Exposure and Host Adaptation

Question 1

What are the six steps to become a pathogen

Answer 1

1. Exposure (pre infection), surviving in the environment
2. Adherence, attaching to host cells and colonizing
3. Cell innovations and immune evasion, persist in the host
4. multiply in the host, bacterial growth
5. toxicity and invasiveness disseminate, spread or invade distant sites, within or between hosts
6. produce symptoms of disease, microbe induced and host response induced

Question 2

How are people exposed to pathogens

Answer 2

some pathogens move from host to host (person to person transmission) and some are unable to survive outside of hosts for extended periods of time

STDs and other blood or bodily fluid transmission by, Neisseria gonorrhoeae, Chlamydia trachomatis, and Treponema palladium

some pathogens are able to survive outside the host in the environment

Question 3

What must pathogens cope with while surviving in the environment

Answer 3

being eating by eukaryotes, prokaryotes, or phages

exposure to noxious chemicals, human and bio made

lack of nutrients, nutrients aren’t everywhere

exposure to sunlight and weather extremes, lack of adherence sites and UV exposure causing mutations and death

Question 4

What are pathogen survival strategies for pathogens in the environment

Answer 4

endospores

desiccation tolerance

secondary metabolites (bacteriocins)

efflux pumps against disinfectants and antibiotics

metabolic diversity so they can grow on diverse substrates

biofilm formation

motility

Question 5

What are endospores, what are they resistant to, what type of bacteria are they common in

Answer 5

a dormant bacterial structure that is coated in thick layers of peptidoglycan

usually form in a response to lack of nutrients

survive desiccation because of cortex area that contains the nucleic acid that is metabolically inert

UV and heat resistance

can survive millions of years, some were found in mummies in egypt

some gram + such as Bacillus and Clostridia

Question 6

What is desiccation tolerance

Answer 6

limit protein oxidation ROS/SOD example

limit DNA damage during dehydration

membrane phospholipid adaptation, increases in saturated fatty acids, increase of cis-trans isomerization, and increase in the proportion of negatively charged phospholipids these all help hold onto water

a pathogen might encounter this is they end up on an empty hospital bed and try to stay alive

Question 7

What are the four steps of biofilm formation

Answer 7

1. Adhesion: finding a home usually formed at the air liquid layer
2. Aggregation: secreting extracellular matrix/glycocalyx (polymeric matrix outside cell) and becoming 3D
3. Maturation: forming the film
4. Dispersal: continuous release of new microbes

active cells proliferated around the outside of the biofilm and dead cells are in the middle, the dead cells provide DNA and nutrients to the living cells

polysaccharide coat on the outside of the biofilm

channels inside the biofilm to get rid of waste products and receive nutrients inside the biofilm

Question 8

What are bacteria living inside of biofilms resistant to

Answer 8

phagocytosis: predators or phagocytosis, the biofilm is too big for a phagocyte to consume
antibiotics: 100 fold less effective in a biofilm, diffusion rates through the biofilms are limited, metabolically the bacteria in the middle are not susceptible, antibiotics ONLY effect bacteria that are activity dividing

mechanical displacement: its hard to mechanically remove biofilms from tissues think of how hard it is to scrap biofilms off teeth, usually requires surgical removal

Question 9

When are antibiotics not efficient against bacteria

Answer 9

antibiotics ONLY effect bacteria that are ACTIVELY dividing

this is why antibiotics aren’t as effective against bacteria in biofilms or bacteria that divide very slowly

Question 10

How are bacteria motile and why is it advantageous for bacteria to be motile

Answer 10

use a flagella, spirochetes, for motility and chemotaxis

to help bacteria find food and survive conditions inside and outside the hosts

Question 11

What types of bacteria mainly make flagellas

Answer 11

gram - mainly make flagella

some gram + do too

Question 12

What are spirochetes

What bacteria have them

Answer 12

corkscrew shaped internal flagella it is in the periplamsic space between the inner and outer membrane

the flagella never sees the outside world so antibody responses are nullified and TLR 5 cannot detect (innate)

Rotation causes twisting of bacterial shape its like one big corkscrew propeller

Treponema pallidum which causes Syphilis
Borrelia burgdorferi which causes Lyme Disease

Question 13

When a bacteria goes to colonize a host what are the two main barriers they must overcome

Answer 13

1. cross primary barriers such as skin and mucosa

Question 14

How do bacteria penetrate the skin

Answer 14

there are no known pathogenic bacteria that can penetrate the skin without help

bacteria can use an arthropod as a vector

bacteria are opportunists that wait for the skin to be bypassed in some way

Question 15

Can any know bacteria penetrate the skin

Answer 15

no

Question 16

What are the known arthropods that are used as vectors

Answer 16

Borrelia burgdorferi causes lyme disease and is carried by ticks

Yersina pestis causes the bubonic plague and is carried by fleas

Virures use mosquios to carry west nile fever, yellow fever, dengue fever and malaria

Plasmodium spp is a protist that uses mosquitos to transit malaria

Question 17

What are ways that the skin is bypassed by opportunistic bacteria

Answer 17

cuts, surgery, catheters, burns, etc

IV: staphepidermis takes advantage of the breached surface

Question 18

Recap of the Mucosal defense

Answer 18

mucus is highly effective at preventing microbes from reaching the surface fo the underlying epithelial cells

vicious, sticky substance filled with anti microbial peptides
defensins, lysozyme, slgA, lactoferrin, lactoperoxidase

traps bacteria, kills bacteria, and is resistant to degradation by enzymatic attacks

Question 19

Why is GALT a liability in humans

Answer 19

some bacteria exploit the M cells to pass through the epithelial layer and enter the body

bacteria avoid mucus and go for the M cell where antigenic sampling occurs by transferring it to the phagocyte and the bacteria can pass through the epithelial layer

Question 20

What bacteria use M cells to bypass the epithelial layer and enter the body

Answer 20

Salmonella enterica

Yersinia pseudotuberculosis

Question 21

How do bacteria penetrate or evade the mucin defenses

Answer 21

GALT and M cells
using flagella to move and out of
degrade slugs

Question 22

How to bacteria move away from mucus and what is a bacteria that does this

Answer 22

with motility methods

Helicobacter pylori uses a flagella to move through the mucus layer that has a more neutral pH than the above stomach acid which has a more acidic, lower pH

Question 23

How do bacteria avoid slgAs

Answer 23

slgAs have an antigen binding domain and the Fc region has a docking point on the mucin to neutralize the activity of the bacteria

bacteria can produce enzymes to break apart slgAs these enzymes are slgA proteases

we have slgA1 and slgA2 pathogens can degrade igA1 sot they think that our bodies formed IgA2 which cannot be degraded by pathogens

Question 24

What is the common type of host produced natural antibodies in humans

Answer 24

defensins

Question 25

what are defensins

Answer 25

cationic (positively charged) peptides that bind to the negatively charged surface of bacteria and disrupt the bacterial membranes

Question 26

How do bacteria combat defensins, four main ways

Answer 26

bacteria try to make their membrane surface more positively charged so the defensins that are positively charged are not attracted to them LPS and LTA modification to change the net negative charge, become more positive to not attract defensins they can make a capsule to protect their membrane, the thick polysaccharide layer protects the bacteria by slowing or preventing defensin diffusion through microbial proteases can degrade defensins, not allowing the defensins to disrupt the membrane counteract defensin channels by using cytoplasmic proteins to 'plug the hole' that is formed by defensins in the bacterial membrane

Question 27

What is the main nutrient required by bacteria to proliferate, which bacteria does not use this and what does it use

Answer 27

many, but not all, pathogens require iron to proliferate Borrelia burgodorferi uses Mn2+ lyme disease free iron is often a limiting factor for growth 10^-18 M of free iron inside the body, so not a lot at all

Question 28

How much free iron is in the body, where is the other iron found

Answer 28

10^-18 M of free iron in the body almost all iron is bound to a protein this is chelated considered antimicrobial peptides "nutritional immunity" ``` Lactoferrin Transferrin Ferritin Heme Siderocalin ```

Question 29

Where is Lactoferrin found in the body and what is its role

Answer 29

mucosal sites and its present in neutrophil granules has a high affinity for iron so it takes up iron before pathogens can when inside of mucosal sites and around neutrophil granules

Question 30

Where is Transferrin found and what is its role

Answer 30

in the blood serum, induced by IL-6 and produced by the liver deliver iron from absorption centers in the duodenum and white blood cell macrophages to all tissues

Question 31

Where is Ferritin found and what is its role

Answer 31

intercellular iron storage | 30% of bound iron in the body

Question 32

Where is Heme found and what is its role

Answer 32

Hemoglobin | 70% of the bodies iron

Question 33

What are siderocalins

Answer 33

siderocalins interfere with the function of bacterial siderophores the anti siderophore we produce siderocalins to take away the bacterial siderophore

Question 34

Iron in the body is highly controlled within the host so how does bacteria get it from the host

Answer 34

compete with the host via siderophores or steal the iron

Question 35

What are siderophores and what are the two primary structural groups

Answer 35

low molecular weight compounds that chelate iron with very high affinities they take a lot of work for bacteria to make them caterchols: enterbactin have very high affinity for iron and is produced by bacteria, this takes a lot of enzymatic processes to form and can bind to iron better than our host defenses, it outcompetes the host hydroxamates: angulibactin bind iron with affinity that competes with host iron binding but not as good as catechols

Question 36

What are other ways that bacteria can get iron without producing siderophores

Answer 36

take other bacterias siderophores: easier than making their own simply steal the hosts iron-chelators: directly take up transferrin, lactoferrin, or heme: they can destroy the protein in the hosts cytoplasms and release the iron for their own use produce toxins such as hemolysis and other cytolysins that destroy host cells and release their iron stores (ferritin, the intracellular iron storage protein)

Question 37

What are gram + strategies for iron acquisition

Answer 37

they can make two siderophores: Staphyloferrin A and Staphyloferrin B they both have binding proteins that bind to iron and push it through a complex below into the bacterial cell for use, this requires ATP best way to get iron by them is to strip the heme away from the host cell through a complex, staph, strep, listeria

Question 38

What are gram - strategies for iron acquisition

Answer 38

they have transferrin and lactoferrin binding proteins along with a hemopore that can bind and uptake hemoglobin through the membrane they also have two different siderophores one that uses an outer membrane receptor and not that uses TBDT (transmembrane protein)

Question 39

What are stealth siderophores

Answer 39

bacteria take their siderophore and coated it in glucose to make it appear different and make it less recognizable by the hosts siderocalin, therefore the siderocalin cannot bind to stealth siderophores there is an evolutionary tug of war between hosts and bacteria with siderophores and siderocalins

Question 40

What are key detemerinants of bacterial adhesion inside of hosts

Answer 40

pili and fimbriae are key parts of binding to cells and tissues inside hosts

Question 41

What are the different ways bacteria can adhere to cells and tissues

Answer 41

pili/fimbriae: these are interchangeable surface adhesions MSCRAMMS if you can block attachment you can block infection

Question 42

What are MSCRAMMS, what bacteria uses MSCRAMMS

Answer 42

Microbial surface components recognizing adhesive matrix molecules type of adhesion uses by Staphlyococcus aureus not the same as pili and fimbriae

Question 43

What is the difference between pili and fimbriae

Answer 43

interchangeable terms pili: generally refers to longer, thicker surface structures fimbriae: generally refers to shorter, thinner structures the best understood mechanism of adherence is the attachment of bacteria to the hosts through rod-shaped filamentous structures first identified in gram - but more recently they also appear prevalent in gram + pili come in a variety of shapes and types, there are over 30 types identified for E. Coli alone

Question 44

How is tissue tropism governed by pili

Answer 44

by the piling tip, this establishes the contact between the host and the bacterial surface contributes to the host-cell or tissue-specificity of the pathogen some pathogens can interchange the piling tip but keep the same shaft

Question 45

What do UPEC strains of E. coli P Pili attach to

Answer 45

attaches to the mannose sugars on the bladder epithelium idea to put mannose sugars in the bladder to try and get pili of E. coli to bind to that instead of the epithelium on the bladder

Question 46

What are the three types of pili

Answer 46

P Pili Type IV or Bundle forming pili (BFP) Curli Pili

Question 47

How are Type I Fimbriae aka P Pili formed

Answer 47

by chaperone-usher pathway holds onto the proton with a beta strand to help with stability while it is being moved this beta strand is called the donor chaperone strand assembly is the tip going out list and then slowly pushes it out This occurs in the periplasm Fim C is the donor chaperone strand chaperone never becomes part of the pili, just helps stability?

Question 48

What type of pili are formed by the chaperone-usher pathway

Answer 48

Type I fimbriae and P. pili

Question 49

How are curli pili formed

Answer 49

CsgE, F, G dependent assembly, after secretion past outer membrane, pilin subunit CsgA self-polymerizes CsgD is a transcription factor that regulates expression of the csgBAC operon CsgC is a chaperone that escorts it to the outer membrane that is located in the periplasmic space, secreted as it self polymerize Csg: curli specific genes

Question 50

How are type IV aka bundle forming pili formed

Answer 50

secretion dependent monomers in the inner membrane protrude out the cell surface stable protein protein interactions work to assemble it to retract they do the opposite, its pulled back through the same opening

Question 51

What type of pili do Neisseria gonorrhoeae use

Answer 51

type IV bundle forming pili

Question 52

What type of pili do E. coli use

Answer 52

type I aka P pili and curli pili

Question 53

What types of pili are found in both E. coli and Salmonella spp.

Answer 53

Curli fibers

Question 54

What are the csg in E. Coli

Answer 54

csgBAC and csgDEFG

Question 55

What are the csg in Salmonella

Answer 55

curli specific genes afg: aggregative fimbriae agfBAC and agfDEFG Agf: aggregative fimbriae which promotes the aggregation between bacteria, more bacteria bacteria interaction but still impacts the host

Question 56

What are the pili of gram + bacteria like

Answer 56

important for biofilm formation and in pathogenic strains: adhesion and invasion pilin subunits are covalently attached to each other and to the peptiodogylcan layer by enzymes called sortases

Question 57

What are sortases

Answer 57

pilin subunits are covalently attached to each other and to the peptiodogylcan layer by enzymes called sortases in gram + pili sortases recognize sequence motifs in their substrates LPXTG to cleave the substrate at the threonine residue this cleaved substrate is coupled to pepitdoglycan or the next available pilin subunit through a second sequence motif YPKN all the pilin subunits will have this signature at the C-terminus and this links it to another monomer or the cell wall itself

Question 58

How are pili assembled in gram + bacteria

Answer 58

sortase is how everything can get through the cell wall

Question 59

What are non-fimbrial adhesions of gram + bacteria

Answer 59

hair-like protrusions that resemble pili many of them bind to extracellular matrix and connective tissue such as fibronectin, collagen, fibrinogen, vitronectin, laminin = MSCRAMMs

Question 60

What does Streptococcus pyogenes use to bind to cells

Answer 60

gram + bacteria nonfimbrial adhesion F protein binds Fibronectin pilus-like structures made of M protein that binds to factor H binds factor H, destroying C3 convertase and avoiding C3b opsonization: this is complement and phagocytosis avoidance has a sortase to bind to cell wall

Question 61

What are afimbrial adhesions

Answer 61

InIA and InIB of listeria monocytogenes triggers bacterial uptake by host cells causes actin cytoskeleton of host cell to rearrange and allow internalization

Question 62

To maintain a persistent infection and to be a successful pathogen what must happen

Answer 62

the pathogen must be able to combat the immune defenses of the host the innate and adaptive immunity innate: complement and phagocytosis adaptive: antibodies/phagocytosis and CTLs

Question 63

How do bacteria use capsules to avoid complement

Answer 63

prevent alternative pathway activation inhibits formation of the C3 converts binds serum protein H rather than factor B steric hindrance is used by the capsule to prevent phagocytosis factor H and protease I inactive C3b prevent the complement in our own tissues

Question 64

How do capsules avoid complement

Answer 64

prevent alternative activation: inhibits formation of the C3 convertase by binding factor H instead of factor B and this inhibits phagocytosis prevents formation of the MAC complex: proteins are unable too get through the capsule of the membrane, this prevent direct lysis

Question 65

How do bacteria use host mimicry

Answer 65

make capsules out of sialic or hyaluronic acid

Question 66

What is sialic acid and how is it used by bacteria

Answer 66

found in relatively high amounts in all animal tissues prevents comment the sialic acid is used by bacteria in host mimicry, they make capsules out of it to avoid detection by the host immune system

Question 67

What is Hyaluronic acid and how is it used by bacteria, what bacteria is an example of it

Answer 67

found as glycosaminoglycan found in connective, epithelial, and neural tissue make capsules out of hyaluronic acid in bacterial host mimicry streptococcus pyogenes

Question 68

What is the role of C5a peptidase/toxins

Answer 68

secrete enzymes (proteases) that destroy the complement proteins, C5a for instance by some gram +, then the neutrophils don't know where to attach to produce toxins that kill, inactivate, immobilize, or reduce the strength of immune cells such as phagocytes they can also prevent cytokine signaling

Question 69

What do pathogens avoid if they become intracellular

Answer 69

pathogens that live inside the host cells are not directly exposed to the immune system ``` no antibodies no complement proteins no defensins no lysozyme no phagocytes no direct exposure to any immune cells really advantageous if you can survive inside a macrophage ``` they could also escape the phagosomes into the cytoplasm before the bacteria are killed, they produce toxins that disrupt, degrade, or make holes in the hosts membrane

Question 70

How do bacteria escape the phagosome

Answer 70

alternatively bacteria just escape from the phagosome into the cytoplasm before the bacteria are killed they produce toxins that disrupts, degrade, or make holes in the hosts membrane

Question 71

What kind of bacteria lyse the phagosome

Answer 71

Listeria monocytogenes produces a pore forming hemolysin called listeriolysin O LLO only active at pH 5.5 as phagosome becomes acidified and it escapes PlcA result in the lysis of the phagosome membrane vacuole is lysed and bacteria escapes into cytosol and replicates

Question 72

What is actin-based motility of bacteria and what bacteria use this

Answer 72

many pathogens that can direct their own endocytosis and can also manipulate the actin cytoskeleton once inside the host cell use actin-based motility able to push themselves around the cell and into neighboring cells ``` never have to leave the intracellular enivrionemt Listeria monocytogenes Shigella flexneria (dysentary) Rickettsia rickettsii (Rocky Mtn Spotted Fever) ``` don't every have to exit the cell cytotoxic T lymphocytes can enter the cell, but this results in inflammation

Question 73

How does Listeria monocytogenes move pithing and between cells

Answer 73

uses actin-based motility

Question 74

How does Legionella pneumophilia avoid phagolysosomal fusion

Answer 74

removes proteins necessary for membrane fusion from phagosome, LAMP-1 and LAMP -2 1. Legionella is taken up inside the cell 2. the phagosome does not become acidified because it does not fuse with the lysosome 3. phagosome surrounded by the endoplasmic reticulum studded with ribosomes 4. bacteria multiply in phagosome 5. phagosome ruptures 6. host cell lyses and bacteria escape

Question 75

How does Salmonella Typhimurium prevent phagolysomal fusion?

Answer 75

hijacks cell's actin cytoskeleton to create its own space and make its own vesicle called the SCV the salmonella containing vesicles 1. bacteria trigger actin rearrangements on the surface of the cell, ruffling occurs and ruffles grow into pseudopods 2. pseudopods encircle and engulf bacteria and the bacteria are taken up into spacious vacuoles 3. bacteria remodel the vacuoles creating a growth-conducive environment and the bacteria replicate in the vacuoles

Question 76

How does Mycobacterium tuberculosis prevent phagolysomal fusion

Answer 76

uses host protein TACO to coat the phagosome 1. bacteria bind CR3 on surface of macrophage and the bacteria are taken up in a vesicle 2. bacteria recruit host protein to surface of phagosome, no fusion of lysosome with phagosome 3. bacteria prevent endocytic acidification, have reduced bacterial oxidative burst, and bacteria can replicate

Question 77

How does Brucella abortus prevent phagolysomal fusion

Answer 77

only replicates upon acidification of vacuole directing it to the ER 1. Brucella abortus enters the cell and binds and fuses with the lysosome 2. prefers fusion with the lysosome and the acidification processionals and then it gets sent to the ER to escape from the cell

Question 78

How does Chlamydia replicate inside the cell

Answer 78

1. Chlamydia enters the cell in EB form (non-replicative form) 2. EB changes into RB form (replicative form) 3. RBs replicate and some stay RB and others switch back to EBs 4. EBs are released from the cell to go infect other cells

Question 79

How does Coxiella replicate inside the cell

Answer 79

promotes replication upon acidification 1. Coxiella enters the cell in the SCV form (non-replicative form) 2. SCV fuses with the lysosome 3. this fusion changes it to LCV and this is the replicative form producing SCVs and LCVs 4. the SCVs are released from the cell to go infect other cells

Question 80

How do bacteria resist reactive oxygen species ROE's, what is an example of a bacteria that does this

Answer 80

reactive oxygen species are the primary way the oxidative burst kills bacteria produce enzymes that neutralize oxygen radicals catalase H2O2 --> O2 + H2O superoxide dismutase O2- --> O2+H2O2 Salmonella SodCl enzyme is phage encoded

Question 81

What type of bacteria can avoid nitric oxide (reactive nitrogen compound)

Answer 81

Neisseria meningitidis produces nitric oxide reductase that converts NO to N2O (laughing gas) which is less toxic E. Coli uses nitric oxide dioxygenase to convert NO to NO3- (nitrate)

Question 82

How does Streptococcus pygoenes cope with the adaptive immune system

Answer 82

uses protein G uses it as a surface domain to bind the antibody backwards and not identify the bacterial cell

Question 83

How does Staphylococcus aureus cope with the adaptive immune system

Answer 83

uses protein A bind to the Fc regions of antibodies specifically IgG coat the antibodies which face outwards surface domain that binds the antibody backwards

Question 84

What are all the ways that bacteria can cope with the adaptive immune response

Answer 84

protein G protein A Collagen/fibronectin/fibrinogen which are ECM proteins, clumping factors bind fibrinogen host mimicry: bind host collagen they can entirely coat their surfaces, host views it as self and doesn't emit an immune response

Question 85

What are the ways that bacteria can spread cell to cell into new parts of the body

Answer 85

actin based motility flagella or chemotaxis breakdown pus secrete spreading factors that break down connective tissue and ECM secrete blood thinners to escape from blood clots want to move to different parts of the body so they are harder to find by the immune system and to disseminate through the body

Question 86

How do bacteria breakdown pus, what is the reason for this

Answer 86

pus is a thick substance that tends to trap bacteria pus is composed of proteins, dead cells and DNA, NETS hold onto bacteria while neutrophil is functioning bacteria secrete DNases to thin it to become untapped and spread to disseminate through the body

Question 87

What is the role of bacterial spreading factors

Answer 87

collagenases, elastases, hyaluronidases and other proteases break down connective tissue and extracellular matrix proteins to be able to infect different areas and move to new areas to disseminate through the body

Question 88

Why does bacteria secrete blood thinners

Answer 88

secrete blood thinners to degrade fibrin to escape from blood clots and spread to other parts of the body Streptokinase degrades fibrin to disseminate through the body