic obstructive pulmonary disease patients. More than 70% of the strains exhibited multidrug resistance but remained sensitive to polymyxin B. The checkerboard assay revealed a significant synergistic effect between polymyxin B and tetracycline against different resistant strains, with fractional inhibitory concentration index values consistently below 0.5. Further time-kill curve analysis demonstrated that the use of minimal inhibit concentration of polymyxin B or tetracycline alone had limited bactericidal effects, while their combination significantly reduced bacterial counts by 2-3 log colony-forming units within 12 h. Additionally, the survival rate of larvae treated with the polymyxin B and tetracycline combination was significantly higher than that of the mono-therapy and untreated groups. In brief, this study demonstrates that the combination of polymyxin B and tetracycline exhibits potent antibacterial activity against multidrug resistant Gram-negative bacteria both in vitro and in vivo.

Plant richness and microbiota have been associated with plant health; hardly any studies have investigated how plant taxa differs in microbiota in the context of human health. We investigated the microbial differences in buds of 83 woody plant taxa used in urban green spaces in hemiboreal climate, using 16S rRNA and whole metagenome shotgun sequencing. Bud microbial community was the richest in Cotoneaster Nanshan and C. integerrimus, and Malus domestica cultivars "Sandra" and "Lobo" and poorest in Ribes glandulosum. Metagenomic shotgun sequencing of two M. domestica and four Ribes varieties confirmed differences in taxa in bud microbiota and indicated higher siderophore synthesis in Malus. Microbial richness, including bacteria, archaea, and viruses, and functional richness of gene pathways was higher in Malus compared to Ribes. The 10 most abundant amplicon sequence units, often referred as species, belonged to the phylum Proteobacteria. The differences between plant taxa were evident in classes Alpha- and Gammaproteobacteria, known for potential human health benefits. Since environmental microbiota contributes to human microbiota and immunoregulation, horticultural cultivars hosting rich microbiota may have human health benefits. Further studies are needed to confirm the effectiveness of microbially-oriented plant selection in optimizing human microbiota and planetary health.

This study aimed to explore antibiotic resistance characteristics and species of heterotrophic endophytic bacteria (HEB) in four kinds of edible raw vegetables, including radishes, lettuces, onions, and tomatoes. A total of 144 HEB were isolated and tested for resistance to sulfamethoxazole (SMZ), tetracycline (TET), cefotaxime (CTX), and ciprofloxacin (CIP), and their species were identified by 16S rRNA gene sequencing. Antibiotic resistance genes (ARGs) and class I integron in antibiotic-resistant isolates were analyzed by polymerase chain reaction. The results showed radishes had the highest, while tomatoes had the lowest concentration of antibiotic-resistant HEB. SMZ and CTX were predominant antibiotic-resistant phenotypes in HEB. The multi-resistant phenotypes, the combinations SMZ-TET-CTX and SMZ-TET-CIP, accounted for 9.34% of all antibiotic-resistant phenotypes, mainly in radishes and lettuces. Bacillus, Pseudomonas, Staphylococcus, and Stenotrophomonas showed resistance to two antibiotics and existed in more than one kind of vegetable, and were the main carriers of sul1, sul2, blaTEM, and intI1 genes. Therefore, these four genera were considered potential hosts of ARGs in edible raw vegetables. The study provides an early warning regarding health risks associated with ingesting antibiotic-resistant bacteria through raw vegetable consumption.

Vibrio alginolyticus, the causative agent of aquatic vertebrates and invertebrates, can cause severe infections (e.g. septicemia, gill necrosis, and surface ulcers) and high mortality in aquatic organisms, leading to serious economic losses in global aquaculture. Small non-coding RNAs (sRNAs), emerging modulators of gene expression, played vital regulatory roles in virulence, pathogenicity, and physiological metabolism of bacteria. In this work, the modulation of physiological functions and metabolome of V. alginolyticus by the quorum-regulatory sRNA, Qrr1, was figured out. We found that the deletion of qrr1 induced significant cell shape elongation. Meanwhile, Qrr1 could inhibit the production of alkaline serine protease by weakening the expression of main regulator LuxR in the quorum sensing (QS) system. Moreover, the untargeted metabolomics and lipidomics approaches showed that most of nucleotides, organic acids, carbohydrates, and lipidome (both lipid content and category) were significantly altered in response to the qrr1 deletion. Spearman correlation analysis demonstrated that most of the intermediates involved in glutamate metabolism, sphingolipid metabolism, and glycerolipid metabolism displayed high correlations with cell virulence factors. These findings illuminate the mechanism of bacterial virulence regulation and further exploit potential therapeutic targets for virulence prevention in V. alginolyticus.

A consortium of five distinct bacterial strains was evaluated for their ability to biodegrade multiple polyaromatic hydrocarbons (PAHs) in sewage sludge under microcosm studies. The presence of PAHs was determined from the sludge samples collected during pre- and post-monsoon seasons from three different wastewater treatment plants (WWTPs). Among the 16 PAHs found, the lowest concentration detected was 1.75 ng g-1 of benz(k)fluoranthene, and the highest concentration of 5.41 mg g-1 indeno(1,2,3-cd) pyrene was found in both dry and wet samples, perhaps owing to its multiple origin of contamination. A bacterial consortium comprising of well characterized bacteria Stenotrophomonas maltophilia IITR87, Ochrobactrum anthropi IITR07, Microbacterium esteraromaticum IITR47, Pseudomonas aeruginosa IITR48, and Pseudomonas mendocina IITR46 employed for PAHs bioremediation in a microcosm study. In 20 days, 65%-70% of PAHs were remediated, and low molecular weight PAHs such as naphthalene, phenanthrene, and pyrene showed enhanced degradation. Bioremediated samples showed a significant reduction in phytotoxicity using plant germination of wheat (Triticum aestivum), black chickpea (Cicer arietinum), and mustard (Brassica juncea), whereas the contaminated soil showed severe inhibition of plant growth. The results comprehensively suggest a possible remediation option for PAHs occurring in complex sewage sludge, preventing further contamination into other environmental compartments.