ABSTRACT
Frequent harmful cyanobacteria blooms limit the sustainable development of aquaculture. Algicidal bacteria can efficiently control harmful algae without secondary pollution. The algicidal bacteria CZBC1 can lyse Oscillatoria spp. and other harmful cyanobacteria, but its effector mechanism and algicidal threshold are unknown. In this study, we examined the algicidal effect of CZBC1 on O. chlorina, O. tenuis, and O. planctonica by microscopic enumeration and scanning electron microscopy observation. Then, we examined the alginolytic effects of CZBC1 (concentrations 103-106 colony forming units (cfu)/mL) on these three species (concentrations 103-106 cells/mL) to determine the effective concentrations of CZBC1 for Oscillatoria spp. alginolysis. Results showed that CZBC1 can directly lyse O. chlorina and O. tenuis but indirectly lyse O. planctonica. When the initial concentration of CZBC1 was 106 cfu/mL, alginolytic effects were high for all three species at all concentrations, and the alginolytic rate could reach 100% in 3-9 days. When the initial concentration of CZBC1 was lower (103 cfu/mL), its inhibitory effects were delayed by 2-5 days, but the cell counts were significantly decreased compared with the control, evidencing significant alginolysis. In addition, the higher the concentration of the algicidal bacteria suspension, the more significant the alginolytic effects. Our results indicate that CZBC1 has different alginolytic mechanisms for O. chlorina, O. tenuis, and O. planctonica, and that different initial concentrations of CZBC1 have different alginolytic effects on these algal species.
ABSTRACT
The objective of the present study was to characterize the pattern of gene expression at the last stage of ovarian maturation in Chlamys farreri. Dynamic transcriptomic analysis of ovaries was performed at four time points prior to ovulation, using the Illumina HiSeq 2500 platform. A total of 174,928 unigenes were obtained, among which 42,534 were annotated according to bioinformatics databases, such as NT, NR, Swiss-Prot, KOG, GO, and KEGG. Results from the transcriptome analysis revealed a time-dependent pattern of global transcriptional responses. When compared to the 0 d library, 99, 152, and 3248 differently expressed genes (DEGs) were obtained in the 3, 10, and 21 d libraries, respectively. Those three libraries shared only 10 DEGs, the majority of which were time-specific. Pairwise comparisons of each profile demonstrated that DEGs were related to hormone metabolism and receptors, cell division, gametogenesis, and vitellogenesis pathways. Notably, when adjacent sampling time point groups were compared, the only DEG throughout the experimental period was related to the G protein-coupled receptor signaling pathway. The present study provides the first dynamic transcriptomic analysis of C. farreri for evaluation of the molecular basis of gonadal maturation.
