Microbiology Test I

Who performed an experiment to disprove spontaneous generation theory?

Louis Pasteur conducted experiments that demonstrated microorganisms are responsible for fermentation and spoilage, proving that life does not arise spontaneously.

Who was the first to link a disease to a specific bacterium?

Robert Koch developed the germ theory of disease, establishing a connection between infectious diseases and bacteria.

Who attempted to synthesize life in a test tube?

Stanley Miller and Harold Urey conducted experiments in the 1950s that simulated early Earth conditions, aiming to create organic compounds and explore the origins of life. They were not successful but did manage to give rise to amino acids and other simple molecules.

Bacterial shape: Spherical

Coccus or Cocci

Bacterial shape: rod-shaped

bacillus or bacilli

Bacterial shape: curved-rod

Vibrio or vibrios

Bacterial shape: waves or spirall

Spirillum or spirilla

Bacterial shape: varied

Pleomorphic

How big are bacterial cells?

Most are smaller than eukaryal cells and larger than viruses (.5-5micrometers).

**Thiomargarita namibiensis is up to 700micrometers

**Some mycoplasma cells are smaller than .2micrometers

What is in the cytoplasm of bacterial cells?

Nucleoid, chromosome packing proteins, enzymes, regulatory factors, ribosomes, plasmids, enzyme breaking down substrates, inclusion bodies, gas vesicles, cytoskeletal structures

What is the nucleoid of the bacterial cell?

The largest area. Mass of DNA, usually consisting of 1 circular chromosome. Not surrounded by a phospholipid membrane bilayer and is coated with protein and RNA molecules.

What are the inclusion bodies of a bacterial cell?

Granules that store carbon, nitrogen, sulfur, or phosphorus.

Polyhydroxybutyrate granules store carbon

Sulfur globules store sulfur

What are the gas vesicles of bacterial cells?

Vesicles filled with air, found in aquatic bacteria— and used for buoyancy control. It can regulate cells position in water in response to light or nutrients.

What is the bacterial cytoskeleton made of?

FtsZ

MreB

ParM

Function of FtsZ microfilament?

Involved in bacterial cell division by forming a Z-ring (involved in separation of cell after replication). Recruits new membrane and new cell material.

What is a protein filament?

Monomers: individual polypeptide chains folded into 3-dimensional tertiary structure. They form the filaments.

Function of MreB filament?

Provides structure to non-cocci bacteria. Create a helix internal structural support (for bacilli)

Function of ParM filament?

Directs plasmid movements during cell division

What is a plasmid?

A plasmid is extrachromosomal— floating in the free space of cytosol

What is the cell envelope made of?

The plasma membrane and the bacterial cell wall. Order is cytoplasm → plasma membrane → cell wall. Made up of phosphoric (phosphate head group and non polar fatty acid tail).

What can diffuse freely through the membrane?

Nonpolar, uncharged molecules like O2 and CO2

Osmosis:

Diffusion of water through plasma membrane— through aquaporins.

Does diffusion need energy?

No

Does facilitated diffusion require energy?

No

What is facilitated diffusion useful for?

Polar molecules that can not freely pass muss pass through facilitated diffusion (channels)

What is Co-Transport

It is used to drive movement against the concentration gradient

Co-transport: Symporters

Both molecules move in the same direction

Co-transport: Antiporters

Molecules move in opposite directions

Active Transporter: ABC Transporters

ATP binding cassette. ATP binds to membrane protein, and provides energy to move molecules against their concentration.

Where is the cell wall?

Outside the membrane

What does the cell wall do?

Provide protection & shape

What is the cell wall made up of in the bacterial cell?

Peptidoglycan

What is peptidoglycan?

Varies from species to species but is an amino acid sequence in peptides

Can the cell wall be degraded naturally and if so by what?

Yes, by lysozyme

Where else is lysozyme found?

Tears, saliva, and milk

Can the cell wall be degraded artificially and by what?

Yes, by B-lactam antibiotics.

How do beta lactam antibiotics work?

They bind to penicillin binding proteins (PBP) which are essential in peptidoglycan cross linking.

What happens when the cell wall is degraded?

Cell cannot withstand osmotic stress

What is a gram stain and who invented it?

A gram stain is a stain method invented by Hans Christian Gram.

Describe a gram positive cell and its characteristics

Stains purple, narrow peiplasmic space, teichoic acids in the peptidoglycan.

examples: mycobacterium tuberculosis, streptococcus

Describe a gram negative cell and its characteristics

Stains pink, varied periplasmic space, outer membrane of LPS (why stain is lost— washing with alcohol removes the membrane)

examples: escherichia coli, neisseria gonorrhoeae

What is the periplasmic space?

The space between the cell membrane and the cell wall

What are porins?

Diffusion channels in gram negative

What are TonB-dependent receptors?

Catalyze high affinity active transport across outer membrane for gram ne

What is LPS

Lipopolysaccharide which stabilizes the membrane in gram negative

What is LTS?

Lipoteichoic acid with unknown function found in gram positive.

Describe flagella in bacterial cells?

Used for motility and made of rigid filaments. The number and location depend on the species.

How do bacterial cells get their flagella to move?

Chemotaxis, which is a process that uses chemical signals to direct movement

Describe pili in bacterial cells?

Adherence molecules to stick to surfaces

What are the two types of pili

Adhesive and sex.

What are sex pili specifically for?

Conjugation— which is when bacteria share plasmid DNA

Describe capsules of the bacterial cell

Can provide adhesion, defense against host immunity, and protection against desiccation (drying). They also form biofilms which help them survive in harsh environments. It is made up of a thick layer of polysaccharides.

Describe a surface-array (S Layer) in bacterial cells?

Can act as armor against bacteriophages and is made up of interlocking proteins.

How do we classify & name organisms?

By genus (related species) and species (strains sharing common features).

What does classification of bacteria depend on?

Cell morphology, colony morphology, growth characteristics, biochemistry, physiology, DNA sequence data

Function of nucleus in eukaryotic cells?

Stores genetic info and has a double membrane structure.

Contains linear chromosomes

Nucleolus exists within nucleus (ribosome synthesis)

How is DNA organized in the eukaryotic cell?

DNA is wrapped around an octamer of histone proteins to form a chromosome.

Which domains out of the three have histones?

Eukarya and Archaea

What does the Rough ER do?

Translates RNA to protein

Function of Golgi apparatus

Packages, modifies, and distributes proteins

What process does mitochondria use to produce ATP?

Chemiosmosis

Similarities between Mitochondria and Chloroplast?

Both have 2 membranes, involved in energy production/metabolism, both are semiautonomous (their own DNA, ribosomes, and transcription), roughly same size/shape of bacterial cell

Contents of plasma membrane in eukaryotic cells?

Phospholipid bilayer, cholesterol and proteins, maintains homeostasis, embedded protein allow molecule transport

Which eukaryotic microorganisms have a cell wall?

Fungi & Algae

What are cell walls of Fungi made of?

Chitin

What are cell walls of algae made of?

Cellulose

What is the eukaryotic cytoskeleton made of?

Microtubules, microfilaments, and intermediate filaments

Building blocks of microtubules?

Alpha and beta tubulin

Building blocks of microfilaments?

Actin

Building blocks of intermediate filaments?

Varied: laminated, keratin, vimentin

Function of microtubules?

Separation of chromosomes in cell division

Function of microfilaments

Maintain cell shape, create division furrow, cell movement

Function of intermediate filaments?

Nuclear structure, cell-cell interactions. (*not as dynamic as microtubules and microfilaments)

Extracellular structures involved in movement?

Flagella & cilia

What is a model organism and why do we use them?

Model organisms are organisms which were commonly study due to being cheap and easy to grow.

Fungi Model

Saccharomyces cerevisiae: heterotrophic, found in bread, beer, and wine

Protozoa Model

Giardia lamblia. “animal-like” protist: genetically old, causes intestinal infection and diarrhea (does not have a mitochondria - anaerobic)

Algae Model

Chlamydomonas: plant like protist, some are single celled but many are multicellular, all autotrophic

Model Slime-mold

Dictyostelium discoideum: fungi like protist, cellular or a-cellular. Model for ecology, cell motility, and cell-cell communication

How do eukaryotes divide asexually?

Starts with 1 cel and creates 2 identical daughter cells. Both haploid and diploid cells can undergo mitosis (prophase, anaphase, metaphase, telophase)- followed by cytokinesis.

How do eukaryotes divide sexually?

Starts with 1 diploid cell and creates 4 non-identical haploid cells. 1 round of DNA replication followed by 2 rounds of cell division (meiosis II & II).

Describe life cycle of S. cerevisia

Can alternate between haploid and diploid, yeast bud when dividing via mitosis, and ascus is formed following meiosis.

Describe life cycle of Chlamydomonas

They maintain a motile haploid state, and when conditions become bad they fuse into diploid form and generate a spreadsheet (protection)

Examples of symbiotic relationships:

Amoeba + bacteria & protozoa + algae (paramecium)

What eukaryotic organism causes the most sickness in humans?

Protists

Which eukaryotic organisms cause disease in plants?

Protozoa and fungi

Shapes of Archaea

Rods, spheres, spirals, irregular (sulfolobus), rectangular (thermoproteus)

What is similar between Archaea and Bacteria?

No nucleus, use nuclei and plasmidsW

hat is similar between Archaea and Eukarya?

Chromosomal DNA organized around histones (but 4 instead of 8)

Describe cell envelope (plasma membrane) of Archaea

Have isoprenoids instead of fatty acids, G1P instead of G3P, and can exist in a monolayer (which stabilizes membrane in extreme environments)

Describe cell wall of archaea

May be composed of pseudomurein instead of peptidoglycan. Some lack a cell wall.

Describe flagella of Archaea

Same function of motility but different structure

Describe adhesion in Archaea

Can also produce s layers like bacteria, which protects and adheres to surfaces. Some use cannulae to adhere to each other.

How many super phyla can Archaea be broken down into?

Four. Euryarchaeota, TACK, DPANN, and Asgard

Describe Euryarchaeota: Methanogens

All identified methanogens are anaerobes and cannot survive in the presence of oxygen. Found in GI tract of animals, male and ocean sediments. They perform anaerobic respiration. They reduce H2 to CH4.

Describe Euryarchaeota: Halophiles

Oldest. Require NaCl concentration greater than 1.5M and live in salty environments. Great Salt Lake and Dead Sea. Ocean is .6M. They maintain high intracellular ion concentration. They have higher content of GC nucleotides which are joined by hydrogen bonds — weak but plentiful. They also have highly acidic proteins that remain stable in high salt.

Describe Crenarchaeota (TACK)

Thermophiles and hyperthermophiles (high temps). Many are acidophilus (thriving in low pH). Some are barophiles (high pressures).

Modifications to help extremophiles adapt to their environments?

More argine/tyrosine and less cysteine/serine.

Form lipid monolayers (stronger and more stability in plasma membrane)

More alpha helical regions

More salt bridges and more side chain interactions in proteins

Strong chaperone protein complexes

Describe Nanoarchaeota: (DPANN)

Most recent. Appears to be one of the smallest. F

orm distinct relationships with host organism.

Small genome sizes, small cells, metabolic

Dependence on another organism.