Bacterial Cells Their Structure

Structure of a Bacterial Cell Cell Wall Outside membrane- maintains cell structure May have cell wall + capsule (second wall) Protects the cell Eubacteria-composed of peptidoglycan, a polymer of sugars and amino acids Plasma Membrane Controls what enters and exits, selectively permeable phospholipid bilayer surrounding cell contains proteins that play a role in transport of ions, nutrients, and wastes Flagella (not found in all bacteria) tail-like structure used for locomotion http://en.wikipedia.org/wki/Image:Average_prokaryote_cell-_en.svg

Structure of a Bacterial Cell Nucleoid region DNA is found in prokaryotes single double-stranded circular chromosome Contains all genetic information Plasmid (some bacteria) small circular chromosome carrying special genes may carry an antibiotic resistance gene Can be exchanged through conjugation Ribosomes site of protein synthesis (translation) http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Bacterial Structure Ribisomes Respiratory Enzymes Cytoplasm Bacteria have ribosomes that make all proteins for the cell Respiratory Enzymes Use enzymes in the cytoplasm to undergo respiration Cytoplasm Fluid filling cell

Two Kingdoms of Bacteria Kingdom Archaebacteria - “Ancient”, most primitive earliest known form of life - Fluorescent micrograph of an archaeon microbeworld.org Kingdom Eubacteria - includes bacteria and cyanobacteria (blue-green)

Eubacteria

EUBACTERIA the “true” bacteria- more common

Cell Walls eubacterial cells have two different cell wall structures. A technique called gram staining can distinguish between: Gram-positive: cell wall containing mainly peptidoglycan- stains purple Gram-negative: bacterial cell has a second, outer layer of lipids and carbs- stains pink

Kingdom Eubacteria Photosynthetic – 2 groups 1) cyanobacteria (aerobes) Have chlorophyll a and phycocyanin (blue) Other colors, too Most live in fresh water Others live in salt water, soil and lichens Starr, 315 Nostoc Schraer, 637

- colors range from pink to black - photosynthesize without water More photosynthetics 2) green-sulfur and purple bacteria - anaerobic - colors range from pink to black - photosynthesize without water - make no oxygen - live in pond and sea mud

Cyanobacteria This is a group of bacteria that includes some that are single cells and some that are chains of cells. You may have seen them as "green slime" in your aquarium or in a pond. Cyanobacteria can do "modern photosynthesis", which is the kind that makes oxygen from water. All plants do this kind of photosynthesis and inherited the ability from the cyanobacteria.

Cyanobacteria were the first organisms on Earth to do modern photosynthesis and they made the first oxygen in the Earth's atmosphere.

Biologic Importance of Bacteria Essential to nutrient cycling Decomposers – in soil, inside animals Enterobacteria – live inside us, break down waste, make vitamins 3) Process foods – cheese, yogurt etc.. 4) Some MAKE antibiotics (streptomyacin) 5) Aid in human digestion- make vitamins

Many Bacteria live symbiotically in the guts of animals or elsewhere in their bodies. For example, bacteria in your gut produce vitamin K which is essential to blood clot formation.

Bacterial uses cont. 6) Help with sewage treatment Break down wastes 7) Can be utilized in genetic engineering, molecular research… Insert foreign genes into new organism Can be used to make specialized products like insulin 8) Indicate pollution levels Provide visual clue to presence of pollution

9) Nitrogen Fixation Still other Bacteria live on the roots of certain plants, converting nitrogen into a usable form.

Some cause disease We call these “pathogens” Anthrax, as seen by Koch microbeworld.org But most are beneficial Bacteria ferment cheese Schraer, 641

Archae are extremophiles Live in habitats like early earth Too harsh for most organisms 1) methanogens – decomposers, live in intestines, swamps & bogs sewage treatment 2) Halophiles – “love salt” Great Salt Lake, Dead Sea 3) Thermophiles – hot springs, geysers 4) Acidophiles – acidic environments Starr,635

Kingdom Archaebacteria Why a separate kingdom? Archae differ chemically from other bacteria. 1) cell wall - different amino acids and sugars. Eubacteria have peptidoglycan Archaebacteria have varied polysaccharides but not peptidoglycan. 2) membrane lipids 3) ribosomes 4) enzymes - - - - - - - - - - - - > 5) gene sequences . . . And MORE RNA polymerase

Archaebacteria Lack important carbohydrate found in cell walls Have different lipids in their cell membrane Different types of ribosomes Very different gene sequences Archaebacteria can live in extremely harsh environments They do not require oxygen and can live in extremely salty environments as well as extremely hot environments.

Archaea, the “extremophiles” methanogens, thermophiles, halophiles

Nitrogen-fixing Chemosynthetic Eubacteria and Archaebacteria make glucose using energy from chemical compounds **Mostly archae Tube worms at ocean vent Fed by chemoautotrophs Starr, 745 Nitrogen-fixing Fix nitrogen in special cells called heterocysts Legume roots – nodules contain nitrogen-fixing bacteria Starr, 314