Letters in Applied Microbiology最新文献

For the large-scale use of Pochonia chlamydosporia as a bionematicide, cost-effective production coupled with robust stabilization processes is essential. Submerged liquid fermentation yields large amounts of infective blastospores in a short period. This study aimed to evaluate the nematicidal activity of P. chlamydosporia blastospores from two fungal strains against the eggs of two plant-pathogenic nematodes, as well as to assess the use of various additives to enhance their dehydration tolerance and storage stability. For the more promising strain, submerged culture yielded 1 × 109 blastospores mL-1 after 96 h. Juvenile hatch inhibition was more pronounced with blastospores (64.8%-86.7%) than conidia (48.2%-65.3%) on Meloidogyne javanica and M. enterolobii eggs, respectively. Skim milk added to the liquid medium prior to inoculation or 72 h after fermentation protected fungal cells from dehydration. Following dehydration, storage stability after 10 days was significantly greater at 4°C compared to 25°C. Stabilization processes to prevent cell mortality during dehydration are crucial for the development of blastospores as active ingredients in bionematicides.

Southern Africa remains burdened by malaria, with growing concern about the emergence of antimalarial drug resistance. While artemisinin resistance has not yet been observed in the region, molecular surveillance in sub-Saharan Africa has identified Plasmodium falciparum k13 mutations known to confer resistance, making it vitally important to take proactive and creative measures to protect current treatment regimens. Glutathione S-transferases (GSTs), the multifunctional enzymes involved in detoxification and redox control, have emerged as key contributors to drug resistance in Plasmodium species. The role of GSTs in the development of resistance is discussed in the review, and GSTs are presented as prospective molecular targets for the development of novel therapeutic interventions. We examine the complexity of antimalarial resistance in Southern Africa and highlight the potential of GST inhibition as an adjunct therapy to current malaria control measures. The review promotes a paradigm shift towards GST-targeting approaches as a pre-emptive strategy to avert resistance and consolidate malaria control initiatives throughout the region, aligning with Sustainable Development Goal 3 (good health and wellbeing) among Southern African populations.

With the escalating global demand for eco-friendly materials, polyhydroxyalkanoates (PHAs) have emerged as promising biodegradable alternatives to conventional plastics. This study is based on the systematic investigation of microbial community distribution and functional composition associated with PHA biosynthesis across diverse marine environments through metagenomic analysis. Leveraging environmental characteristics and PHA synthesis potential, we developed targeted culture media. We successfully isolated 102 PHA-producing bacterial strains from various marine habitats, including brackish water interfaces and deep-sea sediments. Gas chromatography quantification revealed a significant correlation (R² = 0.67) between Nile red fluorescence intensity and PHA content in metagenomically-predicted strains, effectively addressing false-positive issues in fluorescence-based screening. We subsequently established a high-throughput screening platform combining microplate technology with fluorometric quantification, identifying 10 elite strains for fermentation optimization and PHA characterization. Notably, strain R1-4-2 (identified as Halomonas olivaria) demonstrated exceptional performance with 2.59 g l-1 cell dry weight (CDW) and 52.89% PHA content (1.52 g l-1 CDW), representing both a novel microbial resource for sustainable PHA production and a potential chassis for synthetic biology applications. These findings provide critical scientific insights and technical frameworks for advancing industrial-scale production of biodegradable biopolymers.

Genomics and metabolic profiles were investigated to understand the malathion degradation pathways in Rossellomorea sp. DL-A strain, isolated from North Oconee River, GA, USA. The Rossellomorea sp. DL-A strain was able to grow in the presence of malathion. However, the growth pattern of the DL-A strain was impacted in the presence of malathion. The lag phase of DL-A's growth curve increased in the presence of malathion. Based on different conditions tested, Rossellomorea sp. DL-A had the highest degradation potential at pH 7 and 30°C. Genomic annotation revealed the presence of genes that were previously found in other malathion-degrading bacteria. Gas-Chromatography Mass Spectrometry (GC-MS) analyses also revealed a possible pathway of degradation of malathion by the DL-A strain. The results from untargeted GC-MS analyses and the presence of certain genes in the whole genome suggest that the products of malathion degradation are intermediates of different central carbon metabolism. This indicates that malathion can be used as a carbon source by Rossellomorea sp. DL-A. Further analyses revealed that the abundance of different intermediates of the malathion degradation pathway changed at different pH and temperatures, indicating that environmental conditions influence malathion degradation.

Gut-mediated infections fostered by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli are increasingly prevalent in clinical settings, posing a significant challenge to the efficacy of conventional antibiotic therapy. This underscores the urgent need to identify alternatives-to-antibiotics. In this study, we investigated the antagonistic potential of total surface proteins derived from probiotic strains viz. Limosilactobacillus fermentum LbS4 (MTCC 5954), L. fermentum Lf1 (MTCC 5689), Lactobacillus acidophilus NCFM, and Lacticaseibacillus rhamnosus GG (LGG), against clinical isolates of ESBL E. coli (9/234 and 23/208). Surface proteins were extracted using lithium chloride as chaotropic agent. Surface proteins exhibited strain-specific heterogeneity, as revealed by SDS-PAGE profiling. These proteins significantly (P < 0.05) reduced E. coli muco-adhesion through protective (hampering the bacterial adhesion), competitive (competition for adhesion sites), and displacement (dislodgement of adhered bacteria) mechanisms. While remaining non-toxic, surface proteins revealed anti-colonization efficacy against ESBL E. coli on HT-29 cell line and preserved epithelial integrity, as demonstrated by FITC-dextran transflux assays. In contrast, ESBL E. coli (109 CFU mL-1) compromised epithelial integrity by increasing FITC-dextran permeability, which was significantly (P < 0.05) mitigated by co-treatment with surface proteins. Overall, this study highlights the potential of probiotic-derived surface proteins as promising postbiotic candidates for countering ESBL E. coli colonization and preserving gut barrier integrity.

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.