A bacterium found in the human urinary tract has an unexpected ability: it can make testosterone.
Researchers studied culturable bacteria from urine samples collected before a prostate biopsy. Their method sought bacteria capable of transforming steroid hormones. Among the isolated microbes, three strains of a species called Actinobaculum massiliense caught their attention.
Culture on chromogenic medium used to differentiate several microorganisms responsible for urinary tract infections.
Via Wikimedia Commons.
In the laboratory, this bacterium can use a molecule naturally present in the body, DHEA, to produce testosterone. DHEA already serves as a raw material for human cells to make several hormones. The result therefore reveals that a microbe living in our body can also carry out part of this chemistry.
To understand how, the team searched for the instructions encoded in the bacterium's DNA. Two genes, called dirA and dirB, produce enzymes capable of modifying these molecules. An enzyme is a protein that facilitates a specific chemical reaction. Here, these proteins gradually transform DHEA's structure until more active hormones are obtained.
The two enzymes do not work in the same way, however. Experiments and molecular simulations indicate that DirA can carry out several transformations. The pocket where it accommodates the molecule is wide enough for the molecule to change position. DirB has a narrower space and can perform only some of the reactions.
This discovery is of particular interest to prostate research. Many cancers in this organ use male hormones, including testosterone, to promote their growth. Some treatments therefore aim to reduce their production by the body or prevent them from acting on cancer cells.
It would nevertheless be premature to conclude that this bacterium promotes cancer. The researchers demonstrated a biochemical capability under laboratory conditions. They did not establish that the testosterone produced by these microbes reaches a tumor or that it alters tumor development in a person.
The work mainly broadens what we know about the urinary microbiome, meaning all the microorganisms present in the urinary tract. These bacteria are not merely present: some can transform molecules made by our own bodies and potentially modify their immediate environment.
Researchers now have two specific genes to study in other bacteria and in human samples. It remains particularly important to determine whether this testosterone production actually occurs in the urinary tract and in quantities sufficient to have a biological effect.