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Question 1

Nutrient material called ____ ______ used to grow and isolate microorganisms

Answer 1

culture media

Question 2

what factors are considered when picking a media when trying to determine a bacteria

Answer 2

i. Source of sample tested
ii. Species suspected to be in sample
iii. Nutritional requirement of the suspected organisms

Question 3

Methods of inoculation include

Answer 3

i. Streak plate method
ii. Spread plate method
iii. Pour plate method

Question 4

what temp is inncoulated media kept at

Answer 4

37 degree celsius

Question 5

cell colonys

Answer 5

Each colony is derived from a single cell and all cells within a colony are
identical to each other. Different species have different colonial morphologies therefore can be used as mean
of distinguishing different species in a mix culture

Question 6

Longterm preservation requires cultures to be maintained using one of the following approaches:

Answer 6

frozen in liquid nitrogen (-196ºC)
ii. Frozen in special freezer (-70ºC to -120ºC)
iii. Lyophilization (freeze drying) - dehydration followed by vacuum sealing (most stable form of
storage)

Question 7

Two approaches to the study of microorganisms after being isolated as a pure culture

Answer 7

colonial morphology and the cellular morphology. The latter requires the use of microscope.

Question 8

size of micribials

Answer 8

range of nanometer to micrometer and so there is a need for magnification by using a microscope

Question 9

what is resolution

Answer 9

ability to distinguish two closely located objects as separate, distinct entities
-Resolution is
fixed by the wavelength of light used and by the optical properties of the lenses.

Question 10

what is a Light microscope

Answer 10

system of lenses used to manipulate the path a light beam travels between the specimen
and the eye

Question 11

what is an Electron microscope

Answer 11

a beam of electrons controlled by a system of magnetic fields used in place of the light source of a light microscope.

Question 12

basic protocol for staining of microorganisms

Answer 12

a. A thin film of specimen (smear) is placed onto a clean microscope slide and air dried;
b. The dried smear is fixed by heat to make microorganisms stick to glass slide;
c. Stain with one or more dyes prior to viewing with microscope.

Question 13

Simple staining

Answer 13

staining by a single general dye colours all microorganisms in a specimen and allows
the observation of size, shape, number and arrangement of cells.
-e.g. methylene Blue staining

Question 14

Differential staining

Answer 14

-two or more special dyes are used to observe differences between microbial cells or parts of cells
-acid fast stain
- carbolfuchsin and methylene blue used to differentiate acid-fast bacteria such
as Mycobacterium from other non-acid-fast bacteria
- Gram stain - characterize bacteria into two groups: Gram positive and Gram negative.

Question 15

Gram stain has to do with the cell wall of a bacterium.

Answer 15

Gram stain has to do with the cell wall of a bacterium.

Question 16

cell wall

Answer 16

• rigid structure giving characteristic shape of bacterial cell;
• essential for cell growth and division;
• Gram-negative cell wall usually thinner than Gram-positive cell wall;
• in eubacteria shape determining part is rigid material called peptidoglycan;
• archaeobacteria do not have peptidoglycan

Question 17

Gram-positive cell wall

Answer 17

• thick structure made up mainly of thick layer of peptidoglycan;
• teichoic acids often found attached to peptidoglycan to give negative charge to help transport of positive
  ions and storage of phosphorus

Question 18

(ii) Gram-negative cell wall

Answer 18

• has an outer membrane covering a thin layer of peptidoglycan (i.e., in periplasmic space between outer and
  cytoplasmic membranes);
• outer membrane anchored to peptidoglycan by a lipoprotein;
• another structure found only in outer membrane is lipopolysaccharide (LPS);
• outer membrane is a selective barrier based on size and charge of molecules;
• in Gram strain, alcohol increases permeability of Gram-negative outer membrane but shrinks pores of Grampositive peptidoglycan.

Question 19

when is Fluorescence Microscopy a useful tool

Answer 19

Fluorescence Microscopy is a useful tool when trying to reveal only objects that are of interest in an otherwise
black background
using light mictoscope
-e.g a fluorescent dye is attached to a specific antibody; Any attachment of the labelled antibody to microorganisms in the specimen will fluoresce under the appropriate conditions and can be easily detected

Question 20

Electron Microscopy

Answer 20

short wavelength of the electron beam as compared to light allows for greater resolving power
- Transmission electron microscopy requires staining with heavy metals of whole specimen or
slicing of microorganisms into thin section

• scanning electron microscopy, an electron beam moving back and forth generates a 3-dimensional image of cell surface of microorganisms coated with a fine
  film of metal.

Question 21

*Importance of studying detailed morphology of microorganisms include

Answer 21

a. absence or presence and characteristics of cellular structures help classification
b. morphology of cells help them to respond to environment.
(e.g., extracellular structures such as capsules can make microorganism more pathogenic)

Question 22

why are bacteria mostly used in biology studies

Answer 22

Bacteria are small (0.75 to 1.25 um in diameter/width) but have a much higher ratio of surface area to volume
than larger, more complex organisms
-high rate of metabolism, growth and replication

Question 23

what are the 3 shapes of bacteria?

Answer 23

Spherical cells (called coccus) - usually round, sometimes ovoid
b. Cylindrical or rod shape (called bacillus) - vary in width and length, ends can be
square, rounded, tapered or pointed.
c. Spiral or helical shape (spirillum) - corkscrew like shape

Question 24

what are bacterias that change shapes as they grow called

Answer 24

pleiomoric organisms

Question 25

what patterns do bacterial cell have

Answer 25

a. spiral-shaped and rod-shaped bacteria usually exists as single cells b. when coccus divide in one plane = diplococcus (pairs) e.g., Neisseria gonorrheae c. when coccus divide in one plane but remain attached to form chain = streptococcal arrangement, e.g., Streptococcus spp. d. when coccus divide at right angle to the first plane of division = tetrads, e.g., Pediococcus e. a further division in third plane = cubical packet of 8 cells called sarcinae, e.g., Sarcina spp. f. division in 3 planes in an irregular pattern = grapelike clusters, e.g., Staphylococcus

Question 26

Size, shape and arrangement of bacterial cells is referred to as?

Answer 26

gross morphology.

Question 27

In order to isolate a microorganism, specific media is required:

Answer 27

1- Chemically defined media. - Exact composition of media know thus can alter individual component separately. Undefined media - natural products (e.g., blood, beef extract, peptone, etc.) added to media for routine lab cultivation. 2- When solid support needed, 1.5 % agar is used. 3- Media for growing bacteria - requirements varies between different bacteria.

Question 28

Microorganisms with demanding nutritional requirements are known as fastidious. They require complex, undefined media for cultivation.

Answer 28

4- Media for growing yeasts - all fungi and heterotrophs (requires organic substrates to get its carbon source for growth and development). - generally have higher sugar content and lower pH than bacterial media. 5- Media for anaerobes: -anaerobes are those that tolerate little or no oxygen (sometimes grown deep down in agar or put media in tall test tubes. 6- Selective media - media designed to enhance growth of one kind of microorganism or suppress growth of other kind of microorganism or both. For example, brilliant green agar is used to isolate Salmonella species from food samples. That is, the brilliant green agar inhibits Gram-positive bacteria. Another example is phenylethanol agar that inhibits Gramnegative bacteria. 7- Differential media - used to differentiate organisms based on their unusual nutritional requirements and characteristic appearance in media (e.g., lysis of red blood cells, hemolytic vs. nonhemolytic bacteria). 8- Selective/Differential media - useful in public health microbiology - e.g., MacConkey medium (bile salt and crystal violet inhibits Gram-positive bacteria thus allowing Gram-negative organisms). 9- Enrichment media - used to increase number of specific organism in a sample by favoring the growth of the interested species. 10-Tissue culture media - plant or animal cells grown in lab in specialized media used to cultivate viruses in vitro since viruses can only replicate inside living host cells.

Question 29

temperature

Answer 29

- Microorganisms in general can grow over a wider temperature range than more complex organisms (e.g., Bacillus subitlis can grow from 8 to 53ºC). - Temperature at which a species grows most rapidly is the optimum growth temperature. - Cardinal temperatures of a species of microorganisms 40 (i) Minimum temperature (ii) Optimum temperature (iii) Maximum temperature - Cardinal temperatures changes depending on nutritional content of growth medium. - Optimum temperature usually closer to maximum temperature since enzyme activity increases with temperature until upper limit at which enzymes is degraded is reached.

Question 30

Microorganisms are divided into 3 major groups based on their optimum growth temperature:

Answer 30

Psychrophiles - grow best from 15 to 20ºC (may die if exposed to room temperature for short time probably due to damage to cytoplasmic membrane). Bacteria and fungi from this group found in colder waters and soils such as oceans and the Polar Regions. Particularly problem of food spoilage, e.g., psychrophilic bacteria are Pseudomonas and Flavobacterium. Mesophiles - majority of microorganisms belong to this group. Grow best between 25 to 40ºC. Saprophytic organisms grow at lower part of the mesophilic temperature range. Parasitic organisms of humans and animals grow at upper part of this range (~37ºC). Thermophiles - can grow from 40 to 85ºC but grow best between 50 to 60ºC. Mostly prokaryotes (eucaryotes cannot grow above 60ºC). Commonly found in volcanic areas, compost heaps and hot springs. E.g., Bacillus stearothermophilus. Enzymes are rapidly produced to replace those damaged by high temperatures

Question 31

Gaseous Atmosphere

Answer 31

1. Aerobic Microorganisms -21% oxygen. E.g., Mycobacterium, Legionella, filamentous molds - Require more energy 2.Anaerobic Microorganisms - may be poisoned by oxygen - Wide range in oxygen tolerance -Anaerobic jars, anaerobic chamber or anaerobic glove box can be used cultivate anaerobes 3. Facultative Microorganisms -grow in air atmosphere but can also grow anaerobically -cna use oxygen for chemical reaction -e.g. e. coli 4. Microaerophilic Microorganisms -use oxygen for chemical reaction -1 to 15% oxygen level. - E.g., Campylobacer jejuni.

Question 32

pH

Answer 32

-optimal diff for various organism -microorganisms must maintain intracellular pH at ~7.5 (this is done by the ability of the cell to expel or uptake hydrogen ions. -minimum pH of 4 and maximum pH of 9. Optimum pH normally lies between 6 and 8. -molds and yeasts generally have a broader pH range for growth than bacteria. Optimum pH is ~ 5 to 6. - growing cells release acidic or alkaline waste products into the growth medium environment. Without buffering of the medium, the shift can eventually inhibit growth

Question 33

Other conditions

Answer 33

-water, and light - osmotic pressure (hypertonic, hypotonic, isotonic)