Exam 1 pt 1

state the 3 domains of life

1. bacteria

2. archaea

3. eukarya

representative microorganism for bacteria domain

representative microorganism for archaea domain

representative microorganism for eukarya domain

gram positive cell structure

thick peptidoglycan layer (multiple layers), no outer membrane

• teichoic acids

• narrow/absent perplasmic space

components of cell structure unique to gram positives

teichoic acids (attached to peptidoglycan), lipoteichoic acids (attached to cell membrane)

gram negative cell structure

thin peptidoglycan layer, both inner and outer membranes present

• wide periplasmic space

• lipopolysaccharides (LPS)

• porins

components of cell structure unique to gram negatives

• outer membrane

• lipopolysaccharides (LPS)

• porins

what type of bacteria has an outer AND inner membrane?

gram negative bacteria

what is peptidoglycan

strong, mesh-like molecule that forms the main structure of the bacterial cell wall

• name of sugars: NAG, NAM

sugars in the peptidoglycan

NAG, NAM

function of peptidoglycan

• gives the cell shape

• protects the bacterium from bursting due to water pressure

• is the target of some antibiotics (like penicillin), which weaken it and kill the bacteria

periplasmic space

the area between the inner (plasma) membrane and the outer structures of a bacterial cell wall

• wide in gram-

• narrow in gram+

porins

protein channels found in the outer membrane of gram-negative bacteria

• tiny holes that allow certain molecules to pass through the outer membrane

• gram+ don’t have bc they dont have outer membranes

lipopolysaccharide (LPS)

it’s a large molecule found only in the outer membrane of gram-negative bacteria ; has 3 parts

• lipid A

• core polysaccharide

• o-antigen

lipid A

the toxic part of the lipopolysaccharide (lps) molecule found in the outer membrane of gram-negative bacteria

• released when bacteria die and break apart

• can cause fever, inflammation, and even septic shock

why are gram- infections more dangerous?

bc they have endotoxins that are released when they break down and die

structures involves in bacterial attachment

pili, fimbriae, flagella,

pili

thin, hair-like protein structures that stick out from the surface of many bacteria, especially gram-negative bacteria.

1. fimbriae (shorter, more numerous, for attachment)

2. sex pili (longer, fewer, for gene transfer)

fimbriae

short, hairlike proteins for attachment and biofilm formation

structures involves in bacterial chemotaxis (movement)

flagella

flagella

structure used for motility

structures involves in bacteria horizontal gene transfer

conjugative (sex) pili, bacteriophages

conjugative (sex) pili

long protein appendages (pili) that join bacteria for horizontal transfer of genetic information

L forms

bacteria that have lost their cell wall, either partially or completely

• can arise from gram+ or gram-

L-forms that arise from gram+

protoplasts

structure of protoplasts

• no cell wall at all

• only have the cell membrane

• round or irregular in shape

• very fragile because they lack the thick peptidoglycan layer

L-forms that arise from gram-

spheroplasts

structure of spheroplasts

• partially lost cell wall

• outer membrane is still present

• more stable than protoplasts due to the remaining outer membrane