1. What is Microbiology? Flashcards
what is microbiology?
the study of organisms too small to see with the naked eye (bacteria, viruses, single celled eukaryotes); but some are also visible to the naked eye (fungi, algae); some are multicellular (myxobacteria, slime molds)
What techniques is microbiology defined by?
- culture media for isolation and growth of organisms in pure culture
- Biochemical techniques to study cell components
- molecular and genetic techniques
What is pure culture?
it’s a single population of cells growing in a culture medium where every cell in the population are genetically identical to one another
Why is microbiology importnat?
- microbes are the oldest form of life
- largest biomass on earth
- carry out major processes for biogeochemical cycles (Nitrogen fixation)
- can live in unsuitable locations
- other life forms require microbes to survive
How much bacteria is exchanged in a kiss?
80 million
What neurotransmitter is made in the gut with the help of bacteria?
Serotonin
What do all cells have in common
- cytoplasmic membrane
- cytoplasm
- ribosomes
What is the Cytoplasmic membrane?
barrier that separates the insides of the cell from the outside environment; defining feature of the cell
cytoplasm
aqueous mixture of macromolecules, ions and proteins; mostly water, area of high metabolic activity
ribosomes
site of protein synthesis; protein is the building block of cells
What is the difference between genetic material and a genome?
Genetic material is where all cells store their genetic information as DNA; the information is divided into function units (protein, RNA etc.) called genes. And a genome is a cell’s full component of genes and any other DNA present.
What is a Chromosome
a genetic element carrying genes essential to cellular function; necessary for cells to survive
What is a plasmid
a piece of DNA that carries non-essential genes (genes for antibiotic resistance); cell can survive without it
What are eukaryotes?
have a membrane bound nucleus and organelles; have a complex internal organization and divide by mitosis and miosis
What are the two major groups of eukaryotic microbes?
- protists
2. fungi
What is a protist?
can be unicellular/multicellular without differentiation into tissues
What are example of protists?
- protozoa
- algae
- slime molds & water molds
What are protozoa?
an example of a protist and are animal-like micro-organisms (i.e paramecium)
What are algae?
an example of a protist; and are photosynthetic plant-like microorganisms (i.e filamentous green algae)
What are slime and water molds?
an example of a protist; and are filamentous
What is fungi?
can be unicellular (yeasts); filamentous (molds) or multicellular (mushrooms)
What are prokaryotes?
there is no membrane bound nucleus/organelles; generally smaller; have a simple internal structure; divide by binary fission; most are unicelluar
What is binary fission?
when one cell divides into two
What are the two major groups of prokaryotic microbes?
- Bacteria (eubacteria)
2. Archaea (archaebacterai)
What is bacteria?
genetically diverse; extremely diverse metabolic styles; includes both pathogens and non-pathogens (i.e e.coli)
Characteristics of e.coli
With a light microscope the best you get is clusters of capsule looking things; are gram negative
What is archaea?
genetically and biochemically distinct from bacteria; have diverse metabolism; never pathogenic; most famous for living in extreme environments
What are viruses?
are aceullar infectious particles; come in different shapes and sizes; extremely small (not seen using a light microscope; so use electron); obligate intracellular parasites; lack independent metabolism (no ribosomes; no ribosomal RNA; cannot be classified with other micrboes)
What do viruses need in order to divide?
Since they cannot carry out metabolic activity in order to multiply they need to infect a host in order to use it’s machinery to divide and multiply
When did anaerobic life appear on earth?
between 3.8 and 3.8 billion years ago
When did photosynthetic bacteria oxygenate the Earth?
About 2 billion years ago and this allows the evolution of modern eukaryotic micro-organisms
when did plants and animals appear on earth?
about 0.5 billion years ago; most of earth’s life has been inhabited y organisms; humans are very recent
What did bacteria, archaea and Eukarya originate from?
a Last Universal Common Ancestor (LUCA)
How do we classify organisms based on evolutionary relationships?
by comparing small subunit (SSU) rRNA genes
How many ribosomes do prokaryotes have?
70S ribosomes = 16 SSU rRNA
How many ribosomes do eukaryotes have?
80S ribosomes = 18S SSU rRNA
Why do we use SSU rRNA genes?
- because all cellular organisms have ribosomes; so that means SSU rRNA is present in all organisms as well
- rRNA genes change slowly over time so this allows us to examine genetic differences rather than morphological differences
What are the basic steps in sequencing rRNA genes?
- DNA is collected from pure culture
- the SSU rRNA gene is amplified using the polymerase chain reaction (PCR)
- the gene is sequenced
- the Sequence is aligned with sequences from other organisms
What is used to calculate evolutionary distance?
the number of differences found in comparing organisms to each other based on their sequencing
What is a phylogenetic tree?
a graphic representation of the evolutionary distance between organisms; length of branches = evolutionary distance; the longer it is the more distant
What is a polymerase chain reaction (PCR)
a technique used to synthesize many identical copies of a short sequence of DNA
What is the Tree of Life based on?
it is based on 16S or 18S ribosomal DNA sequences
What are the 3 domains of life?
- bacteria
- archaea
- Eukarya
Why are microogranisms more genetically diverse than plants and animals?
- not as related as plants and animals.
Due to their positioning on the Tree of Life; apples and humans are more related to each other than e.coli and gram negative bacteria. This allows for more genetic diversity.
What are species?
A group of strains that share certain diagnostic traits; are generally cohesive and have a unique recent common ancestor
What should species of Bacteria and Archaea have in practice?
- most (but not all) characteristics in common
- high degree of genome similarity
- similarity in gene sequences to see similarities and differences
What is a strain?
a group of genetically identical cells
What kind of classification do microbiologists use?
Hierarchical classification; in practice species, genus and phylum are commonly used; also use binomial species names
What is the taxonomic hierarchy?
Domain, Phylum, Class, Order, Family, Genus, Species
What are the rules for naming species?
- Names are latinized
- Italicized/underlined
- Genus is capitalized, epithet is not
- Genus name may be abbreviated the second time it’s used
- Trivial names can be used but don’t follow these rules
Who is Robert Hooke?
He was the first to describe and visualize microbes. He used a compound microscope to magnify the image (30x) and used it to observe cells in cork and break filaments. Came up with the beginning of cell theory (all living things are composed of cells)
Who is Antoni van Leeuwehoek?
Was a lens maker who built microscopes (50-300x); observed single celled microorganisms and called them animalcules; he first discovery of bacteria
Who is Louis Pastuer?
Studied wine and beer production; came to the conclusion that bacteria can sour wine by converting alcohols to acid developed pasteurization. He conducted tests and realized that batches of wine that had not spoiled had yeast, and batches that soured had bacteria
What is pasteurization?
a method of gentle heating to kill unwanted bacteria
What is fermentation?
yeasts convert sugar to alcohol in the absence of oxygen
Describe Pasteur’s experiment on spontaneous generation
He prepared meat infusions inside of long swan-necked flasks; boiled the infusion to sterilize it; as long as the flask remains upright dust and microbes cannot enter and the infusion remains sterile. This lead to the development of methods for controlling the growth of microorganisms.
What is spontaneous generation?
belief that life can arise from a non-living substance
What is biogenesis?
belief that any living organism can give rise to another living organism
Who is Robert Koch?
Showed that micro-organisms can be responsible for diseases/cause diseases. Prior to this people thought that disease was caused by bad air.
Describe Robert Koch’s experiment
He studied anthrax which is responsible for epidemics in livestock; he isolated bacteria from the carcass of a diseased animal; injected healthy animals with the bacterium; the animals became ill with anthrax; he re-isolated the bacterium from the test subjects and showed that it was identical
What are Koch’s postulates?
- The suspected pathogen must be present in all cases of the disease and absent from healthy animals
- The suspected pathogen must be grown in pure culture
- Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal
- The suspected pathogen must be re-isolated and shown to be the same as the original
What is the medium that provides a simple way to obtain pure cultures?
A solid medium. Koch found that a broth medium solidified with agar
What is agar?
is a polysaccharide derived from marine algae; won’t result in the degradation; melts around 97C and polymerized at 43C; cannot be degraded by most microogranisms
What is the ratio for a typical petri plate?
nutrient broth medium + 1.5% agar
What is the recipe for nutrient agar?
- Peptone
- Beef Extract
- NaCl
- Agar
- Bring up to 1 L of dH20
What does peptone add to nutrient agar?
Source of carbon, nitrogen and energy; protein from animals
What does beef extract add to nutrient agar?
growth factors, vitamins, amino acids
What doe NaCl add to nutrient agar?
osmolarity
What does agar add to nutrient agar?
ONLY a simplifying agent and is not a source of any nutrient
What is the streak plate technique?
- one edge of the plate is inoculated with a [ ]ed sample of bacteria
- sample is diluted by streaking it across the surface of the plate
- plate is incubated
- individual cells grow to form colonies
What is a colony?
a mass of cells that (ideally) arose from one single cell; can be used to create a pure culture
What is the pour plate technique?
- Sample is diluted before plating
- Diluted sample can be spread over the surface of the plate with a sterile spreader; separate cells grow into colonies on the surface of the plate; or can be mixed with molten agar
What are some advantages of the pour plate technique?
It is good at separating colonies
What are some disadvantages of the pour plate techniques?
Because colonies are formed inside the plate it’s difficult to take them off w/o destroying the agar plate
What is the standard plate count?
It is used to determine how much bacteria is in a sample
What is the equation to find the number of bacteria in a sample?
titre = #of colonies/(volume)(diltion) titire = cfu/mL (colony forming unit/mL)
How do you count plates?
Count plates between 30-300 colonies because <30 is not statistically significant; >300 then colonies grow into each other
What do you do if you have more than one countable plate?
Calculate titre from each and take the average
