HRR: nature of microbial pathogenesis bacteria

Question 1

Describe the general structure of bacteria

Answer 1

They’re a bag of stuff surrounded by a cell wall. They’re prokaryotes, meaning they’re single-celled with no nucleus. Their genetic material is typically on one circular chromosome

Question 2

Describe how bacteria grows and why this is significant

Answer 2

Bacteria grows by binary division, meaning one cell becomes two. Bacterial growth is all about growth of the population. This means infections can rapidly go from mild to life-threatening, and natural selection can occur within hours due to the number of generations made in a short time

Question 3

Describe obligate anaerobes

Answer 3

Oxygen is toxic to them, as they lack superoxide dismutase and catalase. Instead, they make short-chain fatty acids

Question 4

Describe facultative anaerobes

Answer 4

Can use oxygen, but often don’t. they start with respiration but switch to fermentation when oxygen is depleted. They can also make short chain fatty acids

Question 5

Describe obligate anaerobes

Answer 5

Require normal atmospheric oxygen concentrations for normal growth

Question 6

Describe microaerophilic bacteria

Answer 6

Aerobic microorganisms that prefer low oxygen tensions; they grow best in atmospheres enriched with CO2

Question 7

describe cell wall structure and components of gram positive bacteria

Answer 7

monoderm with a thick layer of peptidoglycan

Question 8

describe cell wall structure and components of gram negative bacteria

Answer 8

diderm with a bilayer peptidoglycan; the outer layer contains porins and LPS

Question 9

describe the cell wall structure and components of mycobacteria

Answer 9

diderm with thin peptidoglycan; outer layer has glycolipids and glycolytic acids that make them very waxy

Question 10

Gram positive bacteria take on a ___ color, while gram negative take on a ___ color

Answer 10

Purple; pink

Question 11

Describe differential staining

Answer 11

-Fix
-Add crystal violet
-Iodine treatment aka mordant
-Decolorization (gram positive remains purple, gram negative loses color)
-Safranin stain (gram negative turns pink)

Question 12

What is the function of peptidoglycan in the cell wall

Answer 12

They’re cross-linked to form peptidoglycan polymers that help hold in all the contents of the bacteria…like Spanx. They provide structural integrity and provide shape

Question 13

Bacterial cell walls are composed of alternating units of…

Answer 13

NAM and NAG (components of peptidoglycan)

Question 14

Describe lysozyme and its function

Answer 14

Antimicrobial enzyme and component of the innate immune system that breaks 1,4 beta linkage of NAG and NAM. Present in various secretions in the body such as tears, saliva, milk, and mucus

Question 15

Describe the general composition of gram-positive cell walls

Answer 15

They contain teichoic acid and lipoteichoic acids. Sugars, cholines, and other molecules can attach to the hydroxyls of ribose or glycerol to provide antigenic determinants. They have a thick layer of peptidoglycan

Question 16

What is the function of lipoteichoic acid

Answer 16

Anchors the cell wall to the membrane; can also manifest an IL-10 dependent inhibition of CD4 T cell expansion

Question 17

Describe the general composition of gram-negative cell walls.

Answer 17

They have a bilayer of peptidoglycan embedded in periplasmic gel. Their outer membrane is a phospho-lipoprotein bilayer containing porins. It also contains LPS and confers a strong negative charge

Question 18

What is LPS

Answer 18

An endotoxin produced by gram negative bacteria that facilitates an acute inflammatory response.

Question 19

What are the components of LPS

Answer 19

Lipid A: innermost component that confers toxic properties
Core polysaccharide lends strength to the outer membrane
O antigen: confers unique immunological ID

Question 20

LPS can function as a…

Answer 20

PRR

Question 21

What is the significance of the negative charge on gram negative bacteria

Answer 21

It protects them from phagocytosis, complement, lysozyme, bile, digestive enzymes, and various antibiotics

Question 22

Describe the cell wall of acid-fast bacteria

Answer 22

Thick cell wall with a lot of mycolic acids. It’s very waxy and may take of a variable reaction when gram stained. For example, when gram stained the wax may hang on to the pigment and stain gram positive.

Question 23

In acid fast staining, what are the primary and secondary stains

Answer 23

Carbolfuchsin and methylene blue

Question 24

What are endospores

Answer 24

Defense mechanism against harsh conditions. Essentially, they protect the microbe from things like heat, radiation, enzymes, etc. they’re metabolically at rest and have a spore made of calcium bound to dipicolinic acid that protects its genomic DNA

Question 25

When mentioning C diff, we are also referencing…

Answer 25

endospores

Question 26

Describe capsules

Answer 26

They’re a defense mechanism that keeps bacteria from being engulfed; they can literally slip away from macrophages

Question 27

What is the K antigen

Answer 27

Capsule

Question 28

What are PRRs

Answer 28

Members of the innate immune system that are the frontline defense against viruses in tissues

Question 29

What is virulence

Answer 29

The behavior of a microbe that determines what fraction of those infected suffer morbidity or mortality

Question 30

Describe adhesins as virulence factors

Answer 30

They bind to specific human host sites and determine tissue tropism, aka where the infection will develop. Strong adhesins correlate with ability to cause infection with low levels of bacteria

Question 31

Adhesins are found on which structures

Answer 31

Pili or fimbriae

Question 32

Describe the H antigen

Answer 32

They’re also known as flagella. They use an ATPase-like mechanism for movement. They typically take about 1000 protons per rotation and 7.2 million protons to spin at 100 hz

Question 33

What is phase variation

Answer 33

Genetic process meant to help evade the adaptive immune response; involves changes to the flagella and/or pili. A big one is the changing of the flagellum in salmonella via a transposon that flips direction every 10k divisions

Question 34

What are biofilms?

Answer 34

Microbes grow on a surface and then stop, and antibiotics only work on actively growing cells. This can leave a layer of non-active microbes that cannot be killed.

Question 35

What is quorum sensing

Answer 35

A process that allows bacteria to measure how many other cooperating bacterial cells are nearby; more bacterial cells means more quorum factor means more transcription factor to activate gene expression which results in microbes that manifest traits and behaviors of bioactive molecules

Question 36

What are siderophores

Answer 36

Bacteria use them to acquire iron; they compete with iron-binding molecules to take iron from the host and bring it to the microbes. This is a public good of bacteria

Question 37

Describe type II secretion pathway

Answer 37

Found in all bacteria. Requires Sec gene products, ATP, and accessory proteins. Tat primarily secretes the folded proteins.

Question 38

Describe type I secretion pathway

Answer 38

Proteins are exported directly across both membranes

Question 39

Describe type III secretion pathway

Answer 39

Act as a molecular syringe that injects proteins into other bacteria or human cells

Question 40

39. describe type IV

Answer 40

acts like a syringe that injects proteins and DNA into other bacteria or human cells

Question 41

describe type VII

Answer 41

ENP pathway involved in biofilm formation