Superoxide dismutases (SODs) play crucial roles in protecting cells against oxidative stress by catalyzing the dismutation of superoxide radicals. In Aspergillus nidulans, five putative SOD genes have been predicted in the genome; however, their comparative expression profiles and physiological functions remain largely uncharacterized. In this study, we analyzed the expression levels of all five SOD genes at different growth stages and examined the oxidative stress sensitivity of corresponding gene-disrupted strains. We found that sodA exhibited high and constitutive expression across all growth stages, while sodB was predominantly expressed in conidia (asexual spores). Disruption mutants of sodA and sodB showed increased sensitivity to oxidative agents, confirming their functional importance. Subcellular fractionation and SOD activity assays revealed that SodA was localized in the cytoplasm, whereas SodB was primarily localized in mitochondria. These results highlight the growth stage-specific expression and distinct cellular roles of SodA and SodB in A. nidulans, providing novel insights into the oxidative stress defense system in filamentous fungi.

Superoxide dismutases (SODs) play crucial roles in cellular oxidative stress defense. In Aspergillus nidulans, SodB is a mitochondria-localized SOD whose physiological function remains poorly understood. Here, we show that a ΔsodB mutant displays impaired growth on non-fermentable carbon sources including acetate, ethanol, threonine, and Tween 20/80, suggesting compromised mitochondrial function. Oxygen consumption assays using an extracellular oxygen consumption reagent revealed a ~50% reduction in respiratory activity in the ΔsodB strain compared to the wild type. When mitochondrial respiration was inhibited by Antimycin A or salicylhydroxamic acid, giant colony growth was equally suppressed across wild-type, ΔsodA, ΔsodB, and complemented strains. However, conidial production was significantly reduced in ΔsodB under Antimycin A treatment, and morphological abnormalities in conidiophore heads were observed under this condition. These results indicate that SodB is not only involved in mitochondrial respiration but also required for maintaining normal sporulation under mitochondrial stress conditions. This study provides new insights into the role of mitochondrial ROS defense systems in filamentous fungal development.

An efficient bacterial consortium (designated BPA-1), comprising Bacillus subtilis SX-6, Pseudomonas sp. SX-10, and Georgenia sp. SY-1, was successfully constructed for the decolorization of the azo dye Congo Red (CR). BPA-1 exhibited significant thermotolerance and heavy metal resistance, achieving over 90% CR decolorization within 60 h at 47°C under co-stress conditions with Zn²⁺, Mn²⁺, and Pb²⁺ (50 mg/L each). The consortium demonstrated broad substrate specificity, effectively decolorizing 12 structurally diverse azo dyes. Enzymatic assays revealed the involvement of laccase, manganese peroxidase, lignin peroxidase, and azoreductase in CR biodegradation. Metabolic pathway analysis indicated a three-stage degradation mechanism: (1) Asymmetric cleavage of azo bonds (-N=N-) generated 4,4'-diazaldenylbiphenyl and 4-amino-1-naphthalenesulfonic acid (Intermediate II); (2) Deamination converted Intermediate II to 3,4-dihydroxy-1-naphthalenesulfonic acid, followed by desulfurization to form naphthalene-1,2,3,4-tetraol; (3) Complete mineralization of intermediates occurred through subsequent oxidative steps. Notably, 4,4'-diazaldenylbiphenyl was further transformed into 4,4'-diaminobiphenyl, confirming the consortium’s capacity for multi-step detoxification.

Plastics are indispensable in modern society, but their increasing production and disposal pose serious environmental challenges, including pollution and the depletion of non-renewable resources. Poly(ethylene furanoate) (PEF), a bio-based polyester composed of ethylene glycol and 2,5-furandicarboxylic acid (FDCA), is attracting attention as a sustainable alternative to poly(ethylene terephthalate) (PET). In this study, we developed a fully biotechnological upcycling system for PEF. Our approach involved enzymatic depolymerization of PEF to release FDCA, followed by microbial conversion of FDCA into polyhydroxyalkanoate (PHA), a biodegradable polyester. From soil samples enriched with FDCA as the sole carbon source, we isolated two bacterial strains: Pseudomonas sp. S8-1 and Caballeronia sp. S8-5. These strains produced medium-chain-length and short-chain-length PHAs, respectively, in defined medium containing FDCA. For enzymatic depolymerization, we employed the thermostable ICCG variant (F243I/D238C/S283C/Y127G) of leaf-branch compost cutinase, known for its high PET-degrading activity. The depolymerization of PET by this enzyme was enhanced by the addition of calcium carbonate (CaCO₃) powder to suppress acidification. Furthermore, the enzyme retained high activity even after partial purification by heat treatment at 60°C and efficiently depolymerized PEF as well. Finally, the PEF degradation solution was successfully utilized as a carbon source for PHA production by strain S8-5. These results demonstrate a proof-of-concept biorecycling system for PEF and represent a first step toward sustainable plastic management.

At the 2025 Osaka/Kansai Expo, a bacterial-bioluminescence-based lighting system, called BIOLIGHT, was exhibited. It consists of 80 liters of liquid culture medium and produces enough brightness to illuminate a room. In this study, to make clear the relationship between the liquid culture thickness and the brightness using BIOLIGHT, the world's largest liquid culture aquarium of bioluminescent bacteria, we investigated the brightness of the bacterial liquid culture in relation to optical density (OD). The theoretical brightness of BIOLIGHT was calculated using the transmittance of the liquid culture at 475 nm (the peak luminescence wavelength) derived from the measured OD and was then compared with the brightness actually measured. The calculated (theoretical) brightness was lower than the measured one, suggesting that the light output of BIOLIGHT is influenced not only by cell-induced light shielding but also by another factor, presumably forward scattering. Additionally, depth-dependent brightness measurements showed that brightness became saturated at a liquid culture thickness greater than 7 cm. These findings will contribute to the design of future lighting solutions using bacterial bioluminescence.