MICRB 202 Exam 1 Questions and
Verified Answers 2026
Resolution - <CORRECT ANSWER >>the ability to see objects that are close
together as separate objects, light waves only resolve things 0.2 μm and larger
Magnification - <CORRECT ANSWER >>the enlargement of specimen when it is
seen through the microscope
Magnification = (eyepiece) x (objective lens)
Use of oil - <CORRECT ANSWER >>ONLY for the 100X lens, wipe slide and lens
after switching from 100x to 40X or next slide
Working distance - <CORRECT ANSWER >>the distance between the front edge of
the lens and the specimen
Depth of field - <CORRECT ANSWER >>the thickness of the slice of a specimen in
focus; decreases with increasing magnification
Forms of media - <CORRECT ANSWER >>broths (liquid) and agars
Broths - <CORRECT ANSWER >>nutrient containing liquids in which cells can grow
in 3D; used for large scale production; good for anaerobic metabolism (no oxygen
at the bottom of the liquid); good for observing arrangements of cells
Agars - <CORRECT ANSWER >>solidified nutrient containing media
,Variations: plates, slants, and deeps
Broth: clear - <CORRECT ANSWER >>no growth
Broth: turbid - <CORRECT ANSWER >>cloudy
Broth: flocculent - <CORRECT ANSWER >>visible particles floating throughout
broth
Broth: pellicle - <CORRECT ANSWER >>bacteria growth only on top of broth
Broth: sediment - <CORRECT ANSWER >>bacteria growth on bottom of tube
Advantages of agar - <CORRECT ANSWER >>- used to separate/anchor cells
- required for pure cultures
- non-toxic to most microbes
- can't be digested/degraded by microbes
- doesn't melt until heated to 90 C
- if melted, does not solidify until 45 C which means you can mix cells in before
the agar solidifies
Sterile environments - <CORRECT ANSWER >>contain no viable organisms in any
form (no spores, nothing active)
Non-sterile environments - <CORRECT ANSWER >>contaminated material (ex.
Bench top, outside test tube, body parts)
, Goal of transfer - <CORRECT ANSWER >>to keep pure cultures pure
Pure culture - <CORRECT ANSWER >>a culture containing an isolated species of a
microorganism growing in an environment free from contamination by any other
living organism
Isolation techniques - <CORRECT ANSWER >>the process of physically separating
cells on a solid media; an individual cell will produce a colony of clones which is a
pure culture
Why isolation is important - <CORRECT ANSWER >>- when running experiments
and tests it's important to control the genetic variation of the sample
- each colony on a streak plate will have variations between them
- if you are running a test you want to make sure there is no variation because it
can skew results and cause them to be inconclusive
Streak plating - <CORRECT ANSWER >>- goal is to drag cells apart and to dilute the
culture
- after initially getting cells from broth do NOT get more cells for the next set of
streaks
- in between each set of streaks FLAME THE LOOP to remove cells and allow for
dilution
- after streaking plates -> incubation
- next lab check for isolated colonies
Purpose of staining - <CORRECT ANSWER >>- improves contrast (aka visibility)
Verified Answers 2026
Resolution - <CORRECT ANSWER >>the ability to see objects that are close
together as separate objects, light waves only resolve things 0.2 μm and larger
Magnification - <CORRECT ANSWER >>the enlargement of specimen when it is
seen through the microscope
Magnification = (eyepiece) x (objective lens)
Use of oil - <CORRECT ANSWER >>ONLY for the 100X lens, wipe slide and lens
after switching from 100x to 40X or next slide
Working distance - <CORRECT ANSWER >>the distance between the front edge of
the lens and the specimen
Depth of field - <CORRECT ANSWER >>the thickness of the slice of a specimen in
focus; decreases with increasing magnification
Forms of media - <CORRECT ANSWER >>broths (liquid) and agars
Broths - <CORRECT ANSWER >>nutrient containing liquids in which cells can grow
in 3D; used for large scale production; good for anaerobic metabolism (no oxygen
at the bottom of the liquid); good for observing arrangements of cells
Agars - <CORRECT ANSWER >>solidified nutrient containing media
,Variations: plates, slants, and deeps
Broth: clear - <CORRECT ANSWER >>no growth
Broth: turbid - <CORRECT ANSWER >>cloudy
Broth: flocculent - <CORRECT ANSWER >>visible particles floating throughout
broth
Broth: pellicle - <CORRECT ANSWER >>bacteria growth only on top of broth
Broth: sediment - <CORRECT ANSWER >>bacteria growth on bottom of tube
Advantages of agar - <CORRECT ANSWER >>- used to separate/anchor cells
- required for pure cultures
- non-toxic to most microbes
- can't be digested/degraded by microbes
- doesn't melt until heated to 90 C
- if melted, does not solidify until 45 C which means you can mix cells in before
the agar solidifies
Sterile environments - <CORRECT ANSWER >>contain no viable organisms in any
form (no spores, nothing active)
Non-sterile environments - <CORRECT ANSWER >>contaminated material (ex.
Bench top, outside test tube, body parts)
, Goal of transfer - <CORRECT ANSWER >>to keep pure cultures pure
Pure culture - <CORRECT ANSWER >>a culture containing an isolated species of a
microorganism growing in an environment free from contamination by any other
living organism
Isolation techniques - <CORRECT ANSWER >>the process of physically separating
cells on a solid media; an individual cell will produce a colony of clones which is a
pure culture
Why isolation is important - <CORRECT ANSWER >>- when running experiments
and tests it's important to control the genetic variation of the sample
- each colony on a streak plate will have variations between them
- if you are running a test you want to make sure there is no variation because it
can skew results and cause them to be inconclusive
Streak plating - <CORRECT ANSWER >>- goal is to drag cells apart and to dilute the
culture
- after initially getting cells from broth do NOT get more cells for the next set of
streaks
- in between each set of streaks FLAME THE LOOP to remove cells and allow for
dilution
- after streaking plates -> incubation
- next lab check for isolated colonies
Purpose of staining - <CORRECT ANSWER >>- improves contrast (aka visibility)
