World journal of microbiology & biotechnology最新文献

Rahnella aquatilis causes seafoods to spoil by metabolizing sulfur-containing amino acids and/or proteins, producing H₂S in products. The type II secretion system (T2SS) regulates the transport of proteases from the cytoplasm to the surrounding environment and promotes bacterial growth at low temperatures. To prevent premature fish spoilage, new solutions for inhibiting the T2SS of bacteria should be researched. In this study, global transcriptome sequencing was used to analyze the spoilage properties of R. aquatilis KM05. Two of the mapped genes/coding sequences (CDSs) were matched to the T2SS, namely, qspF and gspE, and four of the genes/CDSs, namely, ftsH, rseP, ptrA and pepN, were matched to metalloproteases or peptidases in R. aquatilis KM05. Subinhibitory concentrations of citric (18 µM) and acetic (41 µM) acids caused downregulation of T2SS-related genes (range from - 1.0 to -4.5) and genes involved in the proteolytic activities of bacteria (range from - 0.5 to -4.0). The proteolytic activities of R. aquatilis KM05 in vitro were reduced by an average of 40%. The in situ experiments showed the antimicrobial properties of citric and acetic acids against R. aquatilis KM05; the addition of an acidulant to salmon fillets limited microbial growth. Citric and acetic acids extend the shelf life of fish-based products and prevent food waste.

D-glucaric acid is an important organic acid with numerous applications in therapy, food, and materials, contributing significantly to its substantial market value. The biosynthesis of D-glucaric acid (GA) from renewable sources such as glucose has garnered significant attention due to its potential for sustainable and cost-effective production. This review summarizes the current understanding of the cell factories for GA production in different chassis strains, from static to dynamic control strategies for regulating their metabolic networks. We highlight recent advances in the optimization of D-glucaric acid biosynthesis, including metabolic dynamic control, alternative feedstocks, metabolic compartments, and so on. Additionally, we compare the differences between different chassis strains and discuss the challenges that each chassis strain must overcome to achieve highly efficient GA productions. In this review, the processes of engineering a desirable cell factory for highly efficient GA production are just like an epitome of metabolic engineering of strains for chemical biosynthesis, inferring general trends for industrial chassis strain developments.

Probiotics are live microorganisms that, when administered in adequate quantities, provide health benefits to the host. In this study, phenotypic and genotypic methods were used to evaluate the probiotic properties of Bacillus altitudinis 1.4. The isolate was sensitive to all antimicrobials tested and presented a positive result in the hemolysis test. B. altitudinis 1.4 spores were more resistant than vegetative cells, when evaluated in simulation of cell viability in the gastrointestinal tract, as well as adhesion to the intestinal mucosa. The isolate was capable of self-aggregation and coaggregation with pathogens such as Escherichia coli ATCC 25922 and Salmonella Enteritidis ATCC 13076. Genomic analysis revealed the presence of genes with probiotic characteristics. From this study it was possible to evaluate the gene expression of pro-inflammatory and anti-inflammatory cytokines for different treatments. Viable vegetative cells of B. altitudinis 1.4 increased the transcription of pro-inflammatory factors, in addition to also increasing the transcription of IL-10, indicating a tendency to stimulate a pro-inflammatory profile. Given the results presented, B. altitudinis 1.4 showed potential to be applied in the incorporation of this microorganism into animal feed, since the spores could tolerate the feed handling and pelletization processes.

Phosphorus (P), an essential macronutrient for various plant processes, is generally a limiting soil component for crop growth and yields. Organic and inorganic types of P are copious in soils, but their phyto-availability is limited as it is present largely in insoluble forms. Although phosphate fertilizers are applied in P-deficit soils, their undue use negatively impacts soil quality and the environment. Moreover, many P fertilizers are lost because of adsorption and fixation mechanisms, further reducing fertilizer efficiencies. The application of phosphate-solubilizing microorganisms (PSMs) is an environmentally friendly, low-budget, and biologically efficient method for sustainable agriculture without causing environmental hazards. These beneficial microorganisms are widely distributed in the rhizosphere and can hydrolyze inorganic and organic insoluble P substances to soluble P forms which are directly assimilated by plants. The present review summarizes and discusses our existing understanding related to various forms and sources of P in soils, the importance and P utilization by plants and microbes,, the diversification of PSMs along with mixed consortia of diverse PSMs including endophytic PSMs, the mechanism of P solubilization, and lastly constraints being faced in terms of production and adoption of PSMs on large scale have also been discussed.

A novel Pseudochrobactrum saccharolyticum strain NBRI-CRB 13, isolated from tannery sludge, was studied to grow up to 500 mgL^-1 of Cr(VI) and showed Cr(VI) detoxification by reducing > 90% of Cr(VI) at different concentrations 25, 50 and 100 mgL^-1. Kinetic studies showed that first-order models were fitted (R² = 0.998) to the time-dependent Cr(VI) reduction with degradation rate constant (k) (1.03-0.429 h^-1). Cr(VI) detoxification was primarily related to the extracellular fraction of microbial cells, which showed a maximum extracellular reductase enzyme activity led to 94.6% reduction of Cr(VI). Moreover, the strain showed maximum extracellular polymeric substances (EPS) production at 100 mgL^-1 Cr(VI), which is presumably the reason for Cr(VI) removal as EPS serves as the metal binding site for Cr(VI) ions. Further, an optimization study using Box-Behnken design was conducted considering parameters viz., pH, temperature, and initial concentration of Cr(VI). The maximum percent reduction of Cr(VI) was obtained at pH 6.5, temperature 30 °C with 62.5 mgL^-1Cr(VI) concentration. Further, the Cr(VI) reduction and adsorption ability of strain P. saccharolyticum NBRI-CRB13 were confirmed by SEM-EDS, FTIR, and XRD analyses. FTIR analysis confirmed the presence of functional groups (-OH, -COOH, -PO₄) on bacterial cell walls, which were more likely to interact with positively charged chromium ions. The study elucidated the reduction of Cr(VI) by the novel bacterium within 24 h using the response surface methodology approach and advocated its application in real-time situations.

Strain Lactiplantibacillus plantarum D1 with bacteriocin producing ability was found in the intestine of Gambusia affinis. The bacteriocin was found to have high inhibitory activity against multiple Streptococcus species and several other Gram-positive and Gram-negative bacteria. Bacteriocin was purified from culture supernatant by ion-exchange chromatography, Sep-Pak C₁₈ cartridge, and reverse-phase high-performance liquid chromatography (RP-HPLC). Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectral analysis determined that purified bacteriocin has a molecular mass of 2,731 Da. A partial N-terminal sequence KRKKHKXQIYNNGM was obtained from the Edman analysis. The N-terminal sequence was employed to search against a translation of the draft genome of strain D1. The translated full amino acid sequence of the mature peptide is as follows: NH₂- KRKKHKCQIYNNGMPTGQYRWC, which has a molecular weight of 2738 Da. A BLAST search revealed that this bacteriocin was most similar to bactofencin A but differed from it with three amino acid residues. No identical peptide or protein has been previously reported, and this peptide, termed bactofencin YH, was therefore considered to be a new bacteriocin produced by Lactiplantibacillus plantarum D1.

This study presents the empirical findings of an in-depth genomic analysis of Enterococcus faecalis and Enterococcus lactis isolates from South Africa. It offers valuable insights into their genetic characteristics and their significant implications for public health. The study uncovers nuanced variations in the gene content of these isolates, despite their similar GC contents, providing a comprehensive view of the evolutionary diversity within the species. Genomic islands are identified, particularly in E. faecalis, emphasizing its propensity for horizontal gene transfer and genetic diversity, especially in terms of antibiotic resistance genes. Pangenome analysis reveals the existence of a core genome, accounting for a modest proportion of the total genes, with 2157 core genes, 1164 shell genes, and 4638 cloud genes out of 7959 genes in 52 South African E. faecalis genomes (2 from this study, 49 south Africa genomes downloaded from NCBI, and E. faecalis reference genome). Detecting large-scale genomic rearrangements, including chromosomal inversions, underscores the dynamic nature of bacterial genomes and their role in generating genetic diversity. The study uncovers an array of antibiotic resistance genes, with trimethoprim, tetracycline, glycopeptide, and multidrug resistance genes prevalent, raising concerns about the effectiveness of antibiotic treatment. Virulence gene profiling unveils a diverse repertoire of factors contributing to pathogenicity, encompassing adhesion, biofilm formation, stress resistance, and tissue damage. These empirical findings provide indispensable insights into these bacteria's genomic dynamics, antibiotic resistance mechanisms, and virulence potential, underlining the pressing need to address antibiotic resistance and implement robust control measures.

Bacteriocins are antimicrobial peptides produced by bacteria to prevent the growth of pathogens. Combining bacteriocins with metal nanoparticles, like silver nanoparticles (AgNPs), has developed into a viable strategy to get over bacteriocin limitations. In this study, bacteriocin BacZY05 was extracted from Bacillus subtilis ZY05 and purified using various techniques. The resulting purified bacteriocin was then combined with silver nanoparticles to form bacteriocin silver nanoconjugates (BacZY05-AgNPs). The physicochemical properties of the BacZY05-AgNPs were characterized using various analytical techniques. The mean diameter of the synthesized AgNPs was approximately 20-60 nm with an oval or spherical shape. The antimicrobial activity of the BacZY05-AgNPs was evaluated against several indicator strains by their zone of inhibition (ZOI), using the agar well diffusion method. Compared to bacteriocin (ZOI- 13 to 20 mm) and AgNPs (ZOI- 10-22 mm) alone, the antibacterial activity data demonstrated a 1.3-1.5-fold increase in the activity of bacteriocin-nanoconjugates (ZOI- 22 to 26 mm). For Staphylococcus aureus MTCC3103 and Klebsiella pneumoniae MTCC109, BacZY05-capped AgNPs exhibited the lowest minimum inhibitory concentration (MIC), measuring 10.93 µg/mL. For Salmonella typhi NCIM2501, the MIC was 28.75 µg/mL. The highest MIC value was 57.5 µg/mL for Escherichia coli DH5α and Vibrio cholerae MTCC3909. With BacZY05-capped AgNPs, the lowest minimum bactericidal concentration (MBC) of 28.75 µg/mL was observed for Staphylococcus aureus MTCC31003. In the cases of Salmonella typhi NCIM2501 and Klebsiella pneumoniae MTCC109 concentration was 57.5 µg/mL. Vibrio cholerae MTCC3909 and Escherichia coli DH5α had the highest MBC values at 115 µg/mL.

Staphylococcus aureus is a gram-positive bacteria, and its virulence factors can cause many kinds of infections, such as pneumonia, sepsis, enteritis and osteomyelitis. Traditional antibiotics can not only kill bacteria, but also easily lead to bacterial resistance. Jingfang Mixture (JFM) has the effects of inducing sweating and relieving the exterior, dispelling wind and eliminating dampness, and is commonly used in clinic to prevent and treat epidemic diseases and infectious diseases. The main purpose of this study is to explore the inhibitory effect of JFM on alpha-hemolysin (Hla) of S. aureus and to alleviate the damage caused by Hla. We found that JFM could inhibit the hemolytic activity, transcription level and neutralizing activity of Hla in a dose-dependent manner at the concentrations of 125, 250 and 500 µg/mL, without affecting the growth of bacteria. In addition, JFM reduced the damage of Hla to A549 cells and the release of lactate dehydrogenase (LDH). We also observed that in the S. aureus - induced pneumonia mouse model, JFM could significantly prolong the life of mice, reduce the bacterial load in the lungs, significantly improve the pathological state of the lungs and alleviate the damage caused by inflammatory factors, and the pathogenicity of gene deletion strain DU 1090 of S. aureus to pneumonia mice was also significantly reduced. In conclusion, this study proved that JFM is a potential drug against S. aureus infection, and this study provided a preliminary study for better guidance of clinical drug use.

The accelerated spread of antimicrobial-resistant bacteria has caused a serious health problem and rendered antimicrobial treatments ineffective. Innovative approaches are crucial to overcome the health threat posed by resistant pathogens and prevent the emergence of untreatable infections. Triggering stress responses in bacteria can diminish susceptibility to various antimicrobials by inducing resistance mechanisms. Therefore, a thorough understanding of stress response control, especially in relation to antimicrobial resistance, offers valuable perspectives for innovative and efficient therapeutic approaches to combat antimicrobial resistance. The aim of this study was to evaluate the stress responses of 8 different bacteria by analyzing reporter metabolites, around which significant alterations were observed, using a pathway-driven computational approach. For this purpose, the transcriptomic data that the bacterial pathogens were grown under 11 different stress conditions mimicking the human host environments were integrated with the genome-scale metabolic models of 8 pathogenic species (Enterococcus faecalis OG1R, Escherichia coli EPEC O127:H6 E2348/69, Escherichia coli ETEC H10407, Escherichia coli UPEC 536, Klebsiella pneumoniae MGH 78578, Pseudomonas aeruginosa PAO1, Staphylococcus aureus MRSA252, and Staphylococcus aureus MSSA476). The resulting reporter metabolites were enriched in multiple metabolic pathways, with cofactor biosynthesis being the most important. The results of this study will serve as a guide for the development of antimicrobial agents as they provide a first insight into potential drug targets.