The team from Research Unit 2251 of the German Research Foundation led by Goethe University has now shed light on a central mechanism via whichAcinetobacter baumanniisettles in such an adverse environment: like many bacteria as well as plants or fungi,Acinetobacter baumanniiis able to synthesize the sugar alcohol mannitol, a substance excellent at binding water. In this way,Acinetobacter baumanniiprevents desiccation.

Almost unique, however, is the way thatAcinetobacter baumanniisynthesizes mannitol: instead of two enzyme complexes as are common in most organisms, the two last steps in mannitol synthesis are catalysed by just one. A team of researchers led by Professor Beate Averhoff and Professor Volker Müller already discovered this "MtlD" enzyme with two catalytic activities back in 2018. The team headed by Professor Klaas Martinus Pos, who is also a member of the Research Unit, has now succeeded in shedding light on the enzyme's spatial structure.

He explains: "We've discovered that the enzyme is usually present in the form of free monomers. Although these have the necessary catalytic activities, they are inactive. Only a dry or salty environment triggers what is known as 'osmotic stress' in the bacterium, after which the monomers aggregate as dimers. Only then does the enzyme become active and synthesize mannitol." The researchers have also identified which parts in the structure are particularly important for the enzyme's catalytic functions and for dimer formation.

Professor Volker Müller, spokesperson for Research Unit 2251, is convinced: "Our work constitutes an important new approach for fighting this hospital pathogen since we've identified a biochemically sensitive point in the pathogen's metabolism. In the future, this could be the starting point for customized substances to inhibit the enzyme."