Microorganisms – Good and Bad Bacteria, Probiotics

July 4, 2019 0 Comments

Microorganisms are extremely small unicellular living things that are invisible to the naked eyes. They can be only visible through specialized instruments like microscopes. Microbes or microorganisms are present everywhere around us including within our body, most are useful and serves various purposes to the environment whereas others are harmful and cause various diseases to plant, animal and the human body.

Types and Examples of Microorganisms

Microorganisms can be divided into six main categories namely,


Archaebacteria are prokaryotes that contain pseudo-peptidoglycan within their cell wall and survive in extremely harsh environmental conditions. They can be divided into 4 major types namely, methanogens (methane-producing archaea), halophiles (archae that survive in extremely salty environments like ocean floor), thermophiles (archae that can survive in extreme temperatures like hot springs) and psychrophiles (those that can survive in extremely cold temperature like Arctic bed).


Fungi like fungus, mushroom, and molds are eukaryotic (contains a true nucleus), spore-forming multicellular organisms with the chitinous cell wall. They obtain their nutrition either by decomposing dead, decaying organisms; or by establishing symbiotic relations with other organisms like lichens; or by living at the cost another host organisms (parasitic relation). They are formed of microscopic hair-like structures called hyphae that intertwine with each other to form mycelium.


A virus can be defined as an intermediate between living and non-living things. They are acellular simple proteins with a nucleic acid (DNA OR RNA) core. They parasitic in nature and can multiply only within their host by using the host mechanism. Viruses can infect both prokaryotic and eukaryotic cells and cause many diseases.


Protozoa are single-celled, eukaryotic organisms. They can either be autotrophs (produce their own foods) or heterotrophs (depend on another organism for nutrition). They have a cellulose cell wall. They are divided by their mode of locomotion. Some contain flagella and locomote by whiplash movement, others contain miniscule hair-like cilia and move by beating movement while amoeboids move by pseudopods or false foot. Sporozoans are non-motile protozoa.


Algae are green microorganisms that can be single-celled or multicelled eukaryotes. They can perform photosynthesis and produce oxygen, carbohydrate, and other nutrients that add to the environment. They exist in a damp atmosphere like swamps, water bodies. Cyanobacteria or blue-green algae are considered to be the forerunner of present-day green plants.


Bacteria are unicellular, prokaryotic (the true nucleus is absent) organisms with the significant cell wall structure. They can be divided into gram positive and gram negative types depending on their cell wall structure. Gram-positive ones contain thick peptidoglycan layer whereas gram-negative ones contain a thin layer of peptidoglycan with an outer membrane. This particular outer membrane is toxic to the human body.

Bacteria can live freely in oxygen (aerobes), without oxygen (anaerobes) or can exist both in the presence or absence of oxygen (facultative anaerobes).


Bacteria are very essential to our living. Our body contains both bad and good bacteria, whose fine balance is essential to maintain the proper functioning of our body.

Bad bacteria are those that cause harm to our body like Staphylococcus, a natural resident of our skin can cause severe pneumonia in immune-compromised persons. P.gingivalis which causes gum disease may cause pancreatic cancer. Streptococcus mutans cause teeth plaques. Vibrio sp causes diarrhea, Clostridium causes gas gangrene, Salmonella causes typhoid. These bacteria colonize the body secreting toxic chemicals causing diseases.

Good bacteria are beneficial bacteria that fight against invading harmful bacteria by competing with them for space and resources. Newborn babies receive these bacteria from their mothers. The natural bacterial flora that colonizes the respiratory and digestive tract of our body balance our immunity by thwarting invading pathogens and repairing damaged tissues. Others even help to break down complex sugars and fats and neutralize toxins.

By preventing the growth of disease-causing pathogens, it, in turn, helps to eliminate the harmful autoimmune disease. Autoimmune disease is caused when the immune system fails to recognize own tissue, as a result, the white blood cells infiltrate the body causing chronic inflammation. This may lead to carcinogenic growth like celiac diseases or colon cancer.


Most bacteria colonize our skin, mouth, and gut. They perform a various beneficial role within the human gut like digesting complex foods, secrete essential vitamins and enzymes and help absorbing water. They most importantly prevent the attachment of harmful bacteria to the human intestine preventing various gastrointestinal diseases. These beneficial gut bacteria are called probiotics like Lactobacilli, Bifidobacteria, Saccharomyces boulardii, Caulobacter.

With the rise of our unhealthy lifestyle, an increase of processed and fast foods, lack of contact with environment boosting the body’s immunity, this fine balance of good and bad bacteria has got disrupted. Hence, it is more advised by medical professionals that we incorporate probiotic containing foods within our diet. This can be achieved by consuming probiotic-rich foods like yogurt, kombucha (fermented tea), kimchi, sauerkraut, miso, kefir, and others. One can even consume probiotics in the form of capsules and powder available in the market.

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