UEA research­ers make break­through in race to cre­ate ​‘bio-bat­ter­ies’

The research shows that it is pos­sible for bac­teria to lie dir­ectly on the sur­face of a met­al or min­er­al and trans­fer elec­tric­al charge through their cell mem­branes. This means that it is pos­sible to ​‘teth­er’ bac­teria dir­ectly to elec­trodes – bring­ing sci­ent­ists a step closer to cre­at­ing effi­cient micro­bi­al fuel cells or ​‘bio-bat­ter­ies’. The team col­lab­or­ated with research­ers at Pacific North­w­est Nation­al Labor­at­ory in Wash­ing­ton State in the US. The pro­ject was fun­ded by the Bio­tech­no­logy and Bio­lo­gic­al Sci­ences Research Coun­cil (BBSRC) and the US Depart­ment of Energy. Shewan­ella oneiden­sis (pic­tured) is part of a fam­ily of mar­ine bac­teria. The research team cre­ated a syn­thet­ic ver­sion of this bac­teria using just the pro­teins thought to shuttle the elec­trons from the inside of the microbe to the rock. They inser­ted these pro­teins into the lip­id lay­ers of ves­icles, which are small cap­sules of lip­id mem­branes such as the ones that make up a bac­teri­al mem­brane. Then they tested how well elec­trons trav­elled between an elec­tron donor on the inside and an iron-bear­ing min­er­al on the out­side. Lead research­er Dr Tom Clarke from UEA’s school of Bio­lo­gic­al Sci­ences said: ​“We knew that bac­teria can trans­fer elec­tri­city into metals and min­er­als, and that the inter­ac­tion depends on spe­cial pro­teins on the sur­face of the bac­teria. But it was not been clear wheth­er these pro­teins do this dir­ectly or indir­ectly through an unknown medi­at­or in the envir­on­ment. Our research shows that these pro­teins can dir­ectly ​‘touch’ the min­er­al sur­face and pro­duce an elec­tric cur­rent, mean­ing that is pos­sible for the bac­teria to lie on the sur­face of a met­al or min­er­al and con­duct elec­tri­city through their cell mem­branes.” ​“This is the first time that we have been able to actu­ally look at how the com­pon­ents of a bac­teri­al cell mem­brane are able to inter­act with dif­fer­ent sub­stances, and under­stand how dif­fer­ences in met­al and min­er­al inter­ac­tions can occur on the sur­face of a cell. These bac­teria show great poten­tial as micro­bi­al fuel cells, where elec­tri­city can be gen­er­ated from the break­down of domest­ic or agri­cul­tur­al waste products.” ​“Anoth­er pos­sib­il­ity is to use these bac­teria as mini­ature factor­ies on the sur­face of an elec­trode, where chem­ic­al reac­tions take place inside the cell using elec­tric­al power sup­plied by the elec­trode through these pro­teins.”

Bio­chem­ist Liang Shi of Pacific North­w­est Nation­al Labor­at­ory said: ​“We developed a unique sys­tem so we could mim­ic elec­tron trans­fer like it hap­pens in cells. The elec­tron trans­fer rate we meas­ured was unbe­liev­ably fast — it was fast enough to sup­port bac­teri­al res­pir­a­tion.” The find­ing is also import­ant for under­stand­ing how car­bon works its way through the atmo­sphere, land and oceans. ​“When organ­ic mat­ter is involved in redu­cing iron, it releases car­bon diox­ide and water. And when iron is used as an energy source, bac­teria incor­por­ate car­bon diox­ide into food. If we under­stand elec­tron trans­fer, we can learn how bac­teria con­trols the car­bon cycle,” said Shi.

Ori­gin­al publication:

​‘Rap­id elec­tron exchange between sur­face-exposed bac­teri­al cyto­chromes and Fe(III) min­er­als’ by Thomas A Clarke, Gaye White, Julea N Butt, and Dav­id J Richard­son (all UEA, UK), and Zhri Shi, Liang Shi, Zhem­ing Wang, Alice C Dohnalkova, Mat­thew J Mar­shall, James K Fre­drick­son and John M Zachara (all PNNL, USA) is pub­lished by PNAS on Monday, March 25. Source: Uni­ver­sity of East Anglia