Microbiology Ch2

Spontaneous generation

theory that microbes can arise spontaneously from vital forces, matter, etc

who started the spontaneous generation theory?

Ancient Greeks

Aristotle

said life arose from nonliving matter if material contained pneuma (“spirit in breath”) (ex- fish in a new water puddle)

Helmont

agreed with spontaneous generation, said mice could arise from wheat

Redi

first to refute spontaneous generation, meat and maggot experiment

Needham

agreed with spontaneous generation, mutton broth experiement

Spallanzani

redid mutton broth experiment over 100 times, said microbes were introduced to flask through air

Pasteur

irrefutably disproved spontaneous generation, swan neck flask experiment

omne vivum ex vivo

“life only comes from life”

what led to cell theory

microscope and biogenesis

1st rule of cell theory

the cell is the most basic unit of life

2nd rule of cell theory

all living things are composed of one or more cells

3rd cell theory rule

all cells arise from pre-existing cells

germ theory of disease

one microbe, one disease concept

Robert Koch

developed Koch’s postulates

1st Koch postulate

the suspected pathogen must be found in every case of disease and not be found in healthy individuals

2nd Koch postulate

the suspected pathogen can be isolated and grown in pure culture

3rd Koch postulate

A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease as seen in postulate 1

4th Koch postulate

The pathogen must be re-isolated from the new host and must be identical to the pathogen from postulate 2

fundamental components of cells

cytoplasm, chromosomes, ribosomes

Basic shapes of a cel

spherical, cubical, and cylindrical

Basic cell types

prokaryotic and eukaryotic

How is cell morphology maintained?

Cell membrane protects from osmotic pressure change, cell wall

Nucleoid

concentrated region of cell with genetic material, NOT bound

Plasmids

extrachromosomal DNA found here, small circular, double-stranded DNA molecules (power ups= advantageous traits)

Ribosomes

responsible for protein synthesis, prokaryotes have 70s ribosomes (30s small subunit and 50s large subunit)

Inclusion bodies

store excess nutrients within prokaryotic cells

Vegetative cells

growing and active

endospores

metabolically inactive and dormant

sporulation

when vegetative cells turn into endospores

germination

when endospores turn into a vegetative cell

plasma membrane (fluid mosaic model)

has selective permeability

Membrane transport mechanisms

simple diffusion, facilitated diffusion, and active transport

simple diffusion

with concentration gradient directly across bilayer

facilitated diffusion

with gradient through membrane protein

active transport

against gradient with pump that requires energy

Cell wall

protects cell from harsh conditions

cell wall functions

determine bacteria shape, provide support, keeps cell from rupturing

peptidoglycan

cell is made from

peptidoglycan composition

N-acetylglucosamine and N-acetylmuramic acid

Gram positive

thick cell wall, peptidoglycan and tetrapeptide chains with pentaglycine cross-bridges

gram negative

thin cell wall, thin layers, has inner and outer layer with periplasmic space

LPS molecule compisition

lipid A, A core polysaccharide, and O side chain

non-typical cell wall

lack cell wall structure, gram positive cell wall structure with lipid mycolic acid

no cell wall

mycoplasma

glycocalyx

sugar coat, 2 types

capsule

type of glycocalyx, firm layer

slime layer

type of glycocalyx, loosely attached to cell

S-layer

help withstand osmotic pressure and interact with host immune system (can serve as cell wall in archaea)

filamentous appendages

fimbriae, pili, and flagella

fimbriae

short bristle proteins (attach to surfaces)

pili

longer and less numerous appendages, aid in attachment to surfaces, can transfer DNA between bacterial cells (F pilus)

Flagella

used for movement, still spiral filaments (basal body is motor)

monotrichous

single flagellum at one end

lophotrichous

small bunches from same site

amphitrichous

flagella at both ends of the cell

peritrichous

dispersed over cell surface

phototaxis

bacteria move in response to light

magnetotaxis

bacteria move from magnetic fields

chemotaxis

bacteria move based on chemical gradients