Micro Exam 1 Study Guide Questions

In what ways are microorganisms important to humans? 

Negative- Food spoilage and foodborne disease 

Positive- Food safety, preservation 

Biofuels, Wastewater treatment, bioremediation, biofilms 

gut microbiomes

What is a bacterial colony and how is on formed? 

streak for isolation- A population of cells all formed from one cell

How can you get a pure culture of bacteria and why are pure cultures important? 

Streak for isolation- Give you one type of bacteria- Important because there are no other bacteria that could influence results 

where do you find microorganisms and do they typically live in a pure culture? 

Microorganisms found everywhere and they do not live in a pure culture- There is not usually only one type of bacteria in an area 

What cellular structures distinguish prokaryotic and eukaryotic cells? 

Pro- Cell wall, 70S Ribosomes, No nucleus 

Euk- No cell wall, 80S Ribosomes, Mitochondria, ER, Golgi, Nucleus,

What are some differences between a cell wall and a cell membrane?   

Cell wall- made of polysaccharides, Rigid 

Cell Membrane- made of phospholipids, Flowy, Contains proteins and carbs within the wall, Selectivity permeable 

In what types of organisms would you expect to find cell walls and or cell membranes? 

All cells have a cell membrane but few have cell wall 

Plants, bacteria, and fungi have cell walls

How has the Earth changed over its history?  How have microorganisms contributed to these changes? 

First cells- 3.8-4.3 billion years ago, Atmosphere had no oxygen, Only anaerobic 

Cyanobacteria- 2.6 billion years ago, started to produce oxygen as a byproduct, Allowed for eukaryotic cells to exist 

Name the three domains of life.  Which of these contain eukaryotic life forms?  How are they similar and different? 

Bacteria- Pro, 0.5-10 micrometers long 

Archaea- Pro, extreme environments 

Euk- Plants, animals, fungi, protists 

Why were cyanobacteria so important in the evolution of life on Earth?  What is a genus name of a cyanobacterium and what is unique about these organisms? 

produced oxygen and allowed for aerobic life

How do microbes contribute to the nutrition of animals such as humans and cows? 

Humans- Found in the gut to help break food and aid digestion, Break down carbs, Synthesize vitamins and nutrients 

Cows- Found in the four chambered stomach, Helps break down cellulose for cows to digest grass 

Describe several ways in which microorganisms are important in the food and agricultural industries. 

Food- Can cause food spoilage and disease but also helps with preservation, Fermentation 

Ag- Soil enrichment, Nitrogen fixing bacteria 

What is wastewater treatment and why is it important? 

Wastewater treatment is the removal of contaminants from waste water- Important because it allows us to recycle water creating an endless resource

What is the difference between magnification and resolution? 

Magnification is the ability to enlarge an image, resolution is the ability to tell 2 different object apart 

what is the function of staining in light microscopy

Cells are not normally colored(Cells are 70% water so usually transparent), and staining cells allows us to have some contrast between the cell and the background 

What color will a gram-negative cell be after Gram staining by the conventional method?  Gram positive?  Why? 

Gram negative- Pink/red- Thin PG cell wall 

Gram positive- Purple- Thick PG cell wall 

What are the steps of a gram stain and the function of each reagent? 

Crystal violet- Stain all the cell purple 

Grams Iodine- mordant- Combines CV and CVI 

70% Ethanol- Decolorizer- Removes CVI from the gram negative bacteria 

Safranin- Counterstain- Makes G- red/pink 

What major advantage does phase-contrast microscopy have over staining? 

Don’t have to stain anything, Cells can be live and in their natural form 

How can cells be made to fluoresce? 

They can be naturally fluorescent or be stain with a fluorescent dye 

What type of microscope would be used to view the three-dimensional features of a cell?  Of the internal parts of a cell?  Why? 

Scanning electron microscope- Coat cells in gold- See the outside 

Transmission microscope- See the inside of cells 

Explain how Pasteur disproved spontaneous generation.

2 flasks- one with a straight neck one with a curved neck and both with nutrient broth 

Boiled both to kill any bacteria 

Let them sit 

Flask with a straight neck became colored showing bacteria growth 

Flask with curved neck stayed sterile 

Bacteria fell into the straight neck and bacteria could not climb up curved neck 

Disproved theory of spontaneous generation of bacteria- Bacteria has to come from somewhere, cannot just apprear 

Explain Koch’s postulates. 

There is a cause and effect in infection diseases, Diseases don’t not just appear- Has to come from bacteria 

What advantages do solid media offer for the isolation of microorganisms?  What is an example of a solid bacteriological medium?  Liquid growth medium? 

In a solid media- You have colonies that are isolated, but in a liquid growth medium there is no separation 

Solid- TSA 

Liquid-TSB 

what is a pure culture?

colony of bacteria only made up of one type of bacteria

Describe Griffith’s transformation experiment. 

transformation- DNA can be picked up and incorporated into another genome

Type R does not kill mice, Type S does

Just R= mice live

Type R and Type S= Eventually just type S- Kill Mice 

Type R and Heat killed type S= Eventually just type S- Kill mice 

Type R and type S DNA= Eventually just type S- Kill Mice 

what is a phylogenetic tree and what does it tell you? 

depicts evolutionary history of all cells

What are the contributions to microbiology associated with the following people…Robert Hooke, Antoni van Leeuwenhoek, Louis Pasteur, Robert Koch, Frederick Griffith, Carl Woese 

Hooke-First to see microorganism 

Leewenhoek- First to see bacteria, made hos own microscope, “wee animulcus”

Pasteur-Disprove theory of spontaneous generation 

Koch-Koch postulates- Infectious disease has to come from somewhere  

Griffith-Transmission- uptake of free DNA 

Woose-RNA could be used to look at evolutionary relationships, Made a new category(Archaea) 

Define sterile in terms of microbiology.  Name at least two ways to sterilize microbiological media…

sterile- free from all living organisms and viruses

autoclave and membrane filtration can be used to sterilize

Why are *Archaea* more closely related to *Eukarya* than *Bacteria* are to *Eukarya*? 

archaea have more similar genes and metabolic pathways to eukarya than bacteria does

How do cocci and rods differ in morphology? Give an example of a bacteria with each morphology. 

Cocci- Round, sphere- Staphylococcus aureus 

Rods- Long, cylindrical- Bacillus cereus 

Using a microscope, could you differentiate a coccus from a spirillum? A pathogen from a nonpathogen? 

coccus are spheres, spirillum are spiral shaped

Draw the basic structure of a phospholipid bilayer and label the hydrophilic and hydrophobic regions. Why is the cytoplasmic membrane a good permeability barrier? 

Polar, hydophilic heads on the outside of the bilayer(Outside of cell and inside of cell), Hydrophobic tails on the inside of bilayer 

Lots of membrane proteins within 

Has selective permeability so only certain things can enter 

how are the membrane lipids of bacteria and archaea similar, and how do they differ?

bacteria/eukarya produce membrane lipids with hydrophobic fatty acid tails that are ester bound to glycerol-3-phosphate (G3P)

archaea make membrane lipids with hydrophobic tails that are ether linked to glycerol-1-phosphate (G1P)

describe the major functions of the cytoplasmic membrane

barrier of outside and inside of cell

allow certain things to pass

Why do bacterial cells need cell walls? Do all bacteria have cell walls?

Allows a higher chance of survival 

Maintain shape and pressure 

Why is peptidoglycan such a strong molecule? 

bonds between amino acids

Describe the major differences between the cell walls of gram-negative and gram-positive bacteria. 

Gram negative has thin cell wall, outer membrane and gram positive has thick cell wall 

Explain whether you expect the enzyme lysozyme to be equally effective against *Bacteria* and *Archaea*

Lysozyme is effective against peptidoglycan as it can cleave the beta 1-4 bonds between the sugars, but archaea does not have peptidoglycan and is not affected by lysozyme.  

What do the enzyme lysozyme and the antibiotic penicillin have in common? 

They both are effective in destroying the cell wall of bacteria as lysozyme can attack the bonds between sugars and penicillin can attack the bonds between peptides 

Describe the major chemical components in the outer membrane of gram-negative bacteria. 

O-polysaccride, core polysaccharide, lipid A 

What is the function of porins and where are they located in a gram-negative cell wall?

transmembrane protein channels for entrance and exit of solutes located in outer membrane

What component of the gram-negative cell has endotoxin properties? 

Lipid A, the toxic component of LPS in the outermembrane  

What is pseudomurein and where is it found? 

the major cell wall component of gram-positive methanogenic archaea, is composed of N-acetyl-D-glucosamine (NAG) and N-acetyl-L-talosaminuronic acid (NAT) located in the cell wall  

What is the value of a cell having a capsule? What is the capsule composed of and where is it found? Name a bacterium that has a capsule. 

Value of a capsule is that it helps the bacteria avoid phagocytosis, assist in attachment to surfaces,  

role in development and maintenance of biofilms, contribute to infectivity, prevent dehydration/desiccation. Composed of polysaccharides. Rhodobacter capsulatus 

How do fimbriae differ from pili?

Fimbriae= attachment (shot multiple projections) bristle like short fibers on surface of bacteria. Pili= conjugation, long hair like tubular microfibers found on surface of bacteria.  

What is dipicolinic acid and where is it found?  

Found in Endospores, enriched in Ca2+, plays a role in the heat resistance of bacterial endospores. 

What is formed when an endospore germinates? What causes a cell to make endospores? 

Sporulation= vegitative cell(active bacteria cell that undergoes metabolism.) Limiting nutrients trigger endospore formation.

Name two genera that produce endospores and how are the different? 

the genus Bacillus (an obligate aerobe often living in the soil) and the genus Clostridium (an obligate anaerobe living in the gastrointestinal tract of animals) produce endospores. 

Cells of *Salmonella* are peritrichously flagellated, those of *Pseudomonas* polarly flagellated, and those of *Spirillum* lophotrichously flagellated. Using a sketch, show how each organism would appear in a flagellar stain. 

what is archealla and where are they found

structure that assists in swimming in bacteria and archaea, respectively found on surfaces of archaea

What is positive and negative chemotaxis? When would you see each? 

Positive chemotaxis= movement towards higher concentration of chemicals

negative chemotaxis- movement of a cell away from chemical or physical gradient

What are the gram reaction, morphology and arrangement of the following bacteria? *E. coli, Bacillus, Staphylococcus, Micrococcus, Streptococcus, Vibrio, Treponema* H

a. E. coli—negative, rod-shaped, single-cell or in clumps

b. Bacillus—rod-shaped, small chains, clumps, or single cell, positive

c. Staphylococcus—cocci in clusters, positive

d. Micrococcus—cocci in tetrads, positive

e. Streptococcus—cocci in chains, positive

f. Vibrio—curved, rod-shaped, negative

g. Treponema—negative, spiral

How big is *E. coli?* How big is *Staphylococcus?* 

E.coli= 1.0-2.0 micrometers long. Staphylococcus= 0.5-1.0 micrometers long 

Compare and contrast gram positive and gram-negative cells. Draw a diagram of each and label the structures. What components are unique to each. 

Gram-negative peptidoglycan is only a few nanometers thick, representing one to a few layers, Gram-positive peptidoglycan is 30–100 nm thick and contains many layers. 

What value do gas vesicles give to bacteria? 

provide buoyancy

What is the function of flagella? What are flagella made of? 

Flagella help organism in movement and they are made of the protein flagellin 

Compare and contrast a prokaryotic and a eukaryotic cell. Give examples of both. What are the functions of each of the components? 

Prokaryotes are always unicellular, while eukaryotes are often multi-celled organisms. Both have plasma membrane, cytoplasm, and ribosomes. Prokaryote= streptococcus. Eukaryote= yeast 

How do prokaryotic and eukaryotic cells differ when it comes to reproduction? In general, how do bacteria, fungi (molds and yeast), plants and animals reproduce?  

Prokaryote= asexual. Eukaryote= sexual. Bianary fission  

explain endosymbiosis

a symbiotic relationship where one organism lives inside the other

do bacteria have cilia

No

How do bacterial endospores differ from fungal spores in function?

Fungal spores are reproductive structures, while bacterial endospores are survival structures. 

what is phototaxsis

directional movement along a light vector towards (positive) or away from (negative) a light source 

How does a chemoorganotroph differ from a chemolithotroph?  A chemotroph from a phototroph?  What does troph mean?

Chemoorganotroph- Get energy from organic materials 

Chemolithotroph- Get energy froim inorganic coumpounds 

Phototrophs- Energy from light 

Troph means feeding 

How does an autotroph differ from a heterotroph? 

Auto- Obtain carbon from CO2 

Hetero-Get carbon from organics 

What are enzymes made of?  Why is that important when it comes to high temperatures? 

enzymes are made of proteins (sometimes RNA) and they can denature in high temps

where on the enzyme does the substrate binds?

active site- very specific for substrate

what is energy activation?

the energy required to being a chemical reaction- minimum energy required for molecules to become reactive

How is catabolism different from anabolism?  

Catabolism- Breaking down of materials and making ATP--- Break bonds to get ATP 

Anabolism- Building up of materials using ATP-----Make bonds  

How is respiration different from fermentation? 

Respiration is the complete breakdown of glucose into O2 and H20, whereas fermentation is the imcomplete breakdown of substrates------End in acids, alcohols, or Gases 

What are some of the endproducts of fermentations? 

acids, gases, alcohols

What yeast is commonly used for fermentations? 

Saccharomyces cerevisiae 

what happens in glycolysis

glucose breaks into 2 Pryuvic Acids (pyruvate)

How does glucose get into a cell? 

facilitated diffusion- use of membrane protein

Where is the most ATP produced?  Glycolysis, Kreb’s cycle or in the ETC? 

electron transport chain

What is the final election acceptor in aerobic respiration and what does it form?   

Oxygen is the final electron acceptor and it forms water 

What is the final electron acceptor in anaerobic respiration?

Anything other than oxygen- Nitrate, Ferric iron(Fe+3), Sulfate(SO4) CO2

What is the carbon source for autotrophic organism?  Energy source? 

CO2, glucose

where do bacteria get their nutrients from?

photosynthesis, decomposing dead organisms and wastes, or breaking down chemical compounds

What happens during nitrogen fixation and what types of organisms fix nitrogen?   

nitrogen fixation- bacteria in the soil and in roots of some plans convert nitrogen gas in the atmosphere to ammonia

typically bacteria

Which four chemical elements make up the bulk of a cell’s dry weight? 

carbon, hydrogen, oxygen, nitrogen

Which two classes of macromolecules contain most of a cell’s nitrogen? 

DNA/RNA, proteins

Differentiate between trace metals and growth factors.  How are these used by the cell? 

Trace metals- Not organic 

Growth factors- Not found in the environment, have to be made/ synthesized----Organic  

How is a complex medium different from a defined medium?  What type of media is TSA and why? 

Complex medium- Do not know the structure of everything within the media- Contain yeast extract and Peptones-small amino acids chains 

Defined medium- Know the structure of everything within the media 

TSA is complex 

What is meant by the word sterile?  Why is aseptic technique necessary for successful maintenance of pure cultures in the laboratory? 

Sterile- No living organisms 

Need aseptic techniques to transfer organisms without contamination- Airborne contaminants everwhere 

Why is a viable count more sensitive than microscopic count?  What major assumption is made in relating plate count results? 

in a microscopic count all organisms dead or alive are included. But in viable cell counts the medium used for plating may support only a certain living organism. Viable counts depend on the different nutrient requirements and thus is why its more sensitive.

Describe how you would dilute a bacterial culture to 10-7. 

(Take one ml of the orginal solution and put it with 10 ml of broth)X7= 10^-7 dilution 

explain the “great plate count anomaly.” 

Microscope counts of actual nature will have more organisms than on plates- “Direct microscopic counts of natural samples reveal far more orgalnisms than those recoverable on plates.” 

Describe how you could use a turbidity measurement to tell how many colonies you would expect from plating a culture of a given OD. 

A certain optical density will match with a certain number of cells- As cells increase so does OD 

What is meant by the term generation time?  What is the average generation time of *E. coli*?

Time it takes for a population of microbial cells to replicate 

How do binary fission and budding cell division differ? 

Binary fission- Parent is split into 2 daughter cells(Equal cell division) 

Budding- Small organism is attached to the parent cell(Unequal cell division) 

in which phase of the growth curve are cells actively growing?

Exponential phase- Preparations to replicate already made in lag phase- Now use resources to replicate 

under what conditions would a lag phase not occur

if the actively dividing cells of the exponential phase are transferred to the same medium under the same environmental conditions like temp and aeration

why do cells enter a stationary phase

All of the resources are used and there is no growth 

How do microorganisms in a chemostat differ from microorganisms in a batch culture? 

Chemostat- Constant nutrients are provided which allows microbial cells to stay in an exponential growth rate(Open system) 

Batch culture- closed system of microbial culture 

Explain how to do a plate count?   How many bacteria would be in the culture if you had 234 colonies on the 1/1,000,000 plate? 

Take one ml of the original solution with the sample to be counted, Put the one ml of orginal solution in 9 ml of nutrient broth, Plate one ml from that mixture ,Repeat but the original solution= previous solution 

To find the colonies= Colonies X Reciprocal of dilution= 234 \* 1,000,000= 2.34 X 10^8 

What are the stages and events that occur during biofilm formation? 

attachment, colonization, development, dispersal

Why is biofilm formation such a major problem in human medicine? 

microorganisms growing as biofilms are significantly less susceptible to antibiotics and host defenses than are planktonic forms of the same microorganisms

How does a hyperthermophile differ from a psychrophile? 

Hyperthermophile- Lives in extreme heat- Over 80 degrees C 

Psychrophile- Lives in extreme cold- Below 15 degrees C 

What are the cardinal temperature for *E. coli*?  To what temperature class does it belong? 

Cardinal temp-the minimum, maximum, optimal temp of organism 

E coli cardianl temp= Optimal=Mesophile(39) 

How do psychrotolerant organisms differ from psychrophilic organisms? 

Psychrotolerant- Can tolerate the cold, not optimal temp( Can grow in 0 but optimal in 20-40) 

Phychrophile- Have to be in cold= optimal below 15)