Bacteria

Bacteria General Information

• Prokaryotes- (no membrane bound

organelles), contain ribosomes

• Unicellular

• Found Everywhere

• 2 Kingdoms:

Archaebacteria & Eubacteria

Archaebacteria

• Archaebacteria (4 types) – live in

extreme habitats

– unusual lipids in their membranes

– no peptidoglycan, unique

polysaccharides

– introns in their DNA

– unique cell membrane

composition

Euryarchaota

1. Methanogens 2. Halophiles

3. Thermoacidophiles

Crenarchaeota

4. Hyperthermophiles

1

2

3

4

Euryarchaota

1. Methanogens - O2 free and produce

methane

Ex: marshes; digestive tracts of

mammals; sewage treatment plants

2. Extreme Halophiles - high salt

concentrations

Ex: Great Salt Lake and Dead Sea

3. Thermoacidophiles - hot, acidic sulfur

springs

Ex: hot springs

Bacterial Structure

Bacterial Structure Composed Of:

• cell wall containing peptidoglycan

• a cell membrane

• cytoplasm

• a single circular piece of DNA located in a region

called the nucleoid

• ribosomes

• sometimes plasmids

– Plasmids – smaller circular pieces of DNA

• some are covered by pili, hairlike projections

• some are covered by glycocalyx, sticky sugars

– Loose layer is called a slime layer

– Firm layer is a capsule

• locomotion by flagella that rotate (not made of

microtubules)

– Movement based on taxis, response to stimuli

Cell Wall Characteristics

• cell wall to provide protection (two

types are identified by gram staining)

Gram Positive - stain purple (thick)

Gram Negative - stain pink (thin)

staining colors differ because of the

thickness of the peptidoglycan layer

Cell Wall Characteristics

Eubacteria Classification • 6 Phylums:

1. Cyanobacteria- abundant

2. Spirochaeles- (spirochetes), corkscrew shape

3. Firmicutes- low GC gram positives

4. Actinobacteria- high GC gram positives

5. Chalmydiales- intracellular parasites

6. Proteobacteria- diverse, 5 groups (α,β,γ,δ,ε)

2

3

6 2

5

4

Firmicutes

Chalmydiales

Eubacteria Classification

• 3 shapes

– bacilli (rod)

• vibrios (bent rods)

– cocci (sphere)

– spirila (spiral)

Eubacteria Classification Growth Patterns

• grow in characteristic patterns

– strepto- chains of cells

– staphylo- resembles grapes

– diplo- paired arrangement of cells

Eubacteria Naming • The two names are put together

to name bacteria

– Growth Pattern + Shape = NAME

• Rod & Pairs

• Round & Clusters

• Spiral & Chains

Eubacteria Classification

Energy Acquisition

• Photoautotrophic

– Perform photosynthesis

– Often called cyanobacteria

• Made aerobic respiration possible

• Chemoautotrophic

– Derive energy from chemical reactions that

break down inorganic molecules

– Chemolithotrophs vs chemoorganotrophs

• Heterotrophic

– Feed on organic substances

– Can create symbiotic relationships

Bacterial Reproduction

Asexual

Reproduction

BINARY FISSION

Vertical Gene Transfer

Bacterial Reproduction Asexual Reproduction

BINARY FISSION-

1. the bacteria copies its chromosome

2. the 2 copies of the chromosome

attach to the plasma membrane

3. cell grows and separates

Bacteria Reproduction

Sexual

Reproduction

Horizontal Gene Transfer

1. Conjugation

One bacteria transfers all

or part of its chromosome

to another cell through a

bridge-like structure called

a pilus/conjugation tube.

Bacteria Reproduction Sexual

Reproduction

Horizontal Gene Transfer

2. Transduction – genetic exchange occurs via a viral vector

Bacteria Reproduction Sexual

Reproduction

Horizontal Gene Transfer

3. Transformation –

bacteria take up

naked DNA without

cell to cell contact

Ways to Gain Resistance

Transformation-

bacterial cells take

in DNA from the

environment

Transduction- a virus

carries a bacterial

gene to another

bacteria

Bacteria Vocabulary • Obligate aerobes- need O

2 to survive

Ex: Mycobacterium tuberculosis

• Obligate anaerobes- killed by O2, require anoxic

environments Ex: Clostridium tetani

• Facultative anaerobes- can live with or without

oxygen Ex: E.coli & Salmonella

• Saprophytes- heterotrophic bacteria that feed

on dead and decaying material

Bacteria Survival

• Bacteria produce endospores during

rough times

– An endospore is a tiny structure that

contains the bacteria’s DNA and a small

amount of cytoplasm and enzymes which is

encased by a tough outer covering.

• During this period of rest, the bacteria

is protected from drying out and harsh

chemicals

• When conditions are favorable again,

the bacteria will reproduce

• Bacteria can remain viable for

thousands of years

Root Nodules