Microbiology Lab Exam 1 Questions and Answers 100% Pass

Microbiology Lab Exam 1 Questions and Answers 100% Pass What is the purpose of a streak plate? - 1) To separate cells so that they grow to form isolated colonies 2) To confirm if a culture is a pure colony or mixed 3) To confirm is there is contamination in your culture What is a colony? - Areas of growth that arise from a single cell. How do colonies form? - They are formed by spreading out cells. Cells are spread and reproduce over and over again through bionary fission until visable mass of cells appear. What is a pure culture? - Culture containing only one type of organism What kind of media are colonies able to form on? - agar slant, broth media, agar plate When is a agar slant used? Pros & cons - 1) Smaller amount of surface area prevents the media from drying out too quickly 2) useful for medium term storage 3) viable for a couple of months if stored properly What are the 4 criteria for labeling a microbial culture? - 1) initials or name AND group number 2) date 3) growth media type 4) culture name or source of inoculum Describe bacillus (bacilli) morphology - rod shaped cells, longer than wide, sausage like, can use rod or bacillus 2 | P a g e Created by Katelyn Whitman © 2025, All Rights Reserved. 100% PASS GUARANTEE describe coccus morphology - cells are ball shaped or spherical Describe coccobacillus morphology - elongated spheres- not quite spherical, but not clearly a rod. Tends to occur in species which are normally rod-shaped during rapid growth. Describe spirillum morphology - Helical, loose or tight coils. Look like wavy lines - morphology has no arrangement Describe filamentous morphology - Long elongated cells. Look like a tangled mass of branched filaments- no arrangement Describe vibrio morphology - A curved rod or comma shape What does No arrangement mean? - Single cells, ungrouped. Not all cells have an arrangement What is the cell arrangement Diplococci/Diplobacilli - Pairs of cells. Diplococci are pairs of cocci, diplobacilli are pairs of rods What is the cell arrangement Streptococci/Streptobacilli? - Chains of cells. Streptococci are chains of cocci, streptobacilli are chains of rods What is the call arrangement staphylococcus? - Irregular clusters of cells- like bunches of grapes. What is the cell arrangement of tetrads? - Sets of 4 regularly arranged cells What is the cell arrangement of palisade? - Bacilli (usually 2-4 cells) arranged side by side. Columns or "V-forms" What genus is an acid fast bacteria? - Mycobacterium tuberculosis What genus is an capsule former? - Klebsiella pneumoniae What is a simple stain? - Involves only one dye to make cells more visable. Involves methylene blue or crystal voilet. 3 | P a g e Created by Katelyn Whitman © 2025, All Rights Reserved. 100% PASS GUARANTEE What is a complex stain? - Two or more stains. Allow the differentiation of cell types or cell structures. (can be called differential stain) What is a differential stain? - Another name for complex stain. Allow us to see the differences between different cell types or cell structures. Uses at least two different stains. What is a negative stain? - Leaves cell or a cell structure unstained while the background is stained. No heat fixing. Used to determine cell shapes more accurately or to see structures which may be unable to accept dyes, or which are adversely affected by heat fixation (capsules) What does water soluble mean? - Bacteria that produce colorful pigments and color spreads into the agar What is non-water-soluble? - Bacteria the produce colorful pigments which remains in the cell and does not diffuse into the agar What do the terms "water-soluble" and "non-water soluble" refer to? - Only bacteria with pigmented colonies What are the components of colony morphology? - Pigment, texture, growth pattern, opacity, size, odor Why is it important to use a 24 hr culture for a gram stain? - Grams stains should be 18-24 hrs old. Many gram positives begin to yield a Gram negative result as the cultures age past 24 hrs Why is it important to use a several day old culture for endospore stains? - Endospores are produced in response to stress, but the process takes 24-48 hours. You will not see endospores in cultures made earlier that 24-48 hrs. Explain the endospore lifecycle - 1) sporulation occurs as stressors accumulate typically @ 12-48 hrs produces an endospore enclosed in a vegetative cell (not reproduction) 2)when vegetative cell lyses, it 4 | P a g e Created by Katelyn Whitman © 2025, All Rights Reserved. 100% PASS GUARANTEE releases endospore (free spore) which can stay dormant until favorable conditions return 3) Germination occurs with favorable conditions typically 1-6 hours 4) binary fission - normal cell reproduction produces vegetative cells @ 12 hrs what is the purpose of heat fixing? - It kills the organisms and aheres them to the slide When is a broth media used? - It is a liquid form of growth media used when you want to grow a lot of a culture. Not useful to determine whether a culture is pure or not. Agar plate- pros and cons - Allows for a large surface area for growth to occur on. Useful to purify a culture and determine whether a culture is pure. Dry out in a couple of weeks not useful for long-term storage Draw and identify the 4 types of flagella - 1) monotrichous- only one flagella 2) amphitrichous- flagella on each end 3) lophotrichous- multiple flagella at one end 4) peritrichous- multiple flagella all over Steps to perform a streak plate- explain purpose of each step - 1) Start with googles, lab coat and gloves- aseptic technique (protection)- label plate appropriately 2) divide plate into three sections and a cool spot - to differentiate the different sections 3) use a flamed, cooled loop (aseptic technique) obtain cells 4) hold the lid above the plate (to prevent contamination) spread organisms on the surface of the first section 5) Dehydrate loop (to prevent creating aerosols that we can breath in from organism) then flame the loop to red-hot to sterile (prevent cells from "opping" off the loop if the loop is heated too much too soon 5 | P a g e Created by Katelyn Whitman © 2025, All Rights Reserved. 100% PASS GUARANTEE 6) Wait 10 seconds then touch the cool spot- to test to make sure loop isn't too hot to kill organisms 7) turn plat 1/4 turn, hold lid above plate, use flamed, cooled loop to spread organisms from the surface of section 1 to section 2 passing through section 1 only 2-3 times, then continue moving the loop side to side to move toward center of plate 8) dehydrate and flame loop, wait 10 seconds and touch cool spot 9) turn plate 1/4 turn, hold lid above plate, use flamed, cooled loop to spread cells from section 2 to section 3 passing through section 2 only 2-3 times, then continue moving the loop sided to side to move toward center of plate 10) replace lid, dehydrate and flame loop, incubate at instructed temperature 11) this flaming technique allows for single cells to separate from other cells to form isolated colonies When would someone want to perform a streak plate? - 1) determine identity of unknown organism 2) biologist wants to study properties of a microbe- performs two times 3) obtain a pure culture of an organism What is the purpose and mechanism of hand washing? - To reduce the number of microbes on our hands by washing with soap for 30 seconds and rinsing for 30 seconds. How can soap help remove organisms from our hands? - Soap is composed of amphiphilic (hydrophobic and hydrophilic properties) that allow soap to organize in a way that facilitates removal of microorganisms from a surface and can also disrupt the cell membrane of some microorganisms causing cell lysis Define the question in The Scientific Method - It is what you are trying to find out in an experiment Define the hypothesis in The Scientific Method - It is your expected answer to your question in your experiment 6 | P a g e Created by Katelyn Whitman © 2025, All Rights Reserved. 100% PASS GUARANTEE What is the experimental treatment? - The treatment that directly answers your question What is a positive control? - It is the treatment that demonstrates the intended result based on the question and the hypothesis. Helps make sure your experimental/detection system is working properly What is negative control? - It is the treatment that does NOT demonstrate the intended result based on the question and hypothesis. Included to make sure there is not unintended result that occurs in the experiment What are the benefits of a capsule? - Protection from dessication (drying out), allows bacteria to attach and adhere to surfaces in preferred environments, for some it offers protection from phagocytes and contributes to pathogenicity (ability to cause disease)- capsule not a required part of cell and can be removed without killing the cell What are the benefits of flagella? - Motility -Allows cell to perfor