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

Taxonomic Hierarchy

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

Figure 11.6

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

Figure 11.7

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

Shigella Found only in humans Causes bacillary dysentery

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

Figure 11.9b

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

Figure 11.12

Firmicutes Low 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

Figure 11.18

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

Figure 11.19

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

Actinobacteria High 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

Phylum Chlamydiae No peptidoglycan in the cell wall Intracellular parasites Spread through direct personal contact or air borne transmission Chlamydia trachomatis –Best known pathogen in this group –Common cause of blindness - trachoma –Most common STD in the US.