[Effects of Fertilization Strategies on the Cadmium Resistance of Paddy Soil Microorganisms].

Cadmium (Cd) is one of the commonly found heavy metal contaminants in soil and has a toxic effect on plants and humans. Understanding the Cd resistance of soil microorganisms under different fertilization regimes can provide a theoretical basis for controlling heavy metal pollution by organic fertilizers. In order to investigate the effects of inorganic and organic fertilizers on the Cd resistance level of soil microorganisms, paddy soil samples were taken in Changzhou, Shanggao, and Fuzhou. A functional gene array (GeoChip 5.0) was used to investigate the distribution of microbial Cd resistance genes. The results indicated that the content of available Cd in soil with organic fertilizer[(1.08±0.70) mg·kg-1] was significantly lower than that in soils with inorganic fertilizer[(3.75±1.22) mg·kg-1](P<0.05). A total of 639 Cd resistance genes were detected. The abundance of microbial Cd resistance gene in soil with organic fertilizer was higher than that of inorganic soil. The content of available Cd, moisture content, pH, and ammonium nitrogen were important environmental factors affecting the distribution of Cd resistant microorganisms. Analysis of the molecular ecological network of Cd resistant microorganisms showed that pH, moisture content, and the effective state of the Cd content were the main factors affecting the potential interaction of functional microorganisms with inorganic fertilizer, and the main factors were total potassium and moisture content with organic fertilizer. Compared with inorganic fertilizers, the application of organic fertilizers can improve the Cd resistance level of microorganisms in soil and promote positive relationships among Cd resistant soil microorganisms.

Distribution and diversity of filamentous bacteria in wastewater treatment plants exhibiting foaming of Taihu Lake Basin, China.

Foaming caused by filamentous bacteria in activated sludge (AS) is a common phenomenon in municipal wastewater treatment plants (WWTPs) in Taihu Lake Basin of South China. In this study, total bacterial and filamentous bacterial communities were comprehensively characterized in AS and foams from eight municipal WWTPs by high-throughput sequencing technology. Results showed that alpha diversities of total bacterial communities in foams were obviously lower than those in AS samples. The bacterial community structures were significantly different between WWTPs rather than sample types (AS vs. foam). For most WWTPs, the Actinobacteria phylum was highly enriched in foams and the most abundant genera in foams were common mycolata. Sixteen filamentous bacteria were identified against the improved bulking and foaming bacteria (BFB) database. Abundance and composition of BFB in different WWTPs and different sample types were significantly different. 'Nostocoida limicola' I Trichococcus and Microthrix were generally dominant in AS samples. The dominant BFB in foams were associated with Microthrix, Skermania, Gordonia, and Mycobacterium. A new Defluviicoccus spp. in cluster III was identified in severe and continuous foams. Moreover, dominant BFB in stable and continuous foams with light level in one typical WWTP were diverse, even, and dynamic. Bacterial co-occurrence network analysis implied that the bacterial community of AS was more sensitive to disturbance than that of foam.