Forest fires can threaten amphibians because ash-associated contaminants transported by post-fire runoff impact both terrestrial and aquatic ecosystems. Still, the effects of these contaminants on the skin microbiome of amphibians have been overlooked. Thus, the main objective of this study was to assess the effects of ash from different severity wildfires (moderate and high) on the skin microbiome of the Iberian frog (Rana iberica). Bacterial isolates sampled from R. iberica skin microbiome were tested for their antimicrobial activity against the pathogen Aeromonas salmonicida. The isolates with antimicrobial activity were identified and further exposed to several concentrations (0, 6.25, 12.5, 25, 50, 75, and 100%) of Eucalypt (Eucalyptus globulus) aqueous extracts (AAEs) of ash from both a moderate and a high severity wildfire. The results showed that 53% of the bacterial isolates presented antimicrobial activity, with Pseudomonas being the most common genus. Exposure to AAEs had diverse effects on bacterial growth since a decrease, an increase or no effects on growth were observed. For both ash types, increasing AAEs concentrations led to an increase in the number of bacteria whose growth was negatively affected. Ash from the high severity fire showed more adverse effects on bacterial growth than those from moderate severity, likely due to the higher metal concentrations of the former. This study revealed that bacteria living in Iberian frogs' skin could be impaired by ash-related contaminants, potentially weakening the individual's immune system. Given the foreseen increase in wildfires' frequency and severity under climate change, this work raises awareness of the risks faced by amphibian communities in fire-prone regions, emphasising the importance of a rapid implementation of post-fire emergency measures for the preservation and conservation of this group of animals.

To develop a test for assessing the immunomodulatory effects of chemical pollutants on fish, we evaluated the effects of dexamethasone on the natural host–pathogen interaction between common carp (Cyprinus carpio) and Aeromonas salmonicida. Carp were exposed to 1mgL−1 dexamethasone for the entire experimental period. One week after the exposure test started, the exposed fish, as well as unexposed fish, were bath-infected with A. salmonicida. One hundred percent mortality was observed in bacteria-infected fish exposed to dexamethasone, whereas no infection-associated mortality was observed in infected fish in the absence of dexamethasone exposure. In a separate experiment, dexamethasone exposure significantly suppressed hemolytic complement activity in bacteria-infected fish. These results clearly indicate that exposure to a high concentration of dexamethasone suppressed the carp immune system and caused subsequent mortality. Thus, this proposed test method is likely to be useful for evaluating the immunomodulatory effects of chemicals in fish.

Microplastics is widespread in the marine environment where it can cause numerous negative effects. It can provide space for the growth of organisms and serves as a vector for the long distance transfer of marine microorganisms. In this study, we examined the sea surface concentrations of microplastics in the North Adriatic and characterized bacterial communities living on the microplastics. DNA from microplastics particles was isolated by three different methods, followed by PCR amplification of 16S rDNA, clone libraries preparation and phylogenetic analysis. 28 bacterial species were identified on the microplastics particles including Aeromonas spp. and hydrocarbon-degrading bacterial species. Based on the 16S rDNA sequences the pathogenic fish bacteria Aeromonas salmonicida was identified for the first time on microplastics. Because A. salmonicida is responsible for illnesses in fish, it is crucial to get answers if and how microplastics pollution is responsible for spreading of diseases.

The current study focuses on utilizing TeO₂-deposited ZnO nanotubes fabricated via a solution-free thermo-mechanical method for aquaculture wastewater remediation. The phase, crystallite size, and morphological studies of the fabricated TeO₂-deposited ZnO nanotubes were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD of TeO₂-deposited ZnO nanotubes (0.5 wt%, 3 wt%, 5 wt%) exhibited crystallite size of 10–20 nm. FE-SEM shows that TeO₂ nanoparticles are uniformly deposited on the surface of ZnO. The photocatalytic studies confirm the higher photocatalytic activity of 3 wt% and 5 wt% TeO₂-deposited ZnO (about 90% and 94.5%) and 80% for pristine ZnO towards the photodegradation of 2,4-dichlorophenol in aqueous medium under both UV and sunlight. The antibacterial activity of synthesized samples was investigated against Gram-positive (Bacillus subtilis MTCC 441 strain) and an aquatic fish pathogenic Gram-negative (Aeromonas salmonicida strain MTCC 1522) bacteria applying the disc diffusion method. This assay showed that 5 wt% TeO₂-deposited ZnO exhibited excellent antibacterial activity compared to pristine ZnO NPs. Reactive oxygen species (ROS) determination assay confirmed that the 2,4-dichlorophenol degradation by TeO₂-deposited ZnO was due to the generation of superoxide radicals. The mechanism of both pollutant degradation and antimicrobial activity is studied in terms of scavenging of produced ROS in the aqueous medium by a scavenger test using histidine and ascorbic acid. The reusability of the TeO₂-deposited ZnO nanotubes was also studied, and it showed stability up to three cycles with a negligible loss of efficiency. The synthesized materials could also be applicable for preparation of electrochemical devices to track bacteria.