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Introduction to Microbiology

• Microbiology is the study of small, living organisms that show the most basic properties of life.
• These simple organisms can help us understand higher forms of life.

Viruses

• Viruses are not considered living organisms, but they show signs of life in the presence of a living cell.
• Viruses are smaller than cells, and are composed of genetic material (DNA or RNA) surrounded by a protein coat.
• Viruses can only reproduce inside a host cell, and they do not carry out metabolic processes on their own.
• There are different types of viruses, including:
  • Bacterial viruses (bacteriophages)
  • Plant viruses
  • Human and animal viruses

Properties of Viruses

• Viruses can cause disease, but some are harmless.
• Viruses can be mutated to produce different strains.
• Viruses can be affected by the environment in which they grow.
• Viruses can vary in virulence (ability to cause disease).

Classification of Viruses

• Viruses are classified based on the type of host cell they infect.
• Examples of virus classifications include:
  • Bacterial viruses (bacteriophages)
  • Plant viruses
  • Human and animal viruses

Bacteriophages

• Bacteriophages are viruses that infect bacteria.
• They have a protein coat and a core of genetic material (DNA or RNA).
• Bacteriophages can be used to combat bacterial diseases.
• However, using phages to combat disease is still a developing area of research.

Human and Animal Viruses

• Many diseases are caused by viruses, including:
  • Chicken pox
  • Measles
  • Warts
  • Virus pneumonia
  • Yellow fever
  • Cold sores
  • Fever blisters
• Viruses can cause cancer, and researchers are studying the link between viruses and cancer.

Bacteria and Related Organisms

• Bacteria are the most common form of life on Earth.
• They are found almost everywhere, including:
  • Air
  • Water
  • Soil
  • Food
  • The bodies of plants and animals
• Bacteria are thought to have been the first form of life on Earth.
• They are capable of taking energy from various sources, including:
  • Iron
  • Sulfur
  • Nitrogen compounds

Louis Pasteur and the Birth of Bacteriology

• Louis Pasteur was a French scientist who made significant contributions to the field of biology.
• He is credited with:
  • Developing the first vaccine for rabies
  • Defeating the theory of spontaneous generation
  • Studying fermentation and its role in the production of alcohol and lactic acid
  • Developing the germ theory of disease, which states that bacteria can cause disease

What are Bacteria?

• Bacteria are small, single-celled organisms that are classified in the kingdom Protista.
• They are typically measured in millimicrons (mµ).
• There are different shapes and forms of bacteria, including:
  • Sphere-shaped (coccus)
  • Rod-shaped (bacillus)
  • Spiral-shaped (spirillum)

Structure of Bacterial Cells

• Bacterial cells have a cell wall that gives them their shape.
• They have a thin plasma membrane that surrounds the cytoplasm.
• They have a nuclear area that contains chromatin bodies made up of DNA.
• They do not have mitochondria, but have respiratory enzymes on or near the cell membrane.
• They have a slime layer that surrounds the cell and helps them to stick to a food supply or host cell.### Bacteria
• The capsule of bacteria is a key factor in their virulence, with forms that produce the capsule causing more serious infections.
• The capsule may protect the bacteria from the host's natural defenses.
• Bacteria can move using flagella, which are thread-like structures that extend from the cell membrane.
• Flagella are made up of protein molecules and can be seen as tiny threads under a light microscope.
• Bacteria can also move by means of Brownian movement, which is caused by the bumping of molecules and other particles against the bacteria.

Conditions for Growth of Bacteria

• Bacteria require certain conditions to grow and reproduce, including temperature, moisture, and darkness.
• Most bacteria are most active at temperatures between 26°C and 38°C, with some forms growing best at temperatures as low as 0°C or as high as 85°C.
• Bacteria require moisture to grow, with dry surroundings causing water loss and inactivity.
• Most bacteria grow best in the dark, with sunlight slowing down growth and ultraviolet rays killing most bacteria.

Nutrition in Bacteria

• Bacteria can be autotrophs, making their own food compounds from inorganic substances such as carbon dioxide.
• Energy is required for this process, which is obtained by breaking down inorganic compounds of iron, sulfur, or nitrogen.
• Some bacteria can also carry out a form of photosynthesis.
• Most bacteria are heterotrophs, relying on organic compounds formed by other organisms for food.

Bacterial Reproduction

• Bacteria reproduce by binary fission, with a cell dividing into two identical cells.
• Under good conditions, bacteria can multiply rapidly, with a cell dividing into two cells in as little as 20 minutes.

Helpful Activities of Bacteria

• Not all bacteria are disease-causing, with many species being harmless and even helpful.
• Soil bacteria play a key role in breaking down dead plants and animals, recycling nutrients and allowing plants to grow.
• Bacteria are used in industry to produce foods such as vinegar and silage, and are important in the dairy industry.

Preserving Food from Bacterial Action

• Bacteria are a major competitor for food, causing spoilage and waste.
• Methods for preserving food include killing all bacteria present, then sealing the food in a container, as well as keeping foods in conditions that slow down bacterial reproduction.
• Chemical preservatives, cooling, freezing, salt curing, and dehydration can also be used to preserve food.

Protozoans

• Protozoans are a group of single-celled organisms that are often classified as animals, but do not fit into the traditional animal kingdom.
• There are four main phyla of protozoans: Sarcodina, Ciliophora, Mastigophora, and Sporozoa.

Sarcodina - Amoeba

• Amoebas are a type of protozoan that move using pseudopodia, which are extensions of the cytoplasm.
• Amoebas respond to their environment, with no eyes, they are sensitive to light and seek dim or dark areas.
• Amoebas also respond to food, and can become inactive and withdraw into a round mass called a cyst when conditions are unfavorable.

Ciliophora - Paramecium

• Paramecia are a type of protozoan that move using cilia, which are hair-like structures.
• Paramecia are complex organisms that have a slipper-shaped cell and respond to their environment, including swimming constantly to avoid bumping into objects.

Mastigophora - Euglena

• Euglenas are a type of protozoan that move using a flagellum and have a second method of movement called euglenoid movement, which involves a gradual change in the shape of the cell.
• Euglenas are often classified as plants, but are actually protists, and carry out photosynthesis.
• Euglenas have a red eyespot, which is highly sensitive to light.

Sporozoa - Plasmodium

• Sporozoans are a type of protozoan that are all parasites, and do not have a method of movement on their own.
• Plasmodium is a type of sporozoan that causes malaria, and is transmitted through the bite of an infected mosquito.

Fungi

• Fungi are a group of organisms that are not plants, but are often mistaken for them.
• Fungi are classified into two phyla: Myxomycophyta, which includes the slime molds, and Eumycophyta, which includes the true fungi.
• The true fungi are further divided into four classes: Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes.

Classifying Fungi

• The classification of fungi is based on the characteristics of their bodies, including the presence or absence of cell walls, the shape of their hyphae, and the formation of spores.
• Fungi are often classified as either molds or yeasts, depending on their growth habits.

Phylum Eumycophyta

• The true fungi are classified into four classes: Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes.
• Phycomycetes are the alga-like fungi, Ascomycetes are the sac fungi, Basidiomycetes are the club fungi, and Deuteromycetes are the imperfect fungi.

Phylum Myxomycophyta

• The slime molds are a type of fungi that are like giant masses of amoebas, and have a plasmodium, which is a mass of protoplasm with many nuclei but no cell walls.
• Slime molds are often classified as "slime fungi" or "fungus animals" due to their unique characteristics.

Microbiology

• Microbiology is the study of microorganisms, including bacteria, viruses, and fungi.
• Microbiology is significant in understanding higher forms of life, as microorganisms have evolved to live in a wide range of environments and have developed unique characteristics to survive.

Viruses

• Viruses are a type of microorganism that are not considered to be living cells, but are capable of reproducing and evolving.
• Viruses are often considered to be on the border between living and non-living, as they require a host cell to replicate and do not have the characteristics of living cells.
• Temperate phages are a type of virus that can integrate into the host cell's DNA and remain dormant, but can also cause the host cell to lyse and release new viral particles.
• The structure and composition of bacteriophages are important in virus research, as they are used to study the genetics of bacteria and the replication of viruses.

Discovery of Viruses

• The discovery of viruses is attributed to Dmitri Iwanowski and Wendell Stanley, who discovered that viruses are capable of reproducing and evolving.

• Viruses were initially thought to be pathogenic, as they were associated with diseases, but it is now known that many viruses are harmless and some are even beneficial.### Discovery of Viruses

• Dmitri Iwanowski discovered viruses

• Wendell Stanley made significant contributions to the field of virology

Virus Diseases Affecting Human Beings

• Three examples of virus diseases that affect human beings are:
• These viruses impact normal cell activity by:

Importance of Understanding Single-Celled Organisms

• Understanding the life processes of single-celled protozoans helps biologists understand the life processes of complicated organisms like humans because:

Comparison of Amoeba, Paramecium, and Euglena

• Locomotion:
  • Amoeba: pseudopodia
  • Paramecium: cilia
  • Euglena: flagella
• Digestion:
  • Amoeba: phagocytosis
  • Paramecium: oral groove
  • Euglena: chloroplasts and phagocytosis
• Sensitive Response:
  • Amoeba: sensitive to touch and light
  • Paramecium: sensitive to touch and light
  • Euglena: sensitive to light