Microbio Exam #1 Review

What are the characteristics of prokaryotic cells?

• Lack organelles

• No nucleus

What are the characteristics of eukaryotic cells?

• Contains organelles(nucleus, ER, golgi, lysosomes, mitochondria, chloroplast)

Where does bacteria fall in relationship to size of other cells?

Bacteria is VERY small compared to eukaryotes, but larger than viruses

How do differences in eukaryotic vs prokaryote relate to antibacterial targets?

Prokaryotes are antibiotic sensitive while Eukaryotes are not

What is the size of bacteria?

0.2 to 2.0 micrometer diameter

2 to 8 micrometer long

What are the shapes of bacteria?

1. Coccus

2. Bacillus

3. Spiral

Coccus

-Spherical

-Low surface to volume ratio

-resists drying

Bacillus

-Rod-shaped bacteria

Spiral

-Spiral-shaped

-Do not survive long

-High S/V

What is the difference between Staph and Strep?

Strep=chain

Staph=Cluster

How is the shape of bacteria determined? What is monomorphic? Pleomorphic?

-Shape is determined by genetics

-Monomorphic: One shape

-Pleomorphic: Multiple shapes

What is this a photo of?

Gram positive bacteria

What is this a photo of?

Gram Negative Bacteria

What are differences between Gram (+) and Gram (-) ?

Gram +: Gram -:

-Thicker cell wall -Thinner cell wall

-No outer membrane -Has an outer membrane

-more penetrable -less penetrable

-One major layer -extensive periplasmic space

-narrow periplasmic space -Two major layers

What are the similarities between Gram (+) and Gram (-) ?

They both contain peptidoglycan, periplasmic space, a cell membrane, and membrane proteins

Describe the cell envelopes of gram positive and gram negative bacteria

Gram + has a thick cell layer wall with teichoic acids while Gram - has a thin cell layer wall between inner and outer membrane

How is a Gram stain performed differently for a Gram (+) than a Gram (-)

Gram + is stained more easily because of its thick cell wall and stains as purple.

Gram - is stained less easily because of this cell wall, which requires more steps to stain. It stains as pink.

What are characteristics of Gram (+) ?

• Has a cell envelope compose of inner membrane surrounded by thick cell wall

• The cell wall is made of peptidoglycan with teichoic acids anchored to them on the surface.

• Inner membrane only

What are characteristics of Gram (-) ?

• Contains both an inner and outer membrane

• The inner membrane promotes fluidity due to phospholipids

• The outer membrane is assymetrical(inner side contains phospholipids and the outer side contains phospholipids, lipopolysaccharides, and 60% protein).

Techoic Acid

• Function: Promotes stability of the cell envelope and evasion of host

Two types of teichoic acids in gram + bacteria:

1. Wall Teichoic Acid: Anchored to peptidoglycan

2. Membrane Teichoic Acid: Anchored to the outer leaflet of the inner membrane’’

• Makes up 50% of cell wall

What is the prototype for Gram (+) cells?

Bacillus Subtilis

What is the prototype for Gram (-) cells?

E. Coli

Porins

• Protein

• Found in gram - bacteria

• Make up major part of outer membrane

• Assist in passive transport of molecules across the outer membrane into the periplasmic space in gram negative bacteria

Lipopolysaccharide

Divided into 3 segments:

1. O-side chain: Major antigen

2. Core oligosaccharide: Usually inner and outer core but can vary

3. Lipid A: Brings lipopolysaccharides into the hydrophobic region of the outer membrane. Very toxic.

How do penicillin binding proteins contribute to cell wall synthesis.

Penicillin-binding proteins (PBPs) are essential bacterial enzymes that catalyze the final stages of peptidoglycan synthesis, responsible for building and maintaining the bacterial cell wall.

Describe the structure and function of the bacterial cell wall

Typically made of peptidoglycan

Describe the methodology and importance of the acid-fast stain for mycobacteria.

Since mycobacteria has a waxy coat covering the cell wall made of mycolic acid, gram staining is prevented. Therefore, acid-fast stain must be used in order to categorize non acid fast bacteria as brilliant green and acid fast bacteria with carbol fuchsin(pink)

Glycocalyx

• component of Extracellular membrane

• A coat/layer surrounding bacterial cell made of polysaccharides and/or polypeptides

• Two types:

-Capsule: firmly attached to cell wall

-Slime layer: loosely attached to cell wall

Flagella

• long appendages for motility

• rotates like a propellor, clockwise or counter clockwise

• Propels bacteria through a series of runs and then tumbles

• not all bacteria produce Flagella

• extracellular mebrane

Fimbrae vs Pilli

• Both: short-haired like appendages used for attachment or conjugation, gram neg only, composed of protein pilin, extracellular membrane

• Fimbriae: Polar position OR over whole surface, few to 100 per cell, main function is adherence. For example, Gonorrhea cannot colonize genital tract without fimbrae

• Pilli: Longer than fimbriae, only 1-2 per cell, main function is transort of DNA from one bacteria to another during conjugation AKA sex pilli

Cytosol

• Intracellular structure

• substance inside plasma membrane

• 80% water

• thick

• semitransparent

• elastic

What is the difference between chromosomes in prokaryotes vs eukaryotes

Prokaryotes contain a single chromosome while eukaryote has multiple chromosomes

Plasmids

• small, circular, extrachromosomal DNA

• In the cytoplasm

• replicate independently of chromosomes

• can be transferred by conjugation(via pilli)-fertility plasmid

• Carry antibiotic resistance genes, metabolism genes

Ribosomes

• In the cytoplasm

• Site of protein synthesis

• 10,000/cell

• composed of rNA AND Protein

• two subunits

• Good target for antibiotics

What is a cross bridge?

• Provides structural stability

• Few cross links are used in gram - bacteria

• More than half of cross bridge bonds are formed in gram +

Endospores

• In the cytoplasm

• “resting” cell unique to bacteria

• Cells detect an environmental change and form endospores to survive environmental stress

• not a form of sexual reproduction(1 cell=1 spore)

What components make up intracellular bacteria?

cytosol, chromosome, plasmids, ribosomes, and endospores

What structures make up extracellular bacteria?

fimbriae, pili, flagella, porins and capsules

1. Describe the impact of environmental factors (pH) on microbial growth.

• Bacteria are mostly neutrophiles

• Cellular metabolism produces acids that inhibit bacterial growth

• Bodily pH is an innate host defense against invading microorganisms(stomach,skin)

1. Describe the impact of environmental factors (temperature,) on microbial growth

Each organism has a Maximum growth temperature, Minimum growth temperature, and Optimum growth temperature

1. Describe the impact of environmental factors (osmolarity, ) on microbial growth.

1. Isotonic: Concentration inside and outside cell are equal, no net movement

2. Hypotonic: Inside of cell has lower concentration than outside, so water diffuses INTO cell

3. Hypertonic: Inside of cell has higher concentration than outside, so water diffuses OUT of the cell

The higher the osmotic pressure = decrease in bacterial growth because of dehydration

What are the growth phases of bacteria?

1. Lag Phase

2. Log Phase

3. Stationary Phase

4. Death Phase

Lag Phase

• Little or no cell division

• Period of synthesis

Log Phase

• Exponential growth

• Cells are most metabolically active

• Most sensitive to antibiotics

Stationary Phase

• Nutrients are all utilized, pH change

• Constant Number of Cells

• Division Rate=Death Rate

Death Phase

• Death Rate>Division Rate

• No nutrients due to extreme pH

What phase of growth bacteria are most susceptible to antibiotics.

The Log Phase

Aerobic Respiration

Oxygen is the final electron acceptor

Produced the most ATP compared to Anaerobic Respiration and Fermentation

Anaerobic respiration

Has less efficient nonoxygen electron acceptors such as nitrate and sulfate.

Has a lower yield of ATP compared to aerobic conditions, but still more than fermentation

Fermentation

Necessary for bacteria growing under Aerobic and Anaerobic conditions to recycle NADH back to NAD+

An organic molecule is the final electron acceptor and the max amount of ATP produced is 2.

What is the difference between respiration and fermentation?

Fermentation yields a low ATP value and only includes glycolysis and some fermentative pathways. On the other hand, Respiration yields a high ATP value via an electron transport chain.

1. Describe the impact of environmental factors ( oxygen) on microbial growth.

Oxygen can serve as an essential nutrient for SOME bacteria, a toxic substance for others, and a modulator for many

Obligate Aerobes

Require oxygen for bacterial growth

Test tube (bacteria at top)

Facultative Anaerobes

Growth occurs both with and without the presence of oxygen, but more growth where there is more oxygen

Obligate anaerobes

Bacteria dies in the presence of oxygen, so bacteria growth occurs only where there is no oxygen

Aerotolerant Anaerobes

Oxygen has no effect on growth

Microaerophiles

Growth occurs only where there is low concentrations of oxygen

Psychrophiles

Cold loving

Mesophiles

Moderte temperature

Thermophiles

Heat loving

Extreme Thermophiles

Organisms that thrive in extremely hot environments

Ex: Archaea

Acidophiles

Acid loving

Neutrophiles

Neutral loving

Alkalophiles

Base loving

Overview of Endospores

1. Dehydrated

2. Durable spore coat

3. contains DNA of cell

4. Dipicolinic Acid(coating)

5. No metabolic reactions

What is the function of capsule Glycocalyx?

• Protects cell from phagocytosis

• Attachment to tissue

• Food source

What is the function of slime layer Glycocalyx?

• Trap nutrients

• Prevent dessication

Mycobacteria Spp.

• Bacteria that causes Tuberculosis

• Single cell membrane

• Contains a cell wall made of peptidoglycan

• Waxy coat of mycolic acid covers the cell wall

Monotrichous

single flagellum

Amphitrichous

tuft of flagella at each pole

Lophotrichous

tuft of flagella from one pole

Peritrichous

flagellum over the whole surface

infection

• persistence of an organism in or on the host

infectious disease

• colonization or invasion of the host resulting in tissue damage

pathogenicity

• the ability or potential for an organism to cause disease

virulence

• the degree or intensity of an organism’s pathogenicity

Virulence factors

Any component of an organism that contributes to:

• Invasion

• Evasion or subversion of host defenses

• Tissue damage

.Primary pathogen:

• A microorganism that causes disease even in healthy hosts

Ex: Bacillus anthracis, varicella(flu)

Opportunistic pathogen:

• A microorganism that normally causes disease only in hosts that are compromised in some waye

Ex: C. diff, pneumonia,

What are the 5 steps required for microorganisms to produce an infectious disease

1. Adherence

2. Replication

3. Invasion

4. Evasion of host defense

5. Tissue damage

Adhesins

• microbial surface structures that attach to a host cell receptor(integrin)

Integrins

• Host cell receptors that bind to microbial adhesins

Host tropism

• The presence of integrins determine which hosts can be infected

Tissue tropism

• Presence of integrins determines which tissues within a host can be infected

Pili (fimbrae) Adherins

• Hair like projections that are on the surface of bacteria, typically gram negative bacteria

What is an example of pili adherence

• Adherence of uropathogens to the mucosal surface of the bladder

Non-pili adhesins

• Adhesins of gram positive bacteria

What is an example of non-pili adhesins?

• Protein F of strep bacteria, binds to fibronectin on mucosal surface

Replication

• Microbes typically have to replicate to cause infectious disease

What are the sites of replication within a host?

1. Extracellular growth: Outside of host cell

2. Intracellular growth: Growth inside of a host cell

Facultative Intracellular Pathogens:

Bacteria that can grow both inside and outside of host cells.

Ex: Salmonella

Why does bacteria Invade a host cell?

• Strategy for survival and replication

What are the benefits of invading a host cell?

1. Evasion of host defenses

2. Source of nutrients

3. Less competition

4. Access to host cell machinery

What happens to a microorganism after they invade a host cell?

• They must escape and invade a new host cell

• Some bacteria like Listeria and Shigella proper damaged host cells into healthy adjacent host cells

What are examples of microbial defense against host complement?

1. Coat themselves: Coat surface with circulating IgA antibodies(prevents them from being recognized by other antibodies). This is something bacteria had adapted.

2. Inactive complement components: Secret enzymes that will chop components of host complement

3. Capsules

IgA

Found in mucosal surfaces

IgD

Antigen receptor on B cells

IgE

Binds to allergens and to parasitic worms

IgG

• Provides the majority of anti-body based immunity to pathogens

IgM

• Expressed on B-cell surface, can be secreted