bacteriology lecture 2
TRANSCRIPT
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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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