# Biosensor-aided isolation of anaerobic arsenic-methylating bacteria from soil

## TL;DR

This paper introduces a new method to isolate bacteria that methylate arsenic, which helps understand how arsenic behaves in the environment and affects rice crops.

## Contribution

A novel high-throughput method using biosensors to isolate anaerobic arsenic-methylating bacteria is introduced.

## Key findings

- Two arsenic-methylating anaerobes were successfully isolated from paddy soil.
- One isolate was found to methylate arsenate, a new function for anaerobic bacteria.

## Abstract

Microbial methylation of arsenic impacts both the toxicity and fate of this environmental contaminant and is an important component of its biogeochemical cycle. This transformation occurs in flooded paddy fields where soil microorganisms can produce dimethylated arsenic, which causes the straighthead disease in rice. The responsible anaerobic microorganisms have remained elusive because their isolation is laborious, especially as the active methylators cannot be rapidly screened. Here, we introduce a novel approach to specifically target these microorganisms. This approach is based on a high-throughput isolation technique involving microfluidic encapsulation, fluorescence-activated cell sorting, and biosensor-aided screening of microbial function. Using this method, we isolated two arsenic-methylating anaerobes from a paddy soil. This approach has the potential to rapidly obtain novel isolates. For instance, we show that one isolate actively methylates arsenate (AsV), a previously unknown phenotype in anaerobes.