Grade 8 Science Microorganisms

Microorganisms are living creatures and we cannot see them to our naked eye. They are uni-cellular or multi-cellular in nature and we need a microscope to observe these tiny creatures. Did you know that they form the largest number of living organisms on this earth? Fascinating isn’t it? Algae, bacteria, fungi and protozoans (examples: amoeba, paramecium) can be cited as examples for the microorganisms.

Microorganisms are able to exist and survive in all environments. All environments such as the atmosphere, aquatic environments, soil and living organisms are home of microorganisms. There is a vast biological diversity among these creatures and they have differences in their morphological features and means of feeding.

Effects caused by micro-organisms can be both favorable and unfavorable to human beings. The favorable effects are used in several industries that are engaged in the production of cheese, yogurt, curd, food (example: Mushrooms – bodies of fungus), bakery products, anti-biotics, vaccines, vinegar, compost, biogas and etc. It should be noted that yeast (a fungus) is used in the production of bakery products where its activity produces carbon dioxide and this results in the rising of the dough. When the product is being baked, ethyl alcohol evaporates. The microorganism activity influences the environmental balance and helps to establish its well-being. This is made possible through their ability to decompose dead plant and animal matter.

We know that pests are a major threat to crops and micro-organisms are used as a biological method to control the pests.
Micro-organisms cause unfavorable effects too.

Spoilage of food is one of those effects where the microbial activities (enzymes produced by the microbes) change properties such as color, texture, odor, nutritional value, taste and appearance of food. For example, we observed fungi on the slice of bread which we kept for a few days after spraying some water on it. Therefore, microbial growth causes food spoilage just as the fungus spoiled the bread. When food is exposed to suitable temperature and moisture, microbes grow rapidly and act on it. As room temperature is favorable for the growth of microorganisms, it accelerates food spoilage.
Moreover, the activity of micro-organisms can be cited based on the food type on which they
react.

      Fermentation - food rich in sugars
      Putrefaction - food rich in protein
      Rancidity - food rich in fats

 

Thus, it can be stated that favorable temperature, moisture, nutrients and pH values are crucial for the growth of microbes and when these factors are controlled, we can reduce the microbial activity. That is why we preserve food in a refrigerator as the two major factors that support microbial growth; moisture and temperature are controlled in the refrigerator. Infectious diseases can be termed as another harmful effect of micro-organisms. They cause such diseases to man, animals and plants.

 

> Infectious diseases caused to man

   o Virus
           - Chickenpox, COVID-19 (Corona Virus disease 2019), Common cold, Dengue,
           - AIDS (Acquired Immune Deficiency Syndrome), Measles.

   o Bacteria
           - Cholera, Leprosy, Tetanus, Tuberculosis, Typhoid fever.

   o Protozoa
           - Malaria, Public and head lice, Amoebiasis, Scabies, Tapeworm infection.

    o Fungi
           - Pityriasis, Sores, Fungal meningitis, Ring worm.

> Infectious diseases caused to animals
 

     o Virus - eg: Rabies, Monkey pox, Foot and mouth disease
     o Bacteria – eg: Q fever, Glanders
     o Protozoa – eg: Theileriasis
     o Fungi – eg: Aspergillosis , Candidiasis

 

> Infectious diseases caused to plants
   

     o Virus – eg: Tobacco mosaic virus, Curly top, Spotted wilt
     o Bacteria – eg: Bacterial wilt,
     o Protozoa – eg: Phytomonas
     o Fungi – eg: Leaf curled sickness, Rot, Oak wilt, Rust, Scab

 

Microorganisms also cause harm to the surfaces of objects like wood, clothes and walls of buildings and it not only destroys the objects, but these damages incur high costs and affect the economy negatively.
 

On final note, we can come to a conclusion that microbial growth takes place in the event that the required nutrients, temperature, moisture and pH value are available in the given environment. When these factors are controlled, their growth also can be minimized.
Microorganisms cause both positive and negative impacts on human beings.

 

 

 

 

 

 

 

By Mekhala Egodawele

Photo source : Internet