Better out than in

日期:2019-02-26 05:13:01 作者:姬析芗 阅读:

By Andy Coughlan WATER contaminated with pesticides can be cleaned much quicker if the bacteria mopping up the mess wear their antipollution machinery on the outside. William Chen and his colleagues at the University of California in Riverside have engineered cells of Escherichia coli to make a pesticide-eating enzyme on their surfaces, in direct contact with pollutants. This means that the pesticides don’t have to diffuse into the bacteria, as is usual when the antipollution enzymes are manufactured inside the cell. It also avoids the expense of alternative approaches, such as extracting and purifying the enzyme. “We have tried to bypass these limitations by putting the enzyme directly onto the surface,” says Chen. So that the enzyme would appear on the outside of the cell, the team placed the gene for it alongside others that make surface features. The enzyme sticks out because it is attached to a serpentine protein called outer membrane protein A, or OmpA, which snakes in and out of the cell surface. The researchers had equipped their E. coli with a gene found in common soil bacteria, such as Pseudomonas dimunuta and species of Flavobacterium, that breaks down pesticides. The borrowed gene makes an enzyme which degrades common organophosphorus pesticides such as parathion and paraoxon that sheep are dipped in to protect them from insect-borne diseases. Chen’s experiments, reported this month in Nature Biotechnology (vol 15, p 984), show that the rates at which parathion and paraoxon are degraded are improved sevenfold when the enzyme appears at the surface. “We’re looking at a really drastic improvement,