Modified B. subtilis Strain to Replace Levodopa Medication for Parkinson’s

Kyle Sugita


This paper proposes a medication which would safely and effectively replace levodopa (LD) treatment for patients with Parkinson’s disease (PD), thus eliminating levodopa-induced dyskinesia (LID) in the progression of the disease. At present, the most effective treatment for the motor symptoms of PD uses LD combined with carbidopa (CD) to prevent the breakdown of LD in the gut and avoid the associated nausea. CDLD, however, is taken in periodic doses, for example 25 mg three times a day, causing spikes in dopamine levels and thus damaging dopamine receptors. This inability to accurately read dopamine levels causes hyperkinetic movements, otherwise known as LID. Thus, the continued use of CDLD is directly related to the development of LID. This paper identifies the most effective alternative to CDLD as a continual source of dopamine in the brain. The proposed solution is oral ingestion of dopamine-producing B. subtilis bacteria, with the norepinephrine-producing genome removed, combined with the NanA surface protein from pneumococcus to allow transgression of the blood-brain barrier (BBB). B. Subtilis is nonpathogenic and takes on the endospore morphology under stressful conditions, including the gut, and would thus eliminate the need for carbidopa. The only potential complication involves hypoglycemia, as B. subtilis requires glucose to survive. In rare cases, the bacteria may cause low glucose levels, which can be remedied with glucagon injections. The proposed medication would eliminate the threat of LID by removing intermittent dopamine spikes, as well as the need for CD. Patients would only need one medication, administered once.


Current Treatment for Parkinson’s Disease

Bradykinesia, rigidity, and other motor problems in patients with Parkinson’s disease (PD) is presently treated with levodopa (LD), usually combined with carbidopa (CD) to prevent decarboxylase enzymes from decomposing LD in the stomach and inducing nausea [1]. However, CDLD is a temporary fix which tends to treat motor issues only in the early stages of Parkinson’s [2] and, as the disease progresses and use of CDLD continues, patients develop new movement disorders that are a direct result of prolonged CDLD use.

These side effects, most notably levodopa-induced dyskinesia (LID), are a result of CDLD being taken in periodic, controlled-release doses every few hours [3]. The peaks and troughs in dopamine levels that this produces causes complications for PD patients because the pulsatile stimulation of dopamine damages corresponding dopamine receptors [4]. Patients develop LID, or uncontrollable movements, when these damaged receptors periodically perceive “peak doses” of dopamine and later have difficulty reading the amount of dopamine actually present in the brain [5], resulting in uncontrollable movement. While extended-release levodopa is prescribed to lengthen the effect of one dose, it still produces periodic highs and lows, just less frequently, meaning LID still poses a threat to patients, simply later in the disease’s progression.

The goal of this paper is to propose a theoretical treatment which would safely and continually produce dopamine in the brain and thus eliminate the periodic stimulation of dopamine receptors currently experienced under CDLD treatment, effectively eliminating the threat of LID in Parkinson’s patients.


Development of Theoretical Treatment

Initially, one might seek to remedy the side effects of CDLD with further, counter-balancing medication. Neurologists could prescribe the glutamate inhibitor amantadine [23], MAOB inhibitors which prevent breakdown of LD by MAOB enzymes, and COMT inhibitors which inactivate dopamine so it will remain in the brain longer [6]. However, to do so is adding more medication to a treatment which will always incite this pulsatile stimulation, meaning the peaks and troughs will always be there, only less often given different medication. No matter what patients use to extend the presence of dopamine in the brain, there will still exist a “pendulum”, where neurologists try to swing from no movement to normal movement, and potentially overshoot to have patients experience too much movement under LID [6].

With the root of the problem being intermittent spikes of dopamine, the most feasible approach seems to lie in producing the exact opposite: a constant source of dopamine. A living organism which ceaselessly releases dopamine is, in this paper, theorized to be a solution to the peaks and troughs in dopamine levels that Parkinson’s patients experience in taking CDLD and which ultimately leads to LID.

Strains of the bacillus bacteria have been studied and are known to produce norepinephrine and dopamine [7]. With the norepinephrine-producing genome removed, this bacteria could be the constant source of dopamine needed. Additionally, the problem of LD being broken down in the gut by DOPA decarboxylase [8] and tyrosine decarboxylase [9], currently combated with CD which defends levodopa long enough for it to reach the brain, will be remedied by the ability of bacillus bacteria to adopt the endospore morphology, by which stressful environmental conditions cause the bacteria to take on the most durable cell type in nature and become capable of withstanding the ravaging conditions of the gut [10]. Using bacillus bacteria would no longer pose the threat of nausea, as bacillus in the gut is both in the endospore form and biologically inactive, therefore not producing the dopamine that is to instead be produced in the brain [11].

Image result for Scanning electron microscopic image of B. subtilis 168

Figure #1. Scanning electron microscopic image of B. subtilis 168 [22]

Bacillus has a reputation for being the cause of food poisoning, but this is specifically the B. cereus strain [12]. It happens to be the case that another strain of bacillus, B. subtilis, is renowned for being a non-pathogenic [13], benign organism [11] and is currently used in other medical studies. B. subtilis has its own reputation for being one of the safest strains of bacteria for testing in the human body [14], and thus B. subtilis was selected as the strain of bacteria to be used in this study.

Thus far, it is understood that the proposed microorganism would consist of B. subtilis with the norepinephrine-producing genome removed. It had been established that, under the conditions of the gut, B. subtilis would exist in the endospore morphology, meaning it would not produce dopamine for decarboxylase enzymes to break down, eliminating the threat of nausea in patients and the need for additional medications like carbidopa. The B. subtilis would be absorbed into the bloodstream and transported to the brain, and here it must cross the blood-brain barrier (BBB). 

Dopamine alone can not cross the BBB [15], this is a function only of levodopa [16], thus an entire bacteria would not be able to cross the same structure meant primarily to keep pathogenic bacteria out. The solution lies in the bacteria Streptococcus pneumoniae, better known as pneumococcus, which has a surface protein called NanA that allows the bacteria to transgress the BBB and cause bacterial meningitis [17]. With this NanA protein removed from the surface of pneumococcus and combined with the modified B. subtilis, it would be possible for the dopamine-producing bacteria to cross into the brain.

The concern might be raised that bacteria in the brain ought to be detrimental to the patient. A recent study has established the presence of bacteria entering and residing in the brain, including the substantia nigra which lacks dopamine under PD, without inflammation or damage to structures [18]. The study additionally supports the presence of gut bacteria in the brain. In this token, the modified B. subtilis, which is already a non-pathogenic and benign bacteria, would pose no pathological threat to the brain.


Potential Issues

Possible complications do exist in the bacteria’s means of staying alive long enough to divide and continue producing dopamine. While research has shown that B. subtilis will adapt to the gastrointestinal tract (GIT) as its natural habitat and easily germinate and sporulate [26], in the brain B. subtilis will require glucose to continue reproduction [19]. The associated low glucose levels in the brain is called hypoglycemia and can, in very rare and unlikely situations, cause functional brain failure [20]. Should patients develop hypoglycemia during use of the B. subtilis medication, their condition can be remedied by the well-established use of glucagon injections into the bloodstream to raise plasma glucose levels [21]. In any case, if a patient is at risk of developing hypoglycemia, perhaps from already low glucose levels in the body, the patient should be prescribed glucagon injections or be considered a poor candidate for the B. subtilis medication and explore different treatment such as carbidopa-levodopa, dopamine agonists, or deep-brain stimulation (DBS) surgery which has proven to be extremely effective in addressing symptoms of Parkinson’s.

The concern may also be raised that the immune response to the introduction of B. subtilis bacteria could reflect that of bacterial infections such as salmonella, pneumonia, or tuberculosis. Past and ongoing studies have established that B. subtilis is not only safe to use as food supplements and probiotics [25], but additionally improves such bodily functions as intestinal homeostasis, natural growth process, immune response and the body’s ability to resist disease [24]. As a matter of necessity, it has also been discovered that B. subtilis plays a central role in the healthy development of gut-associated lymphoid tissue (GALT) and the buildup of necessary antibody repertoires [26]. Thus, research into the effects of B. subtilis ingestion has established the contrary to that which might be assumed of the effect of B. subtilis bacteria in the body. The bacteria is not simply safe to ingest, but additionally boosts and fortifies a variety of necessary bodily functions such as development and immune response.



After thorough and extensive research to find the safest and most effective solution to LID in Parkinson’s patients, the proposed treatment is composed as follows. The medication would include Bacillus subtilis (with the norepinephrine-producing genome removed) combined with the NanA surface protein from meningitis-inducing pneumococcus (which will allow B. subtilis to cross the blood-brain barrier) ingested once, in a form similar to that of probiotic pills. The new microorganism will endure the conditions of the gut while in the endospore state, be absorbed into the bloodstream, travel to the brain, cross the BBB with the help of NanA, and travel to the substantia nigra where it will safely and constantly produce dopamine. Should physicians evaluate a potential user of this treatment and find that the patient is at risk of hypoglycemia from low levels of glucose, the patient should either be allowed glucagon injections or be advised against taking the new medication and instead consider CDLD, dopamine agonists, or DBS. Introduction of the modified bacteria will not trigger negative immune responses as B. subtilis plays an inherent role in certain bodily functions such as gut tissue development and additionally enhances others functions in regards to growth and immune strength.

While there is no literature that states explicitly why such an approach to Parkinson’s treatment has not been taken, it can be inferred that current treatment (primarily carbidopa-levodopa) does a good enough job for now. In enough cases, carbidopa-levodopa will ease the symptoms of Parkinson’s disease, and ongoing research simply strives to improve old medication and develop new medication that counteracts the dyskinesia that arises as a side effect of the treatment. This paper proposes a solution which will go farther back in the disease’s progression and, rather than applying short-term remedies to the problem, address Parkinson’s at its source (a lack of dopamine in the brain). The goal is to keep patients from embarking on an endless cycle of pill-taking and instead “nib it in the bud” such that it is impossible for side effects to begin, because there will be no medication taken from which side effects can manifest.


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Kyle Sugita

Kyle Sugita

Cornell University (c/o 2024), Biological Sciences (Neurobiology and Behavior Concentration), Publications (2), INS Essay Competition (Top 15), IYNA Member Spotlight (January 2020), IYNA staff member