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What is an epidemic?

an outbreak of infectious disease that then subsides

What is a pandemic?

an epidemic that occurs over a wide area

What is endemic?

continuously spread in a region; regularly found among particular people or in a certain area

What is A plague?

a serious disease afflicting a population

What is THE plague?

a specific disease caused by Yersinia pestis

What are we to microbes?

A rich source of energy (in the form of biological macromolecules) that pathogens can use to grow and multiply

What do microbes "want?"

to become more bacteria

What do microbes not "want?"

to make us sick or cause disease…they do not need to cause disease but can evolve to do so if it aids in transmission or replication

What is zoonoses?

infections from animals

What percent of the worldwide causes of death are from infectious disease?

~24%

What are "the big three" microbes?

HIV (virus), tuberculosis (bacterium), malaria (protozoan parasite)

What can be done about infectious disease?

eliminate poverty

What is epidemiology?

the science of finding and analyzing the causes, patterns, and effects of disease in populations (not just infectious diseases)

What is the miasma theory?

bad air causes disease

What is the germ theory? (19th century)

microbes cause disease

Who mapped the 1854 outbreak of cholera in London and is considered the hero of epidemiology?

John Snow

What did the 1854 outbreak of cholera in London originate from?

The Broad Street Pump

What do vaccines do?

stimulate the immune system to provide long-lasting resistance against infection

Where did the idea of vaccines come from?

Edward Jenner questions why milkmaids had such lovely skin (no smallpox); vaccinated James Phipps in 1796 with cowpox from a millkmaid

What and when was the first antibiotic administered to humans?

penicillin in 1942

What kills more people in the USA than HIV/AIDS?

infections from antibiotic resistant bacteria

How have humans used microbes for a long time?

in alcohol (wine, beer, etc.) without knowing that they existed

What is the doctrine of spontaneous generation?

"new living organisms can arise from decaying matter" (ex meat to maggots)

Who was Antony van Leeuwenhoek?

had a love of grinding lenses, worked in a dry goods store and as a janitor, not well educated, made high end microscopes

Describe Leeuwenhoek's microscope

simple biconvex lens, sample mounted, held close to face, difficult to use, magnification of 50-275X; made hundreds, only 9 remaining

What did Leeuwenhoek call the bacteria he found in teeth, etc?

animacules

What is the significance of Hooke's "Micrographia"?

first use of the term "cell"

Which microscope was more powerful, Leeuwenhoek's or Hooke's?

Leeuwenhoek's, even though the design was not as complicated as Hooke's

Why was the Royal Society skeptical of Leeuwenhoek's discovery?

they believed that the cheese mite was the smallest creature "without doubt"

Leeuwenhoek discovered microbes, but what did he NOT discover?

where microbes came from, that they were required to make bread and wine and beer, and that they cause disease

What did Spallanzani's experiment seek to disprove?

the doctrine of spontaneous generation

Why was Spallanzani's experiment not convincing at the time?

his flask was regular and he boiled it and left the stopper in it and no microbes grew but then he opened it and the microbes grew but people said microbes needed air to spontaneously generate

What did Pasteur discover about microbes and fermentation?

the role of microbes in fermentation of beer and wine

What is fermentation?

a biological process that produces energy without consuming oxygen (ex yeast can obtain energy by fermenting sugar into ethanol)

What is pasteurization?

heating liquids to destroy some (probably not all) microbes

How is pasteurization different than sterilization?

in sterilization, ALL microbes are killed, and it requires much more extreme conditions

How did Pasteur disprove spontaneous generation?

he used a swan neck flask and repeated Spallanzani's experiment, so air could get in but not the microbes.

Why were Pasteur's silkworm experiments important?

they were important because they were some of the first examples of disease being caused by a microorganism: support for the Germ Theory of Disease

What is a microbe?

short for "microorganism"; any microscopic living organism, includes bacteria, fungi, protozoa, etc and viruses in this class

What did Robert Koch receive the nobel prize for?

discovering the microbe that causes tuberculosis

What did Koch's experiments prove?

that microbes make people sick and that specific microbes cause specific diseases…cemented the Germ Theory of disease!

What did Koch want to prove about anthrax?

that it is caused by Bacillus anthracis

What was Koch's experiment on anthrax?

inoculate mice with sliver of wood soaked in blood of animal that died of anthrax. Mice die of anthrax

What was the negative control in Koch's experiment with anthrax?

inoculate mice with sliver of wood soaked in blood of healthy animal. Mice live. (expect opposite result)

What was the positive control of Koch's experiment with anthrax?

Grow bacteria in pure culture and expect the same thing- mice die

How was Koch able to culture "pure" anthrax bacilli?

grown in aqueous humor of ox eye; passaged the bacilli several generations; still caused disease (incredibly innovative approach that made him famous!)

What is serial passaging/how did Koch use this?

passing the bacteria through multiple ox eyes which purifies the bacteria away from the animal that died of the disease

What else did Koch discover about anthrax? (hint: think reproduction)

he observed that anthrax can make spores; the spores are hardy and not metabolically active: they can resist disinfecting treatments that kill vegetative form and can persist in soil/grass for years

What were Koch's other methods of growing pure cultures?

on potato slices and on petri dishes (growth media contains agar, which is a solidifying agent)….Julius Petri was an assistant to Koch

Why is the ability to isolate single colonies a critical technique of microbiology?

the single colony arises from multiplication of a single bacterium; all the bacteria in this colony are identical- thus it is pure and not contaminated with other bacteria that might confuse experimental conclusions. Allows conclusive experiments proving that a particular bacterium is the cause of a disease

Why is it helpful to stain bacteria?

it is critical in visualizing them in the tissue

What is the procedure for Gram staining (invented by Gram not Koch!)

fix bacteria to glass slide by heating; stain with crystal violent (deep purple color); add iodine (promotes adherence of stain); rinse slide with water and ethanol (decolorization); counterstain with safranin or fuchsin (red pink)

What is true about gram positive bacteria? (hint: cell wall structures)

Gram positive bacteria have different cell wall structures that causes them to retain the crystal violet stain better than gram negative bacteria

What colors are gram negative/positive bacteria?

gram-positive is blue and gram-negative is pink

What does a gram negative bacteria have as a part of the outer membrane?

LPS- lipopolysaccharide

Overall, what techniques were developed by Koch?

streaking for single colonies; growing pure cultures of bacteria ex vivo (grown outside of the organism/in external environment); experimental infections; staining bacteria (but he did NOT develop Gram staining)

What do Koch's postulates outline?

necessary conditions that must be fulfilled to prove a microbe causes a disease

What is Koch's Postulate #1?

the microorganism must be found in all organisms suffering from the disease (but not in healthy organisms)

What is Koch's Postulate #2?

the microorganism must be isolated from a diseased organisms and grown in pure culture

What is Koch's Postulate #3?

The cultured microorganism should cause disease when introduced into a healthy organism

What is Koch's Postulate #4?

The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent

What was Tuberculosis like at the time Koch was doing his experiments?

it killed 1 in 7 people in Europe; was called "consumption"; cause was unknown and it was treated by giving patients "fresh air"

How did Koch identify the bacilli that causes tuberculosis? (the process)

took Mycobacterium tuberculosis (MTB), isolated the bacilli from affected patients only, passaged it on blood-serum jelly, and then the reinfected animals develop TB [and aerosolized bacillus also capable of causing disease]

Why is work on Myobacterium tuberculosis (MTB) so challenging?

the bacteria are clumpy, slow-growing and highly infectious; can take 3 weeks to form a colony on a plate; can take a year for a mouse to die from TB

Under what Biosafety Level is MTB handled?

Level 3 (out of a possible 4)…strict control over airflow, sanitary practices, etc.

What did Koch claim about TB that turned out to not be true?

he claimed he could cure TB

What is tuberculin and what is it useful for?

a modified tuberculin (called PPD= purified protein derivative) did have diagnostic value: injected into skin, body will make an immune response (delayed-type hypersensitivity reaction) if previously exposed to TB (skin test)

What is cholera caused by?

a "comma-shaped" bacterium called Vibrio cholerae…flagellum provides motility

Where was cholera found?

in patients in Egypt and India and in water

What were other theories to explain cholera?

Some hypothesized that the disease was caused by atmospheric electricity, shortage of ozone, or is an emanation from the Earth

Who was Max von Pettenkofer and why is he important?

he claimed that the bacteria were not the primary cause of cholera; he drank water contaminated with Vibrio cholerae and did not get cholera!

What are some possible reasons that Pettenkofer did not get cholera?

prior immunity? Vibrios weren't grown in a manner that would make them infective? genetic variation in susceptibility? stomach acidity not neutralized?

Which of Koch's postulates did Pettenkofer show can be difficult to prove?

3: cultured organism should cause disease when introduced into healthy organism (did not happen when he drank cholera)

When is Postulate #2 a problem? (microorganism must be isolated and grown in pure culture)

viruses; they need a host cell

When is Postulate #1 a problem? (microorganisms must not be found in healthy organisms)

asymptomatic carriers; Typhoid Mary…carrier of Salmonella typhimurium serovar typhi (the cause of typhoid; worked as a cook in NY and infected ~40 people)

How should we think about Koch's Postulates?

they are the "ideal" case; fulfillment of all postulates is not always possible, even for genuine infectious diseases

What is the genetic material for all living things?

DNA (deoxyribonucleic acid)

What are A, G, T, C?

deoxyadenosine, deoxyguanosine, deoxythymidine, deoxycytidine

What is DNA's structure?

a double helix

What are "complementary" strands of DNA?

two strands that are "mirror images" of each other; A pairs with T and G with C, two strands are "antiparallel"; even though the two strands have different sequences, each strand contains the same full set of genetic information

What happens in DNA replication?

the two strands separate, and each individual strand serves as a template for the creation of new DNA strands; then the new nucleotides are added, as dictated by the rule of base pairing, to form two new double stranded helices, identical to the original

How is RNA different than DNA?

extra oxygen atom in each nucleotide; RNA uses uridine (U) instead of thymidine; RNA is more chemically unstable and more difficult to repair then DNA so DNA is preferred as the genetic material; RNA viruses mutate more quickly

What is RNA used for?

usually it is a temporary messenger: it carries the information coded in DNA to the machinery that makes proteins

What is the Central Dogma of molecular biology?

DNA -->RNA-->Protein

What is the process of an RNA copy being made from a DNA template?

Transcription! It involves addition of new RNA nucleotides (on one strand only), U added instead of T, RNA strand separates from DNA strand and the result is an RNA copy is made and DNA remains intact

What is protein?

a linear sequence of amino acids; each protein folds up into precise 3D shape that is dictated by the linear sequence of amino acids in the protein

How many different amino acids are there?

20

How is the code read?

DNA sequence -> transcription -> RNA sequence -> translation -> amino acid sequence (= protein)…triplet code, 3:1

What "reads" the RNA and makes proteins?

the ribosome (ribosomes are made up of RNA and protein!)

What is the key difference between the shapes of DNA molecules and proteins?

unlike all DNA molecules which have the same shape regardless of the sequence of nucleotides, Proteins adopt very different shapes depending on the order of amino acids

What are some exceptions to the central dogma?

retroviruses (ex. HIV) can make DNA from an RNA template in the process of reverse transcription; some viruses can make RNA copies directly from RNA in the process of RNA replication

What is a gene?

A segment of DNA that gives rise to a protein

What is a genome?

All the nucleic acids that are passed from parent to progeny; can vary tremendously in size

What is regulatory DNA?

DNA surrounding a gene that tells the cell "turn this gene on when x happens!"

What is a eukaryote?

a cell with a nucleus containing DNA; has organelles (ex. mitochondria); tends to be larger than prokaryotes

What is a prokaryote?

has no nucleus! ex. bacteria. Outer membrane of gram negative bacteria contains lipopolysaccharide (LPS)

What is a virus?

not living (not prokaryote or eukaryote), no ribosomes, not metabolically active, requires a host cell for replication…essentially just a protein (capsid) and/or membrane shell (envelope) that contains a nucleic acid (RNA or DNA) genome

What type of immune system did the "bubble boy" lack?

adaptive immunity; he had innate immunity

What is an autoimmune disease?

when the immune system attacks your own tissue

What is inflammation?

A coordinated immunological response to infection, cellular stress, injury, or other irritants; includes redness, pain, heat, swelling