Letters in Applied Microbiology最新文献

Cold-active cellulases attract significant attention for their potential in energy-efficient bioprocesses under low-temperature conditions. In this study, a psychrotolerant bacterial strain, Pseudomonas fragi HsL3-1, was isolated from Hengshui Lake sediments and found to produce a novel endoglucanase, EG-22SJ. The enzyme demonstrated optimal activity at pH 5.0 and 25°C, retaining over 80% and 60% of peak activity at 15°C and 5°C, respectively, and exhibited exceptional tolerance to 20% organic solvents (e.g. n-hexane enhanced activity by 29.8%) and 1% surfactants (e.g. Tween 80). Kinetic analysis revealed high substrate affinity for CMC-Na with a Km of 0.583 mg·ml-1 and Vmax of 401 μmol·l-1·min-1. Activity was significantly activated by Ca²⁺ and Mg²⁺ but inhibited by Cu²⁺ and Hg²⁺. Culture optimization via response surface methodology increased cellulase production to 8.71 U·ml-1 under conditions of 15.24 g·l-1 CMC-Na, 20.54°C, pH 6.85, and 1.95% inoculation, yielding a 1.24-fold improvement. These integrated properties position EG-22SJ as a robust biocatalyst for sustainable low-temperature applications such as biofuel production, food processing, and detergent formulation, highlighting the potential of nonextreme environments for enzyme discovery.

For efficient removal of COD from the potato processing wastewater, the green alga Haematococcus pluvialis and the bacterium Gordonia terrae were co-cultivated in sterilized wastewater. Results showed that co-cultivation of H. pluvialis and G. terrae enhanced COD removal by promoting cell growth, with the highest removal efficiency (88.9%) on day 12 and removal rate (305.3 mg·L-1·d-1) being achieved at the optimal inoculation ratio of 40:1, increasing 298.6%, 353%, and 159.9%, and 227.6% compared to those of the pure culture of H. pluvialis (22.3%, 67.4 mg·L-1·d-1) and G. terrae (34.2%, 93.2 mg·L-1·d-1), respectively. Supplementation of NaNO3 at the lowest concentration of 0.2 g·L-1 further promoted COD removal efficiency to 100% on day 10. Hence, co-cultivation of H. pluvialis and G. terrae provides an efficient way for complete removal of COD from wastewaters with the suitable COD/nitrogen ratio (C/N) of 8.08.

Water is essential in solid-state fermentation (SSF), but the impact of different water sources on SSF efficiency remains unclear. This study investigated the effects of different water sources on water-supply SSF of Ganoderma lucidum. The results showed that supplementation with normal saline led to the highest levels of laccase, CMCase, FPA activities, and biomass of G. lucidum (93.47, 140.34, 172.42 U/g, and 0.19 g/g, respectively), almost all significantly higher than those in the tap water group (83.57, 126.36, 167.17 U/g, and 0.18 g/g) and the deionized water group (77.25, 120.91, 145.50 U/g, and 0.16 g/g). Normal saline also significantly increased the capillary water content during SSF, which was 5.38% and 19.05% higher than that in the tap water and deionized water groups, respectively. Furthermore, the relaxation time of capillary water in the normal saline group decreased by 49.09%, a reduction that was higher than those observed in the tap water group (43.41%) and the deionized water group (29.56%). In conclusion, normal saline demonstrated distinct advantages in enhancing SSF efficiency, thus providing a scientific basis for the selection of water sources in the fermentation of G. lucidum and other microorganisms.

Using technologies that emit ultraviolet-C (UVC) radiation to inactivate pathogens has gained increasing interest as a strategy for reducing the risk of disease transmission, but it can be difficult to predict their performance in applied settings. Directly irradiating occupied spaces with emerging far-UVC has been proposed, as its shorter wavelength (200-230 nm) is reportedly less damaging to human eyes and skin than longer wavelengths. In this study, we conducted surface tests to evaluate the impact of different inoculum compositions (with and without soil loads) and conditions (wet vs. dried droplets) to determine how these factors affect the efficacy of UVC sources with peak emissions at 254 and 222 nm against five bacteria and two bacteriophages. The presence of a soil load reduced the efficacy of 222-nm UVC more than that at 254 nm, and both UVC sources were generally less effective against microbes in dried (vs. wet) inoculum. Given that pathogens will often be exposed to UVC in the presence of proteins, salts, and other constituents depending on how they are emitted, it is important to consider these challenges when quantifying efficacy.

Psoriasis, a chronic skin autoimmune disease characterized by abnormal immune responses, is influenced by genetic and environmental factors. Recent microbiota research has revealed that short-chain fatty acids (SCFAs), metabolites produced by gut microbiota, play a pivotal role in regulating immune function and inflammation. This review examines the current literature on the relationship between gut dysbiosis, SCFA production, and immune modulation in psoriasis, focusing on emerging evidence from microbiota and immunological studies. SCFAs have been shown to influence key immune pathways, including T-cell activation and cytokine production, which are critical in psoriasis pathogenesis. Reduced SCFA levels have been observed in psoriasis, highlighting the role of gut dysbiosis in disease progression. Understanding the gut-skin axis and the role of SCFAs offers novel insights into developing effective, safe, and accessible treatments for psoriasis. Restoring microbial balance and SCFA production may serve as a promising therapeutic approach for managing psoriasis.

Heavy metal pollution is a growing environmental and public health concern, particularly due to its impact on microbial communities. Pseudomonas aeruginosa, a highly adaptable bacterium, has developed resistance to heavy metals (HMs), which is closely linked to antibiotic resistance through shared genetic and regulatory pathways. This co-resistance poses significant challenges for environmental health and antimicrobial management. Additionally, microplastics act as carriers for HMs and antibiotics, creating a compounded pollution stressor that further influences bacterial resistance patterns. This review explores the molecular mechanisms by which P. aeruginosa resists heavy metal toxicity, focusing on key adaptive strategies such as efflux systems, biofilm formation, enzymatic detoxification, and genetic modifications. These mechanisms enhance bacterial survival in contaminated environments, allowing P. aeruginosa to persist and contribute to the spread of resistance genes. The interplay between HMs, antibiotics, and microplastics underscores the complexity of pollution-driven bacterial adaptation. Addressing these issues requires a multidisciplinary approach that integrates environmental pollution control and antimicrobial resistance management. Understanding how P. aeruginosa thrives under such stress conditions is crucial for developing effective strategies to mitigate the risks associated with heavy metal contamination, antibiotic resistance, and microplastic pollution in both natural and clinical ecosystems.

Controlled environmental agriculture (CEA) is an emerging technology with increasing adoption for commercial applications. However, its impact on the plant microbiome is not entirely clear. The assumption is that controlled conditions reduce the risk of introduction and spread of pathogens, human or plant. Here, we assessed the microbial flux through a commercially relevant CEA plant growth tower from culture-dependent and independent approaches. This allowed the relationship between two of the main entry points for microbes to be determined, the circulating water system and plant growth substrates, on two crop species systems, kale and lettuce. There was a clear distinction between the taxonomic compositions of bacteria in the water-associated and coir-associated compartments. Overall, water did not contribute the most abundant members of the microbiota on plants. Rainwater, used as a top-up source of water, was not the major source of sequenced microbes in either the circulating water system or in coir compartments. The main points of expansion of cultural microbes were in the irrigation tray system and the physical presence and growth of the crop plants. The effect of UV-C, typically used to treat water, and the LED lighting system were quantified for proxy pathogen strains.

Clostridioides difficile is a potentially harmful bacterium that can affect preterm infants more seriously than full-term infants, largely due to their immature immune systems and underdeveloped gut microbiota. Although colonization with C. difficile is often harmless in healthy babies, preterm infants are more likely to develop infections, which can lead to serious health problems. This review looks at how an immature immune system and an imbalanced gut microbiome increase the risk of C. difficile infection (CDI) in early life. To reduce this risk, researchers are exploring postbiotics-non-living bacterial products or byproducts-as a safer alternative to traditional treatments like antibiotics. Postbiotics can help by strengthening the gut barrier, reducing inflammation, and supporting the growth of beneficial bacteria. They are also considered safe for use in vulnerable populations, including infants. This review discusses the types of postbiotics, their functions, and how they may help prevent or manage CDI. It also highlights their potential for use in infant formula as a preventative strategy. Overall, postbiotics may offer a promising new way to protect preterm infants from C. difficile and support healthier immune and gut development.

Viral infections, including arboviruses such as chikungunya, zika, dengue, and mayaro fever, remain significant global health and economic challenges, fueled by the emergence and resurgence of mosquito-borne diseases. Natural products, especially plant-derived compounds, have been crucial in drug discovery and often serve as scaffolds for synthetic drug development. This study focused on modifying paulownin, an isolated lignan, through a Click reaction to incorporate 1,2,3-triazole and quinolinic ring frameworks. The resulting derivative 7 was evaluated for its in vitro antiviral activity against Alphavirus chikungunya (CHIKV). The paulownin derivative 7 did not exhibit cytotoxicity in Vero cells and demonstrated potent activity against CHIKV, with median effective concentration value of 9.05 µM and a selectivity index exceeding 16.8. Furthermore, compound 7 outperformed positive controls, being over 46 times more active against CHIKV. Cytopathic effect assays confirmed this anti-CHIKV activity. The virucidal assay indicated that the compound does not exert a direct effect on CHIKV particles before cell infection. RT-qPCR studies further demonstrated derivative 7 significantly reduces CHIKV replication. These findings highlight the paulownin derivative 7 as a promising and selective candidate for CHIKV treatment.