Impairment of cellulose- and cellobiose-degrading soil Bacteria by two acidic herbicides

Insights of microbial community evolution under benzisothiazolinone exposure in different soil environments

Benzisothiazolinones (1, 2-benzisothiazoline-3-one; BIT) is widely used to control bacterial and fungal diseases of various crops, and their residues in soil may play an important role in the interaction between soil microorganisms. We studied microbial remediation in five representative soils under different soil conditions (unsterilized, sterilized and flooded) using 16S rRNA gene sequencing to investigate the effect of microorganisms on the degradation of BIT residues in soils to minimize the potentially toxic effects of BIT. High-throughput sequencing data showed that the structure and abundance of bacterial communities in BIT soils changed greatly, which might affect their degradation pathways, while Principal Coordinates Analysis (PCoA) results showed that there was no significant difference in the fungal community in different treatments of the five soils, but the degradation rate of BIT was more influenced by anaerobic microorganisms. Furthermore, Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Acidobacteria were the predominant bacterial phyla, accounting for 93.74% of all OTUs, which played an important role in the degradation of BIT. Lysinibacillus had a high relative abundance (21.10%) under flooded treatment conditions in Jilin soil, and its bioremediation may be a reason for the rapid degradation of BIT in flooded treatment. Besides, only soil organic matter (SOM) and pH among the soil properties had significant effects on the microbial community. Based on the further analysis of bacterial phenotype, some microorganisms related to the biodegradation of BIT were found, mainly belonging to Proteobacteria, Bacteroidetes and Firmicutes. This study provides a useful theoretical basis for the biodegradation of BIT using isolated microorganisms.

Basagran® induces developmental malformations and changes the bacterial community of zebrafish embryos

This study aimed to assess the effects of Basagran^® on zebrafish (Danio rerio) embryos. The embryos were exposed to Basagran^® at concentrations ranging from 120.0 to 480.6 mg/L, and the effects on embryo development (up to 96 h) and bacterial communities of 96 h-larvae were assessed. The embryo development response was time-dependent and concentration-dependent (106.35 < EC₅₀ < 421.58 mg/L). The sensitivity of embryo-related endpoints decreased as follows: blood clotting in the head and/or around the yolk sac > delay or anomaly in yolk sac absorption > change in swimming equilibrium > development of pericardial and/or yolk sac oedema > scoliosis. A PCR-DGGE analysis was used to evaluate changes in the structure, richness, evenness and diversity of bacterial communities after herbicide exposure. A herbicide-induced structural adjustment of bacterial community was observed. In this study, it was successfully demonstrated that Basagran^® affected zebrafish embryos and associated bacterial communities, showing time-dependent and concentration-dependent embryos' developmental response and structural changes in bacterial community. Thus, this work provides for the first time a complementary approach, which is useful to derive robust toxicity thresholds considering the embryo-microbiota system as a whole. The aquatic hazard assessment will be strengthened by combining current ecotoxicological tests with molecular microbiology tools.