1. Chapter 18 – Bacteria and Viruses
Section 1 – Bacteria
Section 2 – How Bacteria Affect Humans
Section 3 - Viruses

2. Section 1 - Bacteria
Bacteria are the most successful organisms on Earth.
Bacteria can be found living almost everywhere on the globe, even in the most hostile environment.
Most species of bacteria are one of three different shapes:
Spherical (cocci) – strep throat Streptococcus, form long chains
Spiral – Leptospira, infects the liver or brain
Rod-shaped (bacilli) – Esherichia coli, found in the intestinal tract and synthesizes vitamin K.

3. Bacteria have one of two kinds of cell walls.
The structure of a bacterial cell is simple. Bacteria lack cell nuclei, chromosomes, and membrane-bound organelles.
Bacteria have one of two kinds of cell walls.
The outer wall is composed of polysaccharides.
In some bacteria, there is an additional lipid layer bound to the polysaccharides.
The chemical difference between these two types of bacterial cell walls is revealed by a procedure called Gram staining.

4. The differences between Gram-positive (stains purple) and Gram-negative (stains pink) bacteria make it possible to better diagnose and treat diseases.
Gram negative bacteria are unaffected by many antibiotics because the antibiotic cannot penetrate the additional layer outside the cell wall.
Bacteria reproduce by splitting in two. Each new cell is exactly like the parent cell. Genetic material in some cases is transferred from one bacterium to another through conjugation.
Conjugation does not increase the number of bacteria, but it gives the bacteria more genetic possibilities.
Bacteria reproduce rapidly – as many as 600,000 in 4 hours.

5. Some bacteria are autotrophs
Some bacteria are autotrophs. The autotrophic organisms are either photosynthetic, capturing solar energy to make food, or chemosynthetic, using inorganic molecules to make energy.
Most bacteria cannot make their own food and are therefore heterotrophs. They feed on dead animals and animal wastes, dead plants, and fallen leaves.
Some heterotrophic bacteria are parasites.

6. Section 2 – How Bacteria Affect Humans
Many bacteria are beneficial to the Earth.
Bacteria maintain crucial links with Earth’s nutrient cycles and are important in the manufacture of food and life-saving drugs.
Bacteria decomposers are nutrient recyclers. Without bacteria, nutrients would be locked away in the bodies of dead organisms.
Nitrogen-fixing bacteria is responsible for most of the nitrogen that is available for plant growth. These bacteria are located in swellings on the roots of legumes such as peas, beans, and peanuts.

7. Bacteria are used to manufacture food and drugs through decomposition
Bacteria are used to manufacture food and drugs through decomposition. We have learned to use it because it adds flavor.
Milk converted to yogurt
Olives changed to be edible
Cabbage is changed to sauerkraut
Cucumbers transformed into pickle
Bacteria are used to create drugs like insulin which is needed for diabetics. Before genetic engineering, insulin was harvested from the pancreas of animals killed in slaughterhouses. Being able to produce insulin has helped to make it more available and more affordable.

8. The human body can become the temporary home for parasitic bacteria that cause disease and infection. The disease-causing bacteria is called a pathogen.
Pathogens are harmful because they damage tissues by attacking individual cells or by producing toxins that are released into the hosts body.
Bacteria are transmitted in a variety of ways:
By water
In the air
In food
By insects
By direct human contact
The most common human disease caused by bacteria is dental caries. Diets high in sugar content promote cavities.

9. Pathogenic bacteria can contaminate food and cause food poisoning
Pathogenic bacteria can contaminate food and cause food poisoning. Many cases of the flu are actually food poisoning from mishandled food.
The most dangerous kinds of food poisoning:
Clostridium botulinum- causes botulism due to a toxin produced by the bacteria. Very toxic causing paralysis and death. They can grow in canned food.
Salmonella – found in pork, eggs, poultry and other foods. Cause diarrhea, vomiting and abdominal cramps. Severe infections cause dehydration which can lead to death in the young or the elderly.
Escherichia coli – this bacteria is commonly found in human intestines making vitamin K, a new strain causes severe food poisoning and even death in undercooked meat.

10. The scientific study of disease is called pathology.
Exotoxins are toxic substances that bacteria secrete and release into their environment.
Endotoxins are toxic substances secreted and released when the bacteria dies.
Antibiotics affect bacteria by interfering with the cellular activities and causing death.
Antibiotic resistance is a big worry for modern medicine. Populations of bacteria have developed that are resistant to antibiotics due to mutations and to misuse of antibiotics.
Emerging diseases that pass from wild animals to humans is called zoonosis.

11. Escherichia coli

12. Mycobacteria tuberculosis

13. Borrelia burgdorferi The spirochete of Lymes Disease

14. Haemophilus ducreyi- genital ulcer

15. Syphilis

16. Many bacterial diseases are controlled due to sanitation and hygiene
Many bacterial diseases are controlled due to sanitation and hygiene. Most industrialized nations filter and chlorinate their water. Human waste is collected and treated to remove pathogens before release.
Developing countries do not have the same sanitation laws therefore they often have outbreaks of cholera, typhoid and other diseases caused by contamination.
Vaccination is a shot that contains pathogens or their toxins that have been made harmless and that stimulate your immune system to produce antitoxins that prevent your body from getting a disease.
Antibiotics are antibacterial drugs that prevent bacteria from being able to form new cell walls. Penicillin was the first antibiotic found to fight bacteria. It was found in green bread mold.
Antibiotic resistance is caused by not all the bacteria being killed when exposed to it.

17. Section 3: Viruses
Viruses are microscopic particles that invade the cells of plants, animals, fungi, and bacteria. Viruses often destroy the cells they invade.
A virus is not a cell. It is composed of a protein coat (called a capsid) that protects a core of genetic material.
Some viruses have DNA as its core and some has RNA.
Viruses are so small they only have enough genes for the protein coat and enzymes that allow the virus to take over its host cell.
Viruses have some characteristics of living things – like genetic material, but they lack three things – they are not made of cells, they cannot make proteins by themselves, and they cannot use energy. They are only able to reproduce when inside a living cell.

18. Adenovirus

21. Viruses cause many human diseases.
Chickenpox and shingles are caused by the same varicella-zoster herpesvirus
Hepatitis is caused by at least 5 viruses. Hepatitis A and hepatitis E can be spread by fecally contaminated food and water. Hepatitis B, C, and D are spread by sexual contact, by contact with infected blood, or by the use of contaminated needles
Some viruses contain viral oncogenes, genes that cause cancer by blocking the normal controls on cell reproduction.

22. Acquired Immune Deficiency Syndrome (AIDS)
The human immunodeficiency virus (HIV) causes the disease AIDS.
HIV gradually destroys an infected person’s immune system.
HIV is spread by sexual contact, contact with infected body fluids like blood, and from mother to fetus.
The viral RNA enters the cell and takes over manufacturing viral DNA which in turn release viral proteins.