Bacteria 1

Question 1

size of bacteria

Answer 1

• 10^-6
• order of magnitude smaller than animal cells (10-100X smaller), but order of magnitude bigger than viruses(500-1000X)
• visible by light microscopy with phase contrast or staining

Question 2

characteristics of bacteria

Answer 2

• DNA genome without introns-2000 genes
• DNA clumps in a nucleoid (not membrane bound)
• single circular chromosome
• 70S ribosome
• peptidoglycan cell wall, optional outer LPS/LOS envelope
• reproduce by binary fission

Question 3

major structures

Answer 3

• capsule
• cell wall
• plasma membrane
• cytoplasm
• ribosomes
• plasmid
• pili
• flagellum
• nucleoid

Question 4

microscopic shapes

Answer 4

• cocci-circular-staph, strep, s. pneumoniae, neisseria
• bacilli- bacillius, salmonella, corynebacter, fusobacter (vibrio)
• spirochetes-borrelia, treponema- requires darkfield

Question 5

gram staining

Answer 5

• fixation with heat
• crystal violet
• iodine treatment- gram pos keep, neg don’t
• decolorization-neg loose the violet
• counter stain with safranin-pink

Question 6

gram pos

Answer 6

• 3 layers of peptidoglycan

- no exterior membrane

Question 7

gram neg

Answer 7

• 1 layer of peptidoglycan
• exterior membrane
• LPS (LOS)
• more frequent genetic transfer by plasmid exchange- antibiotic resistance
• porins

Question 8

peptidoglycan cell wall

Answer 8

• both gram neg and pos
• encircles cell in single covalently-closed macromolecule
• unique to bacterial cells
• rigidity and osmotic stability
• vulnerable to attack by enzymes, antibiotics
• penicillins, cephalosporins, vancomycin inhibit synthesis
• lysozyme cleaves it

Question 9

acid fast bacteria

Answer 9

• gram negative but have different structure
• peptidoglycan, arabinogalactan and porins
• keeps pink stain and doesn’t counter stain blue-special system
• TB-mycobacter

Question 10

LPS/LOS/endotoxin

Answer 10

• lipopolysaccharides/lipooligosaccharides
• O antigen, core, Lipid A
• Lipid A is toxic and severely immunogenic-can lead to shock
• not a virulence factor-problem is with our immune system overreacting-so don’t want to vaccingate

Question 11

septic shock in gram pos

Answer 11

• less common
• immunogenic reaction to teichoic acids
• don’t want to vaccinate to

Question 12

glycocalyz

Answer 12

• slime layer-attachment/biofilms

- capsule-antiphagocytic, serologic testing, vaccine target (virulence), attachment

Question 13

biofilms

Answer 13

• organic surface coating and first colonists
• absorption of cells to organic matrix
• more permanent attachment of cells by means of slimes or capsules, growth of colonies
• mature biofilm with microbial community in complex matrix

Question 14

pili/Fimbrae

Answer 14

• attachment, often a virulence factor

- point of gram pos/neg divergence-gram neg more differentiated, gram pos recently discovered

Question 15

type 1 attachment

Answer 15

• gram neg
• stacks of small molecules
• chaperone and curli

Question 16

locomotion

Answer 16

• type IV pili

- gonorrhoeae-jerking movements

Question 17

secretion pili

Answer 17

• type III-smaller- can induce apoptosis (salmonella)

- tyle IV- larger center unit cam send DNA and polypeptides through (agrobacterium tumefaciens)

Question 18

Summary slide

Answer 18

• bacterial are very small-hundreds can fit in a mammalian cell and sometimes do
• defining characteristics of bacteria: intronless circular DNA genome localized to nucleoid, 70s ribosome, peptidoglycan cell wall, reproduction by binary fission
• all bacteria have internal PM, gram +/- designated by second external membrane in gram neg and thicker cell wall in gram pos
• gram stain-pos holds crystal violet, neg doesn’t- narrows Ddx and is fast and cheap
• see slide for others