microbio lab midterm 1

Non-cellular microbes

•Viruses

•Viroids

•Prions

cellular microbes

prokaryotic (bacteria, archaea) and eukaryotic

bacteria

can cause disease; most are beneficial to life

archaea

live in extreme environments; earth’s 1st organisms

algae

photosynthetic

protozoan

unicellular organisms with animal-like characteristics

fungi

often act as decomposers (single or multicellular)

helminths

worms; eggs and juvenile stages are microscopic

viruses

Simplest are just nucleic acid with a protein coat

• Can have DNA or RNA (not both)

• Can have additional structures like envelopes or “tails”

Obligate intracellular parasites

• Reliant on host mechanisms to replicate

Anton van Leeuwenhoek

first to observe and accurately describe live

microorganisms w/microscope

Robert Hooke

developed cell theory → all living things are composed of cells

Francesco Redi

disproved spontaneous generation (forms of life (microorganisms) arise spontaneously from nonliving matter)

Pasteur

demonstrated that contamination occurs because of microbes in the air

• disproved the spontaneous generation theory

forms the basis of aseptic techniques

• any technique that prevents contamination by unwanted microorganisms

discovered process of fermentation

origin of life

a single molecule of RNA (or pre-RNA) was able to replicate itself and metabolize chemicals

all cells have…

• metabolism,

• growth,

• differentiation,

• communication,

• movement,

• evolution

evidence for endosymbiotic theory

•Outer and inner membrane of mitochondria differ in composition

•Mitochondria are roughly the same size as bacteria

•Mitochondria and chloroplasts contain their own DNA and ribosomes, and undergo binary fission

prokaryotes

• DNA in nucleoid is not enclosed within a membrane

• lack membrane-enclosed organelles

• small size increases S/V ratio → efficient nutrient uptake and diffusion of nutrients

• 70S ribosomes (30S + 50S)

• examples: bacteria & archaea

eukaryotes

• DNA is enclosed within a membrane called nucleus

• have membrane-enclosed organelles

• larger size

• 80S ribosomes (40S + 60S)

• examples: protozoa, fungi, plants, animals

bacillus

rods

cocci

circular

spirilla

curved; 2 or more twists

diplo

pairs

staphylo

grape-like clusters

• random plane of division

strepto

chain-like clusters

tetrad

group of 4

sarcinae

group of 8

vibrio

comma-shaped

spirochetes

rigid; corkscrew-shaped

monomorphic

only one shape

pleomorphic

may assume different shapes

bacterial cell wall

almost all bacteria have this

•Provides support and protection

•Determines cell shape

•Prevents lysis of cell in non-isotonic environments

cell wall structure

•Composed of peptidoglycan (peptides linked to glycan sugars)

•N-acetylglucosamine (NAG) and Nacetylmuramic acid (NAM)

•Starts in cytoplasm = subunits made → Subunits transported outside the cell

gram + cell walls

• 6–12 layers of glycan sheets (30–100 nm thick)

• Teichoic acid weaves through peptidoglycan

• Increase cell wall rigidity

• Regulate cation flow through peptidoglycan

• May be involved in attachment

• Repel phagocytes

• Regulate cell growth and division

gram - cell wall

•1–3 layers of glycan (<7 nm thick)

•no teichoic acid

•Thin peptidoglycan layer located between inner and outer membranes

• Includes outer membrane anchored to wall by lipoproteins

• Porin proteins allow traffic across outer membrane

• LPS (lipopolysaccharide) forms most of outer layer of outer membrane → plays role in pathogenicity (endotoxin)

acid-fast bacteria cell walls

thick layer of peptidoglycan linked to mycolic acids (waxy)

• Lipids and mycolic acids make these bacteria impermeable to many drugs and chemicals

• Acid-fast stain – use heat and phenol to permeate

wall-less bacteria

no cell wall; can only survive in isotonic environments

• No cell wall means undefined cell shape

external structures of cells

•Interact with the environment

•Expand potential habitat or enable survival during unfavorable environmental conditions

•Glycocalyx

•Fimbriae and pili

•Flagella

glycocalyx

A viscous, gelatinous polymer external to the cell wall and composed of polysaccharides, polypeptides, or both

• Synthesized by the cells and secreted to the surface

fimbriae

straight, stiff, short filament

• Numerous (hundreds)

• Can be found on both Gram (+) and Gram (-)

• may contribute to pathogenesis (better able to attach = more pathogenic)

pilus

longer, thicker appendage

• May be involved in attachment or transfer of genetic information

• may contribute to pathogenesis (better able to attach = more pathogenic)