Kingdoms Archaebacteria and Eubacteria

General

• Prokaryotes are single-celled organisms. They are the smallest, simplest organisms.

• The group includes:– Archaebacteria - Found in anaerobic and extreme

conditions (high [salt], high temperature, and/or low pH. These are believed to be the conditions on the early Earth. Earth’s early atmosphere did not contain oxygen, therefore the earliest organisms were anaerobic.

– Eubacteria - This group includes the traditional bacteria and is the largest of the two.

• They are found in nearly every habitat studied, including some that no other organism is able to withstand.

• Bacteria have a cell wall, a cell membrane surrounds the cell but no membrane-bound organelles such as a nucleus, mitochondria, chloroplasts, Golgi apparatus, or ER. Some are covered by a layer of “slime” called a capsule.

• They exist in three basic shapes:– Cocci – spherical– Bacilli - rod-shaped– Spirilla - spiral

• Some bacteria are able to move using special cell structures called cilia and flagella.– Hair-like cilia (singular, cilium) and tail-like flagella

(singular, flagellum) are projections from the cell.

– By repetitive beating (like a bending motion), they cause the cell to move. Think of oars in a boat. Flagella can propel the cell by waving back and forth.

– If a cell is fixed in place, they can also cause water to move across the surface of a cell.

Respiration

• Obligate aerobes must have oxygen.

• Obligate anaerobes cannot survive in the presence of oxygen.

• Facultative anaerobes will use oxygen if present but don’t need it.

Nutrition

• Most are heterotrophs– Some are parasites which live on a living host.– Some are decomposers, feeding on dead

organisms and waste.

• Some are autotrophs.– They either use chemicals as a source of

energy (chemoautotrophs) or are photosynthetic (photoautotrophs).

Reproduction

• Prokaryotes have a single circular chromosome attached to the inside of the plasma membrane.

• Asexual reproduction– Prokaryotes reproduce by simply splitting in

two in a process called binary fission.– The DNA is copied and the cell divides into

two identical cells.

• Sexual reproduction– Sexual reproduction combines genes from two

different individuals and increases variation. Prokaryotes that do not technically reproduce sexually can still mix genes with one another.

– Conjugation - Two cells join briefly and one cell donates some DNA (called a plasmid) to the other one. Sometimes part of the cell’s chromosome is donated as well.

– Transformation - Bacteria can also pick up pieces of DNA from the environment.

– Transduction - sometimes viruses transfer pieces of DNA from one cell to another.

• Endospores– Some bacteria form endospores when

environmental conditions become unfavorable.

–  An endospores contains the DNA and a small amount of cytoplasm enclosed in a tough cell wall. They are resistant to extremes in temperature, drying, and harsh chemicals.

• Mutation is a large source of genetic diversity in bacteria.

Energy Acquisition (in a little more detail)

• Aerobic Respiration (cellular respiration)– Requires O2

– Very efficient means of ATP production– Performed by Obligate Aerobes (must have O2)

• Fermentation– Does not require oxygen– Very inefficient means of ATP production– Begins with glucose but ends with various substances

depending on the organism (CO2, methanol, lactic acid, vinegar, etc.)

– 2 types of organisms carry out this form of respiration• Obligate Anaerobes – must have NO O2 to survive (very primative)• Facultative Anaerobes – can live with O2 or without

Bacteria and Disease

• Bacteria that cause disease are known as pathogenic bacteria

• Bacteria cause disease in one of two ways– Damage cells and tissues by breaking down the cells

for food. For example, Mycobacterium tuberculosis destroys lung tissue.

– Releasing toxins that interfere with the normal functioning of the host. For example, Corynebacterium diphtheriae releases toxins into the bloodstream where they cause breathing difficulty, heart failure, paralysis, and death.

Other Diseases Caused by Bacteria:

• Tetanus

• Botulism

• Chlamydia

• Leprosy

• Necrotising Fasciitis (flesh eating disease)

• Salmonella Food Poisening

Control of Bacterial Growth

• Disinfectants– Kill bacteria on surfaces, floors and non-living

objects.– Usually chemicals such as alcohols, bleach,

hydrogen peroxide or iodine

• Antiseptics– Kill bacteria on the skin of humans or animals

• Bactericidal – kill bacteria outright• Bacteriostatic – stop bacteria from growing or

dividing but don’t kill them

• Natural Body Defenses:– Skin– Fever– White blood cells– Antibodies

• Attacks the bacterium

– Antitoxins• Attacks or neutralizes the toxin produced by the

bacterium

• Preventing and treating bacterial diseases– Vaccines - Many bacterial diseases can be

prevented by stimulating the immune system with a vaccine. Most vaccines are small doses of live bacteria, killed bacteria, or parts of bacterial cells which cause an immune response. If you are exposed to that bacterium again in the future, your immune system will launch a strong response to it.

–  Antibiotics - are compounds that interfere with the normal growth of bacteria.

Useful Bacteria

• Most bacteria are useful, not harmful!• Decomposers (saprophytes)

– Break down complex organic molecules into simpler substances

– Used to our advantage in sewer treatment

• Nitrogen Fixation– Take free nitrogen (N2) and “fix” it into a form usable

by plants (ex. Ammonia NH4)– Form symbiotic relationships with plants: bacteria get

home and food and release usable nitrogen compounds to plants

• Intestinal Bacteria– Form symbiotic relationships with animals– Bacteria get home and food and help animal digest

complex carbohydrates and make important vitamins• “Clean-Up Teams”

– Bacteria that digest petroleum products– Remove poisonous wastes from water

• Manufacturers– Produce foods (cheese, yogurt, butter milk, sour

cream, vinegar)– Synthesize drugs and chemicals through genetic

engineering• Take the gene responsible for making a certain protein (ex.

Human growth hormone, insulin, interferon) from one organism and insert it into the bacteria’s DNA

• Q: How is this done??

1. Split bacterial DNA (plasmid) with a special enzyme (restrictive enzyme) which will cut at a specific site

2. Cut human DNA with same enzye to remove gene

3. Gen is inserted into bacterial DNA with another special enzyme (ligase)

4. Result: Recombinant DNA (contains a foreign gene)

Bacteria Assignments

• Complete Bacteria section of Concept Questions (up to #10)

• Read over Gram Staining Handout

• Read over “Bacteria: Form and Structure” Lab for next class

• Read over “Microbes in our Environment” lab for following class