An arsenic biosensor with modified Shewanella oneidensis in a bioelectrochemical system

Arsenic is a transition metal element that is toxic and carcinogenic. High arsenic groundwater is widely distributed around the world, including more than 70 countries in Asia, Europe and the Americas. 94-220 million people worldwide are continuously exposed to high arsenic groundwater. Among them, Bangladesh, India and other Asian regions have the largest number of people affected by high arsenic groundwater, with more than 80 million. In China, more than 2.3 million people are affected by high arsenic groundwater.

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Figure 1. The distribution of high arsenic groundwater in the word [1]

For us living in the Jianghan Plain, it is not only a global but also local problem. More than 73 thousand people, including 20 thousand children, are exposed to the risk of As poisoning in the Jianghan Plain[3,4]. Previous studies found that the depth of high As concentration distributing in groundwater also corresponds well with that of wells where residents obtain for drinking water, which will endanger the safety of residents living in Jianghan Plain. Due to its toxicity and arsenic threshold (<10 μg/L) for drinking water, cost-effective and sensitive environmental monitoring tools to detect arsenic are needed.

Figure 2. Spatial distribution of arsenic concentration (in ppb) in the Jianghan Plain[2]

Field scene

Kid: I'm so thirsty. Can I drink the water here?

Arsenic: Hey! No! Why can't you see me? I'm swimming! All of you ignored me. (wipe the tears)

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Laboratory scene

Scientist (make a brilliant appearance): Maybe I can help you to be seen.

(Bring back water samples for study)

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Scientist: Look at our new biosensor! It's based on an electroactive biofilm to detect arsenite using electroactive bacteria S. oneidensis MR-1 as a chassis cell. We can make you seen now.

Hm hm. Not yet, your concentration is too low.

Arsenic: Yeah, if you want to see me, you need to make it more sensitive and stable.

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Arsenic (happy look): Yahoo!

Scientist: we reduce the non-conductivity polysaccharides through gene knockout and synthetic biology amplifier logic circuits, thus further improving the sensitivity of the sensor. Now you can be seen even at low concentrations.

Arsenic (show it to passers-by): Now you can see me easily. Be careful, I'm toxic.

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In 2023, the CUG-China team aims to develop an electrochemically active biofilms (EABs)-enabled biosensor to sense arsenic by using the electroactive bacterium S. oneidensis MR-1 as chassis cells. To improve the sensitivity of arsenic biosensor, we raise the matrix conductivity of S. oneidensis MR-1 biofilms by reducing the production of non-conductive polychlorides through the deletion of polychloride synthesis gene. Furthermore, cloning arsenic-responsive transcription unit and the gene circuits of a transcriptional amplifier makes the EABs-enabled biosensor specifically and sensitively sense arsenic. The arsenic biosensor constructed in this project is self-sustainable, cost effective and portable devices with a wide range of applications including in-situ water quality monitoring.