microbio 2460 chapter 3

spontaneous generation

ancient belief: life can arise from nonliving matter

Key scientists of spontaneous generation

Francesco Redi, John Needham, Lazzaro Spallanzani

spontaneous generation

ancient belief: life can arise from nonliving matter

Key scientists of spontaneous generation

Francesco Redi, John Needham, Lazzaro Spallanzani

Francesco Redi

This scientist disproved spontaneous generation by showing that maggots do not spontaneously arise from decaying meat.

John Needham

Believed there was a life force that caused spontaneous generation

Lazzaro Spallanzani

replicated redi and needham's experiments, disproved of spontaneous generation

Louis Pasteur

Disproved of spontaneous generation, swan neck experiment (won Alhumbert prize)

Modern Cell Theory

All living organisms are composed of one or more cells

2 Basic Tenents of Modern Cell Theory

1. Cell is a basic unit of structure

2. All cells come from existing cells (recall spontaneous generation)

People of Cell Theory: Tenet 1

1. Robert Hooke- cork tissue

2. Matthias Schleiden- plant tissue

3. Theodor Schwann- compared plant and animal cells

People of Cell Theory: Tenet 2

1. Robert Remak- cells come from other cells (i.e. cell division)

2. Rudolf Virchow -published Cellular Pathology

(all cells arise from cells)

Endosymbiotic Theory

Origin theory about cellular structures (how Mitochondria and chloroplasts were originally prokaryotic cells)

Famous scientist: Konstantin Mereschkowski, Ivan Wallin, Lynn Margulis

Konstantin Mereschkowski (1905)

Proposed that chloroplasts could reproduce independently and must have lived outside plant cell

(said DNA could be found in organelles)

Ivan Wallin (1926)

showed mitochondria outside of cell (but likely contamination)

also said DNA could be found in organelles

Lynn Margulis (1967)

mitochondria and chloroplasts are of prokaryotic origin

-

DNA, ribosomes, binary fission

Germ Theory of Disease

Diseases may result from microbial infection

Famous scientist: Girolamo Fracastoro, Ignaz Semmelweis, John Snow, Louis Pasteur, Joseph Lister, Robert Koch

Girolamo Fracastoro (1546)

"spores" can be carried on clothing and transferred between individuals

Ignaz Semmelweis (1847)

"Contaminated" physicians transferred causative agent to patients

-promoted handwashing as a solution

John Snow (1848)

cholera outbreaks in London traced to sewage in drinking water

Louis Pasteur (1856)

Organisms could spoil food and therefore people

Joseph Lister (1867)

Handwashing + carbolic acid in surgery for disinfection

Robert Koch (1884)

a specific microbe can cause a specific disease

-koch's postulates

Common elements of the general cell

cytoplasm, plasma membrane, chromosome(s), ribosomes

Prokaryotes

No nucleus

domains: bacteria & archaea

eukaryotes

nucleus

domain: eukarya

Unique elements of the prokaryotic cell

1. nucleoid

2. Inclusion bodies

3. plasmids

4. Pili

5. Fimbriae

6. .Endospore

common prokaryotic cell arrangments

cell wall

found in eukaryotes & prokaryotes, Found outside the cell membrane, Aids in protection against osmotic pressure changes

Osmosis

diffusion of water in response to different solute concentrations

isotonic solution

same solute concentration, no movement

hypertonic solution

higher water concentration, water moves out (plasmolysis)

crenation

cell shrivels due to lack of water

hypotonic solution

less water concentration, water moves in

Nucleoid

Central region of cell with DNA and RNA associated proteins, circular/haploid chromosomes

plasmids- circular, non essential DNA

Prokaryotic ribosomes

-Sites of protein synthesis

-70S (50S + 30S)

inclusions

Structures used for storage of glycogens, starches, etc.

Polyhydroxybutrate (PHB)

inclusion with monolayer that can be harvested for biodegradable plastics

Volutin granules

polymerized inorganic phosphates for biofilm formation

Magnetosomes

magnetic iron oxide or iron sulfide allow cell to align along a magnetic field

Gas Vacuole

a prokaryotic inclusion, protein-lined vesicle of gas that alters buoyancy

Carboxysome

a prokaryotic inclusion containing RuBisCO and carbonic anhydrase for carbon metabolism

endospores

Structure formed in dormant state to protect genome

Resistant to extreme temperatures and radiation

Do not absorb Gram stain, only special endospore stains,

Dehydrated (no metabolic activity)

Dormant (no growth or metabolic activity)

sporulation process

1. DNA replicates

2. membranes form around DNA

3. forespore forms additional membranes

4. protective cortex forms around spore

5. protein coat forms around cortex

6. spore is released

vegetative cells

present in normal favorable conditions, Sensitive to extreme temperatures and radiation, Gram-positive, Normal water content and enzymatic activity, Capable of active growth and metabolism

clinically important endospore formers

-B. anthracis - causative agent of anthrax

-C. difficile - causes pseudomembranous colitis

-C. perfringens - causes gas gangrene

-C. botulinum - causes botulism

-C. tetani - causes tetanus

cell (plasma) membrane

-Present in all organisms

-phospholipid bilayer that protects and encloses the cell

-Has selective permeability to move molecules in & out (most important function)

archaea cell membrane

-Ether linkages, not ester

-Many are monolayer, not bilayer

Membrane Transport Mechanisms (4)

1. Passive transport - diffusion of molecules (ex. CO2)

2. Facilitated diffusion - carrier proteins that ferry larger molecules across w/o ATP

3. Active transport - membrane proteins that move molecules with ATP

4. Group translocation - molecule chemically modified as it enters a cell against unfavorable concentration gradient.

Photosynthetic Membrane Structures

-Cyanobacteria and photosynthetic bacteria have specialized structures to perform photosynthesis

- Infoldings of the plasma membrane encloses photosynthetic pigments (e.g. chlorophyll)

Cyanobacteria

Photosynthetic, oxygen-producing bacteria (formerly known as blue-green algae).

Photosynthetic bacteria

chromatophores, lamellae, or chlorosomes

Function of cell wall

-protect cell from adverse environment conditions

-differentiates Gram (+) and Gram (-)

-Peptidoglycan (bacteria) is major component and provides shape

cell wall in myobacteria

have embedded mycolic acid (Recall Acid-fast stain method)

cell wall in gram +

have peptidoglycan in thicker layers than Gram (-) & embedded teichoic acids

cell wall in gram -

-have outer membrane that contains lipopolysaccharide (LPS)

-Contributes to fever, shock, & hemorrhaging

cell wall of archaea

-pseudopeptidoglycan

-a few archaea do not have cells walls

Glycocalyces and S-Layers

1. Glycocalyx - sugar coat outside cell wall that allows cells to adhere to surfaces, protect against desiccation and/or antibiotics and disinfectants

2. S layer - composed of structural proteins and found outside cell wall; thought to help with rigidness and against osmotic pressure changes

2 kinds of glycocalyx

1. capsule- polysaccharides or proteins

2. slime layer- loosely attached and made of polysaccharides, glycoproteins, or glycolipids

Filamentous Appendages (2 Kinds)

1. Fimbriae - short bristly proteins that aid in attachment

2. Pili - longer appendages aid in attachment OR transfer of DNA (sex pilus)

Flagella

-Structures used by cells to move in aqueous environment towards an environmental signal

- Basic structure includes: basal body, hook, & filament

Phototaxis

moving toward light signal

chemotaxis

moving toward chemical signal

magnetotaxis

moving toward magnetic field signal (also uses magnetosomes)

Unique elements of the eukaryotic cell

1.Nucleus

2.Mitochondria

3.Endoplasmic Reticulum

4.Golgi Apparatus

5.Lysosomes

6.Peroxisome

7.Cytoskeleton

8.Cilia*

9.Chloroplasts*

*not all cells contain this structure

nucleus

-DNA material is surrounded by a membrane

-Chromosomes are linear

Nucleolus

-Dense region in nucleus where ribosomal RNA (rRNA) is synthesized

eukaryotic ribosomes

-80S (40S and 60S)

-Chloroplasts & mitochondria have smaller(70S) ribosomes

Endomembrane System function

move materials around & within the cell

Included organelles of Endomembrane System

-Endoplasmic reticulum(smooth & rough)

-Golgi apparatus

-Lysosomes

-Vesicles

Endoplasmic Reticulum

-Group of tubules & flat sacs (cisternae) that function to synthesize various molecules

rough er

ribosomes are present & synthesizes proteins

smooth er

no ribosomes and synthesizes lipids, metabolizes carbs, and detoxifies compounds

Golgi Apparatus

-modifies lipids & proteins that arrive from ER

-Membranous disks (dictyosomes) stacked together

-Vesicles carry modified molecules to other parts of the cell

Lysosomes

-Membrane bound organelles that contain digestive enzymes

-functions to break down food, damaged organelles or cellular debris

Peroxisomes (not part of Endomembrane System)

-Membrane bound organelles that produce hydrogen peroxide

-Function: contribute to lipid synthesis as well as break down molecules

Cytoskeleton

-Filaments inside the cell that provide structure and network for transport

-Main components:

1.Microfilaments

2.Intermediate filaments

3.Microtubules

Microfilaments

allow locomotion

intermediate filaments

-anchor nucleus and other organelles

-form nuclear lamina

microtubules

support the cytoskeleton, largest of the 3, function in flagella and cilia as well as cell division (centrosomes)

mitochondria

-Complex organelles and sites for aerobic respiration

-"power house" of the cell

-Composed of two lipid membranes

2 lipid membranes of mitochondria

1. outer - remnant of ancient cell membrane

2. inner - engulfed by ancestrial organism

chloroplasts

-Present in photosynthesizing eukaryotes(plants and algae)

-Major Components:

1.Outer membrane

2.Inner membrane

3.Thylakoid membrane system

Plasma Membrane

- Similar to prokaryotes but additional embedded molecules (sterols) that add to structure

-help fluidity and shape

Membrane Transport System

Same as prokaryotes: diffusion, facilitated diffusion, & active transport PLUS endocytosis & exocytosis

Eukaryotic Cell Walls of eukaryotic organisms

-Fungi & plants: cellulose

-Protists & algae: silica, agar, or calcium carbonate

-Fungi: chitin

Extracellular Matrix

-no cell wall

- Proteoglycans and fibrous proteins help maintain cell shape and stability

Flagella

-help locomotion

-flexible

-made of microtubules in 9+2 fashion

Cilia

-Unique to eukaryotes but not present in all

-Structure is similar to flagella but are shorter

-Function may be locomotion and also sweeping particles away from or towards cell