Chapter 11: Bacteria. Bacterial Groups u Most widely accepted taxonomic classification for bacteria is Bergey’s Manual of Systematic Bacteriology. u 5000.

Chapter 11: BacteriaChapter 11: Bacteria

Bacterial GroupsBacterial Groups Most widely accepted taxonomic classification for Most widely accepted taxonomic classification for

bacteria is bacteria is Bergey’s Manual of Systematic BacteriologyBergey’s Manual of Systematic Bacteriology..

5000 bacterial species identified, 3100 classified.5000 bacterial species identified, 3100 classified.

Bacteria are divided into four Bacteria are divided into four divisionsdivisions (phyla) according (phyla) according

to the characteristics of their cell walls.to the characteristics of their cell walls.

Each division is divided into Each division is divided into sectionssections according to: according to: Gram stain reactionGram stain reaction

Cell shapeCell shape

Cell arrangementsCell arrangements

Oxygen requirementsOxygen requirements

MotilityMotility

Nutritional and metabolic propertiesNutritional and metabolic properties

Each section contains several Each section contains several generagenera..

Classification of Bacteria

G ra m -N eg a tiv eB a cter ia

(G rac i l icutes )Th in C e ll W alls

G ra m -P os itiv eB a cter ia

(F irm icutes )Th ick ce ll W alls

W a ll-L essB a cter ia

(T enericutes )L ack ce ll wa lls

A rcha eaB a cter ia

(M endos icutes )U n u su a l ce ll wa lls

P ro ca ry o tes

Four Divisions of Bacteria

Division I. Gram-Negative BacteriaDivision I. Gram-Negative Bacteria

1. Spirochetes1. Spirochetes Helical shape. Flexible.Helical shape. Flexible. Contain two or more axial filaments Contain two or more axial filaments

((endoflagellaendoflagella).). Move in corkscrew pattern.Move in corkscrew pattern. Medically important members:Medically important members:

Treponema pallidumTreponema pallidum: Syphilis: Syphilis Borrelia spp.:Borrelia spp.: Lyme disease, relapsing feverLyme disease, relapsing fever LeptospiraLeptospira: Leptospirosis: Leptospirosis

Gram Negative BacteriaSpirochetes

Primary syphilitic chancre and secondary rash.Source: Tropical Medicine and Parasitology, 1997

Syphilis is Caused by a Spirochete

Lyme Disease early lesion at tick bite site.Source: Medical Microbiology, 1998

Lyme Disease is Caused by a Spirochete

2. Aerobic, Motile, Helical/Vibroid Gram-2. Aerobic, Motile, Helical/Vibroid Gram-Negative BacteriaNegative Bacteria Rigid helical shape or curved rods.Rigid helical shape or curved rods. Lack axial filaments (endoflagella); have polar Lack axial filaments (endoflagella); have polar

flagella instead.flagella instead. Most are harmless aquatic organisms.Most are harmless aquatic organisms. GenusGenus AzospirillumAzospirillum fixes nitrogen in soil. fixes nitrogen in soil. GenusGenus BdellovibrioBdellovibrio attacks other bacteria.attacks other bacteria. Important pathogens include:Important pathogens include:

Campylobacter jejuniCampylobacter jejuni:: Most common bacterial food- Most common bacterial food-borne intestinal disease in the United States (2 million borne intestinal disease in the United States (2 million cases/year). Associated with undercooked chicken.cases/year). Associated with undercooked chicken.

Helicobacter pyloriHelicobacter pylori:: Causes most gastric ulcers in Causes most gastric ulcers in humans.humans.

Campylobacter fetusCampylobacter fetus:: Abortions in domestic animals. Abortions in domestic animals.

Gram Negative BacteriaAerobic, Motile, Helical/Vibroid Gram-Negative Bacteria

Helicobacter pylori causes Gastric Ulcers

4. Gram-Negative Aerobic Rods and Cocci4. Gram-Negative Aerobic Rods and CocciContains many medically significant groups.Contains many medically significant groups.

GenusGenus PseudomonasPseudomonas: Rods with polar flagella. : Rods with polar flagella. Many secrete pigments in media.Many secrete pigments in media.

• Pseudomonas aeruginosaPseudomonas aeruginosa:: Urinary tract infections (UTIs), Urinary tract infections (UTIs), septicemia, abcesses, burns, pulmonary infections in cystic septicemia, abcesses, burns, pulmonary infections in cystic fibrosis patients, and meningitis.fibrosis patients, and meningitis.

GenusGenus LegionellaLegionella:: Rods that live in natural waters. Rods that live in natural waters. Frequently found in air conditioning systems, Frequently found in air conditioning systems, humidifiers, showers, spas, and fountains.humidifiers, showers, spas, and fountains.

• Legionella pneumophilaLegionella pneumophila: Legionnaires’ disease : Legionnaires’ disease (pneumonia, 1976) and Pontiac fever.(pneumonia, 1976) and Pontiac fever.

GenusGenus NeisseriaNeisseria:: Diplococci. Frequently found on Diplococci. Frequently found on human mucous membranes. Only grow well around human mucous membranes. Only grow well around body temperature.body temperature.

• Neisseria gonorrheaNeisseria gonorrhea:: Gonorrhea. Gonorrhea.

• Neisseria meningitidisNeisseria meningitidis:: Meningitis. Meningitis.

Neisseria gonorrhea Causes Salpingitis

Ophtalmia neonatorum caused by Neisseria gonorrheaeSource: Microbiology Perspectives, 1999

Neisseria gonorrhea Causes Neonatal Blindness

4. Gram-Negative Aerobic Rods and Cocci 4. Gram-Negative Aerobic Rods and Cocci (Continued)(Continued)

GenusGenus MoraxellaMoraxella: Aerobic egg-shaped cocco-bacilli. : Aerobic egg-shaped cocco-bacilli.

• Moraxella lacunataMoraxella lacunata: Conjunctivitis.: Conjunctivitis.

GenusGenus BrucellaBrucella:: Small nonmotile coccobacilli. Small nonmotile coccobacilli.

All species are obligate parasites of mammals.All species are obligate parasites of mammals.

Cause brucellosis. Can survive phagocytosis.Cause brucellosis. Can survive phagocytosis. GenusGenus BordetellaBordetella: Nonmotile rods. Virulent forms : Nonmotile rods. Virulent forms

have capsules.have capsules.• Bordetella pertussisBordetella pertussis:: Whooping cough ( Whooping cough (P in DPT vaccineP in DPT vaccine).).

GenusGenus FrancisellaFrancisella: Small pleomorphic bacteria.: Small pleomorphic bacteria.• Francisella tularensisFrancisella tularensis:: Tularemia Tularemia

GeneraGenera RhizobiumRhizobium and and BradyrhizobiumBradyrhizobium:: Form Form nodules on legume roots and fix nitrogen in soil.nodules on legume roots and fix nitrogen in soil.

5. Facultative Anaerobic Gram-Negative 5. Facultative Anaerobic Gram-Negative RodsRodsMany cause diseases of gastrointestinal tract.Many cause diseases of gastrointestinal tract.

Contains three medically significant families.Contains three medically significant families.

I. Family Enterobacteriaceae (Enterics)I. Family Enterobacteriaceae (Enterics) Inhabit intestinal tracts of animals.Inhabit intestinal tracts of animals. Motile bacteria with peritrichous flagella or nonmotile.Motile bacteria with peritrichous flagella or nonmotile. Many have fimbriae for attachment to mucous membranes Many have fimbriae for attachment to mucous membranes

and sex pili for exchange of DNA (antibiotic resistance and sex pili for exchange of DNA (antibiotic resistance genes)genes)

Most ferment glucose and other sugars.Most ferment glucose and other sugars. Genus Genus EscherichiaEscherichia: : E. coliE. coli is common inhabitant of is common inhabitant of

human intestinal tract. Most strains are not pathogenic, human intestinal tract. Most strains are not pathogenic, but others can cause but others can cause UTIsUTIs (urinary tract infections), (urinary tract infections), traveler’s diarrhea, and food-borne disease.traveler’s diarrhea, and food-borne disease.

I. Family Enterobacteriaceae (Continued)I. Family Enterobacteriaceae (Continued) Genus Genus SalmonellaSalmonella: Almost all members are potential : Almost all members are potential

pathogens. Common inhabitants of animal GI tract. pathogens. Common inhabitants of animal GI tract. Can contaminate food (eggs, meat).Can contaminate food (eggs, meat).

• Salmonella typhiSalmonella typhi:: Typhoid fever, severe illness. Typhoid fever, severe illness.

• S. enteritidisS. enteritidis:: Causes salmonellosis, the second most common Causes salmonellosis, the second most common bacterial food-borne disease. bacterial food-borne disease.

Over 1.3 million cases/year in the U.S.Over 1.3 million cases/year in the U.S.

Genus Genus ShigellaShigella:: Only found in humans. Second most Only found in humans. Second most common cause of traveler’s diarrhea.common cause of traveler’s diarrhea.

Genus Genus KlebsiellaKlebsiella:: Cause respiratory and UTIs. Cause respiratory and UTIs.• Klebsiella pneumoniaeKlebsiella pneumoniae: : Antibiotic resistant strains causeAntibiotic resistant strains cause

pneumonia and nosocomial infections. pneumonia and nosocomial infections.

Genus Genus SerratiaSerratia: Opportunistic respiratory and urinary : Opportunistic respiratory and urinary tract infections.tract infections.

• Serratia marcescensSerratia marcescens:: Produces a red pigment. Important Produces a red pigment. Important cause of nosocomial infections. cause of nosocomial infections.

I. Family Enterobacteriaceae (Continued)I. Family Enterobacteriaceae (Continued) Genus Genus ProteusProteus: Actively motile. Cause UTIs, wound : Actively motile. Cause UTIs, wound

infections, and infant diarrhea (nosocomial).infections, and infant diarrhea (nosocomial). Genus Genus YersiniaYersinia::

• Yersinia pestisYersinia pestis:: Causes bubonic plague (black death). Causes bubonic plague (black death). Transmitted by fleas, respiratory droplet, and contact with Transmitted by fleas, respiratory droplet, and contact with animals.animals.

Genus Genus ErwiniaErwinia:: Important plant pathogens. Important plant pathogens. Genus Genus EnterobacterEnterobacter: : Cause UTIs and nosocomial Cause UTIs and nosocomial

infections.infections.

5. Facultative Anaerobic Gram-Negative 5. Facultative Anaerobic Gram-Negative RodsRods

II. Family VibrionaceaeII. Family Vibrionaceae Found in aquatic habitats.Found in aquatic habitats. Straight or slightly curved rodsStraight or slightly curved rods

Genus Genus VibrioVibrio: : Slightly curved rods.Slightly curved rods.

• Vibrio choleraeVibrio cholerae:: Cholera, profuse & watery diarrhea. Cholera, profuse & watery diarrhea.

• Vibrio parahaemolyticusVibrio parahaemolyticus:: Gastroenteritis. Shellfish. Gastroenteritis. Shellfish.

Rice-water stool of cholera.Source: Tropical Medicine and Parasitology, 1995

Cholera is Caused by Vibrio cholerae

5. Facultative Anaerobic Gram-Negative 5. Facultative Anaerobic Gram-Negative RodsRods III. Family PasterellaceaeIII. Family Pasterellaceae Found in aquatic habitats.Found in aquatic habitats. Straight or slightly curved rodsStraight or slightly curved rods

Genus Genus PasteurellaPasteurella: : Pathogens of domestic animals.Pathogens of domestic animals. Genus Genus HemophilusHemophilus: Important pathogens that inhabit : Important pathogens that inhabit

mucous membranes of upper respiratory tract, mouth, mucous membranes of upper respiratory tract, mouth, vagina, and intestinal tract. Require blood in culture.vagina, and intestinal tract. Require blood in culture.

• Hemophilus influenzaeHemophilus influenzae: Causes meningitis, ear infections, : Causes meningitis, ear infections, bronchitis, arthritis, and pneumonia in children.bronchitis, arthritis, and pneumonia in children.

• H. ducreyiH. ducreyi: : Cause of sexually transmitted chancroid.Cause of sexually transmitted chancroid.

Genus Genus GardnerellaGardnerella:: Not assigned to any family. Not assigned to any family. • G. vaginalisG. vaginalis causes common form of vaginitis.causes common form of vaginitis.

6. Anaerobic Gram-Negative Rods6. Anaerobic Gram-Negative RodsMay be straight, helical, or curved.May be straight, helical, or curved. Genus Genus BacteroidesBacteroides: : NonmotileNonmotile. . Live in human Live in human

intestinal tract (1 billion/gram of feces) and gum crevices. intestinal tract (1 billion/gram of feces) and gum crevices. Cause peritonitis, abscesses, and deep tissue infections. Cause peritonitis, abscesses, and deep tissue infections.

Genus Genus FusobacteriumFusobacterium: : Long slender rods with pointed Long slender rods with pointed tips. Found in gingival crevices, cause dental abscesses.tips. Found in gingival crevices, cause dental abscesses.

7. Sulfur-Reducing Bacteria7. Sulfur-Reducing Bacteria

Obligate anaerobes that release HObligate anaerobes that release H22S into the S into the

atmosphere. atmosphere.

Found in soil and intestinal tract of animals. Found in soil and intestinal tract of animals. Ecologically important.Ecologically important.

8. Anaerobic Gram-Negative Cocci8. Anaerobic Gram-Negative CocciNonmotile cocci typically found in pairs.Nonmotile cocci typically found in pairs. Genus Genus VeillonellaVeillonella: Cause dental plaque.: Cause dental plaque.

9. Rickettsias and Chlamydias9. Rickettsias and ChlamydiasGram negative bacteria.Gram negative bacteria.Obligate intracellular parasites.Obligate intracellular parasites.

RickettsiasRickettsias: Rod shaped bacteria or coccobacilli, : Rod shaped bacteria or coccobacilli, highly pleomorphic. Transmitted to humans by highly pleomorphic. Transmitted to humans by insects and ticks (except for insects and ticks (except for Coxiella burnettiCoxiella burnetti which which causes Q fever).causes Q fever). Genus Genus EhrlichiaeEhrlichiae: Live in white blood cells: Live in white blood cells..

Genus Genus RickettsiaRickettsia: Cause spotted group fevers (Rocky : Cause spotted group fevers (Rocky mountain spotted fever, endemic typhus).mountain spotted fever, endemic typhus).

ChlamydiasChlamydias: Cocci shaped bacteria. Transmitted to : Cocci shaped bacteria. Transmitted to humans by interpersonal contact or by airborne humans by interpersonal contact or by airborne respiratory routes.respiratory routes.

Unique life cycleUnique life cycle: Form a reticulate and elementary : Form a reticulate and elementary bodies in infected cells.bodies in infected cells.

Three species:Three species: Chlamydia trachomatisChlamydia trachomatis: Causes blindness in humans and : Causes blindness in humans and

nongonococcal urethritis (most common STD in U.S.).nongonococcal urethritis (most common STD in U.S.). C. psittaciC. psittaci: Parrot fever.: Parrot fever. C. pneumoniaeC. pneumoniae: Mild pneumonia.: Mild pneumonia.

Division II. Gram-Positive BacteriaDivision II. Gram-Positive Bacteria17. Gram-Positive Cocci17. Gram-Positive Cocci

Non-spore forming cocci.Non-spore forming cocci. Aerobic to strictly anaerobic.Aerobic to strictly anaerobic. Pyogenic (pus-forming)Pyogenic (pus-forming) Genus Genus StaphylococcusStaphylococcus: Tend to form grape-like clusters. : Tend to form grape-like clusters.

Grow well under high osmotic pressure and low moisture. Grow well under high osmotic pressure and low moisture.

Very common infections, because almost always found on Very common infections, because almost always found on skin and in nasal mucous membranes. skin and in nasal mucous membranes. Staphylococcus aureusStaphylococcus aureus: (aureus = golden) Yellow pigmented : (aureus = golden) Yellow pigmented

colonies. Produce several toxins. Cause pimples, sties, skin colonies. Produce several toxins. Cause pimples, sties, skin abscesses, toxic shock syndrome, food poisoning, and nosocomial abscesses, toxic shock syndrome, food poisoning, and nosocomial infections. infections.

Antibiotic resistance is big problem. Antibiotic resistance is big problem.

VancomycinVancomycin is last line of defense against antibiotic resistant is last line of defense against antibiotic resistant strains.strains.

Diseases Caused by Staphylococcus aureus

Scalded Sty Toxic ShockSkin Syndrome Syndrome

17. Gram-Positive Cocci17. Gram-Positive Cocci GenusGenus StreptococcusStreptococcus: Most are pathogens. Tend to : Most are pathogens. Tend to

appear in chains or pairs. Do not use oxygen, but most appear in chains or pairs. Do not use oxygen, but most are aerotolerant. Classified based on their effect on red are aerotolerant. Classified based on their effect on red blood cells (hemolysis).blood cells (hemolysis).

Cause a wide range of diseases: Strep throat, respiratory Cause a wide range of diseases: Strep throat, respiratory infections, abscesses, puerperal fever, and opportunistic infections, abscesses, puerperal fever, and opportunistic infections. infections.

A flesh eating Streptococcus strain emerged in 1994 and A flesh eating Streptococcus strain emerged in 1994 and 1998. After initial infection, bacteria live on dead flesh, 1998. After initial infection, bacteria live on dead flesh, produce toxins, and are not treatable by antibiotics. produce toxins, and are not treatable by antibiotics. Streptococcus pneumoniaeStreptococcus pneumoniae: Bacterial pneumonia, ear infections, : Bacterial pneumonia, ear infections,

meningitis, and sinus infections.meningitis, and sinus infections. Streptococcus pyogenesStreptococcus pyogenes:: Strep throat, scarlet fever, rheumatic Strep throat, scarlet fever, rheumatic

fever, impetigo, skin infections, erysipelas, puerperal fever, fever, impetigo, skin infections, erysipelas, puerperal fever, glomerulonephritis.glomerulonephritis.

Scarlet Fever is Caused by a Strain of Streptococcus pyogenes

Necrotizing fasciitis with blood filled vesicles.Source: Perspectives in Microbiology, 1995

Flesh-Eating Streptococcus pyogenes

Erysipelas on face due to S. pyogenes infection Source: Color Guide to Infectious Diseases, 1992

Erysipelas is Caused by Strep. pyogenes

18. Endospore-Forming Gram-Positive Rods 18. Endospore-Forming Gram-Positive Rods and Cocciand Cocci Aerobic to strictly anaerobic.Aerobic to strictly anaerobic. Motile and nonmotile.Motile and nonmotile. Survive harsh environmental conditions.Survive harsh environmental conditions. Genus Genus BacillusBacillus: Rod shaped bacteria.: Rod shaped bacteria.

Bacillus anthracisBacillus anthracis:: Causes anthrax a disease of cattle. Large (4- Causes anthrax a disease of cattle. Large (4-8 um) nonmotile facultative anaerobe.8 um) nonmotile facultative anaerobe.

Bacillus thuringiensisBacillus thuringiensis: Kills insects, used by gardeners.: Kills insects, used by gardeners.

Genus Genus ClostridiumClostridium: Rod shaped bacteria, obligate : Rod shaped bacteria, obligate anaerobes. anaerobes. Clostridium tetaniClostridium tetani: Causes tetanus (: Causes tetanus (T in DPT vaccineT in DPT vaccine).). Clostridium botulinumClostridium botulinum:: Causes botulism.Causes botulism. Clostridium perfringensClostridium perfringens: Causes gas gangrene and foodborne : Causes gas gangrene and foodborne

diarrhea.diarrhea.

Neonatal Tetanus (Wrinkled brow and risus sardonicus)Source: Color Guide to Infectious Diseases, 1992

Tetanus is Caused by Clostridium tetani

Severe gangrene caused by Clostridium perfringens.Source: Tropical Medicine and Parasitology, 1997

Gangrene Caused by Clostridium perfringens

19. Regular Nonsporing Gram-Positive Rods19. Regular Nonsporing Gram-Positive Rods Genus Genus LactobacillusLactobacillus: Produce lactic acid which inhibits : Produce lactic acid which inhibits

the growth of other bacteria. In humans live in vagina, the growth of other bacteria. In humans live in vagina, intestinal tract, and mouth. Used commercially to make intestinal tract, and mouth. Used commercially to make yogurt, pickles, sauerkraut, and buttermilk.yogurt, pickles, sauerkraut, and buttermilk.

Genus Genus ListeriaListeria: Contaminates dairy products.: Contaminates dairy products. Listeria monocytogenesListeria monocytogenes:: Survives in phagocytic cells and grows Survives in phagocytic cells and grows

in refrigerators. in refrigerators.

Causes listeriosis. Causes listeriosis.

Infection of pregnant women can cause stillbirth or severe Infection of pregnant women can cause stillbirth or severe damage to fetus.damage to fetus.

20. Irregular Nonsporing Gram-Positive 20. Irregular Nonsporing Gram-Positive RodsRods

Club shaped (Corynebacteria), pleomorphic.Club shaped (Corynebacteria), pleomorphic.

May be anaerobic or aerobic.May be anaerobic or aerobic.

Important pathogens:Important pathogens: Corynebacterium diphtheriaeCorynebacterium diphtheriae: Cause diphtheria (: Cause diphtheria (D in DPT D in DPT

vaccinevaccine).). Propionibacterium acnesPropionibacterium acnes: Causes acne.: Causes acne.

21. Mycobacteria21. Mycobacteria Aerobic, non-spore-forming rods.Aerobic, non-spore-forming rods. Stain Gram-positive, but cell wall structure is more similar to Stain Gram-positive, but cell wall structure is more similar to

Gram-negative bacteria. Gram-negative bacteria. Waxy cell wall with mycolic acids (instead of Waxy cell wall with mycolic acids (instead of

peptidoglycan).peptidoglycan). Acid-fast, drug resistant, resistant to drying, and pathogenic Acid-fast, drug resistant, resistant to drying, and pathogenic

due to waxy cell wall.due to waxy cell wall. Grow very slowly.Grow very slowly. Tend to cause chronic infections.Tend to cause chronic infections.

Important pathogens:Important pathogens: MycobacteriumMycobacterium tuberculosistuberculosis: Causes tuberculosis.: Causes tuberculosis. MycobacteriumMycobacterium lepraeleprae: Causes leprosy.: Causes leprosy.

Mycobacterium leprae Causes Leprosy

Source: Tropical Medicine and Parasitology, 1995

Severe bone destruction in advanced leprosySource: Diagnostic Pictures in Infectious Diseases, 1995

Mycobacterium leprae Causes Leprosy

22. Nocardioforms22. Nocardioforms Gram-positive, filamentous, aerobic.Gram-positive, filamentous, aerobic. Many are acid fast.Many are acid fast. Common in soil.Common in soil. Genus Genus NocardiaNocardia: : Form filaments which fragment into Form filaments which fragment into

short rods to reproduce.short rods to reproduce. Nocardia asteroidesNocardia asteroides: : Pulmonary infections, mycetoma, Pulmonary infections, mycetoma,

abscesses.abscesses.

25. Actinomycetes25. Actinomycetes Gram-positive, filamentous, resemble molds.Gram-positive, filamentous, resemble molds. Common in soil.Common in soil. Genus Genus StreptomycesStreptomyces: : Live in soil. Give soil its musty Live in soil. Give soil its musty

odor. Produce hundreds of antibiotics.odor. Produce hundreds of antibiotics.

Division III. Wall-Less BacteriaDivision III. Wall-Less Bacteria30. Mycoplasmas30. Mycoplasmas Do not form cell walls.Do not form cell walls. Most are aerobes or facultative anaerobes.Most are aerobes or facultative anaerobes. Highly pleomorphic.Highly pleomorphic. Can produce filaments that resemble fungi.Can produce filaments that resemble fungi. Produce very small colonies (1 nm in diameter).Produce very small colonies (1 nm in diameter). Very small cells: 0.1 to 0.25 Very small cells: 0.1 to 0.25 m in diameter.m in diameter. Can pass through bacterial filters.Can pass through bacterial filters.

Most important human pathogen:Most important human pathogen:

Mycoplasma pneumoniaeMycoplasma pneumoniae:: Walking pneumonia Walking pneumonia..