Micro Lab Exam 1

What was the purpose of this microscope laboratory experiment?
to name the parts of a compound light microscope and their functions, learn the correct way to use the c.l.m
what is the difference between magnification and resolution?
magnification: uses special lenses to enlarge image of an object.
resolution: separates or distinguishes structures to close together
what is the purpose of placing immersion oil on the slide?
prevents scattering of light
what are the advantages of electron microscope as compared to light microscopes?
electron microscopes: uses electron beam
light microscope: uses lights to visualize object
two major differences between prokaryotic cells & eukaryotic cells
prokaryotic cells: single celled & no nucleus
eukaryotic cells: membrane bound nucleus & DNA
if the ocular magnification is 40x and the oil immersion objective is in place, what is the total magnification?
40X x 100= 4000X
what is simple staining?
when one stain is used to examine shape and arrangement of bacteria
what is the purpose of the smear prep lab experiment?
1. to prepare a bacterial smear
2. study bacterial morphology
why should one make sure that the commercially available glass slide does not have a layer of grease before preparing the smear?
b/c the stain and smear will not stay
what would happen if you had skipped the heat fixing step and continued with the staining procedure?
the bacterial cells on the slide would shift when the agents are being rinsed off which would mean the bacteria would go down the drain.
what is the reason for sterilizing the whole wire and part of the handle of the inoculating loop before and after each transfer?
to ensure that the bacteria is free of contamination from other microorganisms.
list the most common shapes and arrangements of bacteria and provide a specific example of each:
cocci: oval, elongated, or flat on one side
bacilli: rod shaped
spirillum: spiral with one or more twists
why is knowing the bacterial shapes and arrangement important?
enables scientists to determine what type of bacteria it is and what methods need to be used to control growth
what is the purpose of negative staining
useful for identification of certain bacteria or structures that are normally difficult to stain
why is the technique called "negative staining"
the bacteria is not stained but the the background is. the bacteria appears clear while the bg looks dark
why does nigrosin not stain bacterial cells/structures?
nigrosin is negatively charged and are repelled by bacteria that have the same negative charge.
give 2 situations where the negative staining procedure would be used.
1. used to accentuate capsules that surround certain bacteria/yeasts
2. used to determine if known bacterial infections are either gram + or gram - bacteria due to the composition of the cell wall.
what is the purpose of the streak plate method?
isolate pure colonies of bacteria
on which of the sections of the plate do u see isolated colonies. explain this distribution.
section 3. as we streak through sections 1 & 2 we decrease the streak to 3 which causes isolated colonies.
give 2 reasons why you might have a situation in which bacterial colonies were found on the first section of a steak plate, but not on sections two and three.
1. you missed the bacteria in section when you tried to streak it through section 2 & 3.
2. the bacteria dried up before you could streak it to the next sections.
how would you determine which colonies might be contaminants on a streak plate?
different color/appearance
what was the purpose of gram staining the bacteria?
to determine if a bacteria is either gram + or gram -
what would happen if you do not apply gram's iodine after staining with crystal violet?
the violet will not be pushed into the cell wall and the gram + cells would get decolorized by the alcohol & appear to be gram -
explain the mechanism of gram staining
stain cells with crystal violet, rinse then add iodine which traps the stain inside the cell. when the alcohol is applied the gram - bacteria lose the outer membrane which allows the crystal violet staining inside to be washed away & allow for these to be counterstained with safranin, leaving them red.
differences between cell wall of gram - and gram + bacteria
gram -: thin & red
gram +: thick & purple
what is the purpose of the acid-fast staining technique?
to identify the bacteria belonging to genus mycobacterium
what might account for the fact that some bacteria are acid-fast and others are non-acid fast
a multiple layer of peptidoglycan makes it difficult for some stains to penetrate wall
what is the clinical significance of determining whether or not a bacterium is acid-fast?
acid-fast bacteria have unusual cell wall structures that hold onto the stains used in common diagnostic staining protocols, like gram stain. An acid fast bacterium holds onto the dye.
list the genus and species of 2 acid fast pathogenic bacteria and the diseases they cause
Mycobacterium tuberculosis- tuberculosis (TB)
Mycobacterium leprae- leprosy
Why was Mycobacterium smegmatis used instead of Mycobacterium tuberculosis in this exercise?
Tuberculosis is an air born disease and can be caught by breathing
what was the purpose of the bacterial endospores lab 7 experiment?
to perform positive & negative staining on bacterial endospores
to differentiate bacterial endospores from the vegetative cells
list the genus and species of 2 endospore forming bacteria and list the diseases they cause
1. Bacillus anthracis- anthrax
2. Clostridium tetani- tetanus
List 2 unique properties of bacterial endospores
1. help bacteria survive harsh environmental conditions such as high temperature.
2. chemical damage
what was the purpose of bacterial capsule lab 8 experiment?
to recognize bacterial capsules & to understand the nature & function of the capsules
explain the relationships between capsules & bacterial virulence.
encapsulated bacteria can escape the body's defense mechanisms. these bacteria can, therefore, survive longers in the host & cause disease.
list some of the chemical substances that are present in bacterial capsules.
polypeptides & glycoproteins
2 specific functions of capsules
protect bacteria from bacteriophages & allow bacteria to survive longer in the host & cause disease.
name 2 pathogenic bacteria that have a capsule and the disease they cause
1. Klebsiella pneumoniae - Klebsiella pneumonia
2. Haemophilus influenzae- pneumonia & acute meningitis
what was the purpose of the bacterial flagella lab 9 experiment?
understand the function of flagella & observe bacterial flagella & their arrangements
besides flagella, what other modes of locomotion for bacteria?
cilia & pseudopud (false feet)
list the major arrangements of bacterial flagella & describe how these structures might contribute to pathogenicity
two main types: peritrichous or polar

polar consists of monotrichous, lophotrichous, and amphitrichouse

flagella allow bacteria to move from one region of the body to another, thus are more pathogenic to the host
list 2 advantages for using the hanging drop technique and the motility test medium method
1. allows you to examine sample immediately
2. drop of liquid suspended below coverslip which tends to be free & move more easily.

motility medium:
1. can setup a series of tests quickly
2. culture of any age can be used
describe how the motility medium demonstrates motility
the agar medium contains a colorless dye, tetratrizolium chloride. bacteria reduce the dye & the color is changed to purple whenever the bacteria moved to & grew
compare differences between the flagella of prokaryotic & eukaryotic organisms
flagella in eukaryotic cells are composed of several filaments & far more complex than flagella in prokaroytic cells.
what are the two common techniques used to visualize endospores?
schaeffer fulton method and crystal violet method
Staphylococcus aureus
round, staph infections
Bacillus anthracis
rod shaped, anthrax
Clostridium tetani
rod shaped, tetanus
Spirillum volutans
amphitrichous, tuft of flagella at both ends, microtubules inside, rotate clockwise
Proteus vulgaris flagella
peritrichous, all around, microtubules inside, rotate clockwise