Screening and Identification of Arsenic-resistant Endophytic Bacteria from Different Rice Tissues (Oryza sativa L.) in Different Growth Stages

Abstract

Soil microorganisms are critical for arsenic transport and transformation in the soil-plant system. Endophytes are a very rich microbial resource, but to date no study has reported the responses of endophytes to arsenic pollution. In this study, the cultivable endophytic bacteria were isolated from the root, stem, leaf, and panicle of rice (Oryza sativa L. cv. Yongyou-538) at the seedling stage, tillering stage, flowering stage, and productive stage. All isolates were first screened by 1 mmol ·L-1 arsenite[As (Ⅲ)] and 10 mmol ·L-1 arsenate[As (Ⅴ)], and further screened by 2 mmol ·L-1 As (Ⅲ) and 20 mmol ·L-1 As (Ⅴ). From this study, a total of 126 strains of rice endophytes were obtained, belonging to 13 genera. Among them, 37 strains (8 genus) were isolated from the rice seedling stage, 25 strains (5 genus) were isolated from the rice tillering stage, 24 strains (8 genus) from the rice flowering stage, and 30 strains (8 genus) from the rice productive stage. The dominant genera were Bacillus sp., Psoudomonas sp., and Acinetobacter sp. After twice screening, 20 strains were found to be resistant to 1 mmol ·L-1 As (Ⅲ) and 10 mmol ·L-1 As (Ⅴ), including 16 strains that were resistant to 2 mmol ·L-1 As (Ⅲ) and 13 strains were resistant to 20 mmol ·L-1 As (Ⅴ). Importantly, the strain CS1 was found to be the most resistant bacteria to both As (Ⅲ) and As (Ⅴ) among all the isolated strains.