The Hidden Bacteria Within
Most microbes in the intestinal tract have only a brief existence in our bodies. They are ingested or “born” at their beginning and then pass right on through and are “eliminated” with fecal material. Some microorganisms, however, take up a more permanent residence. Why doesn’t normal flora multiply out of control and take over the body? What holds them in check? How do we protect ourselves from these bacteria? What about pathogenic organisms?
We have our immune system; we have the enzymes, acids and bile salts that are added into the gastrointestinal tract along with its continuously secreted mucosal lining. We also have the metabolic activities of bacteria. There is actually a “check and balance” system in place.
Besides this long tube that begins at the mouth and ends at the anus, there are organs involved in your digestive tract. These organs include the liver, pancreas, and gall bladder.
Bacteria in the mouth and stomach
The first line of defense is the saliva secreted by salivary glands into the mouth. Saliva suppresses bacterial overgrowth by first removing bacteria from the mouth, and then sending it into the acidic environment of the stomach. Saliva is constantly cleansing particles from the teeth and gums and cleansing the mouth. In addition, it contains enzymes and antibodies that directly destroy bacteria. In the stomach, bacteria that have made it into the digestive system with our food and beverages encounter hydrochloric acid (HCL).
As a result of the acidity, the bacterial count falls to almost undetectable levels after a meal. Newborn infants and the elderly have less HCL than is normal, and people who are not healthy may find the same thing. Low stomach acid levels allow pathogens to survive. The HCL also aids in digestion by breaking down complex sugars, and the change in pH activates protein enzymes for protein digestion. Low HCL levels open the body up for an increase in pathogens and a decrease in the nutrients that the body digests and assimilates.
There are glands in the stomach that secrete mucus to line the stomach wall, which protects it from the harsh stomach acids and digestive enzymes. In addition, this mucus protects the gastrointestinal tract from abrasion as the food passes through. It is also a barrier that prevents harmful bacteria from attaching to the intestinal wall. People with inflammatory bowel diseases do not have the same healthy mucus that is found in a healthy gut (Quigley and Kelly 1995). It is believed that disease-causing bacteria disrupt the protective mucus layer by degrading it, penetrating through it, and causing ulcers and inflammation.
When the mucosal lining is broken down, the lining of the gut becomes inflamed. Toxic and carcinogenic compounds are also absorbed, while the harmful, multiplying bacteria attach to the intestinal wall. I have found, however, that people who have this problem and take Caucasus Kefir Capsules recover. It seems that the good flora take over and the pathogenic bacterial populations diminish. This allows the lining of the stomach to heal.
I have also noticed that when there is pain, and the mucosal lining is not protecting the body from harmful microorganisms, that the Caucasus Kefir Capsules, along with aloe vera juice (preferably organic), can do wonders. Aloe Vera, Slippery Elm Bark, ground Flax Seeds, and pectin are all both high in soluble fiber and mucilaginous. They help to heal damaged, bleeding membranes that line the intestinal tract and can be very instrumental in the healing process.
Bacteria in the small intestine
The bacteria that survive the high acid content of the stomach then pass into the small intestine. The first section of the small intestine is called the duodenum. Most people develop ulcers in this area. The pancreas and liver dump their digestive enzymes, bicarbonate and bile salts, respectively, in this part of the small intestine.
The digestive enzymes from the pancreas protect us from harmful bacteria such as E. coli, Klebsiella pneumoniae and Shigella (Rubenstein et al., 1985 Sarker and Gyr 1992) by digesting the cells walls of these bacteria.
The bile salts coming from the liver are acidic. They are made in the liver, stored in the gall bladder and released when needed. Bile salts are primarily used for fat digestion and transportation. Yet bile acids are also potent as antimicrobial agents, so much so that they are currently being evaluated for use as antibiotics (Li et al., 1999; Guan et al., 2000). When bile salts are altered within the duodenum, it has been shown to lead to an overgrowth of some bacterial species (Kocoshis et al., 1987). In addition, a substance called lysozyme is secreted by cells that line the digestive tract. Lysozyme is a potent enzyme that attacks bacterial cell walls, and is believed to be another primary control preventing bacterial overgrowth in the upper GI tract.
The environment in the small intestine (unlike the stomach) is more of a neutral pH. This is because of the bicarbonate secreted from the pancreas. This allows for the growth of healthy intestinal flora. So as food travels through the small intestine, it gradually becomes more and more “populated” (Linskins et al 2001). The body’s defense against these organisms is the secreted enzymes and bile sales and the mucus secreted by the cells lining of the GI tract. Peristalsis also helps to keep the bacteria from adhering to the epithelial cells of the small intestines (Kirjavainen, 1999). Constipation, drugs that slow peristalsis, or other problems increase the tendency for the gut to become colonized by harmful bacteria.
The predominant organisms in the small intestine are largely lactobacilli, streptococci, staphylococci and yeasts, although some coliforms and anaerobes are present in low concentrations. What is definitely missing, however, are the normal flora organisms such as Bacteroides and E. coli. These organisms are in very high numbers in the last section of the small intestine, however (Gorbach et al. 1967a; Gorbach et al. 1967b; Gorbach et al 1967c). Bifidobacteria, Fusobacteria and Clostridia are also present in the last section of the small intestine (the ileum). It is here that the organisms greatly rise in number and the gram negative organisms begin to out-number gram-positives (Linskins et al., 2001).
The bacteria that are able to survive the above environment need to be able to adhere to the lining of the intestinal wall. To adhere they must contain adhering proteins, have their own means of locomotion, and be able to multiply rapidly enough to overcome the forward peristaltic movements. Bacteria that fail to meet the criteria for attachment, motility and propagation will pass on into the fecal matter and into the large intestine.
Bacteria in the large intestine
Eventually the small intestine connects to the large intestine. It is here that most normal flora lives and there is a very high bacterial count. Separating the small intestine from the large intestine is the ileocecal valve. This valve prevents the backflow of microorganisms from the colon into the small intestine. In the large intestine there are over 350 different species of bacteria numbering from the billions to the trillions in every gram of dry feces. Over 99% of these organisms die in the presence of oxygen. This class of bacteria is called obligate anaerobes. Bacterial growth here is largely dependent upon the availability of nutrients.
Even though there is extensive digestion and absorption that occurs in the small intestine, many nutrients still pass into the colon not yet completely digested. Interestingly, the very nutrients that stimulate some bacterial species, simultaneously suppress the activities of other bacteria. It appears that the important factors governing bacterial composition within the large intestine are the amount of food eaten and the types of nutrients available to them.
Energy from bacteria?
The bacteria in our intestines obtain their energy by breaking down carbohydrates and proteins – a process called fermentation. The major result of this fermentation process are short-chain fatty acids, containing 2,3 or 4 carbon atoms (Legakis et al., 1982). We supply food for the bacteria through our diet, and they supply us with necessary vitamins and energy, and protect us from disease-causing invaders.
The short-chain fatty acids produced by our gut flora are tremendous sources of energy (Roediger 1980). This energy is used both by the bacteria for growth as by us. The cells that line the intestinal tract get up to 70% of their energy from bacterial fermentation products (Cummings1995). The liver, muscles and all the cells of the body greatly benefit from these short-chain fatty acids. It is estimated that up to 10% of the body’s total daily energy requirements come from these fatty acids (Roediger, 1980).
Nutrients from bacteria?
Bacterial flora in the colon are involved in synthesizing hormone and vitamin precursors. One example is vitamin B12. This vitamin is not found in significant amounts in plant sources (there can be some vitamin B12 on the roots of plants if they are not washed away, and some people believe that spirulina may contain a form of vitamin B12). Instead, it is produced almost entirely by gut bacteria. Vitamin B12 is essentially for red blood cell function and is also required for nerve activities. Deficiencies are not uncommon and they lead to diseases like anemia and painful nerve disorders.
The colon, cancer and microorganisms
Of all the short-chained fatty acids (SCFA’s) produced by intestinal flora, butyric acid sees to be the most important. Numerous studies have shown its affect on the growth and health of intestinal epithelial cells (These are the cells that line the intestinal tract.). In contrast, butyric acid inhibits the growth of cancerous tumors (Siavoshian, 2000). There is a direct relationship between the amount of butyric acid produced in the gut and colon/rectal cancer. It has also been demonstrated that some bacteria in the colon actually neutralize dietary carcinogens such as nitrosamines, which are produced when high protein diets are eaten (Kailaspathy and Chin, 2000).
SCFA’s have been shown through much research to inhibit the growth of disease-causing bacteria like salmonella (Durant, 2000, Rabbani et al. 1999). Short-chain fatty acids lower the pH of the large intestine, which greatly helps to reduce pathogenic bacterial growth in the intestine. In addition, SCFAs have many similar anti-microbial properties as those of medium-chain fatty acids found in oils such as coconut oil. Normal gastrointestinal flora compete with other bacteria for nutrients and for binding sites on the intestinal wall (Kailasapathy and Chin 2000). It is speculated that normal gut flora serve as a final defense against invading disease-causing organisms.
In addition to the short-chain fatty acids produced by friendly flora (“the good guys”), they produce other anti-microbial substances such as peroxides and bacteriocins. Bacteriode organisms in the colon actually produce toxins that selectively destroy the disease-causing Clostridium difficile. Many people suffering from life-threatening, chronic, persistent Clostridium difficle-associated diarrhea have been cured when bacteroides species were replaced in their colons (Borody 2000).
SCFA’s speed the rate of peristalsis, which indirectly removes invading microorganisms, and accelerates their movement through the digestive tract (Kailasapathy and Chin, 2000). When “probiotic” foods such as plantains and pectin are added to the diet, it results in increased growth of good flora, which in turn changes the environment in the intestines (increases SCFA’s), reducing pathogens, and improving diarrhea and inflammation (Rabbani et al., 2001).
Nutrients that promote healthy flora
There are many nutrients studied in human milk that play a protective role in the guts of infants. The roles of lactoferrin (and other glycoproteins), oligosaccharides and iron in altering the microflora have been well studied. There has been a fair amount of research recently with oligosaccharides. This substance is also present in breast milk and concentrations of oligosaccharides in the feces and urine of breast-fed infants are much higher than those found in formula-fed babies. They are complex sugars that appear to act as scavengers, collecting, removing and neutralizing disease-causing bacteria and their toxins. These oligosaccharides promote the clearance of pathogenic organisms. In addition, these substances selectively stimulate the growth of “healthy” gut bacteria and have been given the name “prebiotics.” For more information, read our article on prebiotics.
In general, the bacteria living in the large intestine are living under starvation conditions. Most of the sugars and carbohydrates have been digested and assimilated into the blood stream. Therefore, by the time the remaining food reaches the large intestine there is little “energy” food available. By adding probiotic foods to our diets, we can dramatically increase healthy gut flora. This type of food does not get totally digested and the intestinal flora use it for energy. Most bacteria, including bifidobacteria, lactobacilli, ruminococci, eubacteria, clostridia and bacteroides, prefer to use carbohydrates as their preferred energy sources. They are well-adapted to be able to breakdown complex sugars and synthesize many glycosidase enzymes.
Proteins are found abundantly throughout the entire digestive tract. The breakdown of proteins occurs by digestive enzymes secreted into the digestive tract, and by bacteria-secreted digestive enzymes. Bacteria are very important in their assistance in digesting proteins. When undigested proteins show up in a live blood analysis, this is a strong sign that the person has gut flora issues. Not all flora can breakdown proteins; some can only breakdown carbohydrates.
The important knowledge to gain from all this is:
1. Stomach acids reduce the number of live bacteria in the intestinal tract.
2. Digestive enzymes not only break down food, but also prevent bacterial overgrowth.
3. Bile salts, additionally, helps to provide a line of defense against bacterial overgrowth in the small intestine.
4. The fermentation of our food by friendly flora creates B vitamins and other nutrients that we need are difficult obtain from our food.
5. The fermentation of our food by friendly flora creates short-chain fatty acids (which our bodies use for energy), inhibits the growth of pathogenic bacteria, and aids in the health of the cells lining the intestinal tract.
6. Peristalsis, the constant movement throughout the digestive tract, helps to prevents bacteria from adhering to the epithelial cells of the small intestine.
7. A lack of digestive enzymes and abnormal gut flora is directly related to gut inflammation, allergies, asthma, eczema etc.
Meet the family that should be living inside us
Gram negative bacillus (rods) obligate anaerobes (can not survive in the presence of oxygen)
The major organisms in this category are in the bacteroides genus. These are the bacteria that make bacteroicins or toxins to inhibit the growth of other bacterial species. Fusobacterium also fit into this category and are commonly found in the colon. These organisms are the ones that produce butyric acid, which is a major short-chain fatty acid that we use for energy and many other benefits.
Also in this category are bacteria such as Eubacterium, Lactobacillus and Bifidobacterium. These three species are capable of digesting a wide variety of substances such as cellulose, mucin, polysaccharides (complex carbohydrates) and proteins. Like Fusobacterium, the major metabolic product from Eubacterium is butyric acid. Lactic acid is the most abundant byproduct of lactobacilli and bifidobacteria. These species also produce peroxides and bacteriocins. The overall effect of these products is an acid environment with anti-microbial activity which inhibits the growth of pathogenic bacteria. In addition, these bacteria compete with pathogens for attachment sites on the walls lining the intestinal tract. This is called competitive exclusion.
Most people firmly believe that these organisms are essential for good intestinal health. Lactobacillus and Bifidobacterium species are used in most studies that have been done with probiotics and disease. These are an important category of normal flora.
Gram positive cocci
Peptostreptococci and enterococci are members of this family. They reside in the large intestine and account for approximately 10 billion organisms per gram of fecal material. All these strains found in the intestines are resistant to an acidic environment, and they actually produce acetic acid as a major metabolic byproduct (Onderdonk, 2000).
Spore-forming Gram Positive Bacillus (Rods)
Clostridium species are found in the intestinal tract, but their numbers are usually under 100 million organisms per gram of fecal matter. These bacteria are harmless, yet they are capable of producing toxins that can damage the intestinal tract. Clostridium difficile is the most important disease-causing anaerobic microorganism acquired in hospital settings (Onderdonk, 1000/ Kelly et al., 1994).
These organisms rarely cause problems unless changes occur in the gastrointestinal environment, such as what happens with antibiotic therapy. Clostridium difficile is suppressed by good bacteria, but when these organisms are killed off, it has the chance to proliferate and produce toxins that cause abdominal cramps, bloody and mucus-filled diarrhea, fever, weight loss, yellow plaques on the intestinal wall, etc. Failure to obtain prompt treatment when Clostridium difficile is overgrown can lead to a very toxic intestinal tract and even death.
Coliforms
Enterobacteriaceae bacteria are probably the most widely studied group in the large intestine. This group includes Escherichia coli (E. coli). These bacteria are closely monitored by water treatment facilities, and swimming beaches. Normally, these bacteria only cause disease when they get outside the intestinal tract. Examples of infections caused by enterobacteriacea include those of the abdominal cavity that occur following an injury to the intestinal tract, pelvic inflammatory infections, urinary tract infections, or injections in newborn infants.
In recent years, the spread of disease-causing E. coli of the 0157:H7 genus has caused considerable concern for the general public. It is this genus that has caused several deaths due to contaminated food in restaurants during the past decade. However, under normal circumstances, within the confines of the intestinal tract, the total number of enterobacteriacea are kept under control by butyric acid produced by other microbial species. Fortunately, these organisms typically do not migrate, but tend to remain relatively localized in the digestive tract (Onderdonk, 2000).
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