• A microorganism, or microbe is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells and live in water, soil, and in the air.
• The most common types are bacteria, viruses and fungi.

What are the beneficial effect on mankind ?

• Gut Microbiota: The gut bacteria are able to produce a variety of vitamins, synthesize all essential and nonessential amino acids, and carry out biotransformation of bile. They are crucial in digestion, nutrient absorption, and immune system function contribute to overall health and well-being.
• Probiotics: Probiotics are live microorganisms that are intended to have health benefits when consumed or applied to the body. They can be found in yogurt and other fermented foods, dietary supplements, and beauty products.
• Fermentation: It is the process in which a substance breaks down into a simpler substance. Microorganisms like yeast and bacteria usually play a role in the fermentation process like creating beer, wine, bread, kimchi, yogurt and other foods with increased nutrient bioavailability.
• Bioremediation: It employs the use of living organisms, like microbes and bacteria to decontaminate affected areas. It is used in the removal of contaminants, pollutants, and toxins from soil, water, and other environments through enhacing human and surrounding health.
• Antibiotic Production: Many antibiotics are derived from microorganisms, such as penicillin from Penicillium. These drugs are essential for treating bacterial infections and have saved countless lives.
• Biotechnology and Pharmaceuticals: Biotechnology is often used in pharmaceutical manufacturing. Notable examples include the use of bacteria to produce things such as insulin or human growth hormone.
• Human Microbiome: They play an important roles in the maintenance and development of the human body (Figure 3). These organisms are responsible for launching the immune system, affecting inflammatory homeostasis and immune regulation in neonates and young children
• Nitrogen Fixation: In order for plants and humans to get the nitrogen they need, the nitrogen must be converted into ammonia to NH3. The conversion of this atmospheric nitrogen to the usable form of ammonia is known as nitrogen fixation. Ex: Azotobacter, Bacillus, Clostridium, and Klebsiella

Harmful effect on mankind

• Infectious Diseases: Bacteria are responsible for a wide range of infectious diseases, including pneumonia, tuberculosis, cholera, and food poisoning. These diseases can cause illness, discomfort, and, in severe cases, lead to death.
• Antibiotic Resistance: The most serious concern with antibiotic resistance is that some bacteria have become resistant to almost all of the easily available antibiotics. These bacteria are able to cause serious disease and this is a major public health problem. Important examples are: methicillin-resistant Staphylococcus aureus (MRSA)
• Food Spoilage: Bacteria can cause food spoilage by breaking down the food, producing acids or other waste products during this process. Harvested crops decompose from the moment they are harvested due to attacks from microorganisms.
• Issues on Human health: They can cause skin infections, such as boils, cellulitis, and impetigo. Certain bacteria in the mouth can contribute to dental decay and gum disease. These conditions can lead to tooth loss and other oral health problems.
• Environmental Contamination: Lack of clean water supply, sanitation and hygiene (WASH) are major causes for the spread of waterborne diseases through bacteria. Ex: cholera
• Nosocomial Infections: Hospitals and healthcare settings can be sources of healthcare-associated infections caused by bacteria. These infections can be especially dangerous for patients with compromised immune systems.