Lecture 4-Cellular Structure of Prokaryotic cells

Slides(1-34)

pre-nucleus

Prokaryote comes from the Greek word for __________

true nucleus

Eukaryote comes from the Greek word for _________

• Size

– small but varies

• Shape

– cocci and bacilli most common

– various others

• Arrangement

– determined by plane of division

– determined by separation or not

Size, Shape ,Arrangement of prokaryotic cells

• smallest – 0.3 μm (Mycoplasma)

• average rod – 1.1 -1.5 x 2 – 6 μm (E. coli)

• very large – 600 x 80 μm Epulopiscium, fishelsoni

list the measurement for smallest size(w/ example), Average size(w/ example, Very Large(w/ example) of Prokaryotes

Single bacillus

Name of this prokaryotic arrangement

Diplobacilli

Name of this prokaryotic arrangement

Streptobacilli

Name of this prokaryotic arrangement

Coccobacilli

Name this prokaryotic arrangement

Diplococci

Name of this cocci arrangement

Streptococci

Name of this cocci arrangement

Tetrad

Name of this cocci arrangement

Sarcinae

Name of this cocci arrangement

Staphylococci

Name of this cocci arrangement(grape like structure)

bacilli (s., bacillus)

prokaryotic rod name

coccobacilli

very short rods prokaroytes

vibrios

resemble rods, comma shaped prokarytoes

spirilla (s., spirillum)

rigid helices structure for prokaryotes

spirochetes

flexible helices for prokaryotic arrangement

b. staphylococci

Bacteria that divide and form grapelike structures are

a. streptococci.

b. staphylococci.

c. coccobacilli.

d. vibrios.

-Biochemical analysis, eg.

-subcellular fractionation

-Structural analysis

-Genetic analysis

Main techniques to study plant cells(4)

cytoplasm

In bacterial cells, __________ surrounded by envelope

nucleoid

bacterial cytoplasm contains DNA in __________

nucleoid

Non-membrane-bound area of the cytoplasm in prokaryotes that contains the chromosome in the form of looped coils

rare

Some bacteria have cytoplasmic organelles--but it is ______

envelope

Cell “________” around the outside of the cells(prokayotes)

Cell membrane

____________ directly surrounds the cytoplasm

“inner membrane”

Cell membrane directly surrounds the cytoplasm

-In Gram negative bacteria, this is the _____________

only membrane

Cell membrane directly surrounds the cytoplasm

-In Gram positive bacteria, this is the ____________

negative

In Gram-_______ bacteria, there is another membrane outside the cell wall

Cell wall

this is on the outside of the cell membrane

flagella

Many bacteria have a _______—rotary swimming motor

- Structural support

- Detection of environmental signals

- Secretion of virulence factors and communication signals

- Ion transport and energy storage

Membrane proteins serve numerous functions, including(4):

-Single unit—network of sugars and peptides

-Confers shape and rigidity on the bacterial cell

-“Sacculus” made of “peptidoglycan” aka “murein”

-Sugar chains wrapped in circles around cell

-“glyco” = “sweet”

-Sugar chains linked to each other by short polymers of amino acids

-short amino acid chain = “peptide”

The Bacterial Cell Wall

geodesic dome

The bacterial cell wall resembles this shape

vancomycin and penicillin

Peptide addition and crosslink formation can be blocked by these antibiotics

unique

Peptidoglycan is ______ to bacteria

-- Thus, the enzymes responsible for its biosynthesis make excellent targets for antibiotics

Penicillin inhibits the transpeptidase that cross-links the peptides of the peptidoglycan layer

how does penicillin work as an anti-biotic

Vancomycin prevents cross-bridge formation by binding to the terminal D-Ala-D-Ala dipeptide of the peptidoglycan layer

how does Vancomycin work as an anti-biotic

resistant strains

Unfortunately, the widespread use of such antibiotics selects for evolution of _________

Capsule (not all species)

-Polysaccharide(made of Glycosyl chains)

 S Layer (not all species)

-Made of protein or glycoprotein

 Thick cell wall

-9-amino acid crosslinks in peptidoglycan

-Teichoic acids for strength

-There can be proteins, including channels, that span the cell wall

 Plasma membrane

describe the gram positive cell envelope(outer to inward)

 Capsule (not all species)

 Polysaccharide

Outer Membrane

 Lipopolysaccharide

-In outer leaflet only

-Also known as ‘endotoxin’

-This makes most Gram-negative bacteria tougher and harder to kill than Gram- positive bacteria (unless they can form endospores)

 Thin cell wall

-4-amino acid crosslinks in peptidoglycan

 Plasma membrane

Describe the Gram-Negative Envelope

• Consists of three parts

– lipid A

– core polysaccharide

– O side chain (O antigen)

Lipopolysaccharide (LPS) has 3 parts

outer membrane

Lipopolysaccharide (LPS): Lipid A embedded in __________

extend out from the cell

Lipopolysaccharide (LPS): Core polysaccharide, O side chain _____________

• contributes to negative charge on cell surface

• helps stabilize outer membrane structure

• may contribute to attachment to surfaces and biofilm formation

• creates a permeability barrier

• protection from host defenses (O antigen)

• can act as an endotoxin (lipid A), is a PAMP (Pathogen associated molecular pattern)

Importance of LPS:

• Gram stain: purple.

• Thick peptidoglycan (more sensitive to certain antibiotics).

• One membrane.

• No periplasmic space

• No LPS

• Teichoic acids

Characteristics of Gram-Positive

• Gram stain: pink.

• Thin peptidoglycan.

• Outer membrane (two membrane).

• Large periplasmic space

• Lipopolysaccharide-LPS

• No teichoic acids

Characteristics of Gram-Negative

– Alcohol dissolves outer membrane and leaves holes in peptidoglycan.

– CV-I washes out

what does the alcohol step do to the Gram-negative bacteria

Gram Reaction: retain crystal violet dye and stain dark violet or purple

Peptidoglycan layer: Thick(multilayered)

Teichoic Acids:Present

Periplasmic Space:Absent

Outer Membrane:Absent

Lipopolysaccharide:Virtunally None

For gram postiive:

Gram Reaction:

Peptidoglycan layer:

Teichoic Acids:

Periplasmic Space:

Outer Membrane:

Lipopolysaccharide:

Gram Reaction: can be decolorized to accept counterstain(safranin) and stain pink

Peptidoglycan layer: Thin(single layered)

Teichoic Acids: Absent

Periplasmic Space: Present

Outer Membrane: Present

Lipopolysaccharide:High

For gram negative:

Gram Reaction:

Peptidoglycan layer:

Teichoic Acids:

Periplasmic Space:

Outer Membrane:

Lipopolysaccharide:

Fill in the graph

Fill in the graph

D. Endotoxin

The lipopolysaccharide (LPS) that is found in

the outer membrane of Gram-negative

bacteria is also known as

A. Exotoxin.

B. Teichoic acid.

C. Murein.

D. Endotoxin.

E. Antitoxin

d) Teichoic acids

Which of the following is found in the cell wall of

a Gram-positive bacterium but NOT in that of a

Gram-negative bacterium?

a) Peptidoglycan

b) Outer membrane

c) Lipopolysaccharides

d) Teichoic acids

e) Capsule

– Lack cell walls

– Sterols in plasma membrane

2 characteristics of Mycoplasmas

• Archaea

– Wall-less or

– Walls of pseudomurein (lack NAM and D amino acids)

– No peptidoglycan

3 characteristics of Archaea

lysozyme

___________ breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid

penicillin

__________ inhibits peptidoglycan synthesis

lysozyme and penicillin

if cells are treated with either of these(2) they will

lyse if they are in a hypotonic solution

plasmolysis

water moves out of the cell, causing its cytoplasm to shrink

– solute concentration outside the cell is less than inside the cell

– water moves into cell and cell swells

– cell wall protects from lysis

3 characteristics of a hypotonic environement

– solute concentration outside the cell is greater than inside

– water leaves the cell

– plasmolysis occurs

– Salt and sugar have been used to preserve foods

what 4 things occur in Hypertonic environments