VIRUSES & BACTERIA CHAPTERS 2.3, 7.1, AND 7.2

WHAT ARE VIRUSES? A virus is a nonliving strand of hereditary material surrounded by a protein coating.

WHAT ARE VIRUSES?

HOW DO VIRUSES MULTIPLY? Viruses can ONLY make copies of themselves inside a living host cell. Active Viruses: make the host cell produce new viruses, which kills the host cell Latent Viruses: hide in the host cell without destroying it Virus hereditary material becomes part of the host cell’s hereditary material Latent viruses can become active at some point and then destroy the host cells

VIRUS LIFE CYCLE:

HOW DO VIRUSES AFFECT ORGANISMS? Most viruses only infect specific kinds of cells. Viruses are often carried to their host through the air. The virus and host cell must fit together exactly to begin a viral infection. Bacteriophages attach to bacteria and inject their hereditary material.

HOW DO WE FIGHT VIRUSES? Vaccines: weakened virus particles which allow the host to fight some diseases. Treating a Viral Disease Antibiotics are NOT effective treatments for viral infections (WHY NOT?) Infected cells sometimes produce interferons, which are proteins that can protect non-infected cells Antiviral drugs often strong adverse side effects Public health measure can prevent or slow disease spread

WHAT IS GENE THERAPY? Research with viruses—gene therapy, uses viruses to replace defective cell hereditary material with normal cell hereditary material.

WHAT ARE BACTERIA? Bacteria are microscopic, living cells.

WHERE DO BACTERIA LIVE? Bacteria live almost everywhere, even in extreme environments like thousands of meters underground, hot springs with temperatures over 100 degrees C, and very acidic water. Also found in our foods, water, surfaces we touch, and your skin.

WHAT IS THE STRUCTURE OF BACTERIA? Bacteria have 3 basic shapes: Rod-Shaped: Bacilli Sphere-Shaped: Cocci Spiral Shaped: Spirilla

WHAT IS THE STRUCTURE OF BACTERIA? Bacteria are smaller than plant or animal cells. They are prokaryotic, because they do not have a nucleus or membrane-bound internal structures. Some bacteria have a capsule around the cell wall, while others have an outer slime layer. Many have whip-like tails called flagella to help them move.

BACTERIAL CELL

HOW DO BACTERIA REPRODUCE? Most bacteria reproduce by a process known as fission, creating 2 new identical cells; some bacteria exchange genetic material before dividing.

HOW DO BACTERIA OBTAIN FOOD AND ENERGY? Can be producers (like plants) that make their own food Can be consumers (like animals) that obtain energy by eating other organisms Can be parasites that absorb nutrients from a host Most bacteria are aerobes which use oxygen during respiration Some bacteria are anaerobes which do not need oxygen

HOW DO WE CLASSIFY BACTERIA? Bacteria are classified into two kingdoms. Kingdom Eubacteria: The larger group. Diverse. Contains cyanobacteria that produce their own food, and provide food and oxygen for aquatic life. Common name: blue-green algae.

HOW DO WE CLASSIFY BACTERIA? Kingdom Archaebacteria Often found in extreme conditions and are divided into groups based on where they live or how they get energy Some live in salty, acidic, or very hot environments One anaerobic group produces methane gas (in cow stomachs, your intestines, muddy swamps).

HOW CAN BACTERIA BENEFIT YOU? Most bacteria are helpful, not harmful Bacteria are actually necessary for human health Aid in digestion Produce antibiotics, which limit the growth of other bacteria

HOW CAN BACTERIA BENEFIT THE ENVIRONMENT? Bacteria can be used to clean up environmental pollution through bioremediation. Some bacteria break down waste into harmless compounds. Certain bacteria can eat pollutants.

HOW IS BACTERIA USED IN OUR FOOD? Bacteria are used in dairy products such as yogurt and cheese. Sauerkraut and pickles are also among foods made with the help of bacteria.

HOW ARE BACTERIA USED IN INDUSTRY? Bacteria grown in large, carefully controlled containers called bioreactors are used to make medicines and many other products. Methane-producing bacteria can digest wastes and provide a source of fuel.

HOW CAN BACTERIA HARM US? Pathogen: any organism that causes disease. Toxins, or poisons, are made by some bacterial pathogens Some pathogens form thick-walled structures called endospores when environmental conditions are unfavorable; therefore they can survive for very long periods.