Arsenic(As)is a toxic metalloid that is present ubiquitously in the environment.Anthropogenic activities such as mining and smelting have caused widespread As contamination in the environment.Humans are exposed to As mainly from drinking water and food.Due to a greatly enhanced As accumulation in paddy rice,consumption of rice represents a major source of the dietary intake of inorganic As for the population in China.It is therefore imperative to understand the factors that control As transformation and bioavailability in paddy soils in order to minimize its transfer from soil to the food chain.Arsenic is present in different oxidation states and can also undergo various steps of methylation.The transformations of As species have a large impact on As mobility and toxicity.These transformations insoils are mediated predominantly by microorganisms.In this presentation,recent research progress on microbe mediated As oxidation and reduction,methylation and volatilization in paddy soils will be discussed.The potential of using bacteria capable of As volatilization for bioremediation will be highlighted.