UNF General Biology II Lab- Prokaryotes: Archaea and Bacteria

What are prokaryotes?

Unicellular organisms that lack a membrane-bound nucleus and membrane-bound organelles.

What are the three domains of life?

Bacteria, Archaea, and Eukarya

Which domains contain prokaryotic organisms?

Bacteria and Archaea

Which domain contains organisms with a nucleus and membrane-bound organelles?

Eukarya

What type of groups does the domain Archaea include?

1) produced methane gas from simple carbon sources

2) able to live in extreme environments.

Which domain do true bacteria belong to?

Domain Bacteria

What are true bacteria (Eubacteria)?

Prokaryotic organisms belonging to the domain Bacteria that have cell walls containing peptidoglycan.

What is a defining characteristic that distinguishes Archaea from Bacteria?

Presence or absence of peptidoglycan in the cell wall

T/F. Bacterial cell walls contain peptidoglycan

True.

T/F. Archaeal cell walls contain peptidoglycan

False.

What is peptidoglycan?

A macromolecule made of amino sugars linked by short polypeptides that surrounds the plasma membrane.

What is the function of peptidoglycan in bacteria?

Provides structural support and protection.

What is the purpose of Gram staining?

To distinguish bacteria based on cell wall structure.

What stain is retained by Gram-positive bacteria?

Crystal violet

Why do Gram-positive bacteria retain crystal violet/ Purple?

They have a THICK peptidoglycan layer.

Why do Gram-negative bacteria not retain crystal violet?

They have a thin peptidoglycan layer and an outer membrane (an additional membrane).

Describe the cell wall of Gram-positive bacteria.

Thick peptidoglycan layer, no outer membrane.

Are Gram-positive bacteria more or less susceptible to antibiotics like penicillin?

More susceptible. The use of antibiotics such as penicillin interferes with the formation of peptidoglycan resulting in a bacterium with a weakened cell wall increasing its vulnerability to the immune system of the host.

Describe the cell wall of Gram-negative bacteria.

Thin peptidoglycan layer, outer membrane, and periplasmic space.

What is the function of the outer membrane in Gram-negative bacteria?

Acts as a protective barrier.

What are lipopolysaccharides (LPS)?

Molecules found in the outer membrane of Gram-negative bacteria.

What are porins in Gram-negative bacteria?

Protein channels in the outer membrane that allow substances to pass.

What does it mean that bacteria are ubiquitous?

They can live virtually anywhere.

What are heterotrophic bacteria?

Bacteria that rely on organic carbon from other organisms.

What are chemoheterotrophs?

Bacteria that obtain energy and carbon from chemical compounds, often acting as decomposers.

What are autotrophic bacteria?

Bacteria that can synthesize their own food using chemicals or sunlight.

What are cyanobacteria?

Photosynthetic bacteria that use sunlight to make food.

Why are cyanobacteria important in Earth's history?

They increased atmospheric oxygen, enabling aerobic life.

How do bacteria benefit humans?

Aid digestion, produce foods (yogurt, cheese), make antibiotics, and support research.

What is an example of beneficial bacteria in the human body?

E. coli in the intestines to aid digestion

What bacterial structure is most important for Gram stain results?

Cell wall composition

What color are gram-positive bacteria after staining?

Purple

What color are gram-negative bacteria after staining?

Pink

What are the three major cell types?

1) Cocci

2) Bacilli

3) Spirilla

What shape are cocci?

round

What shape are bacilli?

rod

What shape are spirilla (pl. spirillum)

corkscrew/ spiral

What environment can you find cocci?

moist

What environment can you find bacilli?

gut

What environment can you find spirillum?

muddy/ sediment

What does the prefix "diplo" in front of cocci mean?

a bacteria found to be growing in groups of 2

What does the prefix "strepto" in front of cocci mean?

a bacteria found to be growing in chains

What does the prefix "staphylo" in front of cocci mean?

a bacteria found to be growing in custers

Name 3 key differences (extra characterisitcs) in gram negative bacteria?

1) Porin,

2) Lipopolysaccharides,

3) Outer membrane

What is the purpose of Gram staining symbiotic bacteria in this lab?

To determine whether the bacteria are Gram-positive or Gram-negative based on cell wall structure.

What is the first step of the Gram stain procedure?

Apply crystal violet (primary stain).

What is the function of crystal violet in Gram staining?

Stains all bacteria purple initially.

What is the second step of the Gram stain procedure?

Apply iodine (mordant).

What is the function of iodine in Gram staining?

Forms a crystal violet-iodine complex that helps retain the stain.

What is the third step of the Gram stain procedure?

Apply alcohol or acetone (decolorizer).

What is the function of the decolorizer?

Removes stain from Gram-negative cells but not Gram-positive cells.

What is the fourth step of the Gram stain procedure?

Apply safranin (counterstain).

What color do Gram-positive bacteria appear after Gram staining?

Purple

What color do Gram-negative bacteria appear after Gram staining?

Pink or Red

Why is Gram staining important when studying symbiotic bacteria?

It helps identify cell wall structure, which relates to function and antibiotic sensitivity.

Put the steps of the Gram stain in the correct order.

A. Iodine

B. Crystal violet

C. Safranin

D. Alcohol/acetone

B. Crystal violet

A. Iodine

D. Alcohol/acetone

C. Safranin

What does Gram-positive mean?

Bacteria with a thick peptidoglycan layer that retain crystal violet.

What does Gram-negative mean?

Bacteria with a thin peptidoglycan layer and an outer membrane.

What does it mean if bacteria LOSE crystal violet during Gram staining?

They are Gram-negative.

Why does peptidoglycan thickness matter in Gram staining?

It determines whether the crystal violet stain is retained or lost.

What plant structure contains the symbiotic bacteria studied in this lab?

Root nodules.

What is the symbiotic relationship between legumes and root nodule bacteria?

The bacteria fix atmospheric nitrogen for the plant, while the plant provides carbohydrates and shelter.

What genus of bacteria is commonly found in legume root nodules?

Rhizobium

Are Rhizobium bacteria Gram-positive or Gram-negative?

Gram-negative.

What is nitrogen fixation?

The conversion of atmospheric nitrogen (N₂) into ammonia (NH₃), a usable form for plants.

Where does nitrogen fixation occur in legumes?

Inside root nodules.

Define symbiosis.

A close biological relationship between two different species.

Define mutualism.

A type of symbiosis where both organisms benefit.

Define root nodule.

A specialized plant structure that houses nitrogen-fixing bacteria.

Why do plants need nitrogen?

used in the formation of proteins, nucleic acids (DNA, RNA) and ATP.

Define the characterisitcs of Anabaena

genus of filamentous, photosynthetic cyanobacteria capable of nitrogen fixation.

What is Azolla?

Azolla is a small aquatic fern that forms a mutualistic symbiotic relationship with Anabaena

Where do Anabaena live?

lives in the leaf cavities and fixes nitrogen of Azolla.

What are legumes?

flowering plants in the family Fabaceae that form root nodules containing nitrogen-fixing bacteria (usually Rhizobium), allowing them to obtain usable nitrogen from the atmosphere.

How does nitrogen fixation in Azolla differ from nitrogen fixation in legumes?

Azolla relies on cyanobacteria (Anabaena), while legumes rely on bacteria (Rhizobium) housed in root nodules.

Are Cyanobacteria gram-negative or gram-positive?

Gram-negative photoautotrophs

What are phycobilins?

are red, blue, and purple photosynthetic pigments found in cyanobacteria to convert light energy

What structure allows for cyanobacteria to fix nitrogen?

Heterocyst

Why do we LOVE cyanobacteria?

cyanobacteria changed early conditions on planet with their production of oxygen through photosynthesis.

During stressful environmental conditions, cyanobacteria produce ______.

Akinetes

What are Akinetes?

is a spore-like structure that encapsulates cyanobacteria's genetic information until conditions are hospitable again.

Put the steps of a Wet Mount in order.

A. Flatten out specimen

B. Place specimen on slide

C. Add coverslip starting at a 45 degree angle until flat

D. Add one to two drops of water

B > A > D > C

How do cyanobacteria typically grow in nature?

Cyanobacteria often live in colonies, forming filaments or spherical clusters of vegetative cells that are surrounded by a sheath or embedded in a gelatinous matrix.

What are vegetative cells in cyanobacteria?

the normal, metabolically active cells of cyanobacteria that carry out photosynthesis and growth.

What is a sheath in cyanobacteria?

a protective outer covering that surrounds cyanobacterial filaments or colonies, helping protect cells from desiccation and environmental stress.

What are the 3 types of Cyanobacteria?

1) Oscillatoria

2) Anabaena

3) Merismopedia

What is the general shape are Oscillatoria?

long filaments of rectangular cells, width > length, covered with a sheath.

How do Oscillatoria reproduce?

reproduces asexually by fragmentation

What do Oscillatoria dead cells look like?

Dead cells within filaments are indicated by dark bands.

What are the segments in between dead cells called in Oscillatoria?

hormogonia

What are the purpose of hormogonia in Oscillatoria?

where fragmentation occurs in Oscillatoria

What is the general shape of Anabaena?

barrel-shaped vegatative cells surrounded by a gelatinous matrix.

What are the 2 cells types in Anabaena?

Heterocyst- clear balls

Akinetes- large oval balls

(both within the chain)

What type(s) of reproduction do Anabaena go through?

reproduction by fission or fragmentation

What is the general shape of Merismopedia?

flat rows, forming rectangular colonies held together by a mucilaginous matrix.

Which of the following cyanobacteria can form associates with Azolla?

A) Anabaena

B) Merimopedia

C) Oscillatoria

A) Anabaena

B) Merimopedia