microbiology week 2

hierarchical scheme of classification

A classification system based on collecting individuals into groups and groups into progressively more inclusive and broader groups

• The branch of biology that names and classifies species
• The science of classifying organisms

Taxonomy

Classification of organisms

Fewer

Swedish biologist names Carolus Linnaeus

•   1.)  we continue to group organisms hierarchically
•   2.)  we use his nomenclature.

• •The first name is the organism’s genus designation & the second is its specific epithet. 
• •Together, the 2 constitute the species name. 

•Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. 

• 1. Bacteria (modern bacteria)
• 2. Archaea (accient bacteria)dna and anatomy resemble more to eukarya 
• 3. Eukarya

prokaryotes living in extreme habitats

eubacteria

• Protozoans
• Fungi
• Plants
• Animals

Prokaryotes

various protist kingdoms and the kingdoms Plantae, Fungi, and Animalia

extreme environments, such as salty lakes and boiling hot springs

multicellular eukaryotes that ingest other organisms

multicellula eukaryotes that carry out photosynthesis, the conversion of light energy to food

The first part of the name identifies the genus to which the species belongs; the second part identifies the species within the genus. For example, humans belong to the genus Homo and within this genus to the species Homo sapiens.

• Dormancy
• Toxins
• Obligate parasites
• Antibiotics

• Found in harsh enviroment
• Undersea volcanic vents, acidic hot springs, salty water
• None are pathogenic to human

• Called the true bacteria 
• Most bacteria are in this group 
• Include photosynthetic Cyanobacteria

• No nucleus or membrane-bound organelles
• Contain ribosomes
• Single, circular chromosome in nucleoid region

Rod Shape 

Spherical (Round) shape

Comma shaped with flageka

Spiral Shape

Wormlike spiral Shape

• Diplo - Groups of two 
• Strepto - chains
• Staphylo - Grapelike structers

Dormancy 

By forming an endospore

• Survival mechanism
• Dries Out
• Stops all metabolic activity
• Forms an endospore
• Contains genetic material of the vegetative cell

• Take in nutrients 
• Convert nutrients into energy and biomass 
• Expell waste 
• Grow and divide

Endorespore are fille SASPS (small acid soulble proteins that protect DNA)

Keratin like coat

• Vegetative Cell 
• Develop spore coat
• Becomes Mother Cell 
• Free endospre 

They all cause disease

• •Causes botulism (food posioning)
• •Causes infant botulism from honey 
• •Abundant in soil throughout the world

• Type A C. botulinum—found in neutral/alkaline soil west of the Mississippi River
• Type B C. botulinum—found in eastern part of the country 
• Type C C. botulinum—found in wet soils (can effect fish)

• Canning—endospores are not eradicated if the temperature is not sufficiently high
• Honey has endospores 
• The spores germinate and become vegetative bacteria The vegetative bacteria produce botulism toxin—a potent neurotoxin

• Toxin has no taste
• Food is often not spoiled by the bacteria
• A small amount of food with the toxin can be lethal
• End result: Paralysis and respiratory failure
• Treatment: antitoxin

–Soluble substances that alter normal metabolism of host cells with deleterious effects on the host

• Exotoxin
• Endotoxin

protein produced by bacteria either excreted or bound to bacterial surface and released when lysed (lysed = dead bacteria)

• Endotoxin—LPS of the outer membrane of Gram— bacteria ( only release if bacteria dyes if antibiotics are taken makes it worse due to killing of bacteria
• •Acts as toxin only under special circumstances

• Diphtheria
• Botulism
• Scarlet fever
• Toxic streptococci (“flesh-eating”)

• E. coli toxin causes diarrhea
• S. aureus toxin causes “scalded skin syndrome”

• –Examples:
• organisms that cause botulism
• gas gangrene
• tetanus

• 1 g tetanus, botulinus, or Shiga (type of ecoli) toxin is
• enough to kill 10 million people
• 100-fold more is required for diptheria
• 1000-fold more for Pseudomonas A

• –Misleading name
• •Toxin is located on outside of microorganisms
• –LPS of gram – bacteria
• –Lipoteichoic acid or gram + bacteria
• •Only toxic at high levels 

host immune cells and disable them

• –Membrane Damaging Toxins
• –Enzymes which act in the extra cellular matrix
• –Enzymes which subvert drug therapy in patients

• Enzyme destruction of host cell membranes
• Lyse red blood cells 
• Membrane pore forming complex

• Spreading factors
• Breaks down connective tissue
• Attacks blood clots 
• Thins pus filled with DNA

Penicillinase

• α toxin 
• Hemolysins
• Streptokinase 
• Hyaluronidase
• DNasel

alter normal metabolism of host cells with deleterious effects on the host

gastrointestinal and urinary tract infections 

bloody diarrhea, which, in 2 to 7% of cases, lead to hemolytic-uremic syndrome 

• Gram-positive
• Lack spores and flagella
• Common inhabitant of the skin and mucous membranes
• Frequently involved in nosocomial and opportunistic
• infections
• Can cause wound infections by penetrating through broken skin

• Hemolysins (α, β, γ, δ)
• Leukocidin 
• Enterotoxin 
• Exfoliative toxin 
• Toxic shock syndrome toxin (TSST)

lyse red blood cells

lyses neutrophils and macrophages

induce gastrointestinal distress

separates the epidermis from the dermis

induces fever, vomiting, shock, systemic organ damage

• •Vibrio cholera
• –Produces exotoxin
• –Gram negative vibrio
• –Unusual disease 
• •Cholerae does not invade tissue
• •Cholerae does not damage tissue
• –Humans are incidentally infected when ingesting contaminated food or water

• –Produces exotoxin
• –Gram positive spore forming bacteria
• –Found in soil
• –Anthrax disease – direct exposure to spores
• •Inhalation – pulmonary
• •Ingestion – gastrointestinal
• •Invasion into surface wound – cutaneous
• –No cases involve person to person spread

• More than one-third of the world population is infected.
• The organism has caused more human deaths than any other bacterium in the history of mankind. 
• Its unusual cell wall, rich in lipids (mycolic acid is a lipid instead of peptidoglycan), is a key virulence factor (like in TB) 
• Unusual cell wall allows the bacteria to hide from host immune cells

• •Obligate intracellular parasites.
• •(bacteria) Transmitted to humans by insects and ticks
• •Grow and reproduce only within the cells of other organisms. 
• –Genus Ehrlichiae:  Live in white blood cells.
• –Genus Rickettsia:  Cause spotted group fevers (Rocky mountain spotted fever, endemic typhus).

• –Alexander Fleming accidentally contaminated a plate with a fungus.
• –He observed a clearly defined region of no bacterial growth where the fungi had contaminated the plate. 
• –The area around the fungus was eventually referred to as a zone of inhibition.

• Fungi
• Bacteria

• The original natural molecules used by humans as antibiotics have a very narrowspectrum.
• Penicillin activity is restricted to Gram-positive bacteria.
• Natural molecules can be chemically modified making it possible to broaden their spectrum.
• Antibiotics are classified as either broad-spectrum or narrow-spectrum.

• –The bacterial cell wall
• –The bacterial plasma membrane 
• –Synthesis of bacterial proteins 
• –Bacterial nucleic acids 
• –Bacterial metabolism(stop metabolic activity)

• enzyme β-lactamase.
• are resistant to penicillin.

bloodstream infections with a crude mortality rate ~25%.

pneumonia and infections in the blood, bones and urine

• –Permits determination of the minimal inhibitory
• concentration (MIC).
• •The lowest antibiotic concentration that prevents growth
• –Uses plastic-coated strips containing gradients of
• antibiotic concentrations.
• After incubation MIC can be read from the scale

• •An agar plate is covered with known pathogen.
• •Filter-paper disks impregnated with known concentrations of the compound.
• –They are placed on agar
• .–Zones of inhibition can be identified.