Like other organisms, bacteria have to take nutrients up from the environment and use them in various metabolic processes, which have long been thought to be controlled by gene expression. But the importance of small RNAs in the regulation of cellular pathways and the absorption of carbon by microbial cells is increasingly being recognized. Some research has suggested that complex traits in bacteria like drug resistance or virulence are not controlled by a few genes, but instead by a complex network of molecules that may change depending on the situation. A typical bacterium might be able to generate around 150 sRNAs, which might combine with other molecules to exert an effect.
New research has identified an important sRNA in Vibrio cholerae, a pathogenic bacterium that can grow in the human gut and causes cholera. Throughout history, there have been seven cholera pandemics. The seventh started in 1961 and is ongoing; it's sometimes called the forgotten pandemic.
Not all microbes are dangerous, of course. Some are essential to our health. The human gut is home to many microbial species; there may be trillions of microorganisms in a person's gastrointestinal tract. This gut microbiome is known to have a powerful impact on many aspects of human biology, and the species that live in it have to be kept in a careful balance. When that balance is disrupted, nasty pathogens like V. cholerae may be more easily able to cause infection and disease.
A new study in The EMBO Journal has revealed how this sRNA, called VcdRP (Vibrio cholerae dual RNA and protein) acts in two ways, ultimately functioning to help the pathogen. When VcdRP was over expressed in cells, the researchers found that the production of cholera toxin was inhibited. However, the sRNA "also simultaneously takes on the role of a piece of genetic information and encodes the blueprint for a small regulatory protein,” said Professor Kai Papenfort of Friedrich Schiller University Jena. Once transcribed, this regulatory protein acts on an important metabolic pathway, which turns carbon that's been absorbed by the cell into important molecules like amino acids or energy.
“Our work shows that the toxin production and thus the disease-causing properties of the cholera bacterium are directly linked to its metabolism,” said Papenfort, who added that more physiological roles for sRNAs will probably be identified now that their significance is being revealed.