Scientists have figured out that bacteria living inside the gastrointestinal tract or gut, may affect Parkinson's disease symptoms. Over 10 million peoples in the world are currently suffering from Parkinson's and almost one million of them are Americans.

Parkinson's refers to a neurodegenerative disease that involves the following symptoms: tremors, rigid muscles, and difficulty walking. Researchers say that 75% of sufferers experience gastrointestinal (GI) abnormalities, usually constipation. It remains incurable to this day.

"Changes in the composition of gut bacterial populations or possibly gut bacteria themselves are actively contributing to and may even cause the deterioration of motor skills that is the hallmark of this disease," said the researchers from the California Institute of Technology (Caltech), in the journal "Cell."

Previous research on Gut microbiome (collection of bacteria to be found in the human's intestine) indicates that people who have Parkinson's disease have significantly different bacteria colony than those of healthy people.

But it is still unconfirmed whether gut microbiomes are the ones really responsible for this disease, NBC News has reported.. To figure this out, researchers took two samples of gut microbes, one from a healthy person and the other from an affected person and transplanted them between two group of mice.

Those mice were brought up in an entirely sterile environment and predisposed to high levels of human protein alpha-synuclein (α-Syn). This protein is associated with the plaque build-up characteristic of the Parkinson's patients.

Research shows that the mice those were injected with the microbes from Parkinson's patients showed more loss of motor control - a common symptom of this disease, according to Popular Science.  Such is the first time in medical history researchers have discovered the physical deterioration in mice by way of associated gut bacteria.

Although scientists are still confused over which bacteria are causing these kinds of symptoms. There are hundreds and even thousands of different species of bacteria, viruses and fungi living in the human body. These all species are collectively called microbiome, which directly affects people's health.

Not all of them are harmful, some of them are beneficial too. Good bacteria colony directly takes part to digest foods and to build up a better immune system.

Moving forward, researchers are planning to figure out the kind of microbiomes directly connected to Parkinson's. If they can be identified, then it may be possible to treat or prevent the disease someday, perhaps through targeted probiotics or dietary changes.