Zhuojia Li

Occurrence and temporal variation of antibiotic resistance genes (ARGs) in shrimp aquaculture: ARGs dissemination from farming source to reared organisms

Considerable attention has been paid to the occurrence and abundance of antibiotic resistance genes (ARGs) in aquatic environments. However, the temporal variation and dissemination of ARGs in aquaculture environments and reared organisms need further study. This study investigated the abundance and diversity of ARGs and bacterial community in water source, shrimp pond water, sediment, and shrimps during the rearing period in Pearl River Delta region, South China. The results showed that sul1, qnrD, cmlA, and floR were the predominant ARGs in the aquaculture samples. A trend of decreasing abundance of ARGs was observed for pond water samples during the rearing period, whereas an increasing trend was observed in the sediment and shrimp samples. The total concentration of ARGs in water source was significantly higher than that in shrimp pond water (p<0.05). A significant negative correlation was found between the total concentrations of ARGs in pond waters and sediments (p<0.01). The total abundances of ARGs in intestinal tract of adult shrimps were 4.48-19.0 times higher than those in juvenile shrimps. Similar to water source and pond water, cmlA and sul1 were the predominant ARGs in shrimp intestinal tract. The bacterial community in the shrimp intestinal tract changed greatly from juvenile to adult. The results of the present study indicated that the abundances of ARGs in aquaculture varied temporally during the rearing period. Water source was an important medium disseminating ARGs to the aquaculture environments and reared organisms. Sul1 could be used as a potential indicator for ARGs in both water and sediment in aquaculture in the estuary of the Pearl River Delta, South China. This study represents a case study for the temporal variation of abundance and dissemination of ARGs in aquaculture and is a reference for potential risks to food safety and human health.

Metabolic and phylogenetic profile of bacterial community in Guishan coastal water (Pearl River Estuary), South China Sea

Characteristics of a microbial community are important as they indicate the status of aquatic ecosystems. In the present study, the metabolic and phylogenetic profile of the bacterioplankton community in Guishan coastal water (Pearl River Estuary), South China Sea, at 12 sites (S1-S12) were explored by community-level physiological profiling (CLPP) with BIOLOG Eco-plate and denaturing gradient gel electrophoresis (DGGE). Our results showed that the core mariculture area (S6, S7 and S8) and the sites associating with human activity and sewage discharge (S11 and S12) had higher microbial metabolic capability and bacterial community diversity than others (S1-5, S9-10). Especially, the diversity index of S11 and S12 calculated from both CLPP and DGGE data (H>3.2) was higher than that of others as sewage discharge may increase water nitrogen and phosphorus nutrient. The bacterial community structure of S6, S8, S11 and S12 was greatly influenced by total phosphorous, salinity and total nitrogen. Based on DGGE fingerprinting, proteobacteria, especially γ- and α-proteobacteria, were found dominant at all sites. In conclusion, the aquaculture area and wharf had high microbial metabolic capability. The structure and composition of bacterial community were closely related to the level of phosphorus, salinity and nitrogen.

Persistence and spatial variation of antibiotic resistance genes and bacterial populations change in reared shrimp in South China

More attention has been paid to the abundance and diversity of antibiotic resistance genes (ARGs) in aquatic environments. However, few studies have investigated the persistence and spatial variation of ARGs in aquatic organisms. This study investigated the occurrence and abundance of ARGs and the bacterial populations in shrimp intestinal tracts during the rearing period in different regions of Guangdong, South China. The results showed that sul1, sul2, qnrD, and floR were the predominant ARGs. Compared with those of juvenile shrimp, the total concentrations of ARGs in the intestinal tract of adult shrimp in three shrimp farms were 2.45-3.92 times higher (p < 0.05), and the bacterial populations in the adult shrimp intestinal tract changed considerably. Redundancy analysis (RDA) showed that the abundance of Proteobacteria, Firmicutes, and Verrucomicrobia in Farms A, B, and C, respectively, were strongly positively correlated with the most abundant and predominant genes (sul1 and qnrD for Farm A; floR and sul2 for Farm B; floR and sul2 for Farm C) in the shrimp intestinal tract. The results of this study indicated that ARGs gained persistence in the developmental stages of the reared shrimp. Different phyla of predominant bacteria were responsible for the increase of ARGs abundance in the shrimp intestinal tract in different regions. This study represents a case study of the persistence and spatial variation of ARGs in aquaculture and can be a reference for the determination of harmful impacts of ARGs on food safety and human health.

Research Progress in Dinoflagellate Prevention and Control Through Algae-lysing Bacteria

As environmental pollution intensifies, the frequency of dinoflagellates incidents gradually increases at home and abroad in recent years. It causes serious harm to aquatic ecological environment, aquatic animals, tourism industry and human health. This paper introduces the features and harm of dinoflagellates, and related methods to prevent and control dinoflagellates. Among them, the prevention and control of dinoflagellates by algae-lysing bacteria, including species and dissolve mechanisms of algae-lysing bacteria, and the prospect of algae control through algae-lysing bacteria, are mainly introduced.