Current Microbiology最新文献

Panax notoginseng is an important Chinese medicinal plant. Saponins are the major bioactive secondary metabolites with a wide range of medicinal and commercial value in P. notoginseng, so it is crucial to develop environmentally friendly methods to increase their production. The symbiotic relationship between endophytic bacteria and host plants offers a sustainable approach to enhance secondary metabolite biosynthesis. In this study, it was reported that the co-cultivation of an endophytic bacterium Enterobacter cloacae PN7, isolated from P. notoginseng and its host plant could greatly promote saponin accumulation in the root of seedlings. After six days of PN7 treatment, the total saponin concentration reached 21.64 mg/g, representing a 2.01-fold increase over the control. Transcriptome sequencing revealed that PN7 induction upregulated key genes in the saponin biosynthetic pathway (including DXS, HMGR, PMK, DS, CYP450, and GTs), modulated 253 plant hormone signaling genes (such as those related to JA, ETH, and ABA), and affected 284 transcription factor genes and 47 ABC transporter genes. Co-expression network analysis identified DEGs related to plant hormone signaling, transcription factors, and ABC transporters in saponin biosynthesis and distribution. The results suggested that JA signaling, mediated by transcription factors, such as bHLH and MYBs, and its interaction with ETH, played crucial roles in saponin biosynthesis. Additionally, potential ABC transporter candidates involved in saponin transport were identified. This study highlights the role of endophytic bacteria in enhancing saponin production in P. notoginseng and opens avenues for further research on microbial-plant interactions in secondary metabolite production.

Novel viruses in plants can be detected through transcriptome data mining. In this study, a novel cytorhabdovirus, pear rhabdovirus 1 (PRV-1) was identified through reanalysis of RNA-seq data of pear (P. communis 'Bartlett'). The genomic RNA of PRV-1, with complete coding region, measured 15,628 nucleotides (nts) and encompassed six open reading frames (ORF). Homology analysis of PRV-1 genome showed sequence identity of 33.18-56.75% with the existing cytorhabdovirus sequences. Phylogenetic analysis based on genome sequences showed that PRV-1 clustered in the same clade of cytorhabdoviruses. Based on the sequence demarcation criteria, PRV-1 represents a newly discovered species within the Cytorhabdovirus genus of the Rhabdoviridae family. Identification of a novel virus in pear will enhance our understanding on the diversity of plant cytorhabdoviruses.

Endophytic fungi serve as vital reservoirs of natural products. This study investigates the role of the endophytic fungus, Diaporthe amygdali GWS39, isolated from Geranium wallichianum D. Don Ex Sweet aerial stem. Showing a notable resemblance to Diaporthe amygdali, as confirmed through microscopic, molecular and phylogenetic techniques, this fungal endophyte displays promising antifungal and antioxidant capabilities. Remarkably, the present research marks the first report of D. amygdali as a stem inhabiting endophyte in an herbaceous perennial, Geranium wallichianum D. Don Ex Sweet on a global scale. This study pioneers the documentation of broad-spectrum antifungal activity exhibited by endophyte D. amygdali GWS39 against some economically important pathogens. The antioxidant activity of D. amygdali GWS39 crude extracts showed strong positive correlation, with R² values of 0.99 for the methanolic extract and 0.93 for the ethyl acetate extract, indicating high antioxidant potential. In addition, the current investigation likely signifies the initial record of the bioactive chemical constituents of the endophyte D. amygdali GWS39 using GC-MS. In the GC-MS chromatogram of ethyl acetate extract, cyclohexaneamine, phenol, 2,6, dimethoxy-, benzenesulphonamide, N-(2,6, dimethylphenyl)-2-ethoxy-5-(tetrazol-1-yl), morpholine, 1-, beta, -d-Ribofuranosyl-3-[5-tetraazolyl]-1,2,4, triazole were identified. These compounds are previously reported for potent antibacterial, antifungal, antioxidant, antiviral, anticancer activities. The analysis of methanolic crude extract uncovers the presence of compounds such as arsenous acid tris(trimethylsilyl) ester, n-Hexadecanoic acid, methyl 10,11-octadecadienoate with noted antibiotic, antifungal, anti-inflammatory, antiviral, antihistaminic and anticancer activities.

Dazhu glutinous rice wine is a well-known traditional Chinese rice wine, and many local factories and handicraft workshops use different fermentation methods to produce it. Still, the influence of fermentation processes on glutinous rice wine is unclear. This study aimed to compare the difference between the two fermentation methods in the quality and bacterial composition of Dazhu glutinous rice wine. Results showed that the alcoholic content (P < 0.0001) and acidity (P < 0.01) in the rice wine fermented after packaging (PFRW) were higher than in the rice wine packaged after fermentation (FPRW), but the total sugar content was lower. Most amino, such as glutamic acid proline, and lactic acid were significantly higher in FPRW (P < 0.0001). In addition, the aroma, flavor and taste were better in FPRW than in PFRW. The Limosilactobacillus fermentum, Pediococcus pentosaceus, and Lactococcus lactis were dominant bacteria in FPRW, positively associated with amino acid and lactic acid. At the same time, Alcaligenaceae and Pedobacter nutriment were dominant bacteria in PFRW and negatively correlated with the quality. These implied that lactic acid bacteria significantly contributed to accumulating flavor ingredients and improving the quality of Dazhu glutinous rice wine. This study provides reference data for improving the quality of rice wine.

Tigecycline is one of the last-resort treatment options for infections caused by carbapenem-resistant Klebsiella pneumoniae (KP). Unfortunately, tigecycline resistance is increasingly reported and causes an unprecedented public health crisis worldwide. Although studies on tigecycline resistance are expanding, the underlying mechanisms are not fully understood. The goal of this study is to investigate resistance-associated phenotypic changes in descendant tigecycline-resistant KP strains induced in vitro. Compared with the parental KP strains, descendant tigecycline-resistant strains grew slowly and reversed the susceptibility of carbapenems and aminoglycosides from resistance to sensitivity. The efflux pump inhibitor phenylalanyl-arginyl-β-naphthylamine (PAβN) could significantly decrease the MIC values of tigecycline in descendant strains, but the efflux pump inhibitor carbonyl cyanide-m-chlorophenylhydrazine (CCCP), verapamil, and reserpine could not. Although the descendant strains showed inconsistent (increased or decreased) biofilm formation and ethidium bromide uptake, they showed consistently decreased ethidium bromide efflux. As for the expression of efflux pumps and regulators determined by quantitative reverse transcript polymerase chain reaction (qRT-PCR), higher level of efflux pump acrAB-TolC and lower level of regulator ramA were observed in these descendant strains, while the efflux pump oqxAB and the other 6 regulators (acrR, rarA, marA, soxS, bpeT, and Rob) showed inconsistent (higher or lower) expression level. Thus, a global regulatory network driven by regulators (acrR, ramA, rarA, marA, soxS, bpeT, rob, etc.) alone or synergistically might play important roles in conferring tigecycline resistance in KP by regulation of efflux pumps (especially increasing acrAB-TolC) or other pathways.

Vibrio spp. are remarkably diverse bacteria, being worthy of investigation not only for their antibiotic resistance and virulence, but also for their biotechnological potential. Indeed, there is increasing evidence that these bacteria display industrially relevant traits, particularly as producers of antimicrobial substances, tensioactive/emulsifying compounds, and enzymes. Here, our aim was to investigate the potential of Vibrio strains isolated from two different marine sources to produce such biotechnologically applicable substances. From the eighteen analyzed strains, five were isolated from plastic particles from a heavily polluted urban estuary and 13 from calcareous sponges inhabiting submarine caves in an isolated volcanic archipelago in the Atlantic Ocean. Enzymatic screening revealed that most strains were agarolytic and cellulolytic. Overall, six strains showed antimicrobial activity against Staphylococcus aureus ATCC 29,213, with four of them active towards Escherichia coli ATCC 25,922 as well. Additionally, eight strains were positive for the production of bioemulsifiers. Genomic analyses of four strains further revealed insights regarding the enzymatic arsenal, as shown by the detection of several key gene clusters pertaining to the chitin degradation pathway, and also encoding diverse classes of antimicrobial-active metabolites. Our findings highlight the biotechnological potential of Vibrio spp., evidencing their functional diversity and the need for continued and sustained prospecting of this bacterial genus to uncover its potential high-value-added bioproducts.

Lactococcus muris was published in Cell Host & Microbe in November 2022 and validated in validation list no. 213 in October 2023. Lactococcus intestinalis was published in Antonie van Leeuwenhoek in May 2023 and validated in validation list no. 216 in March 2024. Both of them were isolated from the mouse gut. Previous studies indicated that L. muris DSM 109779^T had the highest 16S rRNA gene sequence identity to Lactococcus garvieae (96.7%), and that L. intestinalis M2458^T had the highest 16S rRNA gene sequence similarities to Lactococcus formosensis NBRC 109475^T (97.6%) and L. garviae NBRC 100934^T (97.1%). However, the taxonomic relationship between L. muris and L. intestinalis has not yet been investigated and therefore is the focus of the present study. In the present study, the relationship between L. muris and L. intestinalis was evaluated. The type strains of L. muris and L. intestinalis shared 100% 16S rRNA gene sequence similarity, 100% pheS sequence similarity, 100% rpoA sequence similarity, 99.9% average nucleotide identity (ANI) value and 98.5% digital DNA-DNA hybridization (dDDH) value, indicating that they represented the same species. On the basis of the results present here, we propose L. intestinalis Sun et al. 2024 as a later heterotypic synonym of L. muris Afrizal et al. 2023.

In this study, we reported in vitro probiotic assessment and complete genome sequence of Bacillus subtilis DC-11 isolated from traditionally fermented Idli Batter. The strain was evaluated for probiotic properties, biofilm formation, and antimicrobial compound production. The phenotypic safety was determined by accessing the strain's ability to produce enterotoxins, degrade mucin, and antibiotic sensitivity. Whole genome sequencing (WGS) was performed to identify the strain and determine genetic safety by analyzing the presence of plasmids, antibiotic resistance genes, and virulence factors. In the results, B. subtilis DC-11 showed 88.98% viability in gastric juice, and 98.60% viability in intestinal juice. It showed 18.33 ± 0.44% autoaggregation, 32.53 ± 3.11% adhesion to xylene, 0.98 ± 0.05 OD unit's adhesion to mucin (crystal violet equivalence at 550 nm), 21.2 ± 2.3% adhesion to Caco-2 cells, and - 22.3 ± 0.65 mV zeta potential. The highest co-aggregation was recorded with Escherichia coli (23.62 ± 0.70%). The strain was found negative for enterotoxin production, mucin degradation, and antibiotic resistance to the commonly used therapeutic antibiotics. It formed a good biofilm and capable of producing antimicrobial peptide subtilosin A with a molecular mass of 3400 Da. The peptide has inhibited the growth of methicillin-resistant Staphylococcus aureus (18.6 ± 0.58 mm). In genetic safety, no plasmids, antibiotic-resistant genes, and virulence factors were detected. Moreover, the strain showed close similarity with B. subtilis ATCC 6051 and proteins involved in probiotic attributes. In conclusion, B. subtilis DC-11 is safe potential probiotic candidate.

Vibrio parahaemolyticus, a significant food-borne pathogen that causes economic and public health problems worldwide, can produce two types of flagella, the single polar flagellum responsible for swimming in a liquid environment and the lateral flagella (laf) that enable the bacteria to swarm on the tops of solid surfaces. The polar flagellar genes are expressed either in liquid or on a surface, however, laf genes would only be activated by surface sensing. In this study, the molecular mechanism of surface sensing activating laf gene expression in V. parahaemolyticus was investigated. We found that the c-di-GMP concentration for liquid-grown cells was higher than the concentration for surface-grown cells and laf gene expression could be activated without touching surface if the intracellular level of c-di-GMP was decreased by overexpressing the scrABC operon in the wild-type strain. Surface sensing inhibits the transcription of those c-di-GMP-metabolizing enzymes which could negatively regulate swarming, and enhances those which could positively regulate swarming. Surface sensing also enhances the activity of quorum sensing (QS) of V. parahaemolyticus which plays an important role in regulating the transcription of components of the c-di-GMP network. Combined, the data indicate that V. parahaemolyticus enhances QS by surface sensing to down-regulate the intracellular level of c-di-GMP which results in producing the lateral flagella and swarming on a surface. What we found in this study suggests an important signal transduction pathway of regulating swarming motility by surface sensing in V. parahaemolyticus.

Bacillus sp. TTMP20 has high tetramethylpyrazine (TTMP) yield. However, the mechanism of TTMP production in this strain is unclear at present, which limits the modification for strain TTMP20. In this study, key metabolic pathways related to TTMP synthesis were identified, which included glycolytic pathway, tricarboxylic acid cycle and nitrogen metabolism pathway. Moreover, transgenic Bacillus sp. TTMP20 with recombinant vector PHY-300PLK-BDH was constructed. 2,3-butanediol dehydrogenase gene (BDH) overexpression considerably reduced TTMP biosynthesis. This study will supply new insight into the regulation of TTMP biosynthesis at key enzyme gene level.