Bacteriology lecture 1 Flashcards by Erin Jernstedt

What is the estimated amount of microbial cells on earth?

~5 million trillion trillion (10^30)

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What is the professors favorite bug?

Listeria

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Phylogeny

Science dealing with evolutionary relationships between living organisms

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What is Phylogeny based on?

Sequence of macromolecules such as DNA, RNA and protein - Phylogenetic trees

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What are the 3 phylogenetic distinct lineages of cells?

2 Prokaryotic (Eubacteria and Archea)
1 Eucaryotic

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Who came up with Endosymbiont Theory?

Lynn Margulis

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What was the Endosymbiont Theory?

A major organizational event in the history of life probably involved the merging of two or more lineages through symbiosis.

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Single-celled prokaryotic microorganisms and their DNA is not contained within a separate nucleus as in eukaryotic cells are?

Bacteria

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What characteristic are used to classify and identify bacteria?

Shape and size

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Approximate size of bacteria

0.1-10.0 um in size

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Bacteria, bacillus/bacilli means

Rods (little stick)

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Coccus/Cocci means

Round

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Pleomorphic means

Bacteria which can assume many shapes

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What give spirochete the more pronounced shape?

Internal flagella

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Strepto means

chain

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Diplococci means

two coccus

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Tetrad means

four

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Staphylo means

cluster

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What divides bacteria individual from the environment?

Cell wall

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Cell wall is present in all eubacteria except?

Mycoplasmas

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In prokaryotic cell’s wall is located?

Outside the plasma membrane

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Most archaeobacteria do not have a cell wall, but those that do have?

A different type of peptidoglycan or protein

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Functions of the cell wall?

Prevents osmotic lysis, protects cell from external stress (host), contributes to virulence, target for antimicrobials

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What is a cell wall?

Rigid structure surrounding the cell membrane

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Two ways of characterize a bacteria cell wall

Gram stain | Acid fast stain

The four characterizations of the bacteria cell wall

Gram-positive Gram-negative Acid Fast Wall-less

What is the chief structural & composition component of a eubacteria's cell wall?

Peptidoglycan

Peptidoglycans are composed of?

Long chains of polysaccharides (glycan) cross-linked by short proteins (peptides)

The constitution of the polysaccharide is by what two repeating subunits?

N-acetyl glucosamine and N-acetyl muramic acid

When polysaccharide chains are cross-linked by peptides and then linked together create the?

Single rigid mesh-like molecule that forms the cell wall (chain link fence)

What determines the major difference between gram + and gram -?

Peptidoglycans in the cell wall

Gram neg peptidoglycans

Mesh is only one layer thick

Gram posit peptidoglycans

Wall is many layers thick (40)

Staining

The appearance of bacteria following the gram stain is also used for Identification

Purple/blue stained bacteria are?

Gram-Positive

Gram-Negative bacteria stain?

Pink/red

The difference in response to the Gram stain results form the ?

Composition of the cell envelope

What is the unique structure for Gram-neg bacteria?

Lipopolysaccharide (LPS)

What is an advantage of lipopolysaccharide in Gram-neg?

Major permeability barrier

Where do Gram-neg bacteria store degradative enzymes?

In the periplasmic space

Gram-pos bacteria secrete what? and why?

exoenzymes and preform extracellular digestion

Where is the periplasmic space?

Between the lipopolysaccharide membrane and peptidoglycan membrane.

What are the two staining methods?

1) Simple stain - Basic dyes | 2) Differential Stain - combination of basic dyes

Basic dyes

Have a positive charge and bind to negatively charged bacteria at ~pH-7

Acidic dyes

Have a negative charge and stain background

Gram staining procedure

``` Fixation Crystal Violet (primary stain) Iodine treatment Decolonization (alcohol/acetone) Counter stain with Safranin ```

If you get Coccus with pink stain what have you done?

Very few Gram-neg Coccus. You have left the stain in the decolonization too long.

Acid fast staining procedure

Carbol fuchsin Acid alcohol decolorizer Counterstain malchite green or methylene Blue Rest the dilute acid

Difference between acid fast and non acid fast bacteria?

Acid fast will remain the same color as the first stain used. Non acid fast will show up with a blue color.

What is responsible for Acid Fast staining?

The mycobacterial cell wall contains long chain length fatty acids (mycolic acids and waxes) which contribute to virulence.

Teichoic Acid and Lipoteichoic acid

Appear to extend the surface of the peptidoglycan layer in Gram-Positive Bacteria

What does Teichoic Acid do?

Provide rigidity to the cell wall Assist in regulation of cell growth Receptor molecules for some Gram-Positive bacteriophage

How does Teichoic Acid provide rigidity to the cell wall?

By attracting cations such as magnesium and sodium.

How does Teichoic Acid assist in regulation of cell growth

By limiting the ability of autolysins to break the Beta (1-4) bonds between the N-acetyl glucosamine and the N-acetylmuramic acid

What is the most important part of Gram-Neg bacteria?

Lipopolysaccharide

What are the three parts of the Lipopolysaccharide?

Lipid A- Core oligosaccharide O antigen

What does the Lipid A of the Lipopolysaccharide do?

Embedded in the membrane is responsible for endotoxin activity

What unique about the Lipid A of the Lipopolysaccharide?

C14 Fatty Acid *hydroxy myristic acid, phosphates, glucosamine

What unique about the Core oligosaccharide of the Lipopolysaccharide?

Highly conserved among different bacteria | Unique components -KDO (3-deoxy-D-manno-2-octulosonic) acid and heptose

What unique about the O antigen of the Lipopolysaccharide?

Presents is species dependent Composed of repeating units consisting 3 to 4 CHOs polymerized into polysaccharide Antigenic and highly variable among species and strains

What is the most potent immune system activators in the Lipopolysaccharide?

Lipid A - Endotoxin

What is the test for endotoxin Lipid A?

Limulus Amebocyte Lysate (LAL) Test

What are the specifics of the LAL test?

It is an aqueous extract of the blood cells from the horseshoe crab

What plays a critical role in the architecture and impermeability of the cell wall in mycobacteria?

Mycolic acid

How do we visualize bacteria?

Compound light microscope Dark-field microscope Fluorescent microscope Electron microscope

What is the difference between Light and Electron microscopes?

Light- uses visible light | Electron - uses electron beams

What is the difference between Negative and Positive stain?

Negative - stains the background | Positive - stains the structures