Exam 3 Chapter 10

What is pathogen evolution?

How microbes change over time to become better at infecting hosts.

How do new pathogens evolve?

Through horizontal gene transfer (sharing genes with other microbes).

Three evolutionary "incubators" for new pathogens:

Zoonotic hosts, shelter species, environment

Zoonosis

Disease that normally infects animals but can spread to humans

Shelter species

Organisms that don't infect humans but allow bacteria to evolve

Why incubators matter

Pathogens mix with other microbes and pick up new genes

How do scientists determine bacterial relatedness?

By comparing 16S rRNA gene sequences

Why 16S rRNA is important

Highly conserved, found in all bacteria

16S rRNA mutation rate

~1% change every 50 million years

GEL ELECTROPHORESIS - Why used

Confirm DNA amplification

GEL ELECTROPHORESIS - DNA movement

Moves toward positive electrode

GEL ELECTROPHORESIS- Fragment size rule

Smaller = travels farther

165 rRNA SEQUENCING Size

~1400 bp

165 rRNA SEQUENCING Purpose

Identify unknown bacteria by database comparison

TWO MAJOR GRAM-POSITIVE PHYLA - Gram-positive, low G + C ratio

Firmicutes

TWO MAJOR GRAM-POSITIVE PHYLA - Gram-positive, high G + C ratio

Actinobacteria

FIRMICUTES (LOW G + C) - Rod-shaped, endospore-forming, obligate anaerobes

Clostridium

Clostridium (F) Important Species - (tetanus)

C. tetani

Clostridium (F) Important Species -(botulism)

C. botulinum

Clostridium (F) Important Species -(gangrene)

C. perfringens

Clostridium (F) Important Species -(severe diarrhea)

C. difficile

Why Clostridium spores matter

Very resistant, survive harsh conditions

Bacillus (F) traits

Rod-shaped, endospore-forming, aerobic or facultative anaerobes

Bacillus (F) found where

soil

Bacillus (F) (anthrax)

B. anthracis

Bacillus (F) (food poisoning)

B. cereus

Bacillus (F) (insect pathogen)

B. thuringiensis

Mycoplasma (F) Cell wall?

No cell wall

Mycoplasma (F) Why important

Very small, pleomorphic

Mycoplasma (F) Key species

Mycoplasma pneumoniae (mild pneumonia)

Staphylococcus (F) shape and arrangement

Cocci in grape-like clusters

Staphylococcus (F) Normal habitat

Skin and nose

Staphylococcus (F) Key species

Staphylococcus aureus

Staphylococcus (F) Diseases caused

Wound infections, toxic shock syndrome, food poisoning

Staphylococcus (F) MRSA

Methicillin-resistant Staph aureus (major hospital problem)

Streptococcus (F) Shape

Cocci in chains

Streptococcus (F) Hemolysis types: Alpha

partial (green halo)

Streptococcus (F) Hemolysis types: Beta

complete clearing

Streptococcus (F) (scarlet fever, strep throat)

S. pyogenes

Streptococcus (F) (pneumonia)

S. pneumoniae

Streptococcus (F) (cavities)

S. mutans

Enterococcus (F) Where found

GI tract, vagina, mouth

Enterococcus (F) Why important

Can survive harsh environments, hospital infections

Enterococcus (F) Key species

Enterococcus faecalis (UTIs, wound infections)

Enterococcus (F) VRE

Vancomycin-resistant Enterococcus

Listeria (F) Unique ability

Grows at refrigeration temperatures

Listeria (F) Key species

Listeria monocytogenes

Listeria (F) Why dangerous

Causes food poisoning; severe risk in pregnancy

Listeria (F) Special movement

Uses host actin "tails" to move between cells

Lactobacillus (F) Role

Normal microbiota, probiotic

Lactobacillus (F) Used for

Yogurt, sauerkraut, pickles

Mycobacterium (A) Cell wall feature

Mycolic acids (waxy)

Mycobacterium (A) Why hard to kill

Drug resistant, slow-growing

Mycobacterium (A) Important species

M. tuberculosis (TB)

M. leprae (leprosy)

Corynebacterium (A) Trait

Pleomorphic

Corynebacterium (A) Key Species

C. diphtheriae (diphtheria)

Streptomyces (A) is _______

found in soil

Streptomyces (A) Why Important

Produces most antibiotics

GRAM-NEGATIVE BACTERIA (PROTEOBACTERIA) Why dangerous

Lipid A (endotoxin) causes fever, shock, inflammation

GRAM-NEGATIVE BACTERIA (PROTEOBACTERIA) Five classes

Alpha, Beta, Gamma, Delta, Epsilon

ALPHAPROTEOBACTERIA-Rickettsia Lifestyle

Obligate intracellular

ALPHAPROTEOBACTERIA-Rickettsia Disease

Rocky Mountain spotted fever

ALPHAPROTEOBACTERIA-Rhizobium Role

Nitrogen fixation in plant roots

ALPHAPROTEOBACTERIA-Nitrosomonas & Nitrobacter Metabolism

Chemoautotrophs

ALPHAPROTEOBACTERIA-Nitrosomonas & Nitrobacter Function

Nitrogen cycle

BETAPROTEOBACTERIA-Bordetella Key Species

B. pertussis (whooping cough)

BETAPROTEOBACTERIA-Neisseria Unique trait

Only Gram-negative cocci causing disease in humans

BETAPROTEOBACTERIA-Neisseria Diseases

Gonorrhea

Meningococcal meningitis

GAMMAPROTEOBACTERIA-Pseudomonas Trait

Opportunistic pathogen

GAMMAPROTEOBACTERIA-Pseudomonas Key species

P. aeruginosa (CF infections)

GAMMAPROTEOBACTERIA-Legionella Where found

Freshwater

GAMMAPROTEOBACTERIA-Legionella Disease

Legionnaires' disease

GAMMAPROTEOBACTERIA-Vibrio Shape

Curved Rods

GAMMAPROTEOBACTERIA-Vibrio Disease

Cholera

Enterobacteriales (gut bacteria) Escherichia coli

Indicator of fecal contamination

Some strains cause food poisoning

Enterobacteriales (gut bacteria) Salmonella

Food poisoning, typhoid fever

Enterobacteriales (gut bacteria) Shigella

Dysentery

Enterobacteriales (gut bacteria) Klebsiella

Pneumonia

Enterobacteriales (gut bacteria) Yersinia pestis

Black plague

Enterobacteriales (gut bacteria) Haemophilus Diseases

Ear infections, epiglottitis, meningitis

Does NOT cause influenza (virus does)

DELTAPROTEOBACTERIA- Bdellovibrio Unique trait

Eats other Gram-negative bacteria

DELTAPROTEOBACTERIA- Desulfovibrio Metabolism

Sulfate reduction

EPSILONPROTEOBACTERIA - Campylobacter Disease

Foodborne diarrhea

EPSILONPROTEOBACTERIA- Helicobacter Unique Trait

Lives in stomach acid

EPSILONPROTEOBACTERIA- Helicobacter Disease

Ulcers, stomach cancer

Chlamydia Cell wall

No peptidoglycan

Chlamydia Lifestyle _____

is to Obligate intracellular

Chlamydia Diseases

STIs, trachoma (blindness)

Spirochetes Movement

Corkscrew motion

Spirochetes Diseases

Syphilis (Treponema)

Lyme disease (Borrelia)

ARCHAEA Key traits

No peptidoglycan

Extremophiles

ARCHAEA Types

Halophiles (salt)

Thermophiles (heat)

Methanogens (methane producers)

DNA base pairs

A-T and C-G

Two base types

Purines: A, G

Pyrimidines: T, C

PCR (Polymerase Chain Reaction) Purpose

to Amplify DNA

PCR (Polymerase Chain Reaction) Required components

Buffer

Heat-stable DNA polymerase

Primers

dNTPs

Template DNA

PCR (Polymerase Chain Reaction) Steps

Denaturation (95°C)

Annealing

Extension (72°C)

Repeat

What does LOW G + C content mean?

The bacterial genome has a lower percentage of guanine (G) and cytosine (C) bases. These bacteria are mainly Firmicutes and are Gram-positive

What does HIGH G + C content mean?

The bacterial genome has a higher percentage of guanine (G) and cytosine (C) bases. These bacteria are mainly Actinobacteria