MBIO1010 Midterm

Prokaryote

A unicellular organism that lacks a nucleus and membrane bound organelles

Robert Hooke

Start of cell theory 1st to see&describe cells following invention of the microscope.

Antoni van Leeuwenhoek

discovered bacteria with the microscope. He calls 'animalcules'

Edward Jenner

Smallpox vaccine. Injected child with cowpox and later discovers child was immune to small pox

Alexander Fleming

discovered penicillin. Presence of the mold Penicillium chrysogenum inhibits growth of bacteria. Accidental discovery that revolutionized medicine

4 important properties of water

polarity, can form 4 hydrogen bonds, temperature stabilizing ability, solvent properties

Carbohydrates

Energy source immediately used by cells. Contain C,H,O.

Monosaccharides-glucose fructose

Disaccharides-sucrose

Polysaccharides-cellulose,glycogen (often too large for human digestion)

Steroids

Made of four rings of carbon. Found mainly in eukaryotes

RNA

Ribose sugar

Single stranded

Communicates instructions of DNA

nucleotides A,C,G,U

Bacterial Motility

Flagellar proteins differentiate between strains

Flagella can move clockwise/counter

Movement depends on energy production

Eukaryotic Cytoplasm

Similar to prokaryotic

Located in plasma membrane but outside of nuclear membrane

Contains cytoskeleton(provides support&shape, transports substances through cell)

2 lenses in compound microscope

ocular and objective. Magnification calculation is ocular X objective

Physical requirements for microbial growth

temperature, pH, osmotic pressure

Thermophiles

heat loving microbes

45-70

Optimal 60

Cannot cause disease in human body

Food Safety

Uses hot&cold temps to control bacterial population

Heat kills mesophiles&psychrotrophs on food

Cold slows growth of microorganisms (only psychrotrophs will grow in fridge and do so very slow)

Eukaryote

A cell that contains a nucleus and membrane bound organelles. Single OR multi cellular. Includes: protistes,fungi,plants,animals

Naming Microorganisms

Genus and species: Must be italicized or underlined. Strain is NOT italicized or underlined

Why is microbiology important?

For human health(antibiotics), Environment(nutrient cycling, decomposition)

used for fermentation

cell theory

All living things are composed of cells. All cells come from other cells

spontaneous generation

Hypothesis stating that bactieria/life could arise from nonliving matter. Louis Pasteur rejected

Biogenesis

development of life can only come from preexisting life

Louis Pasteur

Aseptic technique using swan neck flask. Sterilized broth remains sterile indefinitely until flask is tilted & contaminated with microorganism from air.Food spoilage likely comes from air, not spontaneous generation

Fermentation

Yeast converts sugar into alcohol in the absence of air

Pasteurization

treating a substance with heat to kill or slow the growth of pathogens. Prevents souring of milk/beer

Robert Koch

developed the germ theory of disease(belief that microorganisms are responsible for disease). Koch's postulates

Paul Elrich

selective toxicity (kill/inhibit growth of pathogens while leaving host cells unharmed) developed Salvarsan which was used to cure syphillis

Atomic Structure

Electron(-)on outer shell, neutron(n)and proton(+)in center

Atom

Basic unit of matter Smallest particle of an element

Element

A pure substance made of only one kind of atom

Molecule

A group of atoms bonded together

Ions

positively and negatively charged atoms. Cation is + and anion is -

covalent bond

A chemical bond that involves sharing a pair of electrons between atoms in a molecule

ionic bond

Formed when one or more electrons are transferred from one atom to another. Weaker than covalent

hydrogen bond

weak covalent attraction between a hydrogen atom and another electron loving atom. Electrons not evenly shared, results in partial charges

inorganic compounds

Compounds that do not contain carbon

organic compounds

contain carbon

Lipids

Energy storage. Non polar/hydrophilic

Fats

glycerol and fatty acids. Monoglyceride,diglyceride,triglyceride

fatty acids

saturated:no double bonds , saturated with H atoms

unsaturated: Atleast 1 double bond, less H atom

Phospholipids

glycerol + 2 fatty acids + 1 phosphate group

Found in membranes of living cells.Primary component of the plasma membrane

Proteins

Chains of amino acids(20 different). AA joins together by peptide bonds . Sequence of AA is important in determining the shape of protein

amino acids

monomers of proteins. Contain C,O,H,N(and some have sulfur)

nucleic acids

DNA and RNA

3 components of a nucleotide

Pentose sugar, phosphate group, nitrogenous base (A,C,G,T,U)

DNA

Deoxyribose sugar

Double helix

Double stranded (held together by H bonds)

Makes up genes (contains genetic info)

Nucleotides A,C,G & T

Bacterial Morphology

Cocci (spheres)

Bacilli (rods)

Spirilla (spirals)

Glycocalyx

"Sugar coat"

Gelatinous & sticky polymer composed of sugar/protein/both

Secreted onto cell wall

Slime layer is disorganized and loosely attached

Capsule is organized and firmly attached

capsule

Contributes to virulence (protects organism from phagocytosis)

Capsule is sticky and allows organism to adhere and colonize

Some organisms use capsule as energy source

Flagella

A long, whip-like filament that helps in cell motility. Found in prokaryotes (only sperm in eukaryotes)

basal body

anchors the cilium or flagellum to plasma membrane & cell wall

filament

Composed of circular flagellum protein, forms a helix around a hollow core

Flagellar Arrangements

monotrichous:single polar flagella

Lophotrichous: 2+ flagella on 1 or both ends of the cell

amphitrichous:a tuft of flagella on each end

peritrichous:flagella on entire cell surface

Bacterium changes direction&speed

Run/swim:Movement in 1 direction for continuos period of time

Tumble:abrupt/random changes in direction

Phototaxis

Bacterial movement in response to light

Chemotaxis

Bacterial movement in reaction to a chemical stimulus

Fimbriae

Hairlike appendages that allow for attachment

Shorter thinner & straighter than flagella

Made of pilin protein

Found in many G- bacteria

Without fimbriae colonization can't occur=disease can't occur

Pili

Join bacteria together for DNA transfer

Conjugation

In bacteria, the direct transfer of DNA between two cells that are temporarily joined by pili

bacterial cell wall

composed of peptidoglycan.

Semi-rigid & permeable

Provides cell with characteristic shape

Prevents cell rupture

Important to classify G+ vs. G- bacteria

peptidoglycan

consisting of modified sugars (a repeating disaccharide) cross-linked (lattice) by short polypeptides. Composed of NAM N-acetyl muramic acid @ NAG N-acetyl glucosamine

Gram positive cell wall

Thick peptidoglycan

Teichoic acids(wall teichoic extend out from peptidoglycan. Lipotechoic connect plasma membrane to peptidoglycan)

G+ only have the plasma membrane

gram negative cell wall

thin peptidoglycan layer

Plasma membrane

outer membrane containing lipids , proteins , and lipopolysaccharides (lipid portion=toxic. Endotoxins)

Polysaccharide portion composed of O sugars

Gram stain

A staining method that distinguishes between two different kinds of bacterial cell walls.

steps of gram stain

crystal violet, iodine, alcohol, safranin

Importance of peptidoglycan

Only in bacteria

Common target for host defence & chemotherapy

Many antibiotics target peptidoglycan (ex.penicillin)

plasma membrane

- selectively-permeable phospholipid bilayer

-Barrier between intra&extra cellular environments

-alcohol disrupts it

Cytoplasm

A jellylike fluid inside contained inside the plasma membrane.

Contains materials needed for life (AA,carb,enzymes)

Contains organelles

Nucleoid

Contains chromosome & all genetic info required

No nuclear membrane

Bacteria may also have plasmids ; small circular double stranded DNA molecules (these non essential genes can help bacterium survive in adverse conditions)

Ribosomes

site of protein synthesis.

Several antibiotics target ribosomes (selective toxicity) . Targets prokaryotic ribosomes only

subunit of ribosome

Prokaryotes: 50S+30S = 70S

Eukaryotes 60S+40S= 80S

inclusion bodies

Storage sites for nutrient granules

Different bacterial species contain different inclusion bodies ; can serve as a basis for identification

Include: polysaccharide granules, enzymes, lipid inclusions

Endospore

Allow bacterium to resist heat,desiccation,chemicals&radiation

ONLY G+ bacteria have endospores

Spores are extremely difficult to get rid of(requires an autoclave)

true sterilization

Requires endospores to be destroyed

steps of sporulation

1) bacterial cell replicates DNA

2)septum forms dividing the cell

3)larger compartment engulfs smaller one forming a forespore within the mother cell

4)peptidoglycan & other protective material forms around forespore(spore coat)

5) spore is freed from mother cell

Eukaryotic flagella and cilia

Long&flexible

Contain protein&cytoplasm

Move in whip like fashion

Used for motility

Eukaryotic cell wall

- not in animal cells

- composed of single polysaccharide

- cellulose=plants and algae

- chitin=fungi

- not made of the polypeptide peptidoglycan

Eukaryotic plasma membrane

Same structure as prokaryotic

Contains phospholipids,proteins&sterols

Capable of endocytosis

membrane bound organelles

Only eukaryotic cells have

Ex)nucleus, mitochondria , chloroplasts(only in plants)

2 types of microscopes

light microscope and electron microscope

Resolution

Distinguish fine detail&structure

Distinguish 2 points a certain distance apart (6nm resolving power can distinguish 2 point at LEAST 6nm apart)

General principle of resolution

the shorter the wavelength, the better the resolution

electron microscope

Beams of electrons instead of light

Electrons have shorter wave length

Better resolution

Can achieve greater magnification(

transmission electron microscope

View internal cell structure

Cell must be cut (thin sectioning)

AND stained with a heavy metal

scanning electron microscope

Can only view surface of an object

Specimen must be coated with thin film of heavy metal

Wide range of magnifications

scanning tunneling microscope

Most powerful of electron microscopes, used to visualize atoms

Thin metal probe scans specimens revealing surface irregularities

Staining procedure

1)'smear' this film of material containing microorganism

2)sample is fixed by passing through flame

3)stain is applied(sometimes mordant also)

4)stain is removed by rinsing

5)stained sample is viewed under light microscope

positive stain

Basic stain

dye sticks to the specimen and gives it color

Background appears clear

Ex)crystal violet

negative stain

Acidic stain

simple stain that stains the background but leaves the bacteria unstained

Ex)nigrosin

simple stain

use of a single basic dye

Sometimes mordant is used, intensifying the stain

differential stain

Used to distinguish between bacteria

Important for diagnostics

1)Gram stain

2)Acid-fast stain

Gram stain

A staining method that distinguishes between two different kinds of bacterial cell walls.(G+ or G-)

steps of gram stain

crystal violet, iodine, alcohol, safranin

Rinse between each

special stains

Capsule stain

Endospore stain

Flagella stain

capsule stain

Bacterial cell is stained with positive stain

Background is stained with negative

Capsule does not take up dye, giving it a clear halo

endospore stain

Malachite green colors the endospore green

Counterstain safranin colors the rest of the cell pink

flagella stain

The staining agent adheres to and coats the otherwise thin flagella, making them visible with the light microscope.

Temperature Requirements for microbial growth

Minimum:lowest temp that supports growth.organism is alive but not growing

Optimum:preferred temp that best supports growth

Maximum:highest temp that can support grown. Bacteria dies at higher temps

Psychrophiles

cold loving

-5 to +15

Dies at 20

Found in deep ocean & polar environments

Psychrotrophs

0°C - 35C

Optimal 15-30

Cause food spoilage in fridge

Mesophiles

moderate temperature loving microbes

10-45

Optimal 30- 37

Most pathogens optimal temp is 37

Alive in your fridge but not growing