Prokaryotic Microbes
Domain Bacteria Yersinia pestis – Bubonic Plague. science.nationalgeographic.com Clostridium botulism. www.nih.gov
Classifying Bacteria Bergey’s Manual of Systematic Bacteriology A bacteriologist’s “bible”. 5 volumes. www.buy.com
3 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 Classify Bacteria Cell morphology Staining reactions Motility Colony morphology Atmospheric requirements Nutritional requirements Biochemical and metabolic activities Specific enzymes produced Pathogenicity Genetic composition
Cell Morphology 3 Basic Shapes of Bacteria 1. Cocci 2. Bacilli Round or spherical bacteria 2. Bacilli Rectangular or rod-shaped bacteria 3. Spirilla Curved or spiral-shaped bacteria www.foodsafety.gov
Cocci Diplococci Streptococci Staphylococci Tetrads Octads (sarcina) pairs Streptococci chains Staphylococci clusters Tetrads Packets of four Octads (sarcina) Packets of eight
Examples of Cocci Bacteria Staphylococcus aureus – Boils. Staphylococci – cocci in clusters. science.uniserve.edu.au Streptococcus pyogenes – strep throat. Streptococci – cocci in chains. bioweb.uwlax.edu Neisseria gonorrhoeae – causes gonorrhea. Red diplococci cells. www.nature.com
Bacilli 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 Bacteria Escherichia coli. www.lbl.gov Haemophilus influenzae. Strain that causes a type of influenza. www.sanofipasteur.us Bacillus anthracis. www.lbl.gov
Spirilla – Curved and Spiral Shaped 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 Bacteria Vibrio cholerae – cause of cholera. Vibrio. microbewiki.kenyon.edu Treponema pallidum – cause of syphilis. Cell attached to testicular cell membranes. Spirochete. www.britannica.com Campylobacter spp. Causes diarrhea. Spirilla. www.campylobacterblog.com Borrelia burgdorferi – cause of Lyme disease. Spirochete. cellbiology.med.unsw.edu.au
Staining Procedures Prior to staining bacteria must be: Smearing bacteria on slide. www.cvgs.k12.va.us Heat fixing organism. biology.clc.uc.edu Prior to staining bacteria must be: 1. Smeared on glass slide. 2. Air-dried. 3. Fixed on slide by heat or methanol.
2 Types of Fixation 1. Heat Fixation 2. Methanol Fixation Run slide over a Bunsen burner. 2. Methanol Fixation Flood slide with methanol for 30 seconds.
Staining 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 Procedure Process that allows differentiation of one group of bacteria from another. 2 common procedures: Gram Stain Acid-fast Staining Procedure
Gram Stain Dr. Hans Christian Gram (1883) developed the gram stain. Differentiates gram-positive bacteria from gram-negative bacteria. www.scielo.org.ve
Bacterial Cell Wall Gram-positive Bacteria Gram-negative 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-negative Bacteria pathmicro.med.sc.edu
Gram Stain Procedure – Step 1 www.cvgs.k12.va.us
Gram Stain Procedure – Step 2 biology.clc.uc.edu
Gram Staining Procedure – Step 3 z.about.com
Gram Staining Procedure – Step 4 z.about.com
Gram Staining Procedure – Step 5 z.about.com
Gram Staining Procedure – Step 6 z.about.com
Gram Staining Procedure – Step 7 z.about.com
Gram Staining Procedure – Step 8 z.about.com
Gram Staining Procedure – Step 9 z.about.com
Gram Staining Procedure – Step 9 z.about.com
Gram Staining Procedure – Step 10 www.carolina.com www.slic2.wsu.edu
Gram Stain Results Gram-positive bacteria stains violet to blue. Gram-negative bacteria stains pink to red. homepage.ntlworld.com
Bacterial Cell Wall www.biologie.uni-hamburg.de
Mycobacterium Species 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 Motility Axial filaments Gliding motility Flagella 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 Filaments http://classes.midlandstech.com/carterp/Courses/bio225/chap04/lecture3.htm
Flagella 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 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 Flagella student.ccbcmd.edu/courses/bio141/lecguide/unit1/prostruct/flag.html
Other Methods for Determining 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 Morphology Appearance of bacterial colonies Size, color, overall shape, elevation, appearance of the edge of the colony www.foodmate.net
Atmospheric 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 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 Activities All bacteria produce specific metabolic byproducts, which may be specific enzymes or gases. These are additional clues in determining the identity of certain bacteria.
Pathogenicity Does a bacteria produce a certain disease?
Genetic 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 bacteria when we get to the disease reports
Domain 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 Archaea www.nsf.gov
The End