Parkinson's disease affects 1 in 100 people over the age of 65, but the time between Parkinson's disease onset and diagnosis can be many months or years. Interestingly, pathological hallmarks of Parkinson's in the brain can also be seen in the neurons in the gut and symptoms like constipation often precede the onset of tremor and incoordination by many years. It is now believed that Parkinson's disease may begin in the gut, at least in some people. Unlike the neurons in the brain, the neurons in the gut are accessible through routine colonoscopy, and so can be obtained by biopsy to study in the laboratory. In addition, there are links between gut microbes, including bacteria, and the diagnosis of Parkinson's disease. This research study is therefore being done to discover whether the pathology and types of bacteria in the gut can serve as an indicator of Parkinson's disease in subjects aged 45-75 that could eventually help in earlier diagnosis. It will also strengthen our understanding of the link between the gut and brain in Parkinson's disease.