Effects of Different Ratios of Sewage Sludge and Cattle Manure on Growth and Propagation of Eisenia Fetida

A Comparative Study of Zinc Oxide Nanotoxicity on Reproductive Potential of an Earthworm in Natural and Artificial Substrates

The toxic impacts of zinc oxide nanoparticles (ZnO NPs) on reproductive potential of the earthworm, Eisenia fetida were studied in relation to varying temperature and pH in natural (NS) and artificial substrate (AS). The ZnO NPs decreased cocoon production, hatching and rate of reproduction as a function of increasing concentration, temperature and exposure period. The gradation of temperature and pH to get a better reproductive potential was found to be [Formula: see text]C and [Formula: see text], respectively. Cocoon production was higher in NS than the AS. It may be due to sufficient food availability in NS. Survival of adult worms was decreased with increase in ZnO NPs and exposure period. The rate of reproduction was significantly higher in NS as compared to AS at [Formula: see text]C. The present findings suggested that ZnO NPs retard the reproductive potential of E. fetida and may also be hazardous to pedoecosystem and fauna living there in. Temperature of [Formula: see text]C, pH 6.5 and NS as vermibed were the most suitable conditions to maintain worthy rate of reproduction and reduce ZnO NPs toxicity.

The effects of tetracycline concentrations on tetracycline resistance genes and their bacterial hosts in the gut passages of earthworms (Eisenia fetida) feeding on domestic sludge

Vermi-composting is considered to be a feasible method for reducing tetracycline resistance genes (TRGs) in the sludge. Nevertheless, the way different gut passages of earthworm might affect the fates of TRGs and whether this process is affected by tetracycline (TC) concentrations need to be further investigated. In this study, we examined the effects of TC concentrations on changes in TRGs and bacterial communities in gut passages of earthworm were determined by using quantitative PCR and Illumina high-throughput sequencing. TRGs and intI1 were mainly reduced in the hindgut under the TC concentrations ranging from 0 to 25 mg/kg, while they were enriched under higher TC stress exposure. Consequently, we suggest the TC limitation of 25 mg/kg in the domestic sludge (DS) for vermi-composting. Although the predominant genera were TC sensitive under TC stress, many bacterial hosts harboring multiple TRGs (especially those in the hindgut) should be paid further attention to. In the foregut, five genera with abundant tetracycline-resistant bacteria (TRB) were specialized taxa. Among these genera, Unclassified_Solirubrobacterales and Pirellulaceae were probably related to the digestion processes. Other unclassified taxa related to the TRGs were probably derived from the DS. Five genera with abundant TRB were shared in the gut passages, and three specialized genera in the hindgut. These genera could spread TRGs and intI1 to the environment. These results suggest that vermi-composting is a feasible approach for TRG control in the DS containing TC concentration that does not exceed 25 mg/kg. Fates of TRGs and intI1 widely differ in the gut passages, showing inevitable connections with bacterial communities.