AIMS Microbiology最新文献

Plant growth-promoting microorganisms (PGPM) are a sustainable and promising alternative to enhance agricultural production. The Brazilian Amazon, and its mostly unexplored biodiversity, have great potential for identifying and isolating beneficial microorganisms to develop sustainable protocols for plant production with less environmental damage and to meet the increasing demand for food production. Thus, this study aimed to synthesize the findings over the last decade on microorganisms from the Amazon biome that promote plant growth while also addressing the challenges and prospects of this biotechnology. Rhizobacteria (PGPR) and fungi native to the Amazon have been shown to enhance the development of various crops, spanning agriculture and forestry, including palm cultivation and forage crops. The potential of PGPM in the Brazilian Amazon discussed throughout this review highlights the importance of further research in this region. Amazon PGPM is promising for use in the inoculant industry, which would contribute to the agricultural production of diverse crops, reduce costs, minimize the use of chemical inputs, mitigate adverse environmental impacts, and support the conservation of the Amazon biome. Furthermore, the advancement of knowledge in this region holds a great potential, thus offering access to different strains for the formulation of new inoculants that can, in a more sustainable manner, enhance the productivity of various crops, thereby promoting global food security.

Background: Drug repositioning has emerged as a promising strategy for assessing its antimicrobial efficacy in treating infectious diseases.

Methods: Seventy-five samples were collected and investigated for the presence of Pseudomonas aeruginosa. Antibiotic resistance, hemolytic activity, twitching motility, and biofilm formation were assessed. lasI and lasR genes were detected using conventional PCR. Minimum inhibitory concentrations of paroxetine, fluoxetine, and levofloxacin were determined by broth micro-dilution. The fractional inhibitory concentration index was calculated to assess the interaction between fluoxetine/levofloxacin and paroxetine/levofloxacin combinations. Half the MIC values of the drugs were selected for inhibitory effect assessment for virulence factors. Antibacterial and healing effects of fluoxetine were investigated on 30 male albino rats using a digital camera, bacterial count, and histological examination.

Results: Our 25 P. aeruginosa isolates were highly drug-resistant. 80%, 92%, and 80% of isolates were positive for twitching motility, hemolysis, and biofilm formation, respectively. 92% of isolates were positive for lasI gene and 96% for lasR gene. MICs of fluoxetine and paroxetine ranged from 32 to 512 µg/mL and MICs of levofloxacin ranged from 1 to 256 µg/mL. A synergistic outcome was observed in both combinations. Biofilm formation, twitching motility, and hemolysis were inhibited by paroxetine and fluoxetine in the majority of isolates. Fluoxetine/levofloxacin and paroxetine/levofloxacin combinations inhibited twitching motility, hemolysis, and biofilm formation in all isolates. Enhanced wound healing was observed in rats treated with fluoxetine and levofloxacin, with the fluoxetine/levofloxacin combination group demonstrating the most significant wound-healing effect. Bacterial count decreased in rats treated with levofloxacin, fluoxetine, and the levofloxacin/fluoxetine combination. Histological examination revealed higher wound healing in the levofloxacin-treated group than the fluoxetine group, and the combination treatment group displayed the fastest rate of wound healing.

Conclusions: Paroxetine and fluoxetine showed considerable antibacterial inhibitory effects against multi-drug resistant P. aeruginosa isolates. Fluoxetine showed significant improvement in anti-inflammatory effects and wound healing. To the best of our knowledge, this is the first Egyptian study to investigate the repurposing of paroxetine and fluoxetine as antibacterial agents. Further studies are needed to investigate their applicability as antibacterial agents as single agents or in combination with other antibiotics.

Bioencapsulation in alginate capsules offers an interesting opportunity for the efficient delivery of microbial inoculants for agricultural purposes. The present study evaluated the ionic gelation technique to prepare beads loaded with two plant growth-promoting bacteria (PGPB), Bacillus thuringiensis strain B25 and Pantoea agglomerans strain Pa in 1% alginate supplemented with 5mM proline as an osmoprotectant. Capsule morphology, survival rate, encapsulation efficiency, and viability during 24 months of storage as well as the stability of PGP activities were studied. Our results indicate that more than 99% of bacteria were effectively trapped in the alginate beads, which successfully released live bacteria after 60 days of storage at room temperature. A considerable survival of B. thuringiensis B25 throughout the storage period was detected, while the inoculated concentration of 8.72 × 10⁹ (±0.04 ×10⁹) CFU/mL was reduced to 99.9% for P. agglomerans Pa after 24 months of storage. Notably, a higher survival of individually encapsulated bacteria was observed compared to their co-inoculation. The colonization capacity of model plant Arabidopsis thaliana roots by free and encapsulated bacteria was detected by the triphenyltetrazolium chloride test. Moreover, both strains effectively colonized the rhizosphere, rhizoplane, and endosphere of durum wheat plants and exerted a remarkable improvement in plant growth, estimated as a significant increase in the quantities of total proteins, sugars, and chlorophyll pigments, besides roots and shoots length. This study demonstrated that alginate-encapsulated B. thuringiensis B25 and P. agglomerans Pa could be used as inoculants in agriculture, as their encapsulation ensures robust protection, maintenance of viability and PGP activity, and controlled bacterial biostimulant release into the rhizosphere.

Waterproofing coatings are composite materials made of different layers with complementary functionalities. They may suffer damage that can modify their aesthetic appearance and/or their functionality. In this study, dark stains appearing on a waterproofing coating of a public swimming pool were mapped and characterized at a macroscopic scale through visual observation and by colorimetric analysis, as well as at a microscopic scale with a digital microscope, a confocal laser scanning microscope, and a scanning electron microscope. Five stains were differentiated macroscopically and characterized using colorimetry and principal component analysis. Microscopic observations showed the presence of microorganisms of varied morphology, some filamentous but mostly unicellular. Biofilms consisting of ovoid fluorescent cells with the morphology of Chlorophyta and unicellular cyanobacteria were particularly abundant. The pigmented stains were located at top coat disorders where microbial colonization and biofilm development were observed. The microscopic observations suggested that physical degradation of the surface of the material would have constituted a prerequisite for colonization by pigmented microorganisms which would have led to the development of macroscopically visible pigmented areas. In this case study, the damage remained superficial and did not alter the watertightness of the material so far.

Phosphorus (P) plays important roles in the arbuscular mycorrhizal (AM) colonization and rhizobium nodulation processes. Additionally, biochar's positive roles in mycorrhizal colonization and nodulation are articulated. However, the effect of the co-application of biochar and P on AM colonization and rhizobium nodulation was poorly studied. This study investigated the effect of the co-application of wheat straw biochar and P using soil columns on mycorrhizal colonization, nodulation, and the growth of subterranean clover. The soil was amended with wheat straw biochar at 0, 5, and 10 t ha^-1 with different levels of P fertilizer at 0, 5, and 10 kg P ha^-1. These studies showed that adding biochar at 5 t ha^-1 along with mineral P fertilizer increased plant growth, mycorrhizal root colonization and nodulation, and P concentration in plants. In most cases, the increasing trend of the biomass yield was higher when biochar and the P fertilizer were applied together at a higher level (P10). These findings suggested that an increased biochar application rate can increase the subterranean clover growth in soil with either no (P0) or a lower P (P5) fertilizer application. Mycorrhizal colonization could help to improve the P supply and subsequently stimulate the root nodulation of leguminous plants.

The study aimed to evaluate the impact of the early addition of a Saccharomyces cerevisiae HD A54 strain before pressing during winemaking. This approach aimed to reduce the dissolved oxygen in the grape must, thus preserving the wine characteristics. Two different treatments were settled: Trial A, where sulphite or other substances were not added during pressing; and Trial B, where a S. cerevisiae strain was added at the pressing stage. The chemical parameters were determined through an enzymatic analyzer, which indicated a faster fructose consumption compared to the glucose in Trial A. The plate counts were measured to monitor the microbial groups during vinification. Both treatments showed regular trends with respect to the Saccharomyces population. Trial B exhibited a higher oxygen consumption compared to the control trial, especially in the early stages of winemaking. This was determined through a dissolved O₂ analysis. Furthermore, Trial B had lower absorbance values at the post-pressing and pre-clarification stages. Both the dissolved oxygen and the absorbance analyses underscored the positive impact of the S. cerevisiae HD A54 strain in protecting against oxidative processes in the grape musts at the pre-fermentative stage. The analysis of volatile organic compounds detected 30 different compounds, including alcohols and esters. Trial B had higher alcohol levels, particularly hydroxyethylbenzene (135.31 mg/L vs. 44.23 mg/L in Trial A). Trial A had almost a four times higher ethyl acetate concentration than Trial B, which is an indicator of oxidation. Interestingly, Trial B showed higher concentrations of 3-methyl-butyl acetate and 2-phenylethyl acetate, which are molecules that correspond to fruity (banana) and floreal (rose) aromas, respectively. Regarding the sensory analysis, Trial B received better scores for the fruity and floral attributes, as well as the overall wine quality.

The effect of cosmetic ingredients on growth and virulence factor expression in Staphylococcus aureus may vary between culture medium and skin. Researchers have used an in vitro skin model with human heel callus to assess bacterial survival and growth on the stratum corneum of the epidermis. Here, we reconstituted a skin model using keratin as a base (instead of callus) and compared it with brain heart infusion (BHI) medium. We investigated the effects of five cosmetic ingredients (macadamia nut oil, sodium myristoyl methyl taurate, methyl p-hydroxybenzoate, 2-phenoxyethanol, and zinc oxide) on growth and virulence factor expression in S. aureus. Interestingly, the survival pattern of S. aureus in our skin model was similar to that reported in models using callus. Upon the addition of cosmetic ingredients to BHI or skin model medium, the sensitivity of S. aureus to these cosmetic ingredients differed between the two media. Notably, after adding the two tested cosmetic ingredients, the expression level of staphylococcal enterotoxin A in S. aureus reduced significantly in skin model medium compared with that in the BHI medium. Additionally, the expression levels of other S. aureus virulence factors (RNAIII, icaA, and hlb) differed between the two media. These findings suggest that our skin model is a valuable tool for evaluating the effects of cosmetic ingredients on growth and virulence factor expression in S. aureus.

The present study evaluated varying inclusion levels (10%, 20%, 30%, 40%, and 50%) of spent mushroom substrate (SMS) derived from Pleurotus ostreatus, ensiled for 0, 21, 42, and 64 d, using an in vitro batch culture technique. The study employed a 6 × 4 factorial design with six inclusion levels and four ensiling durations. The batch culture was conducted over 24 h across two runs. Gas production (GP), greenhouse gases (GHG) production, nutrient degradability, and volatile fatty acids (VFA) were measured. Significant interactions (P < 0.01) between ensiling duration and diet were observed for the concentrations of different nutrients and GHG production. SMS levels in diets increased (P < 0.001) dry matter (DM), neutral (NDF), and acid (ADF) detergent fiber concentrations but decreased crude protein (CP) and cellulose levels. Ensiling period decreased (P < 0.001) DM, NDF, acid-detergent lignin (ADL), and hemicellulose concentrations but increased non-structural carbohydrates (P < 0.05). Diets with higher SMS levels had lower (P < 0.001) GP, methane (CH₄), and carbon dioxide (CO₂) production, together with increased degradability of DM, NDF, ADF, and ADL. Conversely, extending ensiling increased CH₄ and CO₂ production, degradability of DM, and proportions of acetate and propionate but decreased NDF and ADF degradability. Total VFA and butyrate were highest (P < 0.05) in the diet with 50% SMS inclusion. In conclusion, SMS can replace up to 50% of corn silage in the diets of beef and non-lactating dairy cows; however, extending the ensiling duration is not recommended.

Phanerochaete chrysosporium is considered the model fungus for white rot fungi. It is the first basidiomycete whose genome has been completely sequenced. Its importance lies in the fact that its enzymatic system comprises the major enzymes involved in lignin degradation. Lignin is a complex and highly recalcitrant compound that very few living organisms are capable of degrading naturally. On the other hand, the enzymes produced by P. chrysosporium are also powerful agents for the mineralization into CO₂ and H₂O of a wide range of aromatic compounds. However, these aromatic compounds are largely xenobiotic compounds with documented toxic effects on the environment and health. While the economic and environmental benefits of biodegradation with P. chrysosporium are well established, a thorough understanding of P. chrysosporium and its biodegradation processes is essential for successful biodegradation. Our aim of this critical literature review is to provide a concise and comprehensive insight of biodecomposition of organic substrate by P. chrysosporium.

The extremophile microorganism Thermus scotoductus primarily exhibits aerobic metabolism, though some strains are capable of anaerobic growth, utilizing diverse electron acceptors. We focused on the T. scotoductus K1 strain, exploring its aerobic growth and metabolism, responses to various carbon sources, and characterization of its bioenergetic and physiological properties. The strain grew on different carbon sources, depending on their concentration and the medium's pH, demonstrating adaptability to acidic environments (pH 6.0). It was shown that 4 g L^-1 glucose inhibited the specific growth rate by approximately 4.8-fold and 5.6-fold compared to 1 g L^-1 glucose at pH 8.5 and pH 6.0, respectively. However, this inhibition was not observed in the presence of fructose, galactose, lactose, and starch. Extracellular and intracellular pH variations were mainly alkalifying during growth. At pH 6.0, the membrane potential (ΔΨ) was lower for all carbon sources compared to pH 8.5. The proton motive force (Δp) was lower only during growth on lactose due to the difference in the transmembrane proton gradient (ΔpH). Moreover, at pH 6.0 during growth on lactose, a positive Δp was detected, indicating the cells' ability to employ a unique energy-conserving strategy. Taken together, these findings concluded that Thermus scotoductus K1 exhibits different growth and bioenergetic properties depending on the carbon source, which can be useful for biotechnological applications. These findings offer valuable insights into how bacterial cells function under high-temperature conditions, which is essential for applying bioenergetics knowledge in future biotechnological advancements.