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Classification of Bacteria

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Presentation on theme: "Classification of Bacteria"— Presentation transcript:

1 Classification of Bacteria

2 The science of classification
Taxonomy The science of classification

3 Haeckel’s 3 Kingdoms Plant Animal Protista

4 Carl Woese’s 3 Domains Based on rRNA nucleotide sequences Why use this as a basis for classification?

5

6 Organisms in the 3 Domains
Eukarya - kingdoms: plantae, animalia, fungi, protists Archaea - prokaryotes Bacteria - prokaryotes

7 2 Types of Prokaryotic Cells
Eubacteria cell walls contain peptidoglycan different nucleotide sequences in rRNA different membrane lipids Archaebacteria no peptidoglycan rRNA lipids live in extreme environments ex. Thermoacidophiles Extreme halophiles Methanogens

8 Comparison of Archaea, Bacteria & Eukarya

9 Naming organisms (nomenclature)
Binomial system uses 2 names Genus species ex. Bacillus subtilis ex. Clostridium tetani ex. Staphylococcus aureus Is tubercle bacillus the scientific name of an organism or a common name?

10 3. Phylogenetic Classification
An evolutionary arrangement of species. Sharing a recent ancestor as in plants and animals (fossil records) In bacteria? Possible by Molecular Methods Genetic Homology: Base composition (GC ratio) Nucleic acid hybridisation. Ribosomal RNA (rRNA) sequence analysis Protein profiles and amino acid sequences

11 PURE CULTURE: Populations of individuals all derived from the same single organism. STRAIN: A Group of Pure Cultures Derived from a Common Source and Thought to be the Same. SPECIES: A Group of Closely Similar Strains.

12 INTRASPECIES CLASSIFICATION
Biotypes Biochemical properties. Serotypes Antigenic features. Phage Types Bacteriophage susceptibility. Colicin Types Production of bacteriocins.

13 Strain of bacteria - “group of cells derived from a single cell”
Species of bacteria - “population of cells with similar characteristics” Strain of bacteria - “group of cells derived from a single cell” ex. Staphylococcus aureus 13578

14 Naming of microorganisms.
Governed by international rules Rules published in the International Code of Nomenclature of Bacteria. The International Journal of Systematic Bacteriology

15 Rules for the Nomenclature of Microorganisms
There is only one correct name for an organism. Names that cause error or confusion should be rejected. All names in Latin or are latinized. The first word (genus) is always capitalized. The second word (species or specific epithet) is not capitalized. Both genus and species name, together referred to as species, are either underlined or italicized when appearing in print. The correct name of a species or higher taxonomic designations is determined by valid publication, legitimacy of the name with regard to the rules of nomenclature, and priority of publication.

16 Nomenclature Casual or Common Name: Scientific or International Name:
e.g. "typhoid bacillus" Scientific or International Name: Salmonella typhi Salmonella london Staphylococcus aureus Clostridium tetani Mycobacterium bovis Borrelia burgdorferi

17 Classification vs. Identification Techniques
Bergey’s Manual of Determinative Bacteriology uses: microscopic appearance biochemical reactions growth requirements serology phage typing Classification or identification??

18 Biochemical Tests

19 Slide Agglutination Test
Serology Slide Agglutination Test

20 Phage Typing

21 rRNA sequencing – ribotyping
Bergey’s Manual of Systematic Bacteriology establishes phylogenetic relationships by: amino acid sequencing protein analysis rRNA sequencing – ribotyping Why is rRNA rather than other types of RNA used? Chapter 10 nucleic acid hybridization Classification or identification??

22 DNA Hybridization

23 Identification vs. Classification

24 Axial filaments for motility
Spirochetes Axial filaments for motility Examples: Treponema pallidum - syphillis Borrelia burgdorferi - Lyme disease Leptospira interrogans leptospirosis

25 Movement of spirochetes
Axial Filaments Movement of spirochetes Structure Filament Hook Basal body Ex. Treponema pallidum Bundles of fibrils that arise at the end of the cell beneath the outer sheath & spiral around the cell

26 Campylobacter jejuni microaerophilic motile vibrio Gram negative
animals esp poultry & cattle 42oC most commonly identified bacterial cause of diarrhea in world (CDC) unpasteurized milk food

27 Pseudomonas aeruginosa
Gram negative aerobic rod “bacillus of blue-green pus” pyocyanin pigment fermented grape smell normal flora skin & intestine unusual carbon sources antibiotic resistant infections wound, ear, urinary, respiratory, burns

28 Gram negative aerobic cocci
Neisseria meningitidis Branhamella catarrhalis Neisseria gonorrhoeae in pus

29 Family- enterobacteriaceae
Enterobacteriales Family- enterobacteriaceae Non-pathogens Escherichia Klebsiella Proteus Serratia Etc. Describe the microscopic appearance of these organisms.

30 Enterobacteriaceae cont’d
Pathogens Salmonella (typhi) typhoid fever Shigella (dysenteriae) bacillary dysentery Yersinia (pestis) bubonic plague All members of Enterobacteriaceae are facultative anaerobes. Meaning? Can you see why the family, enterobacteriaceae, has been referred to as the Colon-typhoid-dysentery group? Can you differentiate the pathogens from the non-pathogens microscopically?

31 Vibrionaceae Vibrio cholerae
Vibrionales Vibrionaceae Vibrio cholerae Shape? Facultatively anaerobic

32 Hemophilus influenzae
Aerobic Gram negative rod Normal flora in intestine and respiratory tract Most common cause of meningitis in children Hib vaccine Also causes otitis media, pneumonia, epiglottitis Why is the name of this organism misleading? What can you learn from the name?

33 Bacteroidaceae - Bacteroides fragilis
Gram negative anaerobic rods Found in the human intestine & mouth 95% of the bacteria in a stool specimen & 20% of the weight! One billion per gram of feces! Most common anaerobe isolated from infections appendicitis, peritonitis, complicate abdominal surgery

34 Rickettsia & Chlamydia Gram negative obligate intracellular parasites
transmitted to humans by insects & ticks Ex. Rickettsia rickettsii - Rocky Mountain spotted fever

35 Chlamydia Not transmitted by insects Chlamydia trachomatis Causes:
1.Trachoma - world’s leading infectious cause of blindness Middle East, North Africa, India Chlamydia trachomatis 2.Non-gonococcal urethritis common std in U.S.

36 Chlamydia psittaci causes:
1. Psittacosis (“parrot fever”) 2. Ornithosis Chlamydia pneumoniae - pneumonia

37 Mycoplasmas No cell wall Smallest free-living organisms
pleomorphic penicillin sensitive or resistant? Smallest free-living organisms Microscopic fried-egg colonies Ex. Mycoplasma pneumoniae

38 Gram Positive Cocci Staphylococcus Streptococcus Micrococcus luteus

39 Staphylococcus aureus
Gram positive cocci, clusters Yellow pigment Causes common food poisoning surgical wound infections resistance toxic shock syndrome

40 Streptococcus pyogenes
Gram positive cocci in chains Diseases pharyngitis (sore throat) scarlet fever * erysipelas * * look for a description of this disease

41 Endospore-Forming Gram Positive Rods
Bacillales - Bacillus aerobes or facultative anaerobes common in soil ex. Bacillus anthracis, Bacillus subtilis Clostridiales - Clostridium obligate anaerobes found in soil diseases tetanus (Clostridium tetani), botulism (C. botulinum), gas gangrene (C. perfringens)

42 Spore-Forming Organisms
Bacillus cereus - spore stain Clostridium tetani - Gram stain

43 Corynebacterium Characteristics of Corynebacterium sp.:
pleomorphic Gram positive rod metachromatic granules unusual arrangements palisades Chinese letters C.diphtheriae causes diphtheria

44 Mycobacteria Characteristics of Mycobacterium sp.
Gram positive small rods acid-fast mycolic acid complexed with peptidoglycan (waxy) diseases: tuberculosis leprosy (M. leprae) Acid-fast stain of sputum showing Mycobacterium tuberculosis

45 Streptomycetes Characteristics of Streptomyces: mold-like bacteria
branching, spores produce geosmin soil smell several species produce antibiotics ex. streptomycin

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