intro bacteriology

Who is the father of microbio?

Van Leeuwenhoek

Do prokaryotic and eukaryotic cells have DNA with a nuclear membrane?

only eukaryotic

Describe cell division in prokaryotic vs eukaryotic cells

prokaryotic: binary fission

eukaryotic: mitosis

Describe chromosome number in prokaryotic vs eukaryotic cells

prokaryotic: single circular

eukaryotic: 23 pairs

Do prokaryotes and eukaryotes have membrane bound organelles?

only eukaryotes

Describe the ribosomes in prokaryotes vs eukaryotes

prokaryotes: 70S (50 + 30)

eukaryotes: 80S (70S in organelles)

Describe cell walls in prokaryotes vs eukaryotes

prokaryotes: usually present, complex

eukaryotes: not in human cells, simple (chitin, cellulose)

T/F bacteria are prokaryotic multicellular organisms

F, unicellular

Going from innermost to outermost, describe the layers of the bacterial outer membrane. Are these found in ALL bacteria?

plasma membrane → cell wall → capsule

no, only plasma membrane is in all

Briefly describe binary fission.

cell elongates, DNA replicated, cell constricts then splits

What 3 shapes do bacteria come in?

cocci (sphere)

bacilli (rod)

spiral

What does it mean when a bacteria is pleomorphic?

vary in shape and size

Describe cocci shape:

diplococci

streptococci

tetrad

sarcinae

staphylococci

diplo: pair

strepto: chain

tetrad: group of 4

sarcinae: cube of 8

staphylo: grape

Describe spiral bacteria: vibrio, spirillum, and spirochete

vibrio: curved rod, resemble comma

spirillum: corkscrew + rigid

spirochete: thin + flexible

Describe bacilli: single, diplobacilli, streptobacilli, and coccobacillus

single: one rod

diplo: pair of rods

strepto: chain

cocco: short oval rods, resemble cocci

T/F both gram positive and negative bacteria have outer membrane and periplasm

F, gram negative

Describe peptidoglycan in gram positive and negative bacteria

positive: thick

negative: thin

How does the cell envelope differ in gram positive and negative bacteria?

+: peptidoglycan, plasma membrane

-: outer membrane, peptidoglycan, plasma membrane

In the cell wall, peptidoglycan is composed of

alternating NAG and NAM

What is the difference between NAG and NAM?

NAM has tetrapeptide

What major surface antigens are found in gram positive cell wall?

lipoteichoic acid and wall tectonic acid

T/F gram negative outer membrane is unilayered and includes lipopolysaccharide (LPS)

F, bilayered

In LPS, what gives it toxic properties that allow it to be an endotoxin in gram negative?

Lipid A

What major surface antigens is found in LPS and contributes to endotoxin properties?

Ompolysaccharide

The outer membrane of gram negative bacteria have special channels called

Poring

What molecules can pass through porins?

low MW and hydrophilic

T/F different bacteria species have different types and number of porins

T

Do gram negative bacteria have high antibiotic resistance? If so, why?

Yes

Large ABX cannot penetrate outer membrane, need to use specialized ABX

What are the 4 functions of the bacterial cell wall?

Protection

Cell division

Shape

Target site (ABX, lysozymes, bacteriophages)

The gram staining procedure classifies bacteria based on what property?

Amount of peptidoglycan cell wall

Briefly describe the steps of gram staining.

1. Crystal violet dye

2. Iodine (mordant)

3. Alcohol wash

4. Counterstain (safranin)

How do gram negative vs positive bacteria differ in the alcohol wash step?

-: dye washes off

+: dye stays

At the end of gram staining, describe the colour of gram positive vs negative bacteria

+: purple (crystal violet dye trapped)

-: pink (counterstain)

How can you remove bacteria cell wall?

may remove spontaneously or in presence of penicillin

What is the difference between spheroplasts and protoplasts?

Spheroplasts: from gram -

Protoplasts: from gram +

What are L forms?

bacteria without cell wall that can still grow and divide

What are the 2 types of L forms?

unstable: revert back once penicillin removed

stable: no revert

What is mycoplasma?

naturally occurring bacteria without cell wall

What is the cytoplasmic membrane?

deepest layer of plasma membrane

thin and semipermeable

What are the functions of the cytoplasmic membrane?

permeability/transport

biosynthetic function

electron transport and oxidative phosphorylation (energy)

chemotactic systems (respond to envir., how bacteria communicate)

T/F in an electron microscope, you will see an inner nucleoid region composed of DNA and mitochondria

F, no mitochondria

What are ribosomes for?

protein synthesis, sense mRNA

What is the nucleoid?

DNA core

What are plasmids?

carry non essential genes

application in biotech and ABX resistance transfer

What is glycocalyx?

capsule/slimy layer, surrounds cell wall

What are the functions of glycocalyx?

adherence (cause infection)

virulence

biofilm formation

What are flagella?

organ of locomotion, have characteristic patterns of distribution

Describe the following bacterial flagella:

peritrichous

monotrichous

lophotrichous

amphitrichous

peri: multiple, around cell

mono: single

loph: tuft at one end

amphi: at both ends

What are pili and fimbriae?

thin short filamentous appendages, mostly in gram -, made of pilin

What are fimbriae for?

adherence

biofilm formation (adhere to one another)

What are pili for?

twitch/glide motility

conjugation sex pili (transfer DNA; ex: ABX resistance)

adherence

What are bacterial endospores?

gram +, highly resistant dormant stage during unfavourable conditions (starvation) to protect

Briefly describe endospore formation (sporulation)

initiated by clear portion of cytoplasm at one end of cell

membrane grows inward forming double layer (forespore)

spore wall forms thick covering layer

T/F endospores are highly resistant to high temps and boiling

T

What makes endospores so resistant to heating and drying?

outer coat, low H2O content, low metabolic activity, high [calcium dipicolinic acid]

What is germination?

endospore → vegetative cell

3 stages: activation, initiation, outgrowth

What is the susceptibility of gram - vs + bacteria to penicillin and sulfonamide?

-: low, hard to penetrate outer membrane

+: high, can penetrate peptidoglycan

What is the susceptibility of gram - vs + bacteria to streptomycin, chloramphenicol, and tetracycline?

-: high, target porins and ion channels

+: low, no ion channels or porins

What factors impact bacterial growth?

O2 requirements

temp

pH

H2O

What are obligate aerobes?

need O2

What are obligate anaerobes?

cannot use O2

What are facultative anaerobes?

can live aerobic or anaerobically

What are aerotolerant anaerobes?

has some enzymes that detoxify O2 (ferment)

What are microaerophiles?

require specific O2 level (2-10%)

In a tube of growth medium, how would obligate aerobes grow?

at top, need O2

catalase and superoxide dismutase (SOD) neutralize O2

In a tube of growth medium, how would facultative anaerobes grow?

throughout tube, mostly at top

catalase and superoxide dismutase (SOD) neutralize O2

In a tube of growth medium, how would obligate anaerobes grow?

bottom of tube, no O2

lack enzymes to neutralize O2

In a tube of growth medium, how would aerotolerant anaerobes grow?

evenly distributed in tube

SOD neutralizes O2

In a tube of growth medium, how would microaerophiles grow?

middle of tube, need specific O2 level

How does temperature impact bacteria and bacterial growth?

low = rigid and fragile

high = flexible

use fridge to control bacterial growth

What are psychorophiles an psychorotrophs?

grow at low temps (<37*C)

What are mesophiles?

most bacteria

grow at 37*C

What are thermophiles and hyperthermophiles?

grow at high temps (>37*C)

Given a temp vs rate of growth curve, where is the optimal growth temperature?

peak of curve

What are neutrophiles?

most bacteria

grow at pH 6-8

What are acidophiles?

grow at pH <4

high [H+]

What are alkaphiles?

grow at pH up to 11.5

high [OH-]

What do microbes use H2O for?

dissolve enzymes, nutrients, metabolic rxns

T/F endospores can survive in dry environments

T

What is generation time?

time required for bacteria to divide

Mycobacterium tuberculosis is the cause of TB, why is it hard to diagnose?

long doubling time (can use qPCR)

Most bacteria have a doubling/generation time of

1-3h

What are the phases of the growth curve?

lag phase

exponential phase

stationary phase

death phase

What happens during the lag phase?

prep for growth/log phase

accumulate nutrients

What happens during the log phase?

cells divide and grow, most susceptible to antimicrobials

binary fission and double time calculated from this phase

What happens during the stationary phase?

equilibrium (# new cells = # cells dying)

nutrient depletion

What happens during the death phase?

no growth or nutrients

What is a pathogen?

microorganism that can cause disease

What are opportunistic pathogens?

rarely cause disease except in immunocompromised

What is virulence?

ability of agent to cause disease

involve adherence, invasion and toxigenicity

From an organism’s pov, what factors influence infection?

# organisms and virulence

From a host’s pov, what factors influence infection?

host defense (innate and acquired immunity)

What determines bacterial pathogenesis?

1. transmission

2. adherence

3. invasion and intracellular survival

4. toxins

5. intracellular pathogenecity

Why is it important to know the mode of transmission?

know how to prevent spread

What are some major adherence factors?

capsule/slime layer

adherence proteins

lipoteichoic acid

fimbriae (pili)

Provide an example of capsule/slime layer and how it helps in adherence

E coli capsule promotes adherence to intestinal villi

Provide an example of adherence proteins and how it helps in adherence

N gonorrhea have Opa proteins that bind receptors to prevent endocytosis

Provide an example of lipoteichoic acid and how it helps in adherence

S pyogenes lipoteichoic acid helps bind to respiratory receptor and M protein in host cell

Provide an example of fimbriae/pili and how it helps in adherence

N gonorrhea pili help bind to epithelium

What are adhesins?

surface molecule on pathogen binds host cell to open channel and let pathogen into host