1. Spontaneous Generation to Eukaryotic Cells and Movement

A vocabulary-focused set of terms and definitions covering spontaneous generation, cell theory, endosymbiotic theory, prokaryotic and eukaryotic cell features, and key cellular structures and movements.

Spontaneous generation

The old belief that life can arise from nonliving matter; challenged by Pasteur and others; life is believed to come from life.

What is taxonomy?

The classification, description, identification and naming of living organisms.

What is classification?

The practice of organizing organisms into different groups based on their shared charcteristics.

Francesco Redi

Experiment showing maggots appear only when flies can access meat, challenging spontaneous generation.

John Needham

Early experiment that seemed to support spontaneous generation by heating broth to produce life.

Lazzaro Spallanzani

Experiment that countered Needham by showing boiled broth in sealed containers remained free of life.

Louis Pasteur

Demonstrated that life does not spontaneously appear using the swan-neck flask experiment; “Life only comes from life.”

What is biofilm?

A complex community of one or more microorganism species.

When does a biofilm form?

When planktonic (free floating) bacteria of one or mire species adhere to a surface, producing slime, and forming a colony.

What happens when a cell has a negatively charged cell wall?

The positive chromosphere in basic dyes will stick to the cell walls, making the stain a positive stain.

What happens when a cell has a positively charged cell wall?

The negatively charged chromosphere’s in acidic dyes are repelled by negatively charged cell walls, making it a negative stain.

What does simple staining do to the sample?

It is a single dye and it is used to emphasis the structure. All the organisms in the sample will be the same color.

What does differential staining do to the sample?

Distinguishes organisms based on their interactions with multiple stains.

What stains are used for differential staining in clinical settings?

gram staining, cid-fast staining, endospore staining, flagella staining, capsule staining.

What is the first step of gram staining?

Crystal violet, a primary stain, is applied to a heat-fixed smear, gives the whole cell a purple colour.

What is the second step of gram staining?

Gram iodine - a mordant, is added. Remains purple/blue.

What is a mordant?

A substance used to set or stabilize stains or dyes. In gram staining, the mordant iodine works with crystal violet, makes it into a clump and stays in thick layers of peptidoglycan in the cell walls.

What is the third step of gram staining?

Adding a decolorizing agent, usually ethanol or an acetone/ethanol solution. Specimens with thin peptidoglycan layers are more easily accessed and become colorless.

What is the final step of gram staining?

A secondary counterstaining, usually safranin, is added. The decolorized part of the cell will turn pink and will be less noticeable in the cells, then those that still contain crystal violet dye.

What color is a gram positive stain?

Purple

What color is a gram negative stain?

Is colorless when an alcohol is added. When Safranin is added it’s pink or red.

What are examples of basic stains?

Methylene blue, crystal violet, malachite green, basic fuchsin, carbolfuchsin, safranin

What is the purpose of basic stains?

To stain negatively charged molecules and structures, such as nucleic acids and proteins

What should be the outcome of basic stains?

Positive

What are some examples of acidic stains?

Eosin, acid fuchsin, rose bengal, Congo red.

What is the purpose of acidic stains?

To stain positively charged molecules and structures, such as proteins

What is the expected outcome of acidic stains?

Positive or negative, depending on the cells chemistry

What are some example of negative stains?

India ink, nigrosin

What is the purpose of negative stains?

To stain the background, not the specimen.

What is the expected outcome of negative stains?

Dark background with light specimen.

What are examples of gram stain dyes?

Crystal violet, gram’s iodine, ethanol (decolorizer), safranin.

What is the color of Acid-fast bacteria after staining?

Red

What is the color of non-acid-fast bacteria after staining?

Blue

What happens to acid-fast bacteria after staining with basic fuschin?

It resists decolorization by acid-alcohol.

What is non acid-fast bacteria counter stained with?

Methlylene blue

How does endospore stain work?

It uses heat to stain the endospores with malachite green. The cell is then washed and counterstained with safranin.

What is the purpose of endospore staining?

Distinguishes organisms within the sample that have endospores from those without.

What color to endospores appear?

Bluish-green. Other structure appear pink to red.

How is the flagella stain done?

They are coated with tannic acid or potassium alum mordant, then stained using pararosaline or basic fuchsin.

What is the purpose of gram stain?

To distinguish cells by cell wall type (gram-positive/gram-negative)

What happens when you add decolorizing agent to a specimen that’s has thick peptidoglycan layers in the cell walls?

They are much less affected and retain the crystal violet dye and remain purple.

Why are biofilms interesting to microbiologist and clinicians?

They posses unique characteristics, e.g. increased resistance against immune system and to antimicrobial drugs.

What do we use acid fast staining for?

To demonstrate the characteristics of acid fastness in certain bacteria and the cysts of Cryptosporidium and Isospora.

What is the most important application of acid-fast staining clinically?

To detect Mycobacterium tuberculosis in sputum samples to confirm or rule out diagnosis of tuberculosis.

What is capsule staining?

When a negative stain is used with India ink or nigrosin to stain the background, it leaves a clear area of the cell and capsule. Sometimes counterstains will be used to stain the cell and leave the capsule clear.

How do capsules appear in capsule staining?

Clear or as halos.

Biogenesis

Idea that living things arise from preexisting life.

Robert Hooke

First to observe plant cells (cork) in the 1660s, contributing to cell theory.

Schleiden

Helped establish that all plants are made of cells.

Schwann

Helped establish that all animals are made of cells; contributed to cell theory.

Virchow

Proposed that every cell arises from a preexisting cell.

What does a typical prokaryotic cell contain?

Cell membrane, chromosomal DNA (concentrated in nucleus), ribosomes, cell wall.

What are extra things a prokaryotic cell might have?

Flagella, pili, fimbriae, capsules

What shape are coccus?

Round

What shape are Bacillus (Bacilli)?

Rod

What shape are Vibrio (vibrios)?

Curved rod

What shape is coccobacillus (coccobacilli)?

Short rod

What shape is spirillum (spirilla)?

Spiral

What shape are spirochete?

Long, loose, helical spiral

What is tetrad?

The name of a grouping of four prokaryotic cells arranged in a square

What is Streptococcus (streptococci)?

Chain of cocci

What is staphylococcus (staphylococci)?

Cluster of cocci - prokaryotic cells

What is streptobacillus (streptobacilli)?

Chain of rod shaped prokaryotic cell

How is morphology maintained in a prokaryotic cell?

By the cell wall in combination with cytoskeletal element. The cell wall protects the cell from changes in osmotic pressure.

What is sporulation?

A process where a vegetative bacterial cell transforms into a dormant, highly resistant endospore. Allows bacterium to survive extreme conditions like heat, radiation, desiccation and chemicals.

How do endospores form?

1. DNA replicates.

2. Membrane forms around the DNA.

3. Forespore adds a membrane.

4. A cortex forms(thick peptidoglycan) between membranes.

5. Protein coat develops- now it’s extremely resilient.

6. Spores release - mother cell disintegrates.

Why are endospore important?

They are reproductive like fungal spores. Preserve bacterial genome in a dormant state. Enable bacteria (Bacillus and clostridium) to survive for years.

What is the bacterial plasma membrane?

A phospholipid bilayer with a variety of embedded proteins that perform various functions for the cell. Contains glycoproteins and glycolipids.

What is peptidoglycan?

Major component of bacterial cell wall. Only in bacteria! It’s layers composed of alternating molecules of N-acetylglucosamin (NAG) and N-acetylmuramic acid (NAM).

Why is peptidoglycan only being in a bacteria’s cell wall so significant?

Antibiotic drugs are designed to interfere with teh peptidoglycan synthesis , it weakens the cell wall making it susceptible to osmotic presure

Endosymbiotic theory

Theory that mitochondria and chloroplasts originated from ancient bacteria living inside larger cells.

Mitochondria

Powerhouse of the cell; site of respiration; contain their own DNA.

Chloroplasts

Site of photosynthesis in plants; contain their own DNA and have a double membrane.

Nucleoid

Region in prokaryotic cells where DNA is located; no true nucleus.

Plasmids

Small, circular DNA molecules in bacteria that carry extra genes.

70S ribosomes

Ribosomes in prokaryotes (and in organelles like mitochondria/chloroplasts); smaller than 80S.

80S ribosomes

Ribosomes in the cytoplasm and rough ER of eukaryotic cells; larger than 70S.

Endospores

Durable, dormant cell forms that survive harsh conditions.

Inclusions

Storage bodies within bacterial cells for nutrients/chemicals.

Ester-linked phospholipids

Phospholipid type in bacterial membranes with ester bonds.

Ether-linked phospholipids

Phospholipid type in archaeal membranes with ether bonds.

Gram-positive

Bacteria with a thick peptidoglycan layer and no outer membrane.

Gram-negative

Bacteria with a thin peptidoglycan layer and an outer membrane.

Peptidoglycan

Polymer forming bacterial cell walls; target of many antibiotics.

Pseudopeptidoglycan

Archaeal cell wall component similar to peptidoglycan but different.

Glycocalyx

Sticky coating (capsule/slime) that protects bacteria and aids attachment.

Fimbriae

Short, hair-like structures that help bacteria adhere to surfaces.

Pili

Longer projections that enable DNA transfer between bacteria (conjugation).

Flagella

Long, whip-like structures used for movement; structure can differ from prokaryotic to eukaryotic.

Nucleus

Membrane-bound organelle with DNA; contains a double membrane and pores.

Nucleolus

Nuclear substructure that synthesizes ribosomal RNA and assembles ribosomes.

Endoplasmic reticulum (ER)

Network of membranes; Smooth ER makes lipids/detoxifies; Rough ER has ribosomes and makes proteins.

Smooth ER

ER region that synthesizes lipids and detoxifies chemicals.

Rough ER

ER region studded with ribosomes; synthesizes proteins.

Golgi apparatus

Packages, modifies, and sorts proteins and lipids; adds sugars.

Lysosomes

Digestive organelles that break down particles and damaged parts.

Mitochondrion

Powerhouse of the cell; site of respiration; contains its own DNA.

Chloroplast

Organelle for photosynthesis in plants and algae; contains its own DNA.

Cytoskeleton

Network of filaments (microfilaments, intermediate filaments, microtubules) that supports cell shape and transport.

Microfilaments

Actin-based filaments involved in movement and shape.