Lab Methods Flashcards
(27 cards)
all purpose media
grows a broad range of microbes, usually non-synthetic
non-selective enriched media
Contains complex organic substances such as blood, serum, hemoglobin, or special growth factors to support the growth of most organisms (blood agar)
selective media
contains inhibitory substances that suppress the growth of all but ONE microorganisms
differential media
contains specific ingredients that allow the identification of an organism in a mixture
EX: addition of lactose and a pH indicator to detect lactose fermenting orgs.
specialized media
Contains nutrients that support the growth of specific organisms that may be fastidious or present in large mixtures of organisms
agar
- good solidifying agent
- withstands high temps and not digested by most microbes
pure culture
Population of cells derived from a single cell
-mixture of microbes in a sample, streak for isolated colonies, incubate, microbes become visible as isolated colonies
what are the types of methods involved in identifying microbes from samples
Culture methods phenotypic methods molecular methods immunological methods biochemical methods
culture methods
growth in specific type of media
phenotypic methods
(microscopy) cell and colony morphology, cell staining characteristicis
molecular methods
detection of specific bacterial nucleic acids by PCR or bacterial proteins 16S ribosome sequencing
- Does NOT require isolation of the microorganism
- Rapid diagnosis
immunological methods
detection of specific bacterial antigens or of human antibody response to a specific bacterial antigen
biochemical methods
tests to determine an organisms chemical and metabolic characterisitic
how does a biochemical test work
Microbe is cultured in media with special substrate and then tested for a particular end product
-enzyme present –> product formed
how is 16s rRNA used to identify bacteria
- it’s present in all bacteria, gene contains both highly conserved and more variale regions
- use primers directed at conserved regions but flanking variable regions –> amplify 16s rRNA using PCR –> BLAST the sequence –> Genbank
Types of visible light microscopy
Bright field
Dark field
Phase contrast
Bright field
- most common in lab
- stains increase contrast but kill microbes
- cells appear DARK against a light background
dark field
- visualize living organisms
- cells appear as bright against dark background
phase contrast
-visualize intracellular structures in live specimens
UV rays as source of illumination
fluorescent
Fluorescent microscopy
- UV rays
- dyes often attached to antibodies
- diagnosis of specific bacteria and protozoans
Electron beam image microscopy
TEM
SEM
- Highest magnification
- viruses, bacteria, internal cellular structures
TEM
- detailed structures of cells
- viruses
- ultra thin sections
SEM
- electron beam scans back and forth over surface of metal coated specimen
- detailed 3D image
- surface details
