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Researchers uncover new ways that E. coli processes lactose

The results obtained testify to the possible multifunctionality of enzymes, which were considered before to be extremely specialized

MOSCOW, March 15./TASS/. A scientific team under the guidance of Skoltech Professor Mikhail Gelfand has discovered a previously unknown way of converting lactose with the bacteria, Escherichia coli (collibacillus) inhabiting human (and other mammalian) bowels. The bacteria uses genes designed for the metabolism of other substances. The study’s results were published in the journal Scientific Reports.

The results obtained testify to the possible multifunctionality of enzymes, which were considered before to be extremely specialized. This discovery brings up a variety of complementary issues concerning biochemical characteristics, peculiarity, and affinity to various substrates of enzymes.

E. coil tends to routinely feed on glucose, but in the absence of this substance, the bacteria could switch to other substances, for example, lactose. E. coli is capable of efficiently switching between different "foods" within a few hours because the genes responsible for particular tasks, for instance, for absorbing lactose, are not scattered over the entire bacterial chromosome but are amassed in groups, in operons. This sort of composition helps in regulating the genes functioning, switching off needless genes upon shifting from processing glucose to processing lactose.

Previously, it has been assumed that E. coli has only one metabolic pathway of processing lactose, but the researchers have discovered that the operon of collibacillus required for the breakdown of sulfur-containing carbohydrates contain very similar shared arrangements of genes with another operon of other bacteria - bacillus that is responsible for processing lactose.

The researchers assumed that this operon of E. coli might also take part in the utilization of lactose, and the experiments upheld the hypothesis by showing that genes that enable the metabolism of carbon disulfide are involved in processing lactose. These genes were active when the lactose was present in the surrounding medium and switched off upon the absence of lactose. Moreover, even if the traditional pathway of processing lactose is deactivated, the bacteria can grow and breed using lactose as a primary food source.

According to the researchers' article, the case they researched is an example of a successful prediction of genes functioning based exclusively on their location in the genome. "This story shows the power of integration of bioinformatic and experimental methods in solving typical molecular biological challenges," Professor Gelfand commented.