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INTRODUCTION Microorganisms occur in large numbers of most natural environments and bring about many changes. Some are desirable and others are undesirable. Microorganisms affect the well being of people in many ways. Many are beneficial to man and can be called ‘friends’ while some are harmful and can be regarded as ‘foes’ to man. The beneficial impact of microorganisms ranges from the production of goods and pharmaceutical products, to enhancement of soil fertility, environmental cleanup while their harmful effect can be seen in their ability to cause disease in man, animals and plants as well as their usage in biological warfare. However, there are more species of microorganisms that perform friendly and beneficial functions than those that harm other living organisms. This unit gives us a brief survey of microorganisms as friends and foes. Microorganisms as Friends Microorganisms have found application in various aspects of life. They are useful in food industries to produce many ...

INTRODUCTION Microbiology is the study of organisms too small to be seen distinctly with the unaided eyes. The nature of this discipline makes the microscope of crucial importance because the study of microorganisms is impossible without the microscope. Microscopes provide magnification which enables us to see microorganisms and study their structures. The magnification attained by microscopes range from x100 to x400,000 in addition there are different types of microscopes and many techniques have been developed by which specimens of microorganisms can be prepared for examination. This unit examines the different types of microscopes, how the microscopes work and how specimens are prepared for examination. The Microscope A microscope is an instrument for producing enlarged images of objects too small to be seen unaided. Types of Microscopes Microscopes are of two types: Light (optical) and  electron depending on the principle on which magnification is done.  The Light Micros...

INTRODUCTION Modern microbiology is a large discipline with different specialised areas. This is because the entire ecosystem depends on the activities of microorganisms and microorganisms influence human society in countless ways. Microbiology has a great impact on medicine, agriculture, food science, ecology, genetics, biochemistry and other fields. In this unit, we shall examine the different aspects of microbiology and their relevance to human life. Main Branches of Microbiology Microbiology has two main branches:  Basic   Applied  Both branches intertwine and are complementary to each other. The Basic Aspects of Microbiology The basic branch of microbiology is concerned with the study of the biology of microorganisms. Fields of study here include: Bacteriology: This is the study of bacteria.  Mycology: The study of fungi such as yeasts, molds, and mushrooms.  Algology: The study of algae.   Protozoology: The study of protozoa; a branch of pro...

INTRODUCTION Bacteria are characterised based on the cell shape, size and structure cell arrangement, occurrence of special structures and developmental forms, staining reactions and motility and flagella arrangement. They are also characterised by the cell wall component, Gram stain reaction, cellular respiration and mode of nutrition. This unit examines the general characteristics of bacteria, shapes and forms of bacteria, structures external and internal in bacteria among other things. General Characteristics of Microorganism General characteristics of bacteria: They are prokaryotic  They are simplest of all microbial cells   Bacteria are single celled organisms  They have distinctive cell wall which contain peptidoglycan They are measured in unit called micrometer   Bacteria lack a true nucleus but have a region called the nucleroid region, i.e. DNA is free floating  They may have additional DNA called a plasmid  Their reproduction is by binar...

 INTRODUCTION Fungi are eukaryotic spore bearing organisms that lack chlorophyll and generally reproduce both sexually and asexually. They are of great practical and scientific importance. One of the reasons for this is that many fungi are of microscopic cellular dimensions. Fungi have a diversity of morphological appearances depending on the species. Fungi comprise the molds, mushrooms and yeasts. Molds are filamentous and multicellular while yeasts are unicellular. They are widely distributed and found wherever moisture is present. They are of great importance to man in both beneficial and harmful ways. This unit examines the general characteristics of fungi, the distribution, morphology, nutrition and reproduction of fungi. Definition of Fungi Fungi are eukaryotic spore bearing organisms that lack chlorophyll and generally reproduce both sexually and asexually. Distinguishing Characteristics of Fungi They are large, diverse and widespread group of organisms, the molds, mushrooms...

 INTRODUCTION Viruses are acellular entities. They are genetic elements that cannot replicate independently of a living cell called the host cell. Viruses have extracellular forms which enable them to exist outside the host for long periods. But to multiply, they have to enter a cell in which they can replicate causing infection. Viruses are the most numerous microorganisms on earth and infect all types of cellular organisms. The study of viruses is known as virology. This unit examines the general characteristics of viruses, their structures, genomes, symmetry, replication in hosts and purification.  Definition Viruses are simple acellular entities that can only reproduce within living cells.  General Characteristics of Viruses They are the smallest microorganisms. They range in size from 10 to 400mm in diameter and can only be viewed under an electronmicroscope.  They are acellular, i.e. not cellular and non living.   They only reproduce when present wit...

INTRODUCTION Algae (singular, alga) are unicellular microorganisms that have chlorophyll and are photosynthetic. Algae are heterogeneous and range from microscopic unicellular forms to macroscopic seaweeds. They are different from green plants due to their simple reproductive structure for sexual reproduction. Many live in aquatic environments but many also thrive as subterranean algae. Algae are of great importance to biologist because single algal cells are complete organisms capable of photosynthesis and the synthesis of other compounds which constitute the cell. The study of algae is known as phycology. This unit examines the general characteristics, the distribution, the morphology and importance of algae. General Characteristics of Algae Algae are eukaryotic microorganisms.  They are photosynthetic microorganisms.   Chlorophyll and other pigments are found in membrane bound organelles known as chloroplasts. Algae contain a discrete nucleus. Other inclusions are star...

INTRODUCTION Microbiology is the study of microorganisms. These are organisms too small to be seen clearly by the unaided eyes. Microorganisms include bacteria, fungi, algae, protozoa and entities at the borderline of life that are called viruses. The cell is the fundamental unit of life. Most microorganisms are unicellular, in unicellular organisms all the life processes are performed by a single cell. However, some are multicellular, having more than one cell. This unit examines the definition of microbiology, types of microbial cells, the different groups of microorganisms and the domains in which they are placed and why viruses are not placed in any of the domains Microorganisms Microorganisms are organisms too small to be seen clearly by the unaided eyes. They are very small life forms so small that individual microorganisms cannot be seen without magnification. They include fungi, bacteria, algae, protozoa and viruses. Some microorganisms however, like the eukaryotic microorganis...

INTRODUCTION The history of microbiology is the story of men and women who developed a technique, a tool or a concept that was generally adopted in the studying of microorganisms. It is also the history of events and metamorphosis of microbiology as a science. In this unit we will be studying the stages in the development of the science of microbiology, some early scientists and their contributions to the field of microbiology. Discovery of Microorganisms  The advent of the microscope permitted the studying of microorganisms. The first microscopes were simple ground glass lenses that magnified images of previously unseen microorganisms. Among the first to observe this previously unseen and invisible microbial world were Robert Hooke and Anthony Van Leeuwenhoek. Robert Hooke (1635-1703), an English mathematician and natural historian.  * He coined the term “cells” to describe the “little boxes” he observed in examining cork slices with a compound microscope. * He was the first...

Introduction Viruses are extremely small organisms. They are even smaller than bacteria. You know that you cannot see bacteria with your naked eyes. You can see bacteria with an optical microscope but you cannot see virus with optical microscope. There is a kind of microscope called electron microscope, it uses electron beam instead of light. With will learn how scientists came to know about the existence of viruses, their way of behaviour and why it is difficult to treat them. It is difficult to say you are given a particular kind of drug to someone suffering from a disease caused by viruses. Example is the HIV virus.  Discovery of Virus Some tobacco plants infected with mosaic disease were crushed, the juice was passed through a very fine filter. The filter was fine enough to trap bacteria. The filtrate which was supposed to be pure was applied to a healthy leaf of a healthy plant. The disease Mosaic was induced in the leaf. This baffled scientists, before this time they knew abo...