Journal of Applied Microbiology最新文献

Aims: This study aimed to ascertain the active substances in the hydroponic solution of Ulva (U.) fasciata (HSUF) and their effects on antibiotics resistance of pathogenic bacteria Vibrio alginolyticus (Va.) at environmental levels.

Methods and results: Analytical results of HSUF by solid-phase extraction and gas chromatography-mass spectrometry showed that HSUF contained rich active substances and dominated by 2,4,6-tribromophenol, acetal, mono (2-ethylhexyl) phthalate, and 2-(4-hydroxybenzene) ethanol, etc. Thereinto, 2,4,6-tribromophenol had the lowest minimal inhibitory concentrations of 64-128 μg ml-1 for Va. strains. The rich antibacterial substances of HSUF inhibited 47%-63% of isolated Va. strains. After 20 generations of subculture for Va. strains in three dilutes [1/2 (HT), 1/20 (MT), and 1/50 (LT)] of HSUF (20 g l-1), the resistance to streptomycin of Va. S1 and Va. M3 changed from intermediate resistance ability to susceptible level. The large promotion of reactive oxygen species was observed in different HSUF levels, but the biofilm formation of Va. S1 did not change significantly. Transcriptome sequencing of Va. S1 demonstrated that antibiotic resistance gene lpxA was downregulated at different HSUF levels.

Conclusions: Live U. fasciata excreted a variety of active secondary metabolites in HSUF, which exhibited strong inhibitory effects on three isolated Va. strains. HSUF changed the antibiotic resistance of Va. Strain, especially at higher HSUF concentrations.

Aim: This study investigates how replacing fishmeal and fish oil with insect meals in feed impacts the gut microbiota in rainbow trout (Oncorhynchus mykiss), a crucial species in aquaculture.

Methods and results: Dietary inclusion of black soldier fly (Hermetia illucens), cricket (Gryllodes sigillatus), and superworm (Zophobas morio) were evaluated for their impact on intestinal microbial diversity and community composition following a 12-week feeding trial. Fish were fed one of four isonitrogenous and isoenergetic diets: a control diet without insect meal, and diets with 15% defatted black soldier fly meal, full-fat adult cricket meal, or full-fat superworm meal. The microbiota of intestinal digesta and fish feed was characterized using 16S rRNA gene sequencing on the Illumina MiSeq platform. Results revealed significantly lower alpha diversity indices in the cricket treatment compared to the control. Beta diversity analysis showed Bacillota as the dominant phylum across all treatments, with the initial stock population richer in Mycoplasmatota. A novel genus within Mycoplasmataceae was prevalent at Day 0 and in all treatments. Black soldier fly meal increased an unidentified Peptostreptococcaceae genus (bsv123) compared to control and superworm diets, while cricket meal elevated Streptococcus levels.

Conclusions: Insect-based diets, particularly with black soldier fly meal, significantly alter beta diversity within the gut microbiota of rainbow trout, with cricket meal reducing alpha diversity and superworm having minimal impact.

Antimicrobial resistance (AMR) is a significant global health concern, due to the persistence of pathogens and the emergence of resistance in bacterial infections. Bacterial-derived antimicrobial peptides (BAMPs) have emerged as a promising strategy to combat these challenges. Known for their diversity and multifaceted nature, BAMPs are notable bioactive agents which exhibit potent antimicrobial activities against various pathogens. This review explores the intricate properties and underlying mechanisms of BAMPs, emphasizing their diverse applications in addressing AMR. Additionally, the review investigates the mechanisms, analyses the challenges in utilizing BAMPs effectively, and examines their potential applications and associated deployment challenges providing comprehensive insights into how BAMPs can be harnessed to combat AMR across different domains.

Aims: The purpose of this study was to explore impacts of different combinations of co-fermentation plant growth-promoting rhizobacteria (PGPR) broth on the growth and yield of pepper.

Methods and results: The effects of co-fermentation broth containing a random combination of two PGPR strains on the growth of pepper were analyzed. All inoculation treatments promoted growth, yield, and quality of peppers. The relative abundance of the dominant Proteobacteria and Sphingomonas was significantly higher in the planted soil at the seedling and fruiting stages, and the soil available nitrogen, phosphorus, and potassium contents were correspondingly higher. In addition, the co-fermented broth of Bacillus velezensis HP9 and Burkholderia pyrrocinia P10 treatment had the most pronounced effect on plant growth, while the combination of Bacillus flexus HGD12 and P10 had the greatest impact on fruit nutritional indices. This is consistent with the highest enrichment of beneficial bacterial genera at the seedling stage in the HP9 and P10 treatment and at the fruiting stage in the P10 and HGD12 treatment groups, respectively.

Conclusions: Different combinations of co-fermented bacterial broths increased soil nutrient contents and changed the bacterial community, which in turn promoted the growth, yield, and quality of pepper.

Aims: The aryl hydrocarbon receptor (AhR) is a ligand-activated receptor implicated in many inflammatory disorders. The skin microbiota plays a crucial role in maintaining epidermal barrier integrity and is thought to modulate skin homeostasis partly through the production of AhR ligands, including metabolites of microbial tryptophan metabolism such as indole derivatives. Here, we report the skin microbiota that activate AhR and their unique tryptophan metabolite profiles.

Methods and results: Of the bacteria isolated from healthy human skin and screened for the ability to metabolize tryptophan (18 species, five genera), 14 were positive. The tryptophan metabolites of 10 positive and two negative bacteria were then characterized using liquid chromatography-mass spectrometry. Whole genome sequencing confirmed the presence of key genes involved in the indole-3-pyruvic acid pathway within the genomes of indole-3-acetaldehyde, indole-3-acetic acid, and indole-3-aldehyde-producing organisms. A cell-based luciferase reporter gene assay identified functional agonist activity against human AhR in the culture supernatants of 12 of the 18 species tested. High indole derivative-producing organisms induced potent AhR activation.

Conclusions: These data demonstrate the relationship between skin microbiota, tryptophan metabolites, and AhR activation.

Aim: Bacterial consortia exhibiting plant growth promoting properties have emerged as a sustainable approach for crop improvement. As the main challenge associated with them is loss of viability and performance under natural conditions, a robust approach for designing bioformulation is needed. In this study, an efficient bioformulation was developed using spontaneous mutants of three bacterial strains for growth promotion of Cajanus cajan.

Methods and results: Optimization of additives for solid [carboxymethylcellulose (CMC), and glycerol] and liquid [polysorbate, CMC, and polyvinyl pyrrolidone (PVP)] bioformulations was done by response surface methodology using central composite design. The stability of each bioinoculant in the formulation was assessed at 30°C and 4°C. The efficiency of the liquid bioformulation was checked in planta in sterile, and subsequently in non-sterile, soil. The maximum cell count was observed in solid bioformulation with 0.1 g l-1 CMC and 50% glycerol (8.10 × 108, 3.69 × 108, and 7.39 × 108 CFU g-1 for Priestia megaterium, Azotobacter chroococcum, and Pseudomonas sp. SK3, respectively) and in liquid bioformulation comprising 1% PVP, 0.1 g l-1 CMC, and 0.025% polysorbate (8 × 109, 3.8 × 109, and 6.82 × 109 CFU ml-1 for P. megaterium, A. chroococcum, and Pseudomonas sp. SK3, respectively). The bioinoculants showed a higher viability (6 months) at 4°C compared to 30°C. Triple culture consortium enhanced plant growth in comparison to the control. The strains could be detected in soil till 45 days after sowing.

Conclusions: The study established a systematic process for developing a potent bioformulation to promote agricultural sustainability. Using mutant strains, the bioinoculants could be tracked. In planta assays revealed that the triple culture consortium out-performed mono and dual cultures in terms of impact on plant growth.

Aims: The aim of the present study was to evaluate a novel probiotic Pediococcus pentosaceus RC007 used alone and convined with Saccharomyces cerevisiae var. boulardii RC009, as in-feed additives to substitute the nontherapeutic use of antibiotics, and evaluate the different structural characteristics of intestinal bacterial populations between groups, correlated with pig production performance.

Methods and results: The in vivo study was conducted on post-weaning pigs, from 21 to 56 days old. Three dietary treatments were included: T1-basal diet (BD-control group); T2-BD with P. pentosaceus RC007; and T3-BD with a mix of P. pentosaceus RC007 and S. boulardii RC009. The weight gain increase of pigs consuming non-therapeutic antibiotics was similar to those that did not consume antibiotics during the study (P = 0.0234), but had better health indicators. The use of a probiotic combination increased carcass weight and significantly reduced the lumbar fat thickness. In terms of taxonomic composition, there was a tendency to modify the abundance of Proteobacteria, Cyanobacteria, Enterobacteriaceae, and Lactobacillaceae in pigs that consumed the additives. The genus Butyricicoccus, Collinsella, and Ruminococcus tended to be more abundant in the microbiota of pigs at T3.

Conclusions: For the first time, the results of the present study indicate that P. pentosaceus RC007 and S. boulardii RC009, a probiotic combination, could be a good substitute for antibiotics in improving pig production performance, while also contributing to a healthier gut microbiota, especially with the reduced abundance of Proteobacteria and Cyanobacteria.

Aims: To develop and evaluate nisin-loaded chitosan/sodium alginate (CS/SA) microspheres as an improved antimicrobial delivery system targeting Staphylococcus aureus strains.

Methods and results: The microspheres were prepared using a modified water-in-oil emulsion cross-linking method, resulting in spherical particles sized 1-8 µm with a surface charge of -7.92 ± 5.09 mV, confirmed by scanning electron microscopy (SEM) and Zetasizer analysis. Encapsulation efficiency (EE) and loading capacity (LC) of nisin were 87.60% ± 0.43% and 1.99% ± 0.01%, respectively. In vitro release studies over 48 h indicated a controlled release pattern of nisin, described by the Korsmeyer-Peppas model, with higher release rates at 37°C and alkaline pH. Antimicrobial assays showed an enhanced efficacy of nisin-loaded CS/SA microspheres compared to free nisin, with minimum inhibitory concentration values reduced by 50%. Confocal laser scanning microscopy (CLSM), SEM, and transmission electron microscopy showed significant bacterial membrane damage and cellular disruption induced by the microspheres.

Conclusions: This study highlights the potential of nisin-loaded CS/SA microspheres as an innovative antimicrobial delivery system with improved stability and antimicrobial efficacy against S. aureus, addressing limitations associated with nisin applied alone.

Aim: The aim of this study is to engineer Pantoea dispersa MSC14 into a strain capable of producing lycopene and to enhance its lycopene content.

Methods and results: Our laboratory isolated the strain P. dispersa MSC14 from petroleum-contaminated soil in a mining area. Whole-genome sequencing confirmed the existence of a carotenoid synthesis pathway in this strain. This study employed an optimized CRISPR/Cas9 system to perform a traceless gene knockout of the lycopene cyclase gene crtY and to overexpress the octahydrolycopene dehydrogenase gene crtI in the P. dispersa MSC14. This strategic genetic modification successfully constructed the lycopene-producing strain MSC14-LY, which exhibited a notable lycopene content with a biomass productivity of 553 μg of lycopene per gram dry cell weight (DCW). Additionally, the components of the lycopene fermentation medium were optimized using Plackett-Burman design and response surface methodology. The average lycopene content was increased to 5.13 mg g -1 DCW in the optimized LY fermentation medium. Through genetic engineering, P. dispersa MSC14 was transformed into a strain capable of producing lycopene, achieving a yield of 5.13 mg g-1 DCW after medium optimization.

Conclusions: Genetic engineering successfully transformed P. dispersa MSC14 into a strain capable of producing lycopene, achieving a yield of 5.13 mg g-1 DCW after medium optimization.

Aims: Artificial reefs play a vital role in restoring and creating new habitats for marine species by providing suitable substrates, especially in areas where natural substrates have been degraded or lost due to declining water quality, destructive fishing practices, and coral diseases. Artificial reef restoration aimed at coral larval settlement is gaining prominence and initially depends on the development of biofilms on reef surfaces. In this study, we hypothesized that different artificial reef materials selectively influence the composition of biofilm bacterial communities, which in turn affected coral larval settlement and the overall success of coral rehabilitation efforts. To test this hypothesis, we evaluated the impact of six different reef-made materials (porcelain, granite, coral skeleton, calcium carbonate, shell cement, and cement) on the development of biofilm bacterial communities and their potential to support coral larval settlement.

Methods and results: The biofilm bacterial communities were developed on different artificial reef materials and studied using 16S rRNA gene amplicon sequencing and analysis. The bacterial species richness and evenness were significantly (P < 0.05) low in the seawater, while these values were high in the reef materials. At the phylum level, the biofilm bacterial composition of all materials and seawater was majorly composed of Pseudomonadota, Cyanobacteria, and Bacteroidetes; however, significantly (P < 0.05) low Bacteroidetes were found in the seawater. At the genus level, Thalassomonas, Glaciecola, Halomicronema, Lewinella, Hyphomonas, Thalassospira, Polaribacter, and Tenacibaculum were significantly (P < 0.05) low in the coral skeleton and seawater, compared to the other reef materials. The genera Pseudoaltermonas and Thalassomonas (considered potential inducers of coral larval settlement) were highly abundant in the shell-cement biofilm, while low values were found in the biofilm of the other materials.

Conclusion: The biofilm bacterial community composition can be selective for different substrate materials, such as shell cement exhibited higher abundances of bacteria known to facilitate coral larval settlement, highlighting their potential in enhancing restoration outcomes.