microbiology ch 03 lecture_presentation

PowerPoint® Lecture Presentations prepared by Mindy Miller-Kittrell, North Carolina State University

C H A P T E R

© 2015 Pearson Education, Inc.

Cell Structure and Function

3


Processes of Life

• Growth

• Reproduction

• Responsiveness

• Metabolism


Figure 3.1 Examples of types of cells.


Processes of Life

• Tell Me Why• The smallest free-living microbe—the bacterium

Mycoplasma—is nonmotile. Why is it alive, even though

it cannot move?


Prokaryotic and Eukaryotic Cells: An Overview

• Prokaryotes• Include bacteria and archaea

• Have a simple structure

• Lack nucleus

• Lack various membrane-bound internal structures

• Are typically 1.0 µm in diameter or smaller


Figure 3.2 Typical prokaryotic cell.

Ribosome

CytoplasmNucleoid

GlycocalyxCell wall

Cytoplasmic membrane

Flagellum

Inclusions



• Eukaryotes• Have nucleus

• Have internal membrane-bound organelles

• Are typically 10–100 µm in diameter

• Have more complex structure

• Include algae, protozoa, fungi, animals, and plants


Figure 3.3 Typical eukaryotic cell.

Nucleolus

Cilium

Ribosomes

Cytoskeleton

Cytoplasmicmembrane

Smooth endoplasmicreticulum

Rough endoplasmicreticulum

Transport vesicles

Golgi body

Secretory vesicleCentriole

MitochondrionLysosome

Nuclear pore

Nuclear envelope


Figure 3.4 Approximate size of various types of cells.



• Tell Me Why• In 1985, an Israeli scientist discovered a single-celled

microbe, Epulopiscium fishelsoni. This organism is

visible with the naked eye. Why did the scientist think

Epulopiscium was eukaryotic?

• What discovery revealed that the microbe is really a

giant bacterium?


External Structures of Bacterial Cells

• Glycocalyx• Gelatinous, sticky substance surrounding the outside of

the cell

• Composed of polysaccharides, polypeptides, or both



• Two Types of Glycocalyces

• Capsule

• Composed of organized repeating units of organic chemicals

• Firmly attached to cell surface

• May prevent bacteria from being recognized by host

• Slime layer

• Loosely attached to cell surface

• Water soluble

• Sticky layer allows prokaryotes to attach to surfaces as biofilms


Figure 3.5 Glycocalyces.

Glycocalyx(capsule)

Glycocalyx(slime layer)


Motility



• Flagella• Are responsible for movement

• Have long structures that extend beyond cell surface

• Are not present on all bacteria



• Flagella• Structure

• Composed of filament, hook, and basal body

• Basal body anchors the filament and hook to cell wall


Flagella: Structure


Figure 3.6 Proximal structure of bacterial flagella.

Filament

Rod

Protein rings

Directionof rotationduring run

Peptidoglycanlayer (cell wall)

Cytoplasmicmembrane

Cytoplasm

Gram + Gram –

Filament

Outermembrane

Peptidoglycanlayer

Cellwall

Cytoplasmicmembrane

Cytoplasm

Outerproteinrings

Rod

Integralprotein

Innerproteinrings

Integralprotein

Basalbody

Ho

k

o

Ho

o

k


Figure 3.7 Micrographs of basic arrangements of bacterial flagella.


Flagella: Arrangement


Spirochetes


Figure 3.8 Axial filament.

Axial filamentSpirochetecorkscrewsand movesforward

Axial filament

Cytoplasmicmembrane

Outermembrane

Axial filamentrotates aroundcell

Endoflagellarotate



• Flagella• Function

• Rotation propels bacterium through environment

• Rotation reversible; can be counterclockwise or clockwise

• Bacteria move in response to stimuli (taxis)

• Runs

• Tumbles


Figure 3.9 Motion of a peritrichous bacterium.


Flagella: Movement



• Fimbriae and Pili• Fimbriae

• Sticky, bristlelike projections

• Used by bacteria to adhere to one another and to

substances in environment

• Shorter than flagella

• Serve an important function in biofilms


Flagellum FimbriaFigure 3.10 Fimbriae.


External Structures of Prokaryotic Cells

• Pili• Special type of fimbria

• Also known as conjugation pili

• Longer than fimbriae but shorter than flagella

• Bacteria typically have only one or two per cell

• Transfer DNA from one cell to another (conjugation)


Figure 3.11 Pili.

Pilus


External Structures of Prokaryotic Cells

• Tell Me Why• Why is a pilus a type of fimbria, but a flagellum is not?


Bacterial Cell Walls

• Provide structure and shape and protect cell from osmotic

forces

• Assist some cells in attaching to other cells or in resisting

antimicrobial drugs

• Can target cell wall of bacteria with antibiotics

• Give bacterial cells characteristic shapes

• Composed of peptidoglycan

• Scientists describe two basic types of bacterial cell walls

• Gram-positive and Gram-negative


Figure 3.12 Bacterial shapes and arrangements.


Figure 3.13 Comparison of the structures of glucose, NAG, and NAM.


Figure 3.14 Possible structure of peptidoglycan.

Sugarchain

Tetrapeptide(amino acid)crossbridge

Connecting chainof amino acids


Bacterial Cell Walls

• Gram-Positive Bacterial Cell Walls• Relatively thick layer of peptidoglycan

• Contain unique polyalcohols called teichoic acids

• Appear purple following Gram staining procedure

• Presence of up to 60% mycolic acid in acid-fast bacteria

helps cells survive desiccation


Figure 3.15a Comparison of cell walls of Gram-positive and Gram-negative bacteria.

Peptidoglycan layer(cell wall)

Gram-positive cell wall

Cytoplasmicmembrane

Teichoic acid

Lipoteichoic acid

Integralprotein


Prokaryotic Cell Walls

• Gram-Negative Bacterial Cell Walls• Have only a thin layer of peptidoglycan

• Bilayer membrane outside the peptidoglycan contains

phospholipids, proteins, and lipopolysaccharide (LPS)

• Lipid A portion of LPS can cause fever, vasodilation,

inflammation, shock, and blood clotting

• May impede the treatment of disease

• Appear pink following Gram staining procedure


Figure 3.15b Comparison of cell walls of Gram-positive and Gram-negative bacteria.

Integralproteins

Outermembraneof cell wall

Gram-negative cell wall

Peptidoglycanlayer of cell wall

Cytoplasmicmembrane

Lipopolysaccharide(LPS) layer, containinglipid A

Porin

Porin(sectioned)

Periplasmic space

Phospholipid layers



• Bacteria Without Cell Walls• A few bacteria lack cell walls

• Often mistaken for viruses because of small size and

lack of cell wall

• Have other features of prokaryotic cells, such as

ribosomes



• Tell Me Why• Why is the microbe illustrated in Figure 3.2 more likely a

Gram-positive bacterium than a Gram-negative one?


Bacterial Cytoplasmic Membranes

• Structure• Referred to as phospholipid bilayer

• Composed of lipids and associated proteins

• Integral proteins

• Peripheral proteins

• Fluid mosaic model describes current understanding of

membrane structure


Figure 3.16 The structure of a prokaryotic cytoplasmic membrane: a phospholipid bilayer.

Phospholipid

Head, whichcontains phosphate(hydrophilic)

Tail(hydrophobic)

Phospholipidbilayer

Integral protein

Peripheral protein

Integralprotein

Cytoplasm

Integralproteins


Membrane Structure



• Function• Control passage of substances into and out of the cell

• Energy storage

• Harvest light energy in photosynthetic bacteria

• Selectively permeable

• Naturally impermeable to most substances

• Proteins allow substances to cross membrane

• Maintain concentration and electrical gradient


Membrane Permeability


Cell exterior (extracellular fluid)

Integralprotein

Protein

Cell interior (cytoplasm)


Protein

DNA

mV

Na+Cl–

–70 –30 0

Figure 3.17 Electrical potential of a cytoplasmic membrane.


Passive Transport: Principles of Diffusion



• Function• Passive processes

• Diffusion

• Facilitated diffusion

• Osmosis


Figure 3.18 Passive processes of movement across a cytoplasmic membrane.


Figure 3.19 Osmosis, the diffusion of water across a semipermeable membrane.


Figure 3.20 Effects of isotonic, hypertonic, and hypotonic solutions on cells.

Cells without a wall(e.g., mycoplasmas,animal cells)

Cells with a wall(e.g., plants, fungaland bacterial cells)

H2O

Cell wallCell wall

Cell membrane Cell membrane

Isotonicsolution

Hypertonicsolution

Hypotonicsolution

H2OH2O

H2OH2OH2O


Passive Transport: Special Types of Diffusion


Prokaryotic Cytoplasmic Membranes

• Function• Active processes

• Active transport

• Group translocation

• Substance is chemically modified during transport


Figure 3.21 Mechanisms of active transport.

Extracellular fluid

Cytoplasmicmembrane

ATPADP

Cytoplasm

Uniport

Antiport Coupled transport:uniport and symport

Symport

Uniport

ATPADP P

P


Active Transport: Overview


Active Transport: Types


Figure 3.22 Group translocation.


Prokaryotic Cytoplasmic Membranes

• Tell Me Why• E. coli grown in a hypertonic solution turns on a gene to

synthesize a protein that transports potassium into the

cell. Why?


Cytoplasm of Bacteria

• Cytosol • Liquid portion of cytoplasm

• Mostly water

• Contains cell's DNA in region called the nucleoid

• Inclusions • May include reserve deposits of chemicals


Figure 3.23 Granules of PHB in the bacterium Azotobacter chroococcum.

Polyhydroxybutyrate


Cytoplasm of Bacteria

• Endospores • Unique structures produced by some bacteria

• Defensive strategy against unfavorable conditions

• Vegetative cells transform into endospores when

nutrients are limited

• Resistant to extreme conditions such as heat, radiation,

chemicals


Figure 3.24 The formation of an endospore.

1Steps in Endospore Formation

DNA is replicated.

Cytoplasmic membraneinvaginates to formforespore.

Cytoplasmic membranegrows and engulfsforespore within asecond membrane.Vegetative cell's DNAdisintegrates.

Cell wallCytoplasmicmembrane

DNA

Vegetative cell

A cortex of pepti-doglycan is depositedbetween the membranes;meanwhile, dipicolinicacid and calcium ionsaccumulate within thecenter of the endospore.

Spore coat formsaround endospore.

Forespore

Firstmembrane

Secondmembrane

Endospore matures:Completion of spore coat.Increase in resistanceto heat and chemicals byunknown process.

Endospore is released fromoriginal cell.

Cortex

Spore coat

Outerspore coat

Endospore

2

3

48

7

6

5


Cytoplasm of Prokaryotes

• Nonmembranous Organelles• Ribosomes

• Sites of protein synthesis

• Composed of polypeptides and ribosomal RNA

• 70S ribosome composed of smaller 30S and 50S subunits

• Many antibacterial drugs act on bacterial ribosomes

without affecting larger eukaryotic ribosomes



• Nonmembranous Organelles• Cytoskeleton

• Composed of three or four types of protein fibers

• Can play different roles in the cell

• Cell division

• Cell shape

• Segregation of DNA molecules

• Movement through the environment


Figure 3.25 A simple helical cytoskeleton.



• Tell Me Why• The 2001 bioterrorist anthrax attack in the U.S. involved

Bacillus anthracis. Why is B. anthracis able to survive in

mail?


External Structures of Archaea

• Glycocalyces• Function in the formation of biofilms

• Adhere cells to one another and inanimate objects

• Flagella• Consist of basal body, hook, and filament

• Numerous differences from bacterial flagella

• Fimbriae and Hami• Many archaea have fimbriae

• Some make fimbria-like structures called hami

• Function to attach archaea to surfaces


Figure 3.26 Archaeal hami.

Grapplinghook

Prickles

Hamus


External Structures of Archaea

• Tell Me Why• Why do scientists consider bacterial and archaeal

flagella to be analogous rather than evolutionary

relations?


Archaeal Cell Walls and Cytoplasmic Membranes• Most archaea have cell walls

• Do not have peptidoglycan

• Contain variety of specialized polysaccharides and

proteins

• All archaea have cytoplasmic membranes

• Maintain electrical and chemical gradients

• Control import and export of substances from the cell


Figure 3.27 Representative shapes of archaea.


Archaeal Cell Walls and Cytoplasmic Membranes• Tell Me Why• Why did scientists in the 19th and early 20th centuries

think that archaea were bacteria?


Cytoplasm of Archaea

• Archaeal cytoplasm similar to bacterial cytoplasm

• 70S ribosomes

• Fibrous cytoskeleton

• Circular DNA

• Archaeal cytoplasm also differs from bacterial cytoplasm

• Different ribosomal proteins

• Different metabolic enzymes to make RNA

• Genetic code more similar to that of eukaryotes


Cytoplasm of Archaea

• Tell Me Why• Why do some scientists consider archaea, which are

prokaryotic, more closely related to eukaryotes than

they are to bacteria?


External Structure of Eukaryotic Cells

• Glycocalyces• Not as organized as prokaryotic capsules

• Help anchor animal cells to each other

• Strengthen cell surface

• Provide protection against dehydration

• Function in cell-to-cell recognition and communication


External Structure of Eukaryotic Cells

• Tell Me Why• Why are eukaryotic glycocalyces covalently bound to

cytoplasmic membranes, and why don't eukaryotes with

cell walls have glycocalyces?


Eukaryotic Cell Walls and Cytoplasmic Membranes• Fungi, algae, plants, and some protozoa have cell

walls

• Composed of various polysaccharides

• Cellulose is found in plant cell walls

• Fungal cell walls are composed of cellulose, chitin,

and/or glucomannan

• Algal cell walls are composed of a variety of

polysaccharides


Figure 3.28 A eukaryotic cell wall.

Cytoplasmic membraneCell wall


Eukaryotic Cell Walls and Cytoplasmic Membranes• All eukaryotic cells have cytoplasmic membrane

• Are a fluid mosaic of phospholipids and proteins

• Contain steroid lipids to help maintain fluidity

• Contain regions of lipids and proteins called

membrane rafts

• Localize signaling, protein sorting, and movement

• Control movement into and out of cell


Figure 3.29 Eukaryotic cytoplasmic membrane.

Cytoplasmicmembrane

Intercellularmatrix

Cytoplasmicmembrane


Figure 3.30 Endocytosis.

Pseudopod


Eukaryotic Cell Walls and Cytoplasmic Membranes• Tell Me Why• Many antimicrobial drugs target bacterial cell walls. Why

aren't there many drugs that act against bacterial

cytoplasmic membranes?


Cytoplasm of Eukaryotes

• Flagella

• Structure and arrangement

• Differ structurally and functionally from prokaryotic flagella

• Within the cytoplasmic membrane

• Shaft composed of tubulin arranged to form microtubules

• Filaments anchored to cell by basal body; no hook

• May be single or multiple; generally found at one pole of cell

• Function

• Do not rotate but undulate rhythmically


Figure 3.31a-b Eukaryotic flagella and cilia.

Flagellum

Cilia


Figure 3.31c Eukaryotic flagella and cilia.

Cytoplasmicmembrane

Cytosol

Central pairmicrotubules

"9 + 2"arrangementMicrotubules

(doublet)


Portioncut away to showtransition areafrom doubletsto triplets andthe end ofcentralmicrotubules

"9 + 0"arrangement

Microtubules(triplet)

Basal body



• Cilia• Shorter and more numerous than flagella

• Coordinated beating propels cells through their

environment

• Also used to move substances past the surface of the

cell


Figure 3.32 Movement of eukaryotic flagella and cilia.



• Other Nonmembranous Organelles

• Ribosomes

• Larger than prokaryotic ribosomes (80S versus 70S)

• Composed of 60S and 40S subunits

• Cytoskeleton

• Extensive network of fibers and tubules

• Anchors organelles

• Produces basic shape of the cell

• Made up of tubulin microtubules, actin microfilaments, and

intermediate filaments


Figure 3.33 Eukaryotic cytoskeleton.

Microtubule

Tubulin

25 nm

Actinsubunit

Microfilament

Intermediate filamentProteinsubunits

7 nm

10 nm



• Other Nonmembranous Organelles• Centrioles and centrosome

• Centrioles are composed of nine triplets of microtubules

• Located in region of cytoplasm called centrosome

• Not found in all eukaryotic cells

• Centrosomes play a role in mitosis, cytokinesis, and

formation of flagella and cilia


Figure 3.34 Centrosome.

Centrosome (made up of two centrioles)

Microtubules

Triplet



• Membranous Organelles• Nucleus

• Often largest organelle in cell

• Contains most of the cell's DNA

• Semiliquid portion is called nucleoplasm

• Contains chromatin

• RNA synthesized in nucleoli present in nucleoplasm

• Surrounded by nuclear envelope

• Contains nuclear pores


Figure 3.35 Eukaryotic nucleus.

Nucleolus

Nucleoplasm

Chromatin

Nuclear envelope

Two phospholipidbilayers

Nuclear pores

Rough ER



• Membranous Organelles• Endoplasmic reticulum

• Netlike arrangement of flattened, hollow tubules

continuous with nuclear envelope

• Functions as transport system

• Two forms

• Smooth endoplasmic reticulum (SER)

• Rough endoplasmic reticulum (RER)


Figure 3.36 Endoplasmic reticulum.

Free ribosome

Membrane-boundribosomes

Mitochondrion

Rough endoplasmicreticulum (RER)Smooth endoplasmic

reticulum (SER)



• Membranous Organelles• Golgi body

• Receives, processes, and packages large molecules for

export from cell

• Packages molecules in secretory vesicles that fuse with

cytoplasmic membrane

• Composed of flattened hollow sacs surrounded by

phospholipid bilayer

• Not in all eukaryotic cells


Figure 3.37 Golgi body.

Secretory vesicles

Vesiclesarrivingfrom ER



• Membranous Organelles• Lysosomes, peroxisomes, vacuoles, and vesicles

• Store and transfer chemicals within cells

• May store nutrients in cell

• Lysosomes contain catabolic enzymes

• Peroxisomes contain enzymes that degrade poisonous

wastes


Figure 3.38 Vacuole.

Cell wall

Nucleus

Central vacuole

Cytoplasm


Figure 3.39 The roles of vesicles in endocytosis and exocytosis.

Endocytosis(phagocytosis)

Smoothendoplasmicreticulum(SER)Transportvesicle

Lysosome

PhagolysosomeGolgi body

Secretoryvesicle

Exocytosis(elimination, secretion)

Phagosome(food vesicle)Vesiclefuses with alysosome

Bacterium



• Membranous Organelles• Mitochondria

• Have two membranes composed of phospholipid bilayer

• Produce most of cell's ATP

• Interior matrix contains 70S ribosomes and circular

molecule of DNA


Figure 3.40 Mitochondrion.

Outer membrane

Inner membrane

Crista

Matrix

Ribosomes



• Membranous Organelles• Chloroplasts

• Light-harvesting structures found in photosynthetic

eukaryotes

• Use light energy to produce ATP

• Have two phospholipid bilayer membranes and DNA

• Have 70S ribosomes


Granum

Stroma

Thylakoid

Inner bilayermembrane

Outer bilayermembrane

Thylakoidspace

Figure 3.41 Chloroplast.



• Endosymbiotic Theory• Eukaryotes formed from union of small aerobic prokaryotes

with larger anaerobic prokaryotes

• Smaller prokaryotes became internal parasites

• Parasites lost ability to exist independently

• Larger cell became dependent on parasites for

metabolism

• Aerobic prokaryotes evolved into mitochondria

• Similar scenario for origin of chloroplasts

• Theory is not universally accepted



• Tell Me Why• Colchicine is a drug that inhibits microtubule formation.

Why does colchicine inhibit phagocytosis, movement of

organelles within the cell, and formation of flagella and

cilia?


Important topics

• Difference among cilia, flagella, pili, fimberia, pseudopodia.• Structure and function of peptidoglycan, lipid A, mycolic acid.• Differences between gram positive and gram negative bacteria.• Endo vs. exotoxin• Special bacteria such as mycoplasma and mycobacterium• Structure and function of chloroplast, mitochondria, peroxysome,

lysosome• Definition of epidemiology, biotechnology, molecular biology, nosocomial

infection• Transportation across the cell membrane and cell wall, such as simple

diffusion, facilitated diffusion, endocytosis, exocytosis