bacteriology lecture 2

7/31/2019 Bacteriology Lecture 2

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BacteriologyLecture 2

Bacterial Structure, Classification

and Growth Requirements


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Part I.Bacterial StructuresLEARNING OBJECTIVES

Classify microorganisms according to theirmorphology and distinct characteristics

Differentiate between prokaryote and

eukaryote

Identify the different structures andfunctions of a bacterial cell

Describe bacterial morphology

Point out ways of classifying bacteria


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DIVISIONS OF MICROBIOLOGY

1. VIROLOGY: Virusessmallest intact infectiousagents

intracellular reproduction only

consist of:

RNA or DNA core

Protein coat

glycoprotein envelope


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DIVISIONS OF MICROBIOLOGY

2. PARASITOLOGY

______________:

Multicellular parasites/worms

PROTOZOOLOGY:___________

Unicellular eukaryoticorganisms


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3. MYCOLOGY : Fungi 2 Forms: _______, _______

thick cell wall

Develop from spores or fragments of hyphae

4. PHYCOLOGY :________ Mainly aquatic

contain chlorophyll

Some produce neurotoxins which canconcentrate in fish / shellfish and causepoisoning in humans


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5. BACTERIOLOGY :Bacteria

Unicellular, Prokaryotic

Free living

Contain both RNA and DNA

Multiply by _____________

Eubacteria; Archaebacteria


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Prokaryotic Peptidoglycan cell

walls

characterized byshape, motility &metabolism

B A C T E R I A A R C H A E A

Figure 1.1a

Prokaryotic Lack peptidoglycan

Live in extreme

environments


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COCCI (Spherical)

Diplococci

StaphylococciStreptococci

Tetrad

Octad

BACTERIAL MORPHOLOGY

SIZE: 0.2 2.0 m by 1-10 m SHAPE: spherical, rod-shaped, spiral

ARRANGEMENT


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BACILLI (Rod-shaped)

Singles

Diplobacilli

StreptobacilliCoccobacilli

PalisadeSPIRALS

SpirillaSpirochete


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Comparison Between Prokaryotic and Eukaryotic Cells

Characteristic Prokaryotes Eukaryotes

Size of cell Typically 0.2-2.0 m in diameter Typically 10-100 m in diameter

Nucleus No nuclear membrane or nucleoli

(nucleoid)

True nucleus, consisting of

nuclear membrane & nucleoliMembrane-enclosed organelles Absent Present; examples include

lysosomes, Golgi complex,

endoplasmic reticulum,

mitochondria & chloroplasts

Flagella Consist of two protein building

blocks

Complex; consist of multiple

microtubules

Glycocalyx /Capsule Present as a capsule or slimelayer

Present in some cells that lack acell wall

Cell wall Usually present; chemicallycomplex (typical bacterial cellwall includes peptidoglycan)

When present, chemicallysimple

Plasma membrane No carbohydrates and generally

lacks sterols

Sterols and carbohydrates that

serve as receptors present

Cytoplasm No cytosketeton or cytoplasmic

streaming

Cytoskeleton; cytoplasmic

streaming

Ribosomes Smaller size (70S) Larger size (80S); smaller size

(70S) in organelles

Chromosome (DNA) arrangement Single circular chromosome;lacks histones

Multiple linear chromosomeswith histones

Sexual reproduction No meiosis; transfer of DNAfragments only (conjugation)

Involves meiosis

Comparison Between Prokaryotic and Eukaryotic Cells

Characteristic Prokaryotes Eukaryotes

Size of cell Typically 0.2-2.0 m in diameter Typically 10-100 m in diameter

Nucleus No nuclear membrane or nucleoli

(nucleoid)

True nucleus, consisting of

nuclear membrane & nucleoliMembrane-enclosed organelles Absent Present; examples include

lysosomes, Golgi complex,

endoplasmic reticulum,

mitochondria & chloroplasts

Flagella Consist of two protein building

blocks

Complex; consist of multiple

microtubules

Glycocalyx /Capsule Present as a capsule or slimelayer

Present in some cells that lack acell wall

Cell wall Usually present; chemicallycomplex (typical bacterial cellwall includes peptidoglycan)

When present, chemicallysimple

Plasma membrane No carbohydrates and generally

lacks sterols

Sterols and carbohydrates that

serve as receptors present

Cytoplasm No cytosketeton or cytoplasmic

streaming

Cytoskeleton; cytoplasmic

streaming

Ribosomes Smaller size (70S) Larger size (80S); smaller size

(70S) in organelles

Chromosome (DNA) arrangement Single circular chromosome;lacks histones

Multiple linear chromosomeswith histones

Sexual reproduction No meiosis; transfer of DNAfragments only (conjugation)

Involves meiosis


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General Structure

of a Prokaryote


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A. Flagella

PARTS filament Hook

basal body

Flagella rotates to move

Flagellin (H Ags)

Purpose: ___________________


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Flagellar Arrangement

Figure 4.7

1. Monotrichous: _______flagellum at one end

2. ____________ : smallbunches arising from one

end of cell3. Amphitrichous:

____________________

4. ____________ : flagelladispersed over surface ofcell


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Internal Flagella

Also known as: ___________________

Periplasmic filaments

enclosed between cell wall & cellmembrane of spirochetes

motility


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B. Appendages for Attachment

fine hairlike bristles from the

cell surface

function in adhesion to othercells and surfaces

FIMBRIAE


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Pili

Appendages for Mating rigidtubular structure

Made up of: __________

Found in ____________ cells

only

Functions:

joins bacterial cells for DNA

transfer adhesion


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C. Bacterial Surface Coating

external to the cell wall

Made of sugars and/or proteins

FUNCTIONS

________________

________________

________________

Glycocalyx


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Glycocalyx

2 TYPES:

1.capsule_____________________

2.slime layer_____________________


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The Cell Envelope: Cell Wall

peptidoglycan

provides strong, flexible support to the

bacterial cell

Maintains cell integrity

N-acetylglucosamine (NAG)

N-acetylmuramic acid (NAM) Linked by ____________


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Figure 4.13a


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4 Groups Based on Cell Wall

Composition1. Gram positive cells

2. Gram negative cells3. Bacteria without cell walls

4. Bacteria with chemically unique cell walls


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Gram Positive Cell Wall

Consists of :

thick peptidoglycan

tightly bound acidic polysaccharides

cell membrane

Retain crystal violet and stain ________


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Gram Negative Cell Wall

Consists of: outer membrane with lipopolysaccharide

thin shell of peptidoglycan

periplasmic space

inner membrane LPS

endotoxin

may function as

receptors and blockingimmune response

contains________proteins in upper layer

Lose crystal violet andstain _______ from

_________ .Protective structure while

providing some flexibility

and sensitivity to lysis


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The Gram Stain

Differential stainGram-negative

Gram-positive

Important basis of bacterial classification andidentification

Practical aid in diagnosing infection and

guiding drug treatment


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Atypical Cell Walls

Some bacteria lack typical cell wall structureMycobacteriumand Nocardia

Gram-positive cell wall structure with lipid____________.

basis for____________________

Some have no cell wallMycoplasmacell wall is stabilized by ___________


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Cytoplasm

dense gelatinous solution ofsugars, amino acids, & salts

70-80% water

serves as solvent for materialsused in all cell functions


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intracellular storagebodies

Examples:Glycogen

gas vesicles

carboxysomesPolyphosphate

granules

Inclusions &Granules

Ribosomes

prokaryotic differ fromeukaryotic ribosomesin size & number of

proteins site of ________

synthesis

all cells haveribosomes


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Endospores

Resting cells

Resistant to heat, radiation& chemicals

Examples: _________,_________

___________:

Endospore formation___________:

Return to vegetative state


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Bacterial Morphology


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Part II.Classification of Bacteria

Learning outcomes

Students should be able to:

Understand the basic principles of microbialclassification systems.

Be familiar with structural and biologicalcharacteristics to classify bacteria

List the genetic approaches that can be used inidentification and classification of bacteria


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Interrelated areas of taxonomy:

Classification

the arrangement of organisms into taxonomic groupson the basis of similarities or relationships.

________________

- naming an organism by international rules according to

its characteristics.

Identification

(1) to isolate and distinguish desirable organisms from

undesirable ones;

(2) To verify the authenticity or special properties of aculture, or in a clinical setting;

(3) To isolate and identify the causative agent of a disease

Cl ifi ti S t


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Classification Systems

Numerical Taxonomy

the computer clusters different strains based onthe frequency with which they share traits.

Phylogenetic Classification System

Groups reflect genetic similarity and

evolutionary relatedness

Phenetic/Phenotypic Classification System

Groups are based on convenient, observablecharacteristics.


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Useful Properties in Classification

Colony morphology

Cell shape & arrangement

Cell wall structure (Gram staining)

Special cellular structures

Biochemical characteristics


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Levels of Classification

Kingdom (not used by most bacteriologists)

Phylum/Division

Class

Order

Family

Genus (plural: Genera)

Species (both singular & plural)


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Species:

Classic definition: A collection of microbialstrains that share many properties and differsignificantly from other groups of strains.

Species are identified by comparison withknown type strains -- well-characterizedpure cultures - references for the identificationof unknowns.


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Strain:

A population of microbes descended from a

single individual or pure culture.

Different strains represent genetic variabilitywithin a species.

_________: Strains that differ in biochemical orphysiological differences.

_________: Strains that vary in morphology._________: Strains that vary in their antigenic

properties


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Nomenclature

Scientific name (Systematic Name)

Species name is never abbreviated.

A genus name may be used alone to indicate

a genus group.

A species name is never used alone.

Common or descriptive names (trivial names)

T f Di it


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Types of Diversity

Metabolic diversity

Structural diversity

Morphological diversity

Genetic diversity


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Bergeys Manual of Systematic Bacteriology

main resource for determining the identity

of bacteria species, utilizing every characterizingaspect.

Use successive "key" features to narrow downidentification

Primary emphasis is phylogenetic, not phenetic

Di h K


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Dichotomous Key


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Part III.Physical and Nutritional Growth

Requirements of Bacteria

Identify the growth requirements of bacteria Illustrate and discuss the growth curve with

emphasis on the events happening perstage

Appreciate the importance of thephysiological and nutritional requirements forbacterial growth


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Table 1. Major elements, their sources and functions in bacterial cells.

Element% ofdry

weight

Source Function

Carbon 50organic compounds orCO2

Main constituent of cellular material

Oxygen 20H2O, organiccompounds, CO2, and O2

Constituent of cell material and cell water; O2 is electron acceptor inaerobic respiration

Nitrogen 14NH3, NO3, organic

compounds, N2

Constituent of amino acids, nucleic acids nucleotides, and coenzymes

Hydrogen 8H2O, organiccompounds, H2

Main constituent of organic compounds and cell water

Phosphorus 3inorganic phosphates(PO4)

Constituent of nucleic acids, nucleotides, phospholipids, LPS, teichoicacids

Sulfur 1SO4, H2S, S

o, organicsulfur compounds

Constituent of cysteine, methionine, glutathione, several coenzymes

Potassium 1 Potassium salts Main cellular inorganic cation and cofactor for certain enzymes

Magnesium 0.5 Magnesium salts Inorganic cellular cation, cofactor for certain enzymatic reactions

Calcium 0.5 Calcium saltsInorganic cellular cation, cofactor for certain enzymes and a component ofendospores

Iron 0.2 Iron saltsComponent of cytochromes and certain nonheme iron-proteins and a

cofactor for some enzymatic reactions

TYPES OF ORGANISMS BASED ON PHYSIOLOGIC


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TYPES OF ORGANISMS BASED ON PHYSIOLOGIC

REQUIREMENTS:

Nutritional type Energy sourcePhototrophChemotroph

a.Chemolithotrophs

b.Chemoorganotrophs

Inorganicchemicals

Organic

chemicalsAutotroph

Heterotroph

Metabolic Diversity Among Organisms


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Metabolic Diversity Among Organisms

Nutritionaltype

Energysource

Carbonsource Example

Photoauto-trophLight CO2 Oxygenic:______________

Anoxygenic:______________

Photohetero-

troph

Light Green, purple

nonsulfur bacteria.Chemoauto-troph

Chemical CO2 Iron-oxidizing, sulfur,hydrogen, nitrifyingbacteria.

Chemohetero-troph

Chemical Most bacteria,fermentative bacteria,animals, protozoa,fungi.


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Growth Factors

are essential substances that the organism isunable to synthesize

required in small amounts for biosynthesis

CATEGORIES:

Purines and pyrimidines

Amino acids Vitamins

OXYGEN REQUIREMENT


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OXYGEN REQUIREMENT

A. AEROBES

Obligate Aerobes

Facultative Anaerobes

B. ANAEROBES Obligate Anaerobes

Facultative Aerobes

Aerotolerant AnaerobesC. MICROAEROPHILES

D. CAPNOPHILES


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GroupSuperoxidedismutase

Catalase Peroxidase

Obligateaerobes &mostfacultativeanaerobes

Mostaerotolerant

anaerobesObligateanaerobes

@ Dont forget to fill in the blanks!

THERMAL REQUIREMENT


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THERMAL REQUIREMENT

PSYCHROPHILES

prefer cold temperatures

cause food spoilage

_________________

MESOPHILES

prefer moderate temperature

THERMOPHILESprefer high temperatures

________________


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the solvent in which the molecules of life aredissolved

Supply depends on: relative humidity and water

activity (Aw). Aw = affected by the presence of solutes that

are dissolved in the water.

The higher the solute concentration of asubstance, the lower is the Aw and vice-versa.


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SALT: only common solute in nature that occursover a wide concentration range

____________: microorganisms that require someNaCl for growth.

Mild halophiles Moderate halophiles

Extreme halophiles

_____________ = grows at moderate saltconcentrations, even though they grow best in theabsence of NaCl.

Xerophiles= organisms which live in___________ .

L i t ti it t b t i l th th b i f


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Lowering water activity prevents bacterial growth; the basis forpreservation of foods by drying (in sunlight or by evaporation) orby addition of high concentrations of salt or sugar.

Movement across membranes:

_________diffusion :

Movement of a solute from an areaof high concentration to an area oflow concentration

_________ diffusion :

Solute combines with transporterprotein in membrane

Movement Across Membranes


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Osmosis Movt of H2O across a selectively

permeable membrane from an area of

H2O concn to an area of H2O.

Osmotic pressure

pressure reqd. to stop H2O movtacross the membrane.

Movement Across Membranes

Figure 4.18a

pH REQUIREMENT


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pH REQUIREMENT

the acidity or alkalinity of a solution.

ACIDOPHILE NEUTROPHILE

ALKALIPHILE

Nutritional and Physical


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Nutritional and PhysicalRequirements for Bacteria Growth.

Major and trace elements

Carbon and energy sources

Growth factors Oxygen, Carbon dioxide

Temperature

Water / Moisture

pH requirement


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bacteriology lecture 2

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