International Microbiology最新文献

Alkaline pectinases are pivotal for sustainable industries such as textile scouring, juice clarification, and wastewater treatment; however, strains combining high catalytic activity, true alkalistability, and broad agro-industrial applicability remain scarce. Thirty pectinolytic isolates obtained from decayed fruits in Sidi Bel Abbes, Algeria, yielded three Bacillus amyloliquefaciens strains (SPR6, ST9, SC2) with superior enzyme productivity. Under optimized submerged fermentation (pH 9.0, 37 °C, 48 h), strain ST9 achieved 22.4 U/mL, a 1.78-fold increase over baseline, while replacing commercial pectin with orange peel enhanced yield by 1.32-fold and reduced substrate costs by 99%. The strains exhibited remarkable polyextremotolerance, maintaining viable growth and residual enzymatic activity under abiotic stress conditions (up to pH 12, 50 °C, and 11% NaCl), beyond their optimal production range. Beyond pectinolysis, all isolates co-produced key hydrolases, expressed plant-growth-promoting (PGP) traits (indole-3-acetic acid, siderophores, phosphate solubilization), and suppressed Fusarium and Aspergillus spp. This first report of alkaline-adapted B. amyloliquefaciens producing industrially robust pectinase and exhibiting PGP potential highlights their promise as dual-purpose biocatalysts and bioinoculants for circular-bioeconomy applications.

This study evaluates the antibacterial, antibiofilm, and anti-quorum-sensing (QS) properties of ilimaquinone (IQ) against Gram-positive and Gram-negative pathogens. The agar cup diffusion method revealed significant bacterial inhibition, with minimum inhibitory (MIC) and bactericidal (MBC) concentrations ranging from 6.25 to 25 μM and 12.5 to 50 μM, respectively. IQ exhibited dose-dependent biofilm inhibition, demonstrating its potential as an anti-biofilm agent. QS inhibition was assessed by pigment suppression in Chromobacterium violaceum (violacein), Serratia marcescens (prodigiosin), and Pseudomonas aeruginosa (pyocyanin, pyoverdine), reducing their production by 73.33%, 53.68%, 57.13%, and 62.42%, respectively, at sub-MIC concentrations. IQ also inhibited QS-regulated virulence factors in P. aeruginosa, including LasA protease, elastase, rhamnolipid, and extracellular polymeric substance (EPS) production, disrupting biofilm formation. Molecular docking and dynamics analysis confirmed strong binding affinities of IQ to key QS and biofilm-associated proteins (EsaI, PilY1, LasA, PilT, LasR, RhlR, LasI, PqsR, CviR, and CviR'), highlighting its mechanistic role in QS inhibition. These findings suggest that IQ is a promising antibacterial and anti-QS compound with potential therapeutic applications for managing bacterial infections and biofilm-related complications.

Drought stress poses a severe threat to tea plantations globally, leading to a significant reduction in yields. Use of plant growth-promoting bacteria (PGPB) has emerged as a promising strategy to alleviate the detrimental effects of water stress. This study investigates nine distinct bacterial strains, isolated from a drought-prone region in North-East India, for their plant growth-promoting (PGP) traits and their ability to mitigate osmotic stress. These strains were identified based on morphological characteristics and 16S rRNA molecular analysis. Among them, the strains-Chryseobacterium bernardetii (S₄), Cytobacillus gottheilii (S₅), Kitasatospora aureofaciens (S₇), Kocuria palustris (A), and Brachybacterium rhamnosum (B)-exhibited higher PGP activities under osmotic stress conditions (- 0.19 MPa and - 0.93 MPa induced by PEG-6000). Additionally, K. palustris (A) and B. rhamnosum (B) demonstrate effective adaptation to oxidative stress by reducing proline accumulation and were also found to be catalase (CAT) positive. The effect of these osmotolerant PGPBs was further evaluated on tea seedlings under drought stress. Pot experiments in nursery were conducted with three treatments: a positive control (plants watered frequently), a negative control (no treatment), and eight treatments (T1-T8: bacterial inoculations). When comparing the efficacy of bacterial isolates and delivery methods-bioencapsulation and soil drenching. Treatment T6 (comprising strains S₄, S₅, S₇, A, and B) inoculation via soil drenching method improved drought tolerance by effectively modulating osmolyte concentrations, as evidenced by a reduction in total soluble sugars compared to the negative control, highlighting their potential role as bioformulation enhancing osmotolerance and alleviating drought stress in tea plants.

Microalgae are a rich source of valuable products like astaxanthin, a health-promoting ketocarotenoid, but their carotenoid production is challenging due to demanding culture conditions. Consequently, an attempt was made to isolate and screen a new microalgae strain for astaxanthin production via a two-stage cultivation method. In the first stage (vegetative phase), a nutrient-rich medium was used to promote cell growth and biomass, and in the second stage, astaxanthin accumulation was stimulated by stress conditions (0.2% NaCl and 4.4 mM sodium acetate) with continuous light illumination. The effect of physicochemical factors on cell growth, chlorophyll, and carotenoid content was intensively investigated. The microalgal strain was genomically identified as Desmodesmus sp. PLM2 using 18S rRNA sequencing. Optimised conditions, i.e. 20 mM sodium nitrate, 3 mM glucose, 32 mM potassium chloride, pH 7, and temperature 27 °C yielded a maximum biomass of 4.7 g/L, total chlorophyll content of 27.13 µg mL^-1, and total carotenoid content of 7.88 µg mL^-1. Further, in the red stage, stress induction led to the accumulation of carotenoid in the PLM2 strain. A comprehensive identification of the compound was done using various techniques including UHPLC, FT-IR, and Raman spectroscopy, all of which indicated towards the presence of astaxanthin. The strain Desmodesmus sp. PLM2 produced 20.2 mg/L of astaxanthin as per the UHPLC chromatogram. This study showed that Desmodesmus sp. PLM2 can be grown in two stages using the ideal physicochemical conditions, which could significantly aid in the industrialisation of microalgae for astaxanthin production.

This study analyzed the prevalence and antimicrobial resistance patterns of Enterococcus faecium (Efm) infections within a tertiary pediatric hospital in Mexico, highlighting the critical need to understand the epidemiology of this opportunistic pathogen in vulnerable pediatric populations. The primary objective is to elucidate the current landscape of Efm infections in children, including prevalent resistance profiles, which will enable the development of efficient control strategies and optimize empirical treatment regimens. A retrospective analysis of clinical isolates of Efm collected over 7 years (2018-2024) was conducted, encompassing detailed microbiological data, including species identification, antimicrobial susceptibility testing, and patient demographics. Antimicrobial susceptibility testing was performed using the VITEK 2 automated system and interpreted according to CLSI guidelines. Also, the isolates were typified using RAPD. This study's results revealed a significant prevalence of Efm infections among hospitalized children, particularly those in intensive care units and oncology wards. Many isolates were resistant to multiple antibiotics, including vancomycin, aminoglycosides, and beta-lactams, posing significant therapeutic challenges. Finally, the isolates could be grouped into five RAPD types, supporting the idea that the strains have a genetic relationship. This study demonstrates the impact of Efm infections on the pediatric population in a third-level hospital. The high incidence of XDR strains (85%), although only 40% of the isolates are vancomycin-resistant, exposes a serious menace that Efm represents. Additionally, the correlation identified between certain antibiotic resistance patterns may be important for empirical treatment.

Schyzocotyle acheilognathi is an invasive generalist cestode with a high capacity for adaptation to multiple hosts and freshwater environments. Recent reports suggest that this parasite possesses an intrinsic symbiotic microbiota distinct from that of its fish hosts, and its presence induces gut dysbiosis in the host. In this study, we reassessed these ideas. For this, we collected naturally parasitized fish specimens from different locations in Mexico, encompassing different host species, including Cyprinus carpio, Pseudoxiphophorus bimaculatus, Tlaloc hildebrandi, and Vieja hartwegi. We also tested whether this parasite induces a dysbiotic process in the gut bacterial community of Tlaloc hildebrandi. Parasites were identified based on morphological and molecular criteria, and their bacterial communities were characterized using metataxonomy. Our results revealed that S. acheilognathi does not harbor a consistent microbial community among the different host species surveyed. We also did not detect any dysbiotic effect on the gut microbiota of Tlaloc hildebrandi. These findings contradict previous data and provide evidence of the loose relationship between this parasite and bacteria, which we propose could be a part of its successful generalist strategy. The results presented herein offer a novel perspective on the quest for understanding the microbial ecology in generalist cestodes of freshwater fish.

Bacteriophages are major determinants of bacterial community dynamics. Industrial wastewaters constitute distinctive microbe-phage ecosystems shaped by heavy-metal and chemical stressors, yet they remain sparsely characterized by metagenomics. Most existing studies focus on municipal or hospital wastewaters, while phage and bacteriome communities in industrial effluents such as ceramic wastewater are largely unexplored. This study aimed to comprehensively characterize bacterial and phage communities in influent and effluent samples from a ceramic factory using metagenomic approaches. Phage DNA was sequenced on an Illumina NextSeq and processed with a standard bioinformatics pipeline for taxonomic and functional annotation. Of 657 million raw reads, 66% mapped to phage sequences. Caudovirales predominated, with Autographiviridae comprising 59% of classified viral reads. Functional annotation indicated that 64% of assigned genes encoded structural or replication functions. For the bacteriome, 16 S rRNA (V3-V4) amplicons were sequenced on an Illumina NovaSeq 6000 and classified with Kraken2. Proteobacteria dominated both sample types, but community structure shifted along the treatment line: the influent was enriched in environmental-water genera-Flavobacterium (25%), Aeromonas (16%), and Acinetobacter (11%) -whereas the effluent was dominated by Flavobacterium (37%), Hydrogenophaga (25%), and Rhodoferax (14%). Genus-level richness contracted from 228 (influent) to 67 (effluent), and the number of reads entering taxonomic classification declined sharply (1,482,914 vs. 55,847), consistent with selective removal and physicochemical filtering during treatment. Collectively, these results demonstrate that ceramic wastewater harbors a distinct microbe-phage ecosystem molded by chemical and particulate stress. By illuminating an understudied industrial niche, this work provides actionable insights for wastewater treatment, environmental bioremediation, and microbial risk assessment.

Biosurfactant production by a novel Cyberlindnera fabianii MIAU-1 isolate was achieved using co-carbon substrates glucose and sunflower oil, in addition to yeast extract and urea as nitrogen sources. The surface tension of the fermentation medium, consisting of optimal concentrations of glucose (10%), sunflower oil (10%), yeast extract (3 g/L) and urea (3 g/L), was reduced to 36.39 mN/m. This strain produced 39.85 g/L of biosurfactant after 48 h of fermentation under bioreactor conditions. This indicates a 6.78% increase over the 37.32 g/L biosurfactant produced using shake flask after 72 h. The biosurfactant was purified and then characterized using FT-IR and NMR. The crude (CBS) and purified (PBS) biosurfactants were determined to have glycolipid (sophorolipid) structure. The degradation temperatures of CBS and PBS were determined to be 255 °C and 275 °C, respectively, following thermogravimetric analysis. CBS reduced the surface tension of distilled water to about 40 mN/m at 43.63 mg/L its critical micelle concentration (CMC); and PBS reduced it to about 50 mN/m at 1290.91 mg/L CMC. CBS maintained stable surface activity over the range of pH, salinity, temperature, and heating time. Additionally, CBS used at various concentrations exhibited antibacterial activity and inhibited the growth of Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7. CBS also showed anti-adhesive activity to prevent biofilm formation of Staphylococcus aureus and L. monocytogenes.

Fungal endophytes inhabiting the medicinal plants have been considered repertoire for bioactive metabolites. In the current study, the medicinal plant Polygala sinaica was used for the first time as a source for endophytic fungi, which were screened for novel bioactive compounds. The potent biologically active fungal isolate was morphologically identified and molecularly verified using 18S rDNA sequencing as F. oxysporum with accession # OR616565. Two compounds were isolated using flash chromatography, identified using GC/MS and NMR techniques, and quantified using HPLC. Identified compounds were bis-(2-ethylhexyl) phthalate (DEHP) (1) and dibutyl phthalate (DBP) (2) isolated for the first time from F. oxysporum. The ethyl acetate extract of F. oxysporum exhibited potent activity against different multi-drug resistant Gram-negative and Gram-positive bacteria and Candida tropicalis. The production of DEHP was studied in different modified Wickerham media, using oat flakes, rice, and tomato as carbon sources, while corn steep liquor (CSL) and soy protein were used as nitrogen sources. CSL-containing medium exhibited the highest DEHP production by F. oxysporum at an initial pH of 7.2, 0.1% inoculum size after 15 days of incubation under static conditions at 28 °C. The biosynthesis of DEHP by F. oxysporum would serve as an excellent safe and eco-friendly source for its production to be used medicinally and industrially on a large scale with less toxic effects. The current data brings insights into the potency of Fusarium oxysporum, an endophyte of Polygala sinaica, for the production of bis-(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP).

Biofilm formation and other virulence phenotypes under quorum sensing regulation play a vital role in the pathogenicity of Aeromonas hydrophila, triggering the emergence of multi-drug resistance (MDR) which increases fish mortality, environmental issues, and economic loss in aquaculture, necessitating the discovery of novel drugs to bypass standard antibiotics. Here, quorum quenching (QQ) may be a sustainable anti-virulent approach. β-Lactamase enzyme obtained from Chromohalobacter sp. strain D23 restricted violacein pigmentation in Chromobacterium violaceum CV026 by degrading C4-homoserine lactone (C4-HSL) and C6-HSL up to 70% (P < 0.0001). HPLC study also revealed > 73% enzymatic breakdown of both C4-HSL and C6-HSL within 2 h. Crude β-lactamase also hampered biofilm formation of A. hydrophila by reducing total biomass (> 66%, P < 0.001) and cellular viability (62%, P < 0.0001) without affecting planktonic growth. QS-mediated other virulence factors of A. hydrophila, like hemolysin, serine protease, exopolysaccharides, metalloprotease, and lipase activities, were also significantly inhibited (P < 0.0001). Draft genome size of strain D23 was 3.6 mb, having 64.01% G + C content. Annotation revealed the presence of a MBL (metallo-beta-lactamase)-fold metallo-hydrolase enzyme. Multiple sequence alignment indicated the presence of the conserved ⁶⁶HXHXDH⁷¹ domain. Pairwise alignment showed 65% ≤ sequence identity with known marine lactonase enzymes. The molecular docking study revealed moderate binding affinity of β-lactamase to C4-HSL and C6-HSL (- 5.3 kcal/mol). Thus, the present study shows the potent QQ activity of β-lactamase of strain D23 against MDR A. hydrophila, targeting their pathogenesis without necessarily killing them, which can minimize the use of antibiotics in aquaculture and also suggests possible biomedical use. This study also highlights the usefulness of less explored marine bacteria as a potent source of bioactive enzymes.