Chapter 4 Short Answer Possible Questions Microbiology

Name characteristics that are unique to prokaryotes

Absence of a membrane bound nucleus and organelles, have circular DNA, have plasmids, have cell walls made of peptidoglycans

Compare a Gram positive cell envelope to a gram negative cell envelope

Gram positive:

2 layers

Thick cell wall

Have teichoic acids

stains purple if positive on gram stain

Has interglycine bridge to connect amino acids

Gram negative:

3 layers

thin cell wall

Has outer membrane made of lipopolysaccharides and porin proteins

stains pink/red if positive on gram stain

Has direct bond between amino acids and no interglycine bridge

Name and define the flagellar arrangements

Polar: flagella attached at one or both ends

Monotrichous: single flagella

Lophotrichous: tufts of flagella on one end

Amphitrichous: Flagella on both ends

Peritrichous: flagella dispersed randomly over cell

Atrichous: no flagella present

How is biofilm formed

Bacteria begin working together and secrete exopolysaccharides (EPS)

EPS forms a barrier around the bacteria which helps to protect the bacterial cells. Water in the film protects against heat treatment and chemical treatment. Have to physically scrape biofilms off to remove them

Describe endospore formation

Sporulation: Starts with a vegetative cell which then duplicates and separates its chromosome. The cell is then separated into the sporangium and forespore. The sporangium then engulfs the forespore and begins actively synthesizing spore layers around the forespore. Forespore then matures into an endospore and is released from the cell with the loss of the sporangium

Germination: Begins when favorable conditions arise such as exposure to water and a germination agent which causes the endospore to swell and release a vegetative cell