Chapter 23: Bacteria

Archaea and Bacteria

Kingdom Archaebacteria – the most primitive organisms

(archae = ancient)

live in harsh conditions including

- acidic hot springs

- very salty water

- environments with no oxygen

- near undersea volcanic vents

- different from other bacteria

- cell wall composition (pseudomurien)

- Cell membrane

- rRNA

Phyla 1: Methanogens:

- obligate anaerobes (oxygen kills them)

- metabolizes hydrogen gas and CO2 to methane gas

- live in the bottom of swamps, sewage, and inside the digestive tracks of many animals

Helps

- grazing animals process cellulose

- termites process wood

- in industry to treat sewage, purify water.

Phyla 2: Thermoacidiphiles

- can live in extremely hot and acidic water or deep in the ocean near hydrothermal vents in the ocean floor

- Ex: hot springs of Yellowstone Natl Park

- chemotrophs = process sulfur compounds to produce energy

Phyla 3: Halophiles:

- live in extremely salty (saline) environments,

ex: Dead Sea

- use the salt to generate ATP.

Phyla 4: Psychrophiles

- live in temperatures below 15C

- Found mostly in the Arctic and Antarctic oceans sea ice.

Kingdom Eubacteria (Eu = true) “Germs”

1) Composition of the cell wall – identified with Gram staining technique

Gram positive – stains purple – thick outer layer of peptidoglycan

Gram negative – stains pink/red – lipid layer covering thin layer of peptidoglycan

Peptidoglycan – a protein-carbohydrate compound

Characteristics used for classifying:

3) Type of metabolism

obligate aerobe – must have oxygen; dies without it

obligate anaerobe – dies if exposed to oxygen; processes ATP by fermentation

facultative anaerobe – uses oxygen

when it can but doesn’t need it

4) Shape of bacterial cells

round coccus (cocci)

rod shaped bacillus (bacilli)

spiral shaped spirillus

2. Method of getting energy: autotrophic (chemotroph, phototroph), heterotrophic

5) How cells grow (prefixes)

a) staphylo – clumps

b) strepto - chains

c) diplo - pairs

6) Motility – movement

a) flagellated – move with flagellum or flagella

b) slime layer allows gliding

c) spirochete - cork-screw rotation

A) Proteobacteria

• may have symbiotic lifestyle

• ex. Nitrogen fixing bacteria inside legumes (ex: beans)

• In human and animal intestines, help break down foods (enteric bacteria)

• Some in soil or fresh water and process iron and other minerals as an energy source (chemotrophs)

B) Gram positive

- thick outer layer of peptidoglycan (stains purple)

- may be beneficial or cause disease

- may be used to make yogurt, pickles, and buttermilk

- or to make medicines using biotechnology

Ex. Strep throat ; staph infections; tuberculosis

C) Cyanobacteria

• Gram-negative • contain chlorophyll (but not

chloroplasts), perform a plant-like photosynthesis releasing oxygen as a by-product

• Ex. Filamentous bacteria (grow in stagnant water)

D) Spirochetes

- gram negative

- spiral shaped

E) Chlamydia (no peptidoglycan)

- gram negative

- round shape

- are parasites to animal cells

Reproduction – 2 types

Asexual - most common

Binary fission – divides into two new cells

Sexual – exchanges genetic info giving variation

a) conjugation

- two bacterial cells connect with a hair-like “pili”

- info is passed through the tube

b) transformation

– living bacteria absorbs dead related bacterial DNA and incorporates it into it’s own genome

c) transduction

– a virus transfers DNA

Endospores

- special dehydrated cells formed by some bacteria to survive bad living conditions

- ex: high temperatures

- when conditions improve cell is revived

Bacteria and Disease

Toxins – poisons produced by some bacteria

1) endotoxin

- created inside the bacterial cell

- released as the cell dies

- usually Gram neg.

2) exotoxin

- secreted by living bacterial cell into surrounding environment (host)

- usually Gram-positive

Pathogens – bacteria that cause disease

Antibiotics

- chemicals that kill bacteria by interfering with cellular functions such as protein or cell wall

synthesis - Gram positive bacteria that cause disease need different antibiotics than Gram negative bacteria

Antibiotic Resistance in Bacteria

• most of the population dies, some survive

• Survivors reproduce and are no longer affected by antibiotic

• Occurs when antibiotics are overused or used improperly