MicrobiologyOpen最新文献

Hernández-Valle, J., B. Vega-Baray, S. Poggio, and L. Camarena. 2024. “CerM and Its Antagonist CerN Are New Components of the Quorum Sensing System in Cereibacter sphaeroides, Signaling to the CckA/ChpT/CtrA System.” MicrobiologyOpen 13, no. 6: e012. https://doi.org/10.1002/mbo3.70012.

In Results:

Section 3.1, pages 9 and 10: The mention of Figures 2B, 2C, and 2D was meant to indicate Figures 1B, 1C, and 1D, respectively.

Section 3.2, page 12: The sentence “explaining the polar effect of the allele ΔcerR::aadA (JV16 strain in Figures 3 and 4)” should have actually referred to Figures 2 and 3.

We apologize for these errors.

Cereibacter sphaeroides has a quorum sensing (QS) system that has been partially characterized. Using a bioinformatic approach, six LuxR homologs and one homolog of the acylhomoserine lactone synthase were identified in this bacterium, including the previously characterized CerR and CerI proteins. This study focused on determining the roles of two LuxR homologs, CerM and CerN. CerN lacks the HTH domain and, together with CerM, controls the expression of ctrA, which is part of the TCS CckA/ChpT/CtrA. CtrA is widely conserved in alpha-proteobacteria and regulates flagellar motility and other cellular processes. Genetic and biochemical data suggest that CerM indirectly represses ctrA expression, which is counteracted by its interaction with CerN-AHL. A transcriptomic study identified 181 genes regulated by CerM/CerN, with a conserved sequence in their regulatory regions likely indicating the CerM binding site. This hypothesis was supported by in vitro and in vivo DNA–protein interaction assays. Our results identified a transcription factor that could connect the QS system with the regulation of the two-component system CckA/ChpT/CtrA.

Diclofenac (DCF), a commonly used anti-inflammatory medication, presents environmental concerns due to its presence in water bodies, resistance to conventional wastewater treatment methods, and detection at increasing concentrations (ng/L to µg/L) that highlight DCF as a global emerging pollutant. While microalgae have been effective in degrading DCF in wastewater, immobilization into a matrix offers a promising approach to enhance treatment retention and efficiency. This study aimed to evaluate the efficacy of DCF removal using immobilized freshwater microalgae. Two algal species, Chlamydomonas reinhardtii (Chlamydomonas) and Scenedesmus obliquus (Scenedesmus), were tested for 6 days in both free and immobilized forms to determine if immobilized algae could degrade DCF comparably to free cells. The findings indicate that by Day 3, immobilized Chlamydomonas and Scenedesmus removed 78.0% and 80.1% of DCF, outperforming free-cell cultures. Mixed cultures demonstrated synergistic effects, with removal amounts of 91.4% for free and 92.3% for immobilized systems. By Day 6, all conditions achieved complete DCF removal (100%). Mechanistic analysis showed 80.0% biodegradation and 20.0% bioaccumulation in free Chlamydomonas and 56.8% biodegradation with 43.2% bioaccumulation in Scenedesmus. Immobilization shifted pathways slightly: in Chlamydomonas, 61.6% of DCF removal occurred via biodegradation, 18.3% via bioaccumulation, and 20.1% via abiotic degradation. For Scenedesmus, immobilization achieved 45.6% biodegradation, 36.6% bioaccumulation, and 17.8% abiotic degradation, enhancing abiotic degradation while maintaining biodegradation efficiency. This research serves as a proof of concept for utilizing immobilized algae in DCF removal and suggests an avenue for improved wastewater treatment of emerging contaminants.

Salmonellosis outbreaks are global issues primarily associated with the consumption of poultry products, which may be infected with Salmonella. The use of lytic bacteriophages could be a safe and effective approach to reduce Salmonella prevalence in poultry and subsequently the incidence in humans. This study examined the value of prophylactic phage treatment on Salmonella levels in chickens and the effect of such treatment on their overall gut microbiome. We also investigated phage persistence in vivo and resistance emergence against the six-phage cocktail used. The preventive potential of phages was evaluated on 200 chicks by administering phages via drinking water for 6 days after hatching, followed by the Salmonella Enteritidis challenge on Day 7. The results showed that up to 4 days postinfection, phages had a preventive effect by significantly reducing Salmonella colonization in ceca by three logs. Furthermore, the phage cocktail did not induce dysbiosis, although variations in microbiota in terms of microbial composition were observed between conditions, with the Enterobacteriaceae family being impacted. However, the phage cocktail did not induce a long-term effect, with Salmonella levels rebounding 8 days after phage treatment was stopped. Overall, our data show that phage prophylaxis can reduce Salmonella colonization and explore ways of improving the effectiveness of phages in limiting infections throughout poultry production.

Antimicrobial resistance remains a global issue, hindering the control of bacterial infections. This study examined the antimicrobial properties of 2,3-N,N-diphenyl quinoxaline derivatives against Gram-positive, Gram-negative, and Mycobacterium species. Two quinoxaline derivatives (compounds 25 and 31) exhibited significant activity against most strains of Staphylococcus aureus, Enterococcus faecium, and Enterococcus faecalis tested, with MIC values ranging from 0.25 to 1 mg/L. These compounds also showed effective antibacterial activity against methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecium/E. faecalis (VRE) strains. They demonstrated comparable or superior activity to four current antibiotics (vancomycin, teicoplanin, daptomycin, and linezolid) against a wide range of clinically relevant isolates. Additionally, they were more effective in preventing S. aureus and E. faecalis biofilm formation compared to several other antibiotics. In summary, these two quinoxaline derivatives have potential as new antibacterial agents.

Changes in land use, climate, and host community are leading to increased complexity in eco-epidemiological relationships and the emergence of zoonoses. This study investigates the changes in the prevalence of several Ixodes ricinus-transmitted pathogens in questing ticks over a 10-year interval (2011–2013, 2020) in natural and agricultural habitats of the Autonomous Province of Trento (North-eastern Alps), finding an average prevalence of infection of 27.1%. Analysis of 2652 ticks, investigating four infectious agents (Borrelia burgdorferi sensu lato, Anaplasma spp., Rickettsia spp., and Babesia spp.), revealed the circulation of 11 different zoonotic pathogens, with varying infection rates across different years and habitats. In 2020, we found a decrease in Anaplasma phagocytophilum, associated with agricultural habitats, and Rickettsia spp., found in all habitats. In the same year, Babesia spp. increased in both habitats, similar to Borrelia burgdorferi sensu stricto, which was related to natural habitats. Co-infections were identified in 8% of positive-tested ticks with different spatiotemporal associations, primarily in natural settings. Our results provide new evidence that the risk of infection with tick-borne pathogens in the Alpine region varies over time and in different environments, broadening the current information on co-infection rates and the circulation of zoonotic pathogens, previously not reported in this area.

The persistence and efficacy of biocontrol agents in agricultural fields are crucial for sustainable crop production. In this study, we investigated the persistence of the introduced bacterial strain Pseudomonas sivasensis CF10PS3 in the wheat phyllosphere using a novel qPCR probe protocol. The CF10PS3 strain, known for its in vitro biocontrol properties against wheat pathogens, was applied through foliar spray, and its persistence was monitored over 7 weeks. Our qPCR assays, designed to specifically detect CF10PS3, distinguished it from naturally occurring P. sivasensis strains, providing precise insights into its dynamics in the field. The experimental results indicated that CF10PS3 was already present on the wheat leaves before its application, suggesting its natural adaptation to the foliar environment. Following initial application, a significant increase in CF10PS3 was observed, though subsequent environmental factors such as rain and wind might have caused notable fluctuations in its population. Despite these variations, the introduced strain showed considerable persistence, with population levels significantly higher than those in untreated plots by the end of the study period. This research underscores the importance of understanding bacteria dynamics in the field, highlighting the influence of environmental conditions on their efficacy. The use of specific qPCR probes proved effective in monitoring introduced strains, offering valuable insights for optimizing biocontrol agent application strategies. Our findings contribute to the development of robust biocontrol methods, promoting sustainable agricultural practices and enhancing crop protection.

Moraxella osloensis, a gram-negative rod-shaped bacterium found on human skin, produces 4-methyl-3-hexenoic acid, contributing to clothing and body malodor. M. osloensis is resistant to UV light, drying, and antimicrobials, making its eradication challenging. As the skin is low in nutrients, commensal bacteria compete for resources and use diverse strategies to inhibit their competitors. Therefore, skin-derived bacteria that exhibited growth-inhibitory activity against M. osloensis were searched. Screening skin-derived bacteria using a coculture halo assay revealed that Bacillus xiamenensis formed an inhibition zone with M. osloensis. Coculture plates were extracted with ethyl acetate and fractionated using a silica gel column and preparative thin-layer chromatography to isolate the active compound from the B. xiamenensis metabolites. Nuclear magnetic resonance spectroscopy identified the active compound as indole-3-carboxaldehyde, which has low toxicity in humans. At soluble concentrations, indole-3-carboxaldehyde does not inhibit the growth of other bacteria, such as Staphylococcus aureus, Escherichia coli, and Bacillus subtilis, suggesting M. osloensis is highly sensitive to indole-3-carboxaldehyde. These findings highlight B. xiamenensis as a promising candidate for the development of a skin probiotic to promote skin health and combat malodor-causing bacteria.

Candida albicans, a member of the normal microbial population of healthy humans, is an opportunistic pathogen that can cause serious disease in immunocompromised patients. An important virulence factor of C. albicans is the formation of biofilms. These organized communities of cells are efficient at attaching to host cells and implanted medical devices. Carbonate has been studied as an agricultural antifungal agent, and here we demonstrate that carbonate can affect filamentation, biofilm formation, and antifungal drug resistance in C. albicans.

As technologies advance alongside metabarcoding and metagenomic resources, particularly for larger fungal genomes, DNA extraction methods must be optimized to meet higher thresholds, especially from complex environmental substrates. This study focused on extracting fungal genomic compounds from woody substrates, a challenge due to the embedment of endophytic and saprotrophic fungi within wood cells, the physical recalcitrance of wood, the adsorption of nucleic acids to wood polymers, and the release of downstream inhibitors. Hypothesizing that cetyltrimethylammonium bromide would be the best option, we compared prominent methods by extracting and sequencing microbial DNA from sound and decayed birch (Betula papyrifera) and pine (Pinus resinosa). DNA quantities varied significantly depending on extraction methods and decay stage. The quality of DNA, in terms of purity and integrity, significantly impacted whether the samples could be amplified and sequenced. However, amplicon sequencing of bacterial and fungal communities revealed no significant extraction bias. This, along with the sequencing effectiveness and cost/time efficiency, indicates that Qiagen is the gold standard for woody substrates. This study increases confidence in published amplicon data sets regardless of the extraction methods, provides a cost-benefit table for making protocol decisions, and offers guidance on fungal DNA extractions from complex organic substrates (sound and decayed wood) that would best suit future metagenomic efforts.