PROKARYOTES - Daytona State College · PDF filelayer of membrane that contains lipopolysaccharide ... serve as the basis of the food chain – chemosynthetic bacteria in deep ocean

The Academic Support Center @ Daytona State College (Science 52 Page 1 of 49)

O R 1 0 0 T R I L L I O N F R I E N D S T H A T

Y O U D I D N ’ T K N O W Y O U H A D

PROKARYOTES


Prokaryotes

Or 100 Trillion Friends That You Didn’t Know You Had


The Human Microbiome We are actually a giant ecosystem of microbes

Prokaryotes comprise between 1-3% of the mass of a human body

- up to 6lbs of a 200 lb person can be microbes


Classification: Some Old, Some New

Biologists have typically classified living things into 5 large groups called kingdoms

- Monera, Protista, Fungi, Plantae & Animalia

Then biologists discovered organisms called Archea – they are prokaryotic organisms but aren’t bacteria.

- What to do?



The Challenge of Archea Archea present a problem, they a

are prokaryotes

– They have no nucleus or organelles

They also share traits with eukaryotes

- similarities in DNA and synthesis

They have traits unique to themselves

- cell membrane lipids, ability to

survive extremely high temperature


Enter the Domain System of Classification

Scientists divided living things into 3 Supergroups called domains these consist of Bacteria, Archea and Eukarya




Archea can be Extremophiles

Some species of archea can be found in environments so extreme, that nothing else lives there- extreme temps, extreme pH, extremely salty etc…


Bacteria

Earth’s oldest life forms

– between 3.5 and 3.8 billion years old

Most abundant life form – up to 2.5 billion individual bacteria in 1 gram of fertile soil

Very adaptable – found in all of Earth’s

ecosystems


Bacteria Characteristics

Unicellular

Circular DNA

No organelles

1/10th the size of eukaryotic cells

Flagella-long hair-like structure used for movement

Reproduce asexually –Binary Fission


Bacterial Shapes

3 main shapes

- coccus – sphere

- bacillus – rods

- spirillum - spiral


Bacterial Characteristics Metabolic diversity – Bacteria can produce

energy in a variety of circumstances

autotroph – (self-feeding) – some bacteria can produce their own food

- some use photosynthesis – get energy from light

- some use chemosynthesis – get energy from

chemicals

Heterotroph - (other feeding) – many bacteria

are unable to produce their own food and are required to eat other things


Bacterial Characteristics: Metabolic diversity continued

obligate aerobe – like us these bacteria need oxygen

obligate anaerobe - these bacteria need to be in an oxygen free environment – human gut

facultative anaerobe – these bacteria can live in either an oxygen or oxygen free environment


Bacterial Structure

Cell Wall

Cell Membrane

Pilus

chromosome

plasmid

flagellum

nucleoid

ribosome

cytoplasm

capsule


Bacterial Structure: Cell Wall Made of peptidoglycan – a combination of protein and

polysaccharides

Some bacteria called Gram negative bacteria have an additional layer of membrane that contains lipopolysaccharide

- this extra layer inhibits the uptake of antibiotics – protecting

the bacteria

cell membrane

cell wall

cell membrane

Outer membrane

lipopolysaccharide

cell wall


Gram + vs. Gram -

Absorb stain appear purple

Don’t absorb stain appear pink

The type of cell wall is used by doctors to help diagnose disease

The bacteria are stained with a special stain called Gram stain

Bacteria without the extra membrane, appear purple. These are Gram positive (Gram +) bacteria

Bacteria with the extra membrane appear pink. These are Gram negative ( Gram -) bacteria


Bacterial Structure continued Pili – hairlike structures usually found

in Gram neg. bacteria. Help the bacteria stick to surfaces.

Also forms conjugation bridge

Chromosome – a single loop of DNA

that is folded on itself

- controls the cell’s function

Nucleoid – the region of the cytoplasm

where the DNA is found

Plasmid – an accessory loop of DNA – small contains only a few genes - can be responsible for: conjugation, antibiotic resistance, unique metabolic properties – like the ability to use hydrocarbons

Capsule – found outside some bacteria stores nutrients and protects the bacteria from changing environmental conditions


Reproduction - Binary Fission

Bacterial cells undergoing binary fission


Reproduction - Binary Fission

Asexual reproduction - offspring are genetically identical to parent – no new genetic combinations - under ideal conditions can occur every 20 min - creates large numbers of bacteria in a short time


Each spot represents

a single bacterial

cell that reproduced

by binary fission to

produce millions of

genetically identical

cells.

Genetically identical,

good or bad?


Exchanging Genetic Information

Bacterial cells need to be able to exchange genetic information

- creates new genetic combinations which increases the ability of the bacteria to survive

Bacteria have 3 methods for exchanging DNA

-Transduction – viruses carry DNA from one bacterial

cell to another

-Transformation – bacteria can absorb “naked” DNA

released by dead bacteria from the environment

- Conjugation – two bacteria join at a conjugation bridge,

one bacteria passes on a copy of its

plasmid or chromosome


Exchanging Genetic Information


Transduction – DNA is carried from one

bacteria to another by a virus


Transformation: Bacteria absorb “naked” DNA from the

environment


Conjugation


Conjugation- one cell passes a copy of

its plasmid or chromosome to another

Donor Cell Recipient Cell

A special pilus forms a connection called a conjugation bridge between 2 bacterial cells

Plasmid Conjugation bridge

The donor cell copies its plasmid or chromosome and passes the copy through the conjugation bridge

Cells separate


Bacteria Play Important Roles in Ecosystems Decomposers

– recycle dead organisms releasing their nutrients back to the environment for use by other organisms – SPONCH

Without decomposers,

the elements on earth

would have remained

locked up in dead organisms and life would have ceased


Bacterial Roles: Nitrogen Fixation some bacteria contain enzymes which allow them to

convert (or fix) nitrogen from the air into a useable form

- they are nitrogen fixing bacteria

- Why do living things use nitrogen?


Bacterial Roles: Producers

In some ecosystems

chemosynthetic and

photosynthetic bacteria

serve as the basis of

the food chain

– chemosynthetic bacteria in deep ocean vents

convert hydrogen sulfide (H2S) gas into energy

- cyanobacteria are photosynthetic bacteria

which act as producers in many aquatic

ecosystems


Bacterial Roles: Symbiotic Bacteria

Many bacteria live in or on other organisms (including humans) and aid their host

- some live in the gut of herbivores helping to

digest cellulose

- bacteria in the gut of humans

aid digestion and produce

vitamins

- bacteria on skin and in body

openings help prevent infection

by harmful organisms


Bacterial Roles: Pathogenic Bacteria

Pathogens are organisms that cause disease

- only a small portion of bacteria are pathogens

- most bacteria diseases are caused by toxins

released by the bacteria

- these toxins:

- poison cells and damage tissue

- interfere with cell signaling

- over-stimulate cells causing them to malfunction


Pathogenic Bacteria: Biofilms

Some bacteria can form a biofilm – a matrix made of polysaccharide

- once formed, the matrix traps other bacteria

- the biofilm protects the bacteria, making it hard to kill them


Antibiotics Antibiotics are chemicals which either kill bacteria or

prevent their growth and reproduction

Bacteria and other microbes produce antibiotics to reduce competition from other organisms

Penicillin was the first to be use to fight disease

- discovered accidently by Alexander Fleming in 1928

Two scientists Walter Florey and Ernst Chain determined

how to use penicillin to

treat disease in 1939.

The discovery of

antibiotics revolutionized

the treatment

of disease


Antibiotic Action Antibiotics effect bacteria, but not eukaryotic cells

Antibiotics attack bacteria in 5 ways

- some damage the cell walls or prevent new cell wall from forming

- some damage the cell membrane

- some prevent protein synthesis

- some prevent DNA from being copied

- some interfere with bacterial metabolism


Antibiotic Resistance Some bacteria have developed a resistance to the effect

of some antibiotics

- the number of resistant bacteria is growing

The problem is increased by overuse and misuse of antibiotics

- use of antibiotics to treat viral infections – antibiotics don’t effect

viruses

- the use of antibiotics in livestock (cattle, chickens, pigs)

antibiotics show up in the meat and milk

- people take the antibiotics until they feel better, but stop before all of the bacteria are destroyed

- this kills the most susceptible bacteria, but leaves the more resistant bacteria


Black Plague-Yersinia pestis


Syphilis--Treponema pallidum/Bacterial


Mycobacterium leprae/Bacteria


Clostridium perfringes/Bacteria


Vocabulary Microbiome Archea

autotroph pili

heterotroph nucleoid

peptidoglycan capsule

plasmid conjugation bridge

Gram - obligate aerobe

Gram + obligate anaerobe

binary fission facultative anaerobe

conjugation nitrogen fixing bacteria

transduction cyanobacteria

transformation pathogens

biofilm


SHAPES


Oscillatoria


Anabaena


Rhizobium


Clostridium


Salmonella


Nostoc


Prepared by L. Field – Adjunct Biology Professor Edited by D. Leonard – Learning Specialist The Academic Support Center @ Daytona State College http://www.daytonastate.edu/asc/ascsciencehandouts.html

Questions

http://www.daytonastate.edu/asc/ascsciencehandouts.html

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PROKARYOTES - Daytona State College · PDF filelayer of membrane that contains lipopolysaccharide ... serve as the basis of the food chain – chemosynthetic bacteria in deep ocean