Upload
shon-adrian-stevenson
View
225
Download
0
Tags:
Embed Size (px)
Citation preview
Taxonomy
• Defined as the science of classification of organisms
• Taxonomic categories are arranged to show degree of similarities among organisms
• Relatedness through evolution
Three Domain System
• System of classification above the five kingdoms
• Based on molecular techniques of ribosomal RNA analysis
• Domains consists of the:– Eukarya – Bacteria– Archaea
Prokaryote Classification
• Bacteria• Peptidoglycan in cell
wall• All pathogenic and
non-pathogenic bacteria
• Archaea• No peptidoglycan in
cell wall• Extreme
environments• Methanogens• Extreme halophiles • Hyperthermophiles
How could you classify bacteria?
• Gram reaction• Shape• Nutritional requirements• Oxygen requirements
– Aerobic - requires oxygen– Anaerobic - killed by oxygen– Facultative anaerobe - lives with or without oxygen
• DNA profiles – G+C ratios• Combination of all of the above
Prokaryotes
• Grouped into two Domains
• Domain Archaea
• Domain Bacteria – two major divisions– Proteobacteria – 5 classes– Gram positive bacteria – two groups
• High G+C ratios – phylum Firmicutes• Low G+C ratios – phylum Actinobacteria
Proteobacteria
• Five classes
• Very diverse group
• Most of the gram negative bacteria
• Alpha, beta, gamma, delta, and epsilon – proteobacteria
• General survey of some the better known and medically important members of this group
Alphaproteobacteria
• Genus Rickettsia • Obligate intracellular parasites• Transmission to human by bites of ticks and
insects• Spotted fever diseases• Epidemic typhus• Rocky Mountain Spotted Fever
Betaproteobacteria
Medically important genus:
• Genus Neisseria – aerobic G- cocci– mucous membranes of mammals– Neisseria gonorrhoeae – gonorrhoea – Neisseria meningitidis - meningococcal
meningitis
Gammaproteobacteria
• Largest sub-group of the Proteobacteria
• Many pathogenic orders and genera in this group
• Important groups:– Genus - Pseudomonas– Order Enternbacteriales (enteric bacteria)
Pseudomonas
• Pseudomonas aeruginosa is the important bacteria of this genus
• Motile, G- rod, aerobe – produces a blue-green pigment
• Highly antibiotic resistant
• Important bacteria in urinary tract infections and wound/burn infection
Order Enterobacteriales
• All members of this order are straight G- rods, facultative anaerobes
• Commonly found in the gut of humans and other animals – ENTERICS
• Fimbriae for surface attachment
• Sex pili for exchange of genetic information
Important genera of order Enterobacteriales
• Escherichia
• Salmonella
• Shigella
• Klebsiella
• Serratia
• Proteus
• Enterobacter
Escherichia
• E. coli • Common gut bacteria, usually non-
pathogenic• Used as indicator for fecal contamination
of water• Common cause of traveler’s diarrhea• Most toxic strain is called 0157:H7 -
foodborne disease
Salmonella
• Intestinal tracts of poultry and cattle
• Food contaminate
• Typhoid fever and gastrointestinal illness
• Almost all members of this genus are pathogenic
Klebsiella
• Common in soil and water
• Klebsiella pneumoniae can cause a serious pneumonia in humans
Serratia
• Serratia marcescens produces a red pigment when grown at room temperature
• Cause of urinary and respiratory infections in hospitals
Proteus
• Highly motile bacteria
• Shows swarming growth on agar plates
• Important in urinary tract and wound infections
Enterobacter
• Widely found in humans and other animals, also found in sewage, water, and soil
• Two important pathogens are:
• Enterobacter aerogenes
• Enterobacter cloacae
• Urinary tract infections and nosocomial infections
Epsilonproteobacteria
• Slender G- rods that are helical or vibroid
• Two important genera:– Helicobacter
• Helicobacter pylori – common cause of peptic ulcers in humans and stomach cancer
– Campylobacter• Leading cause of food-borne intestinal disease
especially from chicken
FirmicutesLow G+C Gram + bacteria
• This group includes the following important groups of bacteria:– Clostridium– Bacillus – Staphylococcus– Streptococcus– Lactobacillus – Enterococcus
Clostridium
• Rod shaped, obligate anaerobes
• SPORE FORMERS
• Many medically important members of this genus– Clostridium tetani - tetanus– Clostridium botulinum - botulism– Clostridium perfringenes – gas gangrene– Clostridium difficile - diarrhea
Bacillus
• Rod shaped, facultative anaerobes
• SPORE FORMERS
• Common in the soil, few important pathogens– Bacillus anthracis - anthrax– Bacillus cereus – food poisoning
Staphylococcus
• Cocci usually occur in grape-like clusters
• Facultative anaerobe
• Grow well in high salt
• Found on human skin
• CATALASE POSITIVE - reaction with hydrogen peroxide
• Important pathogen:– Staphylococcus aureus
Lactobacillus
• Rod shaped, non-spore forming
• Aerotolerant, grow in the presence of oxygen, but poorly
• Important in production of lactic acid and also sauerkraut, pickles, buttermilk, and yogurt
• Commonly found in the vagina, intestinal tract, and oral cavity
Streptococcus
• Cocci, growing in chains• CATALASE NEGATIVE• Cause more illness than any other group of
bacteria• Two typical reactions on a media called blood
agar:• β- hemolytic streptococci
– Streptococcus pyogenes
• α- hemolytic streptococci– Streptococcus pneumoniae
Enterococcus
• Common hospital pathogen• Low oxygen requirement, catalase negative• Found in the GI tract, vagina, and oral cavity.
Also fecal matter.• Two important members of this genera:
– Enterococcus faecalis– Enterococcus faecium– Both are highly antibiotic resistant– Nosocomial infections
ActinobacteriaHigh G+C bacteria
• Genus Mycobacterium– Acid-fast bacteria; mycolic acid– Mycobacterium tuberculosis– Mycobacterium leprae
• Genus Mycoplasma– NO CELL WALL– Mycoplasam pneumoniae
• Genus Corynebacterium– Highly pleomorphic
• Genus Propionibacterium– Propionibacterium acne
• Genus Streptomyces– Filamentous bacteria; common in soil; antibiotics