Bacteria Buddies

Beneficial Bacteria

    There are more bacteria in the human gastrointestinal tract than there are actual human eukaryotic cells in the body (Sudo, 2004). The thought of this is probably enough to make most people feel unsettled. The real truth is most bacteria are not pathogenic and are actually helping our body. This natural colonization of microbes in the gastrointestinal tract is referred to as the gut microbiota (also referred to as the gut flora). The microbes provide several benefits including prevention of pathogenic bacteria from entering the gut epithelium, breaking down of macronutrients for absorption, immune function maturation, vitamin K production, development of the brain-gut axis, and many others. With all these benefits, the survival of these microbes becomes very essential for our health.

    The gut microbiota colonize and develop in humans immediately after birth (Del Chierico, 2015). This is a crucial period for the development of these bacteria and is guided by genetics, antibiotic use, breastfeeding, and delivery method (C section vs vaginal). Disruption in colonization can lead to many problems in early childhood and adulthood. One of these problems occurs in the development of the immune system. The immune system is dependent upon these early bacteria to develop and mature properly. One example is the development of gut-associated lymphoid tissues (GALT). If early microbial development is delayed, GALT doesn’t develop properly and leads to an increased likelihood of developing a GI disease (West, 2015). The gut microbiota has also been found to aid in the maturation of Th1 and Treg cells (West, 2015). These cells are important for immune regulation. If these cells don’t mature properly, allergic reactions are more likely to occur throughout life.

    Development of the immune system is not the only way the gut microbiota helps protect us from disease. These bacteria produce many beneficial molecules. Polysaccharide A (PSA) produced by B. fragilis is another one of these beneficial

molecules. PSA plays a role in development of the immune system, but also reduces the risk of developing colitis by reducing inflammation (West, 2015). Aside from reducing inflammation, bacteria help provide a first line of defense from pathogenic bacteria that make it into our gut. The presence of beneficial bacteria causes our epithelial cells to produce secretory IgA (SIgA) (West, 2015). SIgA is important for keeping our epithelial junctions tight. By coating bacteria like Lactobacillus and Bifidobacterium with SIgA, they are able to form a biofilm and bind to the epithelial cells so pathogenic bacteria can’t bind (West, 2015). If bacteria can’t bind to these epithelial cells, they can’t get in to induce their effects. Thus, competition of bacteria is one reason why having a natural gut microbiota helps defend us from incoming pathogenic bacteria.

    Since the gut microbiota has a strong connection to the immune system, many gut diseases can be traced back to an alteration of the gut microbiota. One of the most common diseases is inflammatory bowel disease (IBD). IBD includes Crohn’s disease (CD) and ulcerative colitis (UC). Inflammation of the GI tract is the most underlying symptom in IBD diseases. CD is specifically characterized by periods of inflammation followed by periods of remission, with increasing severity and complication with each occurrence. Chronic CD can lead to thickening of the mucosa, decreased lumen diameter, and ulcers in the mucosal lining. UC is very similar to CD, but occurs mainly in the colon instead of the entire GI tract. UC also produces more uniform effects while CD alternates between healthy and inflamed areas. In both IBD diseases, a change in the major types of bacteria in the microbiota were found (Zhang, 2015). These results make sense due to the relationship gut bacteria have with the immune system and inflammation. Other diseases that have been linked to a change in gut microbiota include liver disease, diabetes, obesity, and heart disease (Zhang, 2015).

    GI disorders can be very serious and extremely uncomfortable. Many individuals with these disorders can experience abdominal pain, cramping, diarrhea, and bleeding. Prolonged symptoms can even lead to dehydration, malnutrition, and anemia. These symptoms can be very hard to deal with even if the person appears to be fine on the outside. I know somebody that was diagnosed with CD and he had a very hard time with it. He had to be extremely careful what he ate to help prevent flare ups. When he

did have a flare up, you could tell he was extremely uncomfortable and in a fair amount of pain. He was able to manage the disease better after being diagnosed though. Some things that can be done to manage symptoms are eating a healthy diet, consuming probiotics (supplemental or natural), performing regular exercise, reduction of stress, and reduced use of antibiotics. Antibiotics can be beneficial, but if they are abused can lead to death of healthy gut microbes. Having healthy gut microbes is the key to prevention of such diseases.

    The relationship between the brain and gut microbiota is more prevalent than previously thought. Gut microbes have a strong connection to the brain in what is commonly referred to as the brain-gut axis. The brain-gut axis is the way the brain and gut cross-talk so feelings can have an actual physiological effect on the digestive system. Some of these physiological effects in the digestive system can then transition back to the brain as feelings like nausea, satiety, and pain (Sudo, 2004). Sudo and his team (2004) have discovered that the gut microbiota plays an important role in the development of this brain-gut cross-talk. Other studies have also shown that gut microbiota can influence behavior, which helps support this theory (Smith, 2015).

    There are several things that bacteria due to help promote this cross-talk between the brain. The production of key metabolites like short-chain fatty acids (SCFAs) are important for the development of tight junctions in the blood-brain barrier, insulin signaling, and other signaling pathway functions (Puddu, 2014). SCFAs have also been found to play a role in diabetes and obesity. Another way the gut microbes affect the brain-gut axis is through hormones. Bacterial metabolites increase serotonin production from nearby colon epithelial cells (Smith, 2015). Serotonin can then be used as a neurotransmitter in the brain for things like sleep, mood, and appetite. Another important factor in the development of the brain-gut axis is the role the immune system plays. The immune system releases cytokines that can help regulate neurophysiology (Smith, 2015). Since a healthy gut microbiota is important for the development of the immune system, it is important for the brain-gut axis as well.

    The important and highly interconnected nature of the gut microbiota is clear. This is why maintaining a healthy and diverse microbiota becomes particularly crucial.
A healthy diet full of probiotics and prebiotics can be very beneficial in maintaining these

microbes. Good sources of probiotics include yogurt, tempeh, soft cheeses, and sourdough bread. There are also many probiotic supplements on the market that can help maintain a healthy bacteria level. Prebiotics are polysaccharides that aren’t digested by the human body that act as a food source for the bacteria. We generally refer to these prebiotics as fiber. Good sources of fiber include whole grains, legumes, fruit, and vegetables. These can also be found in supplemental form but the bioavailability of fiber is usually higher in natural sources. In addition to prebiotics and probiotics, a well balanced diet will help maintain a rich and diverse microbiota. All these things can help ensure the health of you and your ever so important gut microbiota.

References

Del Chierico, Frederica, et al. 2015. Phylogenic and Metabolic Tracking of Gut Microbiota during Perinatal Development. Plos One Vol. 10(9): 1-26

Microbes in the human body. (2015). The Marshall Protocol Knowledge Base (MPKB) Autoimmunity Research Foundation. Web.

Puddu, Alessandra, et al. 2014. Evidence for the Gut Microbiota Short-Chain Fatty Acids as Key Pathophysiological Molecules Improving Diabetes. Mediators of Inflammation Vol. 2014: 1-9

Smith, Peter A. 2015. The tantalizing links between gut microbes and the brain. Nature Vol. 526: 312-314

Sudo, Nobuyuki, et al. 2004. Postnatal microbial colonization programs the hypothalamic-pituitary-adrenal system for stress response in mice. The Journal of Physiology Vol. 558(1): 263-275.

West, C. E., Jenmalm, M. C., and Prescott, S. L. 2015. The gut microbiota and the development of allergic disease: a wider perspective. Clinical & Experimental Allergy Vol. 45: 43-53.

Zhang, Yu-Jie, et al. 2015. Impacts of Gut Bacteria on Human Health and Diseases. International Journal of Molecular Sciences Vol. 16(4): 7493-7519

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