In today’s class, we will discuss microorganisms around us.
Micro-Organisms Around Us
Micro-organisms, Fungi, Bacteria, Viruses, Protists
Microorganisms are tiny organisms that cannot be seen with the naked eye except with the aid of a microscope. Anthony Van Leeuwenhoek (1632 – 1733) was the first scientist to discover microorganisms with his newly invented microscope.
Microorganisms are dreaded as disease-causing agents (germs). However, many of them are beneficial to man, e.g. saprophytic microbes that bring about the decay of organic matter. Those microorganisms that have negative effects on humans are called pathogens.
Micro-organisms are found everywhere – in the air, water, soil, in our food, on our food, on surfaces of objects, and on and inside living organisms, on our bodies, inside of our bodies and on our clothes, everywhere.
Microorganisms can be grouped into the following:
Bacteria
Viruses
Some algae
Protozoa
Some fungi
Most microbes are unicellular, but some, like fungi and algae, are multicellular. Microorganisms form spores during the adverse season. When the favourable season comes, the spores are released, carried in the air and on landing on a suitable substrate, grow and produce more spores.
Bacteria:
Bacteria can be seen with the use of a light microscope and have a simple structure. It is unicellular. It is a prokaryotic cell i.e., it does not have a true nucleus. Hereditary materials are contained in a strand of DNA (Deoxyribonucleic acid) inside the cell.
Bacterial cells are typically surrounded by a rigid, protective cell wall. The cell membrane, also called the plasma membrane, regulates the passage of materials into and out of the cytoplasm. The DNA, located in the nucleoid region, contains the genetic information for the cell. Ribosomes carry out protein synthesis. The flagellum, found in numerous species, is used for locomotion.
Some bacteria contain one plasmid, a small chromosome with extra genes. Others have a capsule, a sticky substance external to the cell wall that protects bacteria from attack by white blood cells.
Types of bacteria
Bacteria can be grouped based on the following:
Oxygen requirement
Shapes
Gram’s staining technique
Based on the oxygen requirement
Aerobic Bacteria: This group of Bacteria uses oxygen in respiration e.g., Vibrio cholerae.
Obligate anaerobes: This group of bacteria does not utilize oxygen in respiration e.g. putrifying bacteria.
Facultative anaerobes: These are bacteria that can exist in two states e. they can use oxygen and they can also do without oxygen.
Based on shape
Cocci:– This group is round.
Bacilli:- They have a rod-like shape.
Spirillae:- These are spiral.
Vibrios:- They are comma-shaped.
Flagellated Spirochaetes:- Some bacteria have a whip-like structure called flagella that affects their movement.
Based on Gram’s staining technique
Gram-positive bacteria retain the purple/violet stain in their cells. (Needed during the culture of bacteria)
Gram-negative bacteria: lose or do not retain the purple stain in the cells
Viruses:
They are unicellular and they have no nucleus, cytoplasm or cell membrane. They are smaller than bacteria and can only be seen under an electron microscope. Viruses lack life. Thus, they cannot respire nor carry out metabolism. They can only survive inside living cells.
Fungi:
These are non-green, simple plants. They feed Saprophytically or parasitically. Saprophytic fungi such as Mucor, yeast, and Penicillium are useful to man. Parasitic fungi cause diseases that are unpleasant to humans. An example of animal diseases caused by fungi is Ringworm, Athlete’s foot, mouth thrush, candidiasis, etc. Plant diseases caused by parasitic fungi are mildew, spots, and wild, blights and Rots.
Protozoa:
These are unicellular microscopic animals. They are found in damp soil and water. Some of them are parasitic while others live freely in their habitat.
Examples of parasitic protozoa are Trypanosoma, Plasmodium, etc. Examples of free-living Protozoa are: Amoeba, Paramecium, etc. Parasitic protozoans are pathogens that cause diseases like Malaria, sleeping sickness, Bilharziasis etc.
Algae:
Algae are mostly free-living microscopic plants. They survive in a wide range of habitats such as wet soil, freshwater, sea, etc. They have chlorophyll with several other pigments, giving rise to green algae, brown algae, blue/green algae, etc. Examples of algae are Spirogyra, Volvox, Chlamydomonas, Nostoc, Diatoms, etc.
Next class, we will discuss the Concept of Culturing. We hope you enjoyed the class. Send your questions in the comment section below and we will respond.