Would you agree with me if I defend, bacteria are more of a gem and less of a germ; Bacteria keep us healthy most of the time rather than producing disease.
It is a common perception that bacteria make you sick. Of course, certain bacteria at certain times on specific organs cause infection and produce disease. Bacterial infections and associated diseases are awful experiences with multiple visits to the hospitals, blood tests, urine tests, antibiotics, sick leaves, etc. and these bad memories fade out more slowly than the good ones.
Do bacterial encounters always result in these miseries? Are they the villains of our life? I would like to differ and put the accusation on us. We always considered bacteria in the framework of disease.
Do you want to know Why bacteria infect us?
?Some people do have a more positive outlook, but almost everyone remembers negative things more strongly and in more detail,? said Clifford Nass, professor of communication, Stanford University. We always remember the dropped catches and missed goals than the wonderful matches.
The confrontation between the bacteria and the human host will result in one of the following outcomes,
Bacteria produce disease
Bacteria lives and multiplies on or inside the human body, but in turn, always produce disease. They are called strict pathogens. Strict pathogens are always associated with the disease.
Mycobacterium tuberculosis?is a strict pathogen causing an infectious disease called Tuberculosis (TB). Tuberculosis generally affects the lungs, but can also affect other parts of the body.
Bacteria do not produce disease
Bacteria lives and multiplies on or inside the human body without interfering in normal body functions and producing any disease. They are called the normal flora or commensal microbes. There are two types of normal flora, namely transient and resident microbes.
The normal flora colonizing the human body transiently is called transient microbes. They just pass through although they might attempt to colonize permanently. Transient flora is unable to stay in the body for a long time or permanently due to the difficulty in competing with established resident flora or the changes within the body that discourage growth. Moreover, they could be cleared by the host immune system.
e. g., Staphylococcus aureus,?Clostridium perfringes,?etc. are the transient flora of the hands by direct skin to skin contact or indirectly by objects.
The normal flora colonizing the human body permanently is called the resident microbes.
e. g., Staphylococcus epidermidis on the skin,?Staphylococcus aureus on the upper respiratory tract,?Enterococcus sp. in the small intestine,?Bifidobacterium?in the large intestine.
Although the normal flora does not cause any disease, certain members are capable of producing disease on an opportunity. However normal flora serves us in numerous ways.
Benefits of the normal flora
- Metabolism of food
- Vitamin synthesis
- Keeping the bad guys away
- Supporting the immune system
1. Metabolism of food
Carbohydrates are an important part of the human diet which varies from the healthiest source of whole grains, vegetables, beans to the unhealthiest source of pastries, soda, sweets, etc.
The simple sugars such as glucose are easily absorbed in the proximal gastrointestinal (GI) tract. The disaccharides such as lactose are broken down into their corresponding monosaccharide components such that they too can be absorbed by the GI tract.
However, a significant portion of the dietary carbohydrates, including complex plant-derived polysaccharides and starch, escape the digestion in the GI tract. To utilize these carbohydrates, it needs to be broken down into their component simple sugars by the enzymes and unfortunately, many of these enzymes are not encoded in the human genome.
Here comes the dense bacterial population colonized in the GI tract with their well-equipped pieces of machinery. Many of the enzymes required to breakdown and utilize the dietary substrates are encoded in the bacterial genome and they produce those enzymes to help in our digestion.
Moreover, in this process of breaking down the complex carbohydrates by the anaerobic bacteria in the large intestine, we get some bonus as well. Short-chain fatty acids are accumulated in the intestine as a result of this process. The main short-chain fatty acids found are acetate, propionate, and butyrate which are of high nutritional value.
Acetate is important for the skeletal and cardiac muscle, butyrate is important as it drives the energy for the colonic epithelium. Propionate is transported to the liver. These short-chain fatty acids also impact water absorption, local blood flow, etc.
The normal flora in the GI tract also plays an important role in protein metabolism by influencing the nitrogen balance by the amino acid synthesis and intestinal urea recycling.
2. Vitamin synthesis
Vitamins are essential micronutrients required to sustain life. Most of the vitamin requirements are met by the diet. The gut microbiota adds its contribution to vitamin production. The normal flora in the gut can synthesize vitamin K and most of the water-soluble B vitamins.
3. Supporting the immune system
The normal flora has a significant role in the induction, training, and function of our immune system and in turn, the immune system evolved widely as a way to maintain the commensal relationship with the host and the diverse population of microbes. The alliance of the immune system and microbiota allows the induction of protective responses against pathogens (disease-causing microorganisms).
The normal flora acts as antigens within us and induces an immunological response particularly antibody-mediated response. The production of low levels of antibody against the components of the normal flora reacts with certain related pathogens thereby preventing infection or invasion.
Normal flora also plays an important role in the maintenance of tolerance to self-antigens.
Changes in the diet and overuse of antibiotics attributed to the lack of diversity in the normal flora required to maintain a balanced immune system which in turn leads to the rise in autoimmune diseases such rheumatoid arthritis, multiple sclerosis, etc.
Therefore whenever you don?t get sick, it’s not just your immune cells that make you immune to the infections or diseases, it?s the team of normal flora and immune system working together for you.
4. Keeping the bad guys away
One of the main factors attributed to the infection or disease produced by the pathogen (disease-causing bacteria) is the infective dose (ID) of the pathogen. The infective dose is defined as the quantity of pathogen (measured in the number of organisms) that is necessary to cause infection in a susceptible host.
The infective dose of some pathogens is low, for example, some strains (enterohemorrhagic strains) of?E.coli?require?an infective dose of only about ten cells. While other pathogens have high infective doses, for example,?Vibrio cholera?requires a large number of cells (approximately 103 to 108) to successfully infect the host and produce disease.
The normal flora is so diverse and large in number they compete with the pathogens for the attachment sites or essential nutrients so that pathogens cannot multiply in the host and reach their infective dose to cause infection. This pattern is highly demonstrated in the oral cavity, the intestine, the skin, and the vaginal epithelium.
In some research experiments, the germ-free animals (animals that lack the normal flora) were infected by 10?Salmonella?bacteria, while the infectious dose of?Salmonella?is nearly 106 cells.
Furthermore, the normal flora can produce relatively nonspecific fatty acids to highly specific toxins to inhibit or kill the nonindigenous species.
Benefits of microbes other than normal flora
Some other bacteria work humbly 24/7 outside the human body to make our life easier and better on this planet.
Bacteria are nature?s little recyclers working in the soil and ocean to decompose organic matter and the cycling of carbon and nitrogen which are necessary chemical nutrients for human life. Certain soil bacteria convert the atmospheric nitrogen into ammonium or nitrates that the plants can absorb to create amino acids and nucleic acids. Humans and animals eat the plants and get the benefits.
They are placed as chefs in many of the food industries. Dairy products such as yogurt and cheese are produced by the fermentation of milk by bacteria (lactic acid bacteria). Bacteria are assigned specific tasks in the chocolate industry, the meat industry, and the wine industry.
The pharmaceutical industry would be indebted to the bacteria for the large scale production of riboflavin, vitamin K, antibiotics, insulin, and other growth hormones, etc.
Bacteria are commissioned at the petroleum industry for the decomposition of petroleum products. The hydrocarbon-oxidizing bacteria are employed to mop up oil spills.
Waste management industries are also benefited by the process of biodegradation. Bacteria are used in agriculture as in the composting process and as pesticides. Certain bacteria are used to separate fibers of jute, hemp, and flax in the process of retting. The manufacturing of chemicals such as ethanol, acetone, organic acids, and perfumes are also attributed to the bacteria.
In a nutshell, bacteria are the greatest biologist, chef, engineer, garbage collector, chemist, and agriculturist. Without bacteria life is impossible. We always contemplate the possibility of destroying the bad microbes; rather it would be even great to take care of the good ones.
Anne Maczulak, a microbiologist and author of the book “Allies and Enemies: How the World Depends on Bacteria” said as long as humans can’t live without carbon, nitrogen, protection from disease and the ability to fully digest their food, they can’t live without bacteria.