Microalgae and bacteria are usually symbiotic in the environment. Algae-bacteria consortia may be potentially applied in wastewater treatment and environmental remediation. Previous research has shown that the algae-bacteria consortia have a strong ability of removing arsenic (As) from solution. However, little is known about the effects of symbiotic bacteria on uptake and metabolism of arsenite (As(III)) by microalgae. In this study, we investigated the effects of symbiotic bacteria on As(III) accumulation and transformation by Chlorella salina.