Bacteria: Part II

Classification of Bacteria:

• Bacteria are microscopic prokaryotes. Prokaryotic cells lack a “true nucleus” that separates their genes from the cytoplasm. They lack the various organelles found in eukaryotic cells

• Eubacteria are prokaryotes that have a peptidoglycan in their cell walls and lack introns in their DNA.

• Archaebacteria are prokaryotes that lack peptidoglycan and have DNA segments similar to those found in Eukaryotic cells (introns). They have unusual lipids in their cell membranes. They can be found in extreme environments---although their is evidence that they may occur in less severe conditions.

TYPES OF ARCHAEBACTERIA

Methanogens – gain energy by converting H2 & CO2 into methane gas. They live in anaerobic conditions, such as the bottom of a swamp and in sewage, where, they are a source of swamp gas. They can be found in the intestinal tracts of humans and other animals, such as cows.

Scientists have stated that

gases such as methane from

cow belches contribute to the

greenhouse effect & global

warming.

Extreme halophiles –live in environments of very high salt concentrations such as the Great Salt Lake and the Dead Sea, These organisms use salt to generate ATP.

Salt formations

at the Dead Sea

• Thermoacidiphiles – extremely acidic environments that have extremely high temperatures, such as hot springs. Some can thrive at temperatures up to 110o C (230oF) and at a pH of less than 2. They live near volcanic vents on land or near hydrothermal vents, which are cracks

in the ocean

floor miles below the

surface that leak scalding

water

II EUBACTERIA:

1) Phylum Cyanobacteria: photosynthetic bacteria (example:

Anabaena – live in phosphates in the water) Some Cyanobacteria can form heterocysts –specialized cells that can fix nitrogen for plants. They are referred to as photoautotrophs.

Anabaena Nostoc

2) Phylum Spirochetes:

• gram negative, spiral- shaped, heterotrophic bacteria.

• They move by corksrew rotation. (Example: Treponema pallidum –causes syphylis.)

3) Phylum Gram-Positive Bacteria :

• This group include: yogurt producing bacteria, streptococci that causes “strep throat,”& the lactobacilli that cause tooth decay.

• Actinomycetes – gram-positive, branching filamentous, soil bacteria. These bacteria can produce antibiotics. (examples: erythromycin, tetracycline)

• Included in the group of Gram + are the endospore-forming bacteria that cause leprosy, tetanus, tuberculosis and diptheria.

Tetanus bacteria

• Also: Clostritium botulinum, an anaerobe, produces a deadly poison called an exotoxin, that causes death from botulism food poisoning. (Botox- used in medical treatment)

4) Phylum Proteobacteria:(Largest and most diverse group)

• Enteric Bacteria – gram negative bacteria that inhabit animal intestines E. coli is one example that can produce Vitamin K for humans. ----E coli can also cause food poisoning

• Another enteric bacteria that can cause food poisoning is the one that causes Salmonella. Salmonella’s endotoxin is the cause. It is often found in poultry, fish and raw eggs.

Chemoautotrophs • They can extract energy from minerals

(inorganic compounds) by oxidizing the chemicals within them.

Rhizobium is a nitrogen-fixing bacteria thatlives symbiotically

plants in root nodules. This bacteria is a major source of

soil nitrogen. (Another isAzotobacter.)

Bacterial Genetic Recombination:

(more genetic variety)

transformation –

bacteria acquire fragments of DNA from the environment and incorporate them into their genome

1. A donor bacterium dies and is degraded.

2. A fragment of DNA from the dead donor bacterium binds to DNA binding proteins on the cell wall of a competent, living recipient bacterium.

3. The Rec A protein promotes genetic exchange between a fragment of the donor's DNA and the recipient's DNA.

transduction –

a virus picks up a fragment of DNA from a donor cell and transports it into the bacterial cell.

Virus (phage)particle infects a

bacterial cell

• conjugation – a fragment of DNA (a plasmid copy) passes from the donor bacteria cell through a specialized pilus, to a recipient bacteria cell. The pilus forms a passageway called a conjugation bridge.

Controlling Bacteria: 1) Antiseptics – chemical used to kill bacteria that

may cause infection such as in wounds. (Used on people such as iodine, and alcohol)

2) Disinfectant – a chemical solution that kills bacteria. It is not usually considered a sterilization method. (Not used on people – used on surfaces.)

3) Sterilization –(Kills all microbial life) certain gases, special boiling procedure, & autoclave – steam under pressure.

ALSO – Radiation, Chemical etc.

autoclave tape

4) Cold temperature – storing food at refrigeration temperature can slow bacterial reproduction.

5) High temperature – raising the temperature of food to destroy bacteria in cooking, frying etc.

6) Canning – heating food to high temperatures and then placing in sterilized glass jars or metal cans and sealing them properly prevents bacterial growth.

7) Chemically-treating foods – treating foods with everyday chemicals such as vinegar, salts and sugar can inhibit bacteria growth. Salted meats, pickled vegetables, and jam are examples of chemically preserved food.

USEFUL BACTERIA: 1) Bacteria are recyclers in the

environment. They can break down organic matter from dead plants and animals. They are decomposers.

2) Bacteria are useful in sewage treatment plants to breakdown sewage into simpler organic compounds.

3) Bacteria are useful in producing foods such as: sour cream, yogurt, sourdough bread, buttermilk, cheese (mozzarella, ricotta,

cheddar …), sauerkraut, soy sauce, & vinegar.

4) Bacteria produce certain antibiotics. (Also insulin – genetically engineered bacteria)

5) Bacteria are used in industrial chemical production .

6) Bacteria have been used in environmental cleanup. Certain bacteria can also clean up hazardous chemicals and oil spills in the environment by converting the chemicals into other harmless, or less toxic compounds. This process is called bioremediation.

ALSO:

Bacteria present in the microflora prevent other pathogens from causing an infection.

Additional Uses of Bacteria (pg 476)

• Heat-loving bacteria are a major source of heat resistant enzymes for biomedicine and industry. The heat tolerant enzyme Taq polymerase allows biotechnologists to copy pieces of DNA rapidly.

• Enzymes from thermophilic archaea, when added to laundry detergent, help dissolve stains.

• Bacillus thuringiensis, (Bt) makes crystals of proteins that act as endotoxin for certain plant pests, such as the corn earworm caterpillar. The consumed proteins kill the insect. (The genes can be put in the cord directly)

Gut bacteria on different continents