Classification of Bacteria Taxonomy The science of classification Haeckel’s 3 Kingdoms • Plant • Animal • Protista Carl Woese’s 3 Domains Based on rRNA nucleotide sequences Why use this as a basis for classification? Organisms in the 3 Domains • Eukarya - kingdoms: plantae, animalia, fungi, protists • Archaea - prokaryotes • Bacteria - prokaryotes 2 Types of Prokaryotic Cells • Eubacteria • Archaebacteria – cell walls contain peptidoglycan – different nucleotide sequences in rRNA – different membrane lipids – – – – no peptidoglycan rRNA lipids live in extreme environments ex. Thermoacidophiles Extreme halophiles Methanogens http://www.ucmp.berkeley.edu/archaea/archaea.html Comparison of Archaea, Bacteria & Eukarya 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? Taxonomic Categories Order ends in –ales in fungi, plantae & bacteria Family ends in- aceae in fungi, plantae & bacteria Species of bacteria - “population of cells with similar characteristics” Strain of bacteria - “group of cells derived from a single cell” ex. Staphylococcus aureus 13578 Classification vs. Identification Techniques Bergey’s Manual of Determinative Bacteriology uses: • microscopic appearance • biochemical reactions • growth requirements • serology • phage typing Classification or identification?? Biochemical Tests Serology Slide Agglutination Test Phage Typing 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?? DNA Hybridization Identification vs. Classification Spirochetes Axial filaments for motility Examples: Treponema pallidum - syphillis Borrelia burgdorferi - Lyme disease Leptospira interrogans leptospirosis 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 Campylobacter jejuni • • • • • • microaerophilic motile vibrio Gram negative animals esp poultry & cattle grows @ 42oC most commonly identified bacterial cause of diarrhea in world (CDC) – unpasteurized milk – food 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 Gram negative aerobic cocci Neisseria meningitidis Branhamella catarrhalis Neisseria gonorrhoeae in pus Enterobacteriales Family- enterobacteriaceae Non-pathogens • Escherichia • Klebsiella • Proteus • Serratia • Etc. Describe the microscopic appearance of these organisms. 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 nonpathogens microscopically? Vibrionales Vibrionaceae Vibrio cholerae Shape? Facultatively anaerobic 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? 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 Rickettsia & Chlamydia Gram negative obligate intracellular parasites Rickettsia transmitted to humans by insects & ticks Ex. Rickettsia rickettsii - Rocky Mountain spotted fever Chlamydia Not transmitted by insects Chlamydia trachomatis Causes: 1.Trachoma - world’s leading infectious cause of blindness Middle East, North Africa, India 2.Non-gonococcal urethritis common std in U.S. Chlamydia psittaci causes: 1. Psittacosis (“parrot fever”) 2. Ornithosis Chlamydia pneumoniae - pneumonia Mycoplasmas • No cell wall – pleomorphic – penicillin sensitive or resistant? • Smallest free-living organisms • Microscopic fried-egg colonies • Ex. Mycoplasma pneumoniae Gram Positive Cocci Staphylococcus Streptococcus Micrococcus luteus Staphylococcus aureus • Gram positive cocci, clusters • Yellow pigment • Causes – common food poisoning – surgical wound infections • resistance – toxic shock syndrome Streptococcus pyogenes • Gram positive cocci in chains • Diseases – pharyngitis (sore throat) – scarlet fever * – erysipelas * * look for a description of this disease 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) Spore-Forming Organisms Bacillus cereus - spore stain Clostridium tetani - Gram stain Corynebacterium Characteristics of Corynebacterium sp.: • pleomorphic Gram positive rod • metachromatic granules • unusual arrangements – palisades – Chinese letters • C.diphtheriae causes diphtheria Mycobacteria Characteristics of Mycobacterium sp. • Gram positive small rods • acid-fast – mycolic acid complexed with peptidoglycan (waxy) • diseases: Acid-fast stain of sputum showing Mycobacterium tuberculosis – tuberculosis – leprosy (M. leprae) Streptomycetes Characteristics of Streptomyces: • mold-like bacteria – branching, spores • produce geosmin – soil smell • several species produce antibiotics – ex. streptomycin The End!