Bacterial Cells

Their Structure

Structure of a Bacterial Cell

http://en.wikipedia.org/wki/Image:Average_prokaryote_cell-_en.svg

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

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)

Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg

Bacterial Structure• Ribisomes

– 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

- •Kingdom Eubacteria - includes bacteria and cyanobacteria (blue-green)

Fluorescent micrograph of an archaeon microbeworld.org

Eubacteria

EUBACTERIAthe “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, 315NostocSchraer, 637

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

CyanobacteriaThis 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

1) Essential to nutrient cycling2) Decomposers – in soil, inside

animals Enterobacteria – live inside us, break down waste, make

vitamins3) 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 diseaseWe 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 lipids3) ribosomes4) 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 Fix nitrogen in special cells called heterocysts

Chemosynthetic make glucose using energy

from chemical compounds

**Mostly archae

Starr, 745

Legume roots – nodules contain nitrogen-fixing bacteria

Tube worms at ocean vent Fed by chemoautotrophs

Starr, 314

Eubacteria and Archaebacteria