622 10/28 GLA Bacteria and Viruses

Bacteria Objective and Outcomes

Microbe Naming

Genus species

3 Domains of Microbes

bacteria

archae

eukarya

6 Categories of Microorganisms

bacteria

fungi

protozoa

small mulitcellular animals aka parasites

algae (do not cause infection/disease in humans)

archaea (do not cause infection/disease in humans

Eukaryotic Microbes

fungi, protozoa, parasites

Prokaryotic Microbes

bacteria, algae, archaea

Viruses

considered microbes, debate over if they are living or not (he seems to lean not)

can’t replicate on their own or perform metabolism

Prokaryote Cell

Prokaryotes

no nucleus, single circular DNA haploid genome, asexual, can have simple flagellum, cytoplasmic membrane, no mito/golgi bodies/ER

ATP production in cytoplasmic membrane

.5-3 um

Eukaryote Cell

Eukaryotes

membrane-bound nucleus, strands of DNA diploid genome, has mitochondria/golgi bodies/ER

contains sterols, sexual and asexual, can have complex flagellum

ATP production in mitochondria

>5um

Eukaryote vs Prokaryote

Prokaryote Cell Wall Components

complex with protein and peptidoglycan

may contain polysaccharides, teichoic acid, and lps

Eukaryotes with Cell Wall

only fungi have them

Eukaryote Ribosome

80S (60S + 40S)

Prokaryote Ribosome

70S (50S + 30S)

diff subunits allow us to target them with antibiotics

Ribosomes Diagram

Ribosomes

have small (30S) and large (50S) subunit

Gram Positive

purple

has thick proteoglycan layer in cell wall, one membrane

Gram Negative

red/pink

call wall has thin proteoglycan layer and lps, two membranes

How do we visualize bacteria?

observing growth colonies on petri dish

microscopically

morphology can refer to the visual of the colony or the microscopic characteristics

Bacerial Morphology: Shapes

cocci/spheres

bacilli/rods

coccobacillus (in-between cocci and bacilli)

curved rods (vibrio)

spirochetes (spiral)

(also gull-winged and barbell)

All Possible Bacteria

-aureus

bacterial colony is golden

Bacterial Morphology: Arrangement

staph

strep

diplococci

short vs long

Diplococci

two cocci bacteria together, uncommon

Strep

chain of bacteria

Staph

cluster of bacteria

Polymicrobial Patient Samples

multiple organisms and types present in one sample because we are a nice environment for organisms, but you are looking for one (we won’t have to do this)

2 Main Types of Cell Walls

one has more peptidoglycan and one cell membrane

the other has an lps (lipopolysaccharides) and two membranes

Mycoplasma

special exception to bacteria that do not have a cell wall

Why is understanding the bacterial cell wall so important for medicine?

structural and functional importance

features that give diagnostic clues (gram + or -)

components that can determine antibiotic resistance

can facilitate adhesion to human cells during infection

can contain components that help evade immune system

Gram + vs Gram - Cell Wall

Gram + Cell Wall

techoic acid, lipotechoic acid

thick peptidoglycan

one cell membrane

Gram - Cell Wall

lipopolysaccharide (lps)

thin proteoglycan

two cell membranes

porin channels

periplasm

secretion systems

3 Peptidoglycan Functions

provides rigid structure/shape by forming a cross-linked mesh

protection from environment (can prevent desiccation)

immune evasion

How does peptidoglycan contribute to immune evasion?

protects from the action of complement (an anti-microbial immune mechanism)

Peptidoglycan Structure

sugar backbone

tetrapeptide (amino acids)

cross links to another molecule via enzymes to form rigid mesh network

Peptidoglycan Structure Diagram

Sugar Backbone of Bacteria

NAG (N-Acetyl-glucosamine)

NAM (N-Acetyl-muramic acid)

Transpeptidase and Carboxypeptidase

create the cross-links of peptidoglycan

transpeptidase is common target of some antibiotics

What is significant about peptidoglycan?

it’s structure is unique, so we can target different parts of it with antibiotics that do not harm the patient

Lysozyme

natural antibiotics our bodies produce that break the bonds between NAG and NAM

in tears, helps prevent eye infections

Techoic Acid

in gram +, inflammatory

adds rigidity to cell wall, negatively charged

adherence to host cells

Inflammatory Function of Techoic Acid on Gram + Bacteria

catches the attention of the immune system

How do we distinguish between bacteria types with techoic acid?

different types of serotypes have different techoic acids

3 Components of LPS (in Gram -)

O antigen

core polysaccharide

lipid a

LPS Diagram

O Antigen

part of LPS, extends away from bacteria surface, many repeating saccharide units made up of 4-7 sugars/unit

Serotype

strain

What part of a gram - bacterial cell wall is important for serotyping?

o antigen

Core Polysaccharide

part of LPS, 9-12 sugar polysaccharide, essential for structure of LPS and bacterial viability (survivability)

Lipid A

part of LPS, endotoxin, fatty acids anchor into membrane, highly inflammatory (often a component of septic shock/toxic shock

Lipid A as an Endotoxin

toxin built into the microbe that is released upon the death of lysis of microbe (vs exotoxins which are secreted from microbes

if gram - bacteria are killed too fast, this will be released and will damage the patient, so this infection must be treated slowly

Porin Channels

part of gram - cell wall, manages movement of molecules into and out of periplasmic space, can restrict some antibiotics

hydrophilic molecules within outer membrane

Periplasm

part of gram - cell wall, allows buildup of virulence factors in space between outer membrane and cytoplasmic membrane

extra barrier for protection, enzymes that can break down certain antibiotics

Bacterial Resistance

gram + are often more resistant to environmental stressors, while gram - are often more resistant to antibiotics

Secretion Systems

component of gram - cell wall, different types, penetrates and delivers proteins across membranes and into host cells

Encapsulated Bacteria

E. coli

neisseria meingitidis

strep pneumoniae

strep agalactiae (group b strep)

haemophilus influensae type B

What types of bacteria can be encapsulated?

gram + and gram -

Encapsulation

carb capsule, provides immune evasion, useful for typing/identification, provides environmental and antibiotic protection, helps bacteria stick to host cell

Immune Evasion of Encapsulation

hard to phagocytose (slippery)

capsule shows up as clear border in staining

Asplenia

more infections with encapsulated bacteria if the spleen is removed or lost due to trauma

3 Other Structural Components of Bacteria

pilus and fimbria

flagella

slime layers

Pilus and Fimbria

bacterial component, adhesion and replication

Flagella

bacterial component, motility

Slime Layers

bacterial component, biofilms, loose network of peptidoglycan amongst neighboring bacteria

helps to adhere bacterial colonies to surfaces

Problem with Slime Layers

issues in hospitals with patients who have in-dwelling catheters, in prosthetic joints

Variety of Flagella

monotrichous

lophotrichous

peritrichous

amphitrichous polar

Amphitrichous Polar

a bacteria with a flagella on each end

Peritrichous

multiple flagella everywhere on a bacteria

Lophotrochus

multiple polar flagella on bacteria

Monotrochus

single polar flagella on bacteria

Gram + vs Gram - Summary