Archea and Bacteria- The PROKARYOTES

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As late as 1977, all prokaryotes were put into one single

kingdom called Monera. Taxonomists no longer accept

that concept. Some prokaryotes are more closely related

to eukaryotes than other prokaryotes. Most taxonomists

now accept the concept of super kingdoms or domains.

Two of the three domains are prokaryotes

EUBACTERIA

Bacteria

I. Three common shapes (cocci, bacilli, spirilla)

II. Small 0.5-5 mm

Within their domains, identification of

microbes begins with their physical

appearance, followed by biochemical

and genetic tests.

SHAPE is/was

the most

commonly used

physical

appearance for

determination of

species.

Classified by shape, size, staining,

environment, & color Cynobacteria &

Salmonella

Autotroph Bacteria Flagellated Bacteria

Strep bacteria of Rheumatic Fever

E.Coli dividing

Nostococ

III. Bacterial cell wall made of carbohydrate polymers that are

connected by polypeptide chains (peptidoglycan). Gram-

positive bacteria (stain purple with Gram-stain) have cell

walls with just the peptidoglycan wall connected to

plasma membrane. Gram-negative bacteria (stain pink)

have peptidoglycan wall sandwiched between two

membranes. The cell wall of Archae are made from

polysaccharides and certain proteins but NOT

peptidoglycans.

Gram positive bacteria

Have an extra layer of

peptidoglycan in their cell

wall, and retain dye.

Gram negative bacteria

Have a thin layer of

peptidoglycan in their cell wall.

AND have lipopolysaccharides

with protein channels in the cell

membrane. This keeps dyes

(along with antibiotics) out!

http://www.sirinet.net/~jgjohnso/monerans.html

Some prokaryotes have a second layer outside the cell wall.

-Capsule-sticky layer of carbohydrates or proteins.

-Fimbriae-protein appendages that allows the prokaryote to

attach to surfaces

Bacilli

Spirilla

Cocci

Nostoc

Oscolitoria

Gloeocapsa

IV. Nucloid region-area where circular DNA chromosome is

located. Chromosome lacks histones (some prokaryotes in

Archae do). May also contain smaller circular pieces of DNA

or plasmids.

V. Ribosomes are smaller than cytoplasmic eukaryotic

ribosomes.

VI. Some prokaryotes have infoldings of the plasma membrane

similar to cristae (mitochondria) and some photosynthetic

prokaryotes have internal membranes similar to thylakoid

(chloroplasts)

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VII. Some prokaryotic cells have flagella. The flagellum is

different from eukaryotic cells. It is a solid core of protein

(1/10th width). It is driven by a system of rings in the cell wall.

ATP pumps transports H+ out cell. When the H+ diffuse back in

it powers the flagella which rotates like a helicopter rotor.

Flagellated prokaryotes can exhibit taxis moving toward or

away chemicals, nutrients or oxygen.

Reproduction-Reproduction is via binary fission. Bacteria

can obtain genetic variation via conjugation, transformation, or

transduction

Conjugation-(Lederberg & Tatum)

1. Conjugation-Certain bacteria that have been mutated, would

need additonal nutrients in their media in order to grow.

Bacteria without these mutations will grow on minimal media.

E.Coli had been mutated and 2 different strains were found

#1- needed methonie and vitamin biotin but could make its own

leucine and threonine.

#2-needed threonine and leucine but could not make its own

methonine and vitamin biotin. When these two types were

mixed, there emerged some new cells that had the ability to

grow on minimal media. Conclusion: There had to be some

exchange of genes or recombination of genes.

Recombination has occurred because the new cells can grow

on minimal media. It was also discovered that in addition to

the main chromosome, prokaryotic cells contained smaller

circles of DNA (plasmids) which also contained genes.

The arrow points to a plasmid in a lysed E.Coli

cell which is then magnified. This plasmid

contains genes that makes the cell resistant to the

antibiotic tetracycline.

Plasmids replicate

independent of the

main chromosome.

These plasmids are

being replicated.

In order for conjugation to occur there must be 2

different mating types F+ (male) and F- (female). F+

males have a plasmid (sex factor) which is replicated.

When a F+ and F- meet, they form a cytoplasmic

bridge or pilus. The copied F+ plasmid is transferred

to F- making it F+.

The population never completely is

converted to F+ because

1. F- can undergo bacterial

reproduction (fission) faster than F+

can conjugate.

2. The formation of the pilus, allows

for cetain viruses to attack, and they

only attack F+ cells.

Some F+ plasmids are inserted into

the main chromosome becoming Hfr

(high frequency recombinants).

When Hfr conjugates with F-, the

entire main chromosome is replicated.

Conjugating bacteria with

the pilli connecting the

cells to one another to

exchange DNA.

However during transfer only part of the

chromosome is transferred.

The gene for Hfr is usually at the end of

the chromosome, so that the receiving cell

F- will stay an F-. The longer the pilus

stays together, the more genes transferred.

Autonomous plasmids-Plasmids that never integrate themselves into

the chromosome. They may carry genes that include antibiotic

resistance or a virulence factor. Plasmids have the ability to

replicate themselves so that a prokaryotic cell may have 1,000 to

3,000 copies of it.

2. Transformation- Involves prokaryotic cells taking up extraneous

DNA from the environment. Genetic engineering uses this technique

in transforming bacteria and using engineered plasmids.

3.Transduction- Bacterial cells obtaining DNA

via a viral vector.

The rapid reproduction, mutations, and genetic

recombination allows for a great variety in their metabolic

pathways.

-Photoautotroph-does photosynthesis and uses CO2 as its

carbon source

-Chemoautotroph-uses CO2 to make organic compounds on

its own and uses chemicals like H2S and NH3 for energy

instead of light

-Photoheterotroph-uses light for energy but obtains carbon

from an organic source.

-Chemoheterotroph-uses organic compounds for both an

energy source and carbon source. Most are decomposers or

pathogens that break organic compounds down.

Types of cell respiration

-Obligate aeorbes must use oxygen for cell respiration or will

die without it

-Obligate anaerobe- oxygen is not used for cell respiration

and the cell is actually poisoned by it.

-Faculative anaerobes-can use oxygen when present or do

fermentation if oxygen is not present.

Nitrogen fixation

Some prokaryotes have the ability to “fix” atmospheric

nitrogen (N2) into ammonia NH3. Then the ammonia can be

converted into nitrates and nitrites. The nitrogen compounds

then can be converted into amino acids. Important part of

nitrogen cycle. Some prokaryotes live in symbiotic

relationships with this pathway. The root nodules of legumes

contain nitrogen fixing bacteria.

Types of photosynthesis-Some prokaryotes are

photosynthetic. There are two types of photosynthesis in

prokaryotes

Type I that gives off O2 as a by product.

Contains photosystem I and II like higher plants

Contains chlorophyll a like higher plants

Splits water

6 CO2 + 6 H2O -> C6H12O6 + 6 O2

Type II that does not give off O2 as a by product.

Contains only photosystem I

Contains bacteriochloropyll

Splits hydrogen sulfide

CO2 + 2H2S -> (CH2O)n + 2 S

Domain Bacteria-Supergroups

1. Proteobacteria-Gram negative with 5 subgroups. Metabolic

diverse photoautotrophs, chemoautotrophs, and

heterotrophs. Some are aerobic while others are anaerobes.

2. Chlamydias-Obligate pararsites only live in other cells.

Major cause blindness.

3. Spirochetes-Spiraled shaped with internal like flagellum.

Caused syphilis and Lyme disease.

4. Cyanobacteria-does type I photosynthesis generating

oxygen. Some cells specialized (heterocysts) for fixing

nitrogen

5. Gram-positive bacteria-Metabolic diverse group. Some

obligate parasites, some secrete antibiotics.

Domain Archaea-Supergroups can live in extreme

environments and more normal environments. More

closely related to eukaryotes than other prokaryote

1. Extreme halophiles can tolerates saline enviroments.

Tolerance from slightly saline to over 9% saline (Marine

enviroments is 3.5% saline).

2. Exterme thermophiles can tolerate very hot environments.

Proteins are very stable at this temperature and DNA

remains as a double helix. One strain of Geogemma

barossii can tolerate temperature of over 121o C.

3. Methanogens- use CO2 to oxidize H2 to make methane gas.

Obligate anaerobes. Found under ice, swamps, guts of

cattle, and termites.

4. Moderate environment-many prokaryotes from the Domain

Archaea are live in moderate environments.

• Archaea are highly diverse organisms, both morphologically

(form and structure) and physiologically (function).

• The organisms' possible shapes include spherical, rod-

shaped, spiral, lobed, plate-shaped, irregularly shaped, and

pleomorphic(2 or more shapes during lifetime). There are

many different types of Archaea that live in extremely

diverse environments.

• Modern-day Archaebacteria are found in extreme

environments, such as areas of intense heat or high salt

concentration.

ALL ABOUT ARCHAEBACTERIA

Prokaryotes in the environment

Symbiotic relationships-

Mutualistic- Ex-certain bacteria in your gut are important to

the digestive system and the bacteria benefit by the food that

is provided to them.

Commensalistic-Ex There a many bacteria living on the

surface of the skin. They do not harm or provide any benefit

to the epidermal cells. The epidermal cells provide oils, food

and a habitat to live

Parasitic-Ex-Some prokaryotes are pathogens (cause

disease). Many bacterial diseases can be treated with

antibiotics which are compounds that destroy prokaryotic

cells but not eukaryotic cells. Usually the disease is caused

by either an exotoxin (made and secreted by the prokaryote)

or endotoxin (made by the prokaryote and only released if the

prokaryote dies). Botulism is caused by an exotoxin made by

Clostridium botulinum and typhoid fever is caused by an

endotoxin made by Salmonella typhi.

Prokaryotes are the most dominant organisms on

this earth. Without them, life as we know would not

exist. They are important in

-decomposers

-nutrient recycling

-nitrogen fixation

-food industry

-symbiosis

-medicine

-producers in food chains.

V. The 4 main functions of bacteria

1. Nitrogen fixation

2. Recycling of nutrients

3. Food & medicines

4. Bacteria cause diseases

Nitrogen wastes are excreted &

cycled by bacteria Nitrogen in

Plant & animal

protein

Ammonia nitrogen

Is excreted in urine Bacteria convert

Ammonia to usable

Nitrate fertilizer

Making cheese & yogurt with bacteria

This chart compares and

contrast three different

domains. It is based on the

sequencing of the rRNA

found in the small subunit.

The Archae prokaryotes are

more closely related to

eukaryotes than it is to the

Bacteria prokaryotes.