bacterial anatomy & physiology

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint® Lecture Slide Presentation prepared by Christine L. Case

M I C R O B I O L O G Y a n i n t r o d u c t i o n

ninth edition TORTORA FUNKE CASE

Part A 4

Dr Mila Nu Nu Htay

Bacterial Anatomy,

Physiology and Growth

(Part 1)


Objectives

Size, shape and arrangements of the bacterial cells

Structures of the bacterial cell and their functions

Differences between Gram positive and Gram Negative

cell walls

Gram Stain Mechanism

Physical and chemical requirements for growth

Phases of growth

Measurement of bacterial growth (direct, indirect)


Comparing prokaryotic and eukaryotic cells

Prokaryote comes from the Greek words for

prenucleus. (eg, bacteria, archaea)

Eukaryote comes from the Greek words for

true nucleus. (eg, algae, fungi, protozoa)

Prokaryotic Cells


Prokaryote Eukaryote

One circular

chromosome, not in a

membrane

No histones

No organelles

Peptidoglycan cell walls

Binary fission

Paired chromosomes,

in nuclear membrane

Histones

Organelles

Polysaccharide cell walls

Mitotic spindle


Prokaryotes and eukaryotes


Size and Shape of the bacterial cells

Average size: 0.2 -2.0 µm (in diameter) 2 - 8 µm (in

length)

Basic shapes

1. Cocci



2. Bacilli



3. Spiral bacteria

Spirillum Spirochete

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.5


Unusual shapes

Star-shaped Stella

Square Haloarcula

Most bacteria are monomorphic

A few are pleomorphic


Arrangements

Pairs: Diplococci,

diplobacilli

Clusters: Staphylococci

Chains: Streptococci,

streptobacilli

Figures 4.1a, 4.1d, 4.2c


Bacteria


Glycocalyx

Outside cell wall

Usually sticky

A capsule is neatly organized

A slime layer is unorganized

and loose

Extracellular polysaccharide

allows cell to attach

Capsules prevent phagocytosis

Figure 4.6a–b


Flagella

Outside cell wall

Three basic parts-

filament, hook, basal

body

Filament attached to a

protein hook

Anchored to the wall

and membrane by the

basal body Figure 4.8a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.8b

Flagella


Flagella Arrangement

Figure 4.7


Motile Cells

Rotate flagella to run or tumble

Move toward or away from stimuli (taxis)

Flagella proteins are H antigens

(e.g., E. coli O157:H7 – associated with foodborne

epidemics.)


Motile Cells

Figure 4.9


Motile Cells

PLAY Animation: Bacterial Motility

Figures 4.9a, 4.23d

../../Local%20Settings/Temp/04PPTLect-anim/BacterialMotility/PLAY_motility.html


Axial Filaments

Endoflagella or axial filament

In spirochetes

Anchored at one end

of a cell

Rotation causes cell

to move

Figure 4.10a


Fimbriae and pili

Fimbriae- the hair like

appendages

thinner, shorter and

straighter than the flagella

Allow attachment

Pili

One or two in number

are used to transfer DNA

from one cell to another

Figure 4.11


Cell Wall

Protect the cell

Prevents osmotic lysis

Made of peptidoglycan (in bacteria)

Site of action of some antibiotics

(eg, penicillin)

Figure 4.6a–b


Peptidoglycan

Polymer of disaccharide

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Linked by polypeptides

Figure 4.13a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.13b–c

Gram Positive and Gram Negative cell walls


Gram-Positive Gram-Negative Cell Walls Cell Walls

Thick peptidoglycan

Teichoic acids

In acid-fast cells,

contains mycolic acid

2 rings in basal body of

flagella

Thin peptidoglycan

No teichoic acids

Outer membrane

4 rings in basal body of

flagella

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.13b

Gram-Positive Cell Walls

Teichoic acids

Lipoteichoic acid links to plasma membrane

Wall teichoic acid links to peptidoglycan

May regulate movement of cations.

Polysaccharides provide antigenic variation.


Gram-Negative Outer Membrane

Lipopolysaccharides, lipoproteins, phospholipids

Forms the periplasm between the outer membrane and

the plasma membrane.

Protection from phagocytes, complement, and

antibiotics

O polysaccharide antigen, e.g., E. coli O157:H7

Lipid A is an endotoxin

Porins (proteins) form channels through membrane.


Gram-Negative Outer Membrane

Figure 4.13c


Gram Stain Mechanism

Crystal violet-iodine crystals form in cell.

Gram-positive

Alcohol dehydrates peptidoglycan

CV-I crystals do not leave (purple color)

Gram-negative

Alcohol dissolves outer membrane and leaves holes

in peptidoglycan.

CV-I washes out

Take safranin stain (pink color)


Gram Stain


Gram Stain Procedure

60 seconds


Gram positive and Gram negative microorganisms


Atypical Cell Walls

Mycoplasmas

Lack cell walls

Sterols in plasma membrane

Eg, Mycoplasma pneumoniae,

M genitalium.

Archaea

Wall-less or

Walls of pseudomurein (lack NAM and D amino

acids)


Damage to Cell Walls

Lysozyme (lysosomal enzyme) digests disaccharide in

peptidoglycan.

Penicillin inhibits peptide bridges in peptidoglycan.

Protoplast is a wall-less Gram-positive cell.

Spheroplast is a wall-less Gram-negative cell.

L forms are wall-less cells that swell into irregular

shapes.

Protoplasts and spheroplasts are susceptible to

osmotic lysis.


Plasma Membrane

Figure 4.14a


Plasma Membrane

Phospholipid bilayer

Peripheral proteins – serves as enzymes

Integral proteins

- Transmembrane proteins

Figure 4.14b


Fluid Mosaic Model

Membrane is as viscous as olive oil.

Proteins move to function.

Phospholipids rotate

and move laterally.

Figure 4.14b


Plasma Membrane

Selective permeability allows passage of some

molecules

Enzymes for ATP production

Photosynthetic pigments or chlorophyll are embedded

in the plasma membrane.

Chloroplast

http://en.wikipedia.org/wiki/File:Chloroplast.svg


Plasma Membrane

Damage to the membrane by alcohols, quaternary

ammonium (detergents), and polymyxin antibiotics

causes leakage of cell contents and subsequent cell

death.


Movement Across Membranes

Simple diffusion: Movement of a solute from an area of

high concentration to an area of low concentration.

(eg, oxygen, carbon dioxide)

Facilitative diffusion: Solute combines with a transporter

protein in the membrane.

(eg, glucose)



Figure 4.17



Osmosis: The movement of

water across a selectively

permeable membrane from

an area of high water

concentration to an area of

lower water.

Figure 4.18a



Figure 4.18a–b

Osmotic pressure:

The pressure

needed to stop the

movement of

water across the

membrane.


PLAY Animation: Membrane Transport


Active transport of substances requires a transporter

protein and ATP.

Group translocation - The substance is chemically

altered during transport across the membrane. Once the

substance is altered inside the cell, the plasma membrane is

impermeable to it. So the substance can’t come out of the

cell.

requires a transporter protein and

PEP(phosphoenolpyruvic acid).

../../Local%20Settings/Temp/04PPTLect-anim/MembraneTransport/PLAY_transport.html


Cytoplasm

Cytoplasm is the substance inside the plasma

membrane.

Figure 4.6a–b


Nuclear Area

Nuclear area (nucleoid)

The bacterial chromosome is a single, circular, double-

stranded DNA, exists freely in the cytoplasm.

Figure 4.6a–b

Plasmids – Small genetic

elements capable of

independent replication in

bacteria and yeasts or it is an

extrachromosomal genetic

material, replicate

autonomously.


Ribosomes

Several antibiotics can inhibit the protein synthesis in

the ribosomes.

Figure 4.6a–b


Ribosomes

Figure 4.19

S – Svedberg Unit


Inclusions

The cell store the excess nutrients in inclusions and

use them when the nutrient is deficient in environment.

Figure 4.20


Inclusions

Metachromatic granules

(volutin)

Polysaccharide granules

Lipid inclusions

Sulfur granules

Carboxysomes

Gas vacuoles

Magnetosomes

Phosphate reserves (used in

synthesis of ATP)

Energy reserves

Energy reserves

Energy reserves

Ribulose 1,5-diphosphate

carboxylase for CO2 fixation

Protein covered cylinders

Iron oxide


Endospores

Resting cells

Resistant to desiccation, heat, chemicals

Bacillus, Clostridium

Sporulation: Endospore formation

Germination: Return to vegetative state


Endospores


Endospores of Clostridium tetani

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