Prokaryotic Microbes

Prokaryotic MicrobesProkaryotic Microbes

Domain BacteriaDomain Bacteria

Yersinia pestis – Bubonic Plague. science.nationalgeographic.com Clostridium botulism.

www.nih.gov

Classifying BacteriaClassifying Bacteria

Bergey’s Manual of Systematic Bacteriology

A bacteriologist’s “bible”.

5 volumes.

www.buy.com

3 Phenotypic Categories3 Phenotypic Categories

1. Bacteria that are gram-negative with a cell wall.

2. Bacteria that are gram-positive with a cell wall.

3. Bacteria that do not possess a cell wall.

Other Characteristics Used to Other Characteristics Used to Classify BacteriaClassify Bacteria

Cell morphology Staining reactions Motility Colony morphology Atmospheric requirements Nutritional requirements Biochemical and metabolic activities Specific enzymes produced Pathogenicity Genetic composition

Cell MorphologyCell Morphology

3 Basic Shapes of Bacteria– 1. Cocci

Round or spherical bacteria

– 2. Bacilli Rectangular or rod-

shaped bacteria

– 3. Spirilla Curved or spiral-

shaped bacteria

www.foodsafety.gov

CocciCocciDiplococci

– pairs

Streptococci– chains

Staphylococci– clusters

Tetrads– Packets of four

Octads (sarcina)– Packets of eight

Examples of Cocci BacteriaExamples of Cocci Bacteria

Neisseria gonorrhoeae – causes gonorrhea. Red diplococci cells. www.nature.com

Streptococcus pyogenes – strep throat. Streptococci – cocci in chains. bioweb.uwlax.edu

Staphylococcus aureus – Boils. Staphylococci – cocci in clusters. science.uniserve.edu.au

BacilliBacilli Come in many variations

of rod-shaped cells. Diplobacilli

– pairs

Streptobacilli– chains

Coccobacilli – Short, elongated-looking

cocci

Palisade arrangement– Side by side arrangement

Examples of Bacilli-shaped BacteriaExamples of Bacilli-shaped Bacteria

Haemophilus influenzae. Strain that causes a type of influenza. www.sanofipasteur.us

Escherichia coli. www.lbl.gov

Bacillus anthracis. www.lbl.gov

Spirilla – Curved and Spiral Spirilla – Curved and Spiral Shaped BacteriaShaped Bacteria

Vibrio– Comma shaped (incomplete spirals).

Spirillum– Large spiral shaped bacteria that have flagella

for locomotion.Spirochete

– Slender spiral shaped bacteria that have axial filaments for locomotion.

Spiral Shaped BacteriaSpiral Shaped Bacteria

Vibrio cholerae – cause of cholera. Vibrio. microbewiki.kenyon.edu

Campylobacter spp. Causes diarrhea. Spirilla. www.campylobacterblog.com

Treponema pallidum – cause of syphilis. Cell attached to testicular cell membranes. Spirochete. www.britannica.com

Borrelia burgdorferi – cause of Lyme disease. Spirochete. cellbiology.med.unsw.edu.au

Staining ProceduresStaining Procedures

Prior to staining bacteria must be:– 1. Smeared on glass slide.– 2. Air-dried.– 3. Fixed on slide by heat or methanol.

Heat fixing organism. biology.clc.uc.edu

Smearing bacteria on slide. www.cvgs.k12.va.us

2 Types of Fixation2 Types of Fixation

1. Heat Fixation– Run slide over a Bunsen burner.

2. Methanol Fixation– Flood slide with methanol for 30 seconds.

Staining BacteriaStaining Bacteria

Used to observe bacterial cell morphology. Size, shape, morphologic arrangement, cell wall

composition, capsules, flagella, and endospores

Simple Stain– Using only one stain.– Enables viewer to determine bacterial shape

and morphologic arrangement.– Example – staining with methylene blue.

Differential Staining ProcedureDifferential Staining Procedure

Process that allows differentiation of one group of bacteria from another.

2 common procedures:– Gram Stain– Acid-fast Staining Procedure

Gram StainGram Stain

Dr. Hans Christian Gram (1883) developed the gram stain.

Differentiates gram-positive bacteria from gram-negative bacteria.

www.scielo.org.ve

Bacterial Cell WallBacterial Cell Wall

Gram-positive Bacteria – Thick layer of

peptidoglycan (60-100%)– Contains teichoic acid and

lipoteichoic acids (0-40%)

Gram-negative Bacteria– Thin layer of

peptidoglycan (10-20%)– Has outer membrane

composed of mostly lipids (80-90%)

Gram-positive Bacteria

Gram-negative Bacteria

pathmicro.med.sc.edu

Gram Stain Procedure – Step 1Gram Stain Procedure – Step 1

www.cvgs.k12.va.us

Gram Stain Procedure – Step 2Gram Stain Procedure – Step 2

biology.clc.uc.edu

Gram Staining Procedure – Step 3Gram Staining Procedure – Step 3

z.about.com


z.about.com


www.slic2.wsu.edu

www.carolina.com

Gram Stain ResultsGram Stain Results

Gram-positive bacteria stains violet to blue.

Gram-negative bacteria stains pink to red.

homepage.ntlworld.com

Bacterial Cell WallBacterial Cell Wall

www.biologie.uni-hamburg.de

Mycobacterium Mycobacterium SpeciesSpecies

Gram-variable bacteria. Is technically considered a

gram-positive bacteria. Does not stain well with

crystal violet because its cell wall contains wax which prevents stains from entering cells.

Use Acid-Stain Procedure to stain this type of bacteria.

Mycobacterium tuberculosis – causes tuberculosis. www.kaiscience.com

Bacterial MotilityBacterial Motility

Axial filaments– Internal flagella found only in spirochete bacteria.– Found between outer membrane and cell wall.

Gliding motility– Encapsulated bacteria (e.g. slime capsule).

Flagella– Can have different arrangements.– Use different stains to identify certain number,

arrangement, and location of flagella.

Axial FilamentsAxial Filaments

http://classes.midlandstech.com/carterp/Courses/bio225/chap04/lecture3.htm

Flagella ArrangementsFlagella Arrangements

Monotrichous flagellation– Single flagellum.

Amphitrichous flagellation– Single flagellum at each end of the cell.

Lophotrichous flagellation– Tuft (2 or more) flagella at one or both poles of the cell.

Peritrichous flagellation– Flagella covering the entire cell surface.

Flagella ArrangementsFlagella Arrangements

Monotrichous Flagellum of Vibrio cholerae

Spirillum with Amphitrichous Arrangement of Flagella

Spirillum with Lophotrichous Arrangement of Flagella Flagella Stain of Proteus

Showing Peritrichous Arrangement of Flagellastudent.ccbcmd.edu/courses/bio141/lecguide/unit1/

prostruct/flag.html

Other Methods for Other Methods for Determining MotilityDetermining Motility

Tube of semisoft motility medium

Hanging-drop technique

Deep tube of semisoft motility medium. Left = positive for motility. Right = negative for motility. www.alpena.cc.mi.us

Colony MorphologyColony Morphology

Appearance of bacterial colonies– Size, color,

overall shape, elevation, appearance of the edge of the colony

www.foodmate.net

Atmospheric RequirementsAtmospheric Requirements Obligate aerobes

– Need oxygen (O2) concentrations comparable to room air. Microaerophilic aerobes

– Need O2 but less concentration. Facultative anaerobes

– Can grow in the presence of either O2 or carbon dioxide (CO2) Aerotolerant anaerobes

– Does not need O2, grows better in its absence, can survive in presence of O2.

Obligate anaerobes– Can only grow in the absence of O2.

Nutritional RequirementsNutritional Requirements

All bacteria need some form of the elements: – carbon, hydrogen, oxygen, sulfur, phosphorus,

and nitrogen to grow.

Depending on the species, there may be additional nutritional requirements (i.e. copper, zinc, calcium, iron to name a few).

Biochemical and Metabolic Biochemical and Metabolic ActivitiesActivities

All bacteria produce specific metabolic byproducts, which may be specific enzymes or gases.

These are additional clues in determining the identity of certain bacteria.

PathogenicityPathogenicity

Does a bacteria produce a certain disease?

Genetic CompositionGenetic Composition

Every species has unique genetic material.Molecular diagnostic procedures can be

used to identify an organism’s specific genetic material.

This may be RNA or DNA.

We will look at specific types of We will look at specific types of bacteria when we get to the bacteria when we get to the

disease reports disease reports

Domain ArchaeaDomain Archaea

Thought to have diverged from bacteria soon after life appeared.

Archaea share more genes with eukaryotes.Therefore, thought that archaea and eukarya

diverged early in life history.Many but not all are extremophiles.Have a cell wall but don’t possess

peptidoglycan.

Domain ArchaeaDomain Archaea

www.nsf.gov

The End The End

Prokaryotic Microbes

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