+

Microbiology Chapter 3

        Test Notes
   or     

Flashcard Set Preview

Side ASide B
The Five I’s:
•Inoculation –Addition of microorganism to supporting medium •Incubation –Proper growth...
How do you culture a microorganism?  
•To identify the agent that causes a specific disease requires that microorganisms be...
Step 1 to cultivate microorganism
–Inoculum (sample to be cultured)•Environmental specimens (water, air, soil)•Clinical...
Step 2 to cultivate microorganism
–Medium(collection of nutrients allowing growth of inoculum)•Liquid broth •Solid media...
Step 3 to cultivate microorganism
–Incubation (placing inoculated media at proper temperature for specific period of time)•Observable...
Clinical Specimens:
•A clinical specimen is a sample of human material to be examined or tested for the presence...
How do you properly handle a clinical specimen? (3 Steps)
•Must take care not to contaminate the sample with organisms from the environment or other...
•Obtaining Pure Cultures:
–Technique for isolating the suspected pathogen from normal microbiota in a culture
Pure culture :
–refers to a cultures composed of cells arising from a single progenitor (parent or original...
Aseptic technique:
refers to a set of instructions used to prevent further contamination by microbes
Two common pure culture isolation techniques:
•Streak plates •Pour plates
•Culture Media:
–Used to support the growth of microorganism or as a means of identification
–3 Physical States of Media
•Liquid •Semi solid •Solid
6 types of general culture media:
•Defined media  •Complex media  •Selective media  •Differential...
Physical States of Media  •Liquid:
–Water-based solution –Growth appears as cloudiness or turbidity
Physical States of Media Semisolid:
–Contains agar that thickens, but does not form a solid Used to determine motility
Physical States of Media Solid:
–Agar:  complex polysaccharide derived from algae –Will allow culture media to...
•Defined Media:
–Exact chemical composition is known –Used for organisms with strict need for specific...
•Complex media:
–Exact composition is not quite known –Yeast, meat, soy or protein extracts provide...
Selective Media:
•Contains substances that favor the growth of particular organisms or inhibit the...
Differential Media:
•Presence of visible changes in the media or differences in the appearance of colonies help differentiate...
Differential Media Blood agar-
differentiates between the ability of bacteria to digest, partially digest or inability to digest...
Differential Media Carbohydrate tubes:
differentiates between the ability to ferment types of sugars and the resulting products (acid or...
Differential Media MacConkey agar-
–selective for Gram – bacteria, differentiates between non-lactose and lactose fermenting Gram...
Anaerobic Media:
•Obligate anaerobes need to be cultured in the absence of oxygen –Agar Stab –Reducing media...
Transport Media:
•Special media to allow for transfer of clinical specimens –Prevent contamination...
Special Culture Techniques Animal and cell culture:  
Not all organisms will grow in media, need live cells or organism
Special Culture Techniques  •Enrichment culture:
–Selective media or technique to increase the growth of bacteria found in very small numbers...
•Preserving Cultures (3 steps):
–Refrigeration •Stores for short periods of time –Deep-freezing (-50°C to...
Microscopy:
Refers to the use of light or electrons to magnify organisms not visible with the unaided...
General Principles of Microscopy (4):
–Wavelength of radiation –Magnification –Resolution –Contrast
General Principles of Microscopy (4) Wavelength of Radiation:
•Using radiation of smaller wavelengths results in enhanced microscopy
General Principles of Microscopy (4) Magnification:
•Increase in the size of an object (number with X, read times) •Determined by multiplying...
General Principles of Microscopy (4) Resolution:
•Resolution or resolving power is the ability to distinguish between objects that are...
General Principles of Microscopy (4) Contrast:
•Refers to the differences in the intensity between two objects or between an object and...
Types of Microscopes (3)  Light Microscopes:
–Bright-field •Simple •Compound –Dark-field –Phase •Phase contrast •Differential interference...
Types of Microscopes (3)  Electron Microscopes:
–Transmission (TEM) –Scanning (SEM)
Types of Microscopes (3)  Probe Microscopes:
–Scanning Tunneling (STM) –Atomic Force (AFM)
Light Microscopy –Bright-field microscopes•Simple:
  –Contain a single magnifying lens –Similar to magnifying glass –Capable of...
Light Microscopy –Bright-field microscopes •Compound
–Series of lenses for magnification –Light passes through specimen into objective...
Light Microscopy –Dark-field microscopes:
•Best for observing pale objects •Only light rays scattered by specimen enter objective...
Light Microscopy  Phase microscopes:
•Used to examine living organisms or specimens that would be damage by attaching them to...
Phase microscopes (2 types)  Phase-contrast microscope:
»Simplest
Phase microscopes (2 types)  Differential interference contrast microscope (Normarski):
Involves prisms to split light into different colors, increasing contrast, 3Dappearance
Light Microscopy  Fluorescent microscopes:
•Direct a UV light source at specimen •Specimen emits visible light when bombarded...
Light Microscopy –Fluorescent microscopy •Confocal microscopes:
Use florescent dyes or antibobies- Uses UV lazer-Creates 3D image
Electron Microscopy:
–Electron microscopes have greater resolving power and magnification (10,000X to 100,000X)  –Detailed...
Two Types of Electron Microscopes  Transmission (TEM): 
–Specimen must be very thin –Electrons are sent through specimen, similar to that...
Two Types of Electron Microscopes Scanning (SEM):
–Specimen is coated with a metal –Electrons are sent across the surface of the specimen –Primary electrons...
Probe Microscopy:
–Magnifies more than 100,000,000 times –Detects individual molecules and atoms –Uses a...
2 Types Probe Microscopes Scanning tunneling microscopes:
•Probe is passed back and forth and slightly above specimen •Measures the flow of...
2 Types Probe MicroscopesAtomic force microscopes:
•Probe is passed along the surface of the specimen •Tip moves up and down with contour...
Staining, what does it do?
•Increases contrast and resolution by  coloring specimens with stains/dyes
Types of stains (4):
–Simple stains  –Differential stains •Gram stain •Acid-fast stain •Endospore...
Wet mount:
–Cells are suspended in liquid, one or two drops are added to slide, slide is overlaid with...
Hanging drop:
–Best for observing motility –Suspended cells are added to coverslip, coverslip...
How to prepare a specimen for staining:2 Steps
•Create a smear by spreading a thin sample of specimen on...
Simple Stains:
•Used to determine size, shape, and arrangement of cells •Composed of a single...
Differential Dyes:
•Used to distinguish between different types of cells or structures •Use more than...
Types of Differential Stains (3):
–Gram stain –Acid-fast -                 -Endospore
Gram Stain is used for:
•Used to differentiate between two large groups of microorganisms (Gram – and Gram...
Clinical Relevance of the Gram stain:  Presence of Gram negative organisms may indicate:
–Serious illnesses •Endotoxins are part of the outermost LPS layer in Gram – bacteria...
Gram positive bacteria:
–Final color: purple  –Thick layer of peptidoglycan in cell wall  –Retains...
Gram negative bacteria:
–Final color: red/ pink  –Much thinner layer of  peptidoglycan in cell wall  –Does...
Acid-Fast Stain:
-have hydrophobic layer  •Waxy layer of acid-fast bacterial cells will retain primary...
Endospore:
dehydrated structure formed inside a bacterial cell in response to harsh environmental conditions
Characteristics of Endospore (5):
–Usually found in Gram + cells  –Dormant, non-reproductive  –Tough...
Endospore Stain, what color does it stain?
•Malachite green is retained in spore •Vegetative (growing) cells will counterstain...
Special Stains  Negative (capsule) stain:
•Negative stains are repulsed by negative charges on cells •Stain the background...
Special Stains  Flagellar stain:
•Used to determine the presence, number, location and arrangement of flagella •Flagella are...
•Staining for Electron Microscopy
-stain in the form of a metal •Prevent electrons from passing through (TEM) •Excited by...


Upgrade and get a lot more done!
Upgrade