Prokaryotes Bacteria Archaebacteria SBI 3 U Ms Zafar

Prokaryotes: Bacteria & Archaebacteria SBI 3 U Ms. 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 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 in a 10 m. L 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=a. J p. Zz. F 3 h 3 kc

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 mitosis 1. 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-t 0 -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