Archives of Microbiology最新文献

The frequency of opportunistic fungal infections has been increasing, impacting agriculture, food, and health sectors. In this work, four thiosemicarbazone-chalcones (TC) were synthesized and evaluated by the radial diffusion method against filamentous fungi. All TCs were effective against Aspergillus parasiticus, especially the fluor-substituted one, with radial growth inhibition of 62,9% and 74,4% at the lower (0.209 µmol/ml) and highest (1.670 µmol/ml) concentrations tested, respectively. On the other hand, the non-substituted derivative was the most active against A. carbonarius, inhibiting radial growth by 47,9% and 74,1% at 0.222 µmol/ml and 1.777 µmol/ml, respectively. Additionally, the compounds were evaluated against the dimorphic fungi Sporothrix brasiliensis, S. schenckii, and a clinical strain of Sporothrix spp, exhibiting minimum inhibitory concentrations (MICs) in the range of 0.396–1.777 µmol/ml. When tested against four yeasts of the Candida genus, the thiosemicarbazone-chalcones demonstrated greater activity against C. krusei (MICs 0.011–0.026 µmol/ml).

Seed endophytes are actively used by the mother plant as both reservoir and vector of beneficial microbes. During seed dormancy endophytes experience significant physiochemical changes and only competent endophytes could colonise successfully in seeds and some of them act as obligate endophyte that are transmitted vertically across generations. The adaptive nature of endophytes allows them to switch lifestyles depending on environment and host conditions. In this review, instead of providing broad discussion on applicability of endophytes in plant growth improvement, the fundamental nature of endophytes, their survival strategies under stress conditions, transmittance, etc. have been broadly highlighted by collaborating recent discoveries and theories. We have also tried to differentiate endophyte with their pathogenic counterpart and their survival mechanism during seed dormancy stages. Critical analyses of physio-biochemical changes in seeds during maturation and parallel modifications of life styles of seed endophytes along with pathogens will enlighten the shaded part of seed-microbiome interactions. The mutualistic interrelations as well as their shipment towards pathogenic behaviour under stress are being discussed acutely. Finally, importances of conservation of seed microbiome to maintain seed quality and vigour have been pointed out. Throughout the manuscript, the knowledge gap on seed-microbiota have been mentioned, thus, in future, studies on these areas could help us to understand properly the actual role of endophytes for the betterment of maintaining seed quality and vigour.

The metabolites gluconic acid, 5-ketogluconic acid, proline, and glutamic acid, produced by Pseudomonas reptilivora B-6bs, are industrially important, particularly in food and pharmaceutical sectors. However, producing these metabolites involves biotin supplementation to enhance yields, which is an expensive additive, and reducing its use can significantly lower production costs. Thus, This study aimed to enhance the production of gluconic acid, 5-ketogluconic acid, proline, and glutamic acid without biotin supplementation. To achieve this, a full factorial design was employed, varying agitation speed, glucose concentration, and temperature to determine the optimal conditions for metabolite production. Metabolite concentration was measured using spectrophotometric analysis and thin-layer chromatography (TLC), and the results were statistically analyzed using Minitab^® 18. The findings demonstrate that Pseudomonas reptilivora B-6bs effectively produce gluconic acid (50.51 ± 0.035 g/L, Y_P/S: 0.917 g/g) and 5-ketogluconic acid (44.46 ± 0.23 g/L, Y_P/S: 0.947 g/g), along with proline (0.1727 ± 0.00085 g/L, Y_P/S: 0.00004 g/g) and glutamic acid (0.853 ± 0.142 g/L, Y_P/S: 0.013 g/g) without biotin supplementation. Optimal production was observed with a glucose concentration of 55 g/L. These findings provide a viable biotin-independent strategy for high-value metabolite production. This study contributes novel insights into cost-effective production processes, making it relevant to industrial applications.

The development of new medicines with unique methods of antimicrobial action is desperately needed due to the emerging multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus. Therefore, antimicrobial peptoids have emerged as potential new antimicrobials. Thirteen peptoid analogues have been designed and synthesized via solid phase synthesis. These peptoids have undergone a biological analysis to determine the structure-activity relationships that define their antibacterial activity. Each peptoid is composed of nine repeating N-substituted glycine monomers (9-mer). The monomer units were synthesized with three distinct alkyl side chain lengths: four-carbon butyl monomers, six-carbon hexyl monomers, and eight-carbon octyl monomers. Out of 12 different peptoids, only one peptoid called Tosyl-Octyl-Peptoid (TOP) demonstrated significant broad-spectrum bactericidal activity. TOP kills bacteria under non-dividing and dividing conditions. The Minimum Inhibitory Concentrations values of TOP for Staphylococcus epidermidis, Escherichia coli and Klebsiella were 20 µM, whereas Methicillin-resistant Staphylococcus aureus and Methicillin-sensitive Staphylococcus aureus were 40 µM. The highest MIC values were observed for Pseudomonas aeruginosa at 80 µM. The selectivity ratio was calculated, by dividing the 10% haemolysis activity (5 mM) by the median of the MIC (50 µM) yielding a selective ratio for TOP as 100. This selective ratio is well above previously reported peptidomimetics selective ratio of around 20. TOP shows broad-spectrum bactericidal action in both dividing and non-dividing bacteria in co-culture systems and intracellular bacterial killing activity. These results add new information about the antimicrobial peptoids and aid in the future design of synthetic peptoids with increased therapeutic potential.

Antimicrobial resistance poses a significant global health threat by reducing the effectiveness of conventional antibiotics, particularly against pathogens like Methicillin-resistant Staphylococcus aureus (MRSA). This study investigates the antimicrobial potential of rhizospheric soil bacteria from Prosopis cineraria (Sangri) in the Thar Desert. Bacterial strains isolated from these samples were observed to produce secondary metabolites, notably, Iturin A C-15 cyclic lipopeptide (SS1-3-P) which was extracted from strain Enterobacter cloacae SS1-3 and was purified and characterized using reverse-phase HPLC, ESI-LC/MS, Nile-Red Assay, and FT-IR analysis. The presence of the Iturin A biosynthetic gene cluster was confirmed using gene-specific polymerase chain reaction and the biocompatibility of the purified product was assessed on HEK-293, WI38, and human RBCs. The potential of SS1-3-P to bind to and destroy MRSA membranes was validated using molecular dynamics simulation along with membranolysis and membrane depolarization assays. Antimicrobial assays like growth curve analysis, field emission scanning electron microscopy, and ROS generation confirmed the efficacy of SS1-3-P against clinical MRSA. Furthermore, the antibiofilm and anti-virulence properties of SS1-3-P were studied meticulously. Studies on NIH/3T3 cell lines and a murine excisional wound model showed significant wound-healing attributes of the lipopeptide. These results highlight the potential of desert ecosystems in developing effective antimicrobial therapies against recalcitrant nosocomial pathogens like MRSA.

During the self-healing process of Bacillus subtilis biofilms on a solid MSgg substrate, large-scale ordered clusters emerge within the biofilm, providing an invasive advantages. To investigate the self-healing mechanism, an agent-based model is employed to simulate the self-healing processes of biofilms at two ages. The study reveals that a uniform cell distribution facilitates the healing of biofilm incisions. The nutrient diffusion rate within the biofilm and the elastic modulus (comprising cell and EPS) play a dominant role in the healing of circumferential incisions, while the diffusion rate outside the biofilm governs the healing of radial and penetrating incisions. These influencing factors can adjust cellular ordering, providing valuable insights for controlling the self-healing of Bacillus subtilis biofilms.

Klebsiella pneumoniae is a leading cause of anti-microbial resistance in healthcare-associated infections that have posed a severe threat to neonatal and wider community. The escalating crises of antibiotic resistance have compelled researchers to explore an innovative arsenal beginning from natural resources to chemical modifications in order to overcome the ever-increasing resistance issues. The present review highlights the drug discovery efforts with a special focus on cutting-edge strategies in the hunt for potential drug candidates against MDR/XDR Klebsiella pneumoniae. Nature’s bounty constituting plant extracts, essential oils, fungal extracts, etc. holds promising anti-bacterial potential especially when combined with existing antibiotics. Further, enhancing these natural products with synthetic moieties has improved their effectiveness, creating a bridge between the natural and synthetic world. Conversely, the synthetically modified novel scaffolds have been also designed to meticulously target specific sites. Furthermore, we have also elaborated various emerging strategies for broad-spectrum infections caused by K. pneumoniae, which include anti-microbial peptides, nanotechnology, drug repurposing, bacteriophage, photodynamic, and multidrug therapies. This review further addresses the challenges confronted by the research community and the future way forward in the field of drug discovery against multi-resistant bacterial infections.

Microcystin-LRs (MC-LR) produced by harmful cyanobacterial blooms (HCBs) pose significant hepatotoxic risks to both the environment and public health. Despite the identification and characterization of a limited number of MC-LR degrading bacteria, the challenge of safely removing MC-LRs from freshwater systems without disrupting aquatic ecosystems remains substantial. This study focused on the isolation of lactic acid bacteria from Bapshikhe, a traditional Korean fermented food, and investigated the mechanisms underlying the degradation of MC-LRs by these bacteria. This study also tested the hypothesis that cell wall-associated proteinases in probiotic bacteria play crucial roles in the degradation process. In addition, we verified the hypothesis that the MC-LR degradation mechanism of lactic is correlated with AI-2, a QS-inducing factor. MC-LR degrading bacteria, BSH-02, were successfully isolated from Bapshike, a Korean traditional fermented food, and identified by phylogenetic analysis as Leuconostoc mesenteroides. The BSH-02 strain effectively suppressed cyanobacterial blooms and degraded MC-LR. Ethylenediaminetetraacetic Acid (EDTA), a primary proteinase inhibitor of the BSH-02 strain, reduced the rate of microcystin removal. Based on these studies, the MC-degrading mechanism of BSH-02 was found to involve a metallopeptidase, aligning with mechanisms previously described in other studies. In addition, a correlation between metallopeptidases and AI-2 was identified using RT-qPCR. To the best of our knowledge, this is the first report of Leuconostoc mesenteroides degrading MC-LR. These findings suggest that Leuconostoc mesenteroides strain BSH-02 has high potential for the bioremediation of MC LR-contaminated water bodies.

This work aimed to get compost with cellulose-rich residues for Pycnoporus sanguineus basidiocarp production. Two isolates of P. sanguineus (Ps08 and Ps14) were grown in polypropylene bags containing sawdust of Eucalyptus sp. and rice bran in rates of zero, 5% and 20%, and humidity of 75%. We used two granulometries of sawdust, less than 500 µm and between 500 and 841 µm, compress to get a density of 0.5 g mL⁻¹. Basidiocarps were harvested at 90 and 180 days of incubation, evaluating quantity, diameter, fresh and dry masses and production of the pigment cinnabarin. For the variable granulometry, there was an effect only for the isolate Ps14, which produced basidiocarps with diameters 14.65 mm in granulometry less than 500 µm and 8.56 in granulometry 500–841 µm, however, comparing the isolates, Ps08 produced larger basidiocarps, with an average diameter of 36.99 mm while 11.60 mm for Ps14. Only the isolate Ps08 responded in a dose-dependent manner to rice bran concentrations. As for the fresh mass of basidiocarps, in both harvests the isolate Ps08 presented higher values than the isolate Ps14 in the first and second harvests, in the granulometry less than 500 µm. The cinnabarin content of Ps14 isolate was higher than Ps08, with values of 0.67 e 0.43 mg mL⁻¹, respectively, in the granulometry 500–841 µm, with a tendency to increase in cinnabarin content with higher additions of rice bran. Thus, it was possible to produce basidiocarps of P. sanguineus in an axenic way using cellulosic residues supplemented with rice bran.