Effect of Pond-Based Rice Floating Bed on the Microbial Community Structure and Quality of Water in Pond of Mandarin Fish Fed Using Artificial Diet.

The culture of mandarin fish using artificial feed has been gaining increasing attention in China. Ensuring good water quality in the ponds is crucial for successful aquaculture. Recently, the trial of pond-based rice floating beds (PRFBs) in aquaculture ponds has shown promising results. This research assessed the impact of PRFBs on the microbial community structure and overall quality of the aquaculture pond, thereby enhancing our understanding of its functions. The results revealed that the PRFB group exhibited lower levels of NH4+-N, NO2--N, NO3--N, TN, TP, and Alk in pond water compared to the control group. The microbial diversity indices in the PRFB group showed a declining trend, while these indices were increasing in the control group. At the phylum level, there was a considerable increase in Proteobacteria abundance in the PRFB group throughout the culture period, suggesting that PRFBs may promote the proliferation of Proteobacteria. In the PRFB group, there was a remarkable decrease in bacterial populations related to carbon, nitrogen, and phosphorus metabolism, including genera Rhodobacter, Rhizorhapis, Dinghuibacter, Candidatus Aquiluna, and Chryseomicrobium as well as the CL500_29_marine_group. Overall, the research findings will provide a basis for the application of aquaculture of mandarin fish fed an artificial diet and rice floating beds.

Aggregation-induced emission of TTCPy-3: A novel approach for eradicating Nocardia seriolae infections in aquatic fishes.

Aquatic fishes are threatened by the strong pathogenic bacterium Nocardia seriolae, which challenges the current prevention and treatment approaches. This study introduces luminogens with aggregation-induced emission (AIE) as an innovative and non-antibiotic therapy for N. seriolae. Specifically, the AIE photosensitizer, TTCPy-3 is employed against N. seriolae. We evaluated the antibacterial activity of TTCPy-3 and investigated the killing mechanism against N. seriolae, emphasizing its ability to aggregate within the bacterium and produce reactive oxygen species (ROS). TTCPy-3 could effectively aggregate in N. seriolae, generate ROS, and perform real-time imaging of the bacteria. A bactericidal efficiency of 100% was observed while concentrations exceeding 4 µM in the presence of white light irradiation for 10 min. In vivo, evaluation on zebrafish (Danio rerio) confirmed the superior therapeutic efficacy induced by TTCPy-3 to fight against N. seriolae infections. TTCPy-3 offers a promising strategy for treating nocardiosis of fish, paving the way for alternative treatments beyond traditional antibiotics and potentially addressing antibiotic resistance.

Spectroscopic investigation on the energy transfer process in photosynthetic apparatus of cyanobacteria.

In this work, we employ cyanobacteria, Spirulina platensis, and separate their photosynthetic apparatus, phycobilisome (PBS), thylakoid membrane and phycobilisome-thylakoid membrane complex. The steady state absorption spectra, fluorescence spectra and corresponding deconvoluted spectra and picosecond time-resolved spectra are used to investigate the energy transfer process in phycobilisome-thylakoid membrane complex. The results on steady state spectra show chlorophylls of the photosystem II are able to transfer excitation energy to phycobilisome with Chla molecules selectively excited. The decomposition of the steady state spectra further suggest the uphill energy transfer originate from chlorophylls of photosystem II to cores of phycobilisome, while rods and cores of phycobilisome cannot receive energy from the chlorophylls of photosystem I. The time constant for the back energy transfer process is 18 ps.