prokaryotes: bacteria & archaebacteria

Prokaryotes: Bacteria & ArchaebacteriaSBI 3UMs.Zafar

Photosynthesis Vs. Chemosynthesis• Ecosystems depend upon the ability of some

organisms to convert inorganic compounds into food that other organisms can then exploit

• Together photosynthesis and chemosynthesis, fuel all life of Earth methods of primary food production

Chemosynthetic Bacteria• From inorganic organic• Do not need sunlight for energy• Chemosynthetic bacteria run on chemical energy!• Energy coming from Earth itself• Ex: Beggiatoa

Photosynthetic Bacteria•Conduct photosynthesis•Consist of bacteriochlorophyll•Ex: Cyanobacteria

Bacteria are very abundant!Almost 1,000,000,000,000 in a 10 mL

of soil!

They are the most abundant life forms on Earth!

Characteristics of Bacteria•Prokaryotic All bacteria are single-

celled•Bacterial cells contain no membrane-

bound nucleus or organelles•Bacterial cells have a single chromosome•Bacteria reproduce asexually by binary

fission (splitting into 2)

The Structure of Bacteria• Cell wall support• Cell membrane

controls the passage of materials

• Cytoplasm consists of ribosomes

• DNA genetic information

• Some have flagella for aid in locomotion

Identification & Classification•Bacteria can be classified according to

appearance since most bacteria display one of three basic shapes:

1. Spherical (cocci)2. Rod-shaped (bacilli)3. Spiral (spirilla)

Cocci• If cocci live as separate cells monococci• If cocci live in pairs diplococci• If cocci live in chains streptococci• If cocci live in clusters staphylcocci• Ex: Meningococcus diploccocus

Bacilli•Can exist as single cells bacilli•Pairs diplobacilli•Chains streptobacilli•Ex: Bacillus anthracis

Spiral Bacteria•Spirilla only exist as single cells•Ex: Borellia burgdorferi

Gram Stain: Another way of Classifying Bacteria

• A way of differentiating between two groups of bacteria

• Universally used!• Gram Positive retain crystal violet

stain• Gram Negative appear pink!• The difference between gram-positive

and gram-negative bacteria lies in the ability of the cell wall of the organism to retain the crystal violet

• Gram positive are more common and less pathogenic

• http://www.youtube.com/watch?v=aJpZzF3h3kc

Nutrition•Most bacteria are heterotrophs obtain

energy from other living organisms•Some are autotrophs either

photoautotrophs or chemoautotrophs (sunlight vs. chemical reactions)

Reproduction: Binary Fission!•Asexual reproduction•Similar to mitosis1. Single strand of bacteria DNA

replication identical genetic material being transferred to new cell

2. After replication, bacterium produces a cross wall and divides (the other cell may separate or remain attached)

Binary Fission, Continued…•E.coli bacterium can produce between 10

and 100 million bacteria in 12 hours!•Higher rate of mutations

Conjugation• Not common in bacteria – but does happen!• In conjugation: 2 conjugal bacteria (donor and

recipient), make cell-t0-cell contact by means of a cytoplasmic bridge

• Plasmids transferred from donor to recipient• Plasmid: small circular DNA strand

Endospores• Used during extremely

unfavorable conditions• Endospore inside bacterial

cell• Thickened wall surrounding

genetic info and cytoplasm• Origin cell disintegrates

resistant to heat and cannot be destroyed easily!

• When conditions become better, wall breaks down and an active bacterium emerges