Cultural Methods Flashcards
Why culture microorganisms?
-essential for understanding their properties and functions in the environment
-access to the material needed for detailed studies of their biology
What do culutre-independent methods rely on?
the knowledge from cultivated species for the design of DNA probes, validation of experimental protocols, and interpretation of results
Who pioneered the techniques of cultivation-based
winogradsky and beijerick
what is the disadvantage of culturing microorganisms
strongly underestimate the number of microbes in the environment and cannot quantify the true microbial diversity in nature
what percentage of bacteria population is culturable
<1%
What percentage does carbon constitute?
50% of dry weight
What percantage does N constitute?
13%
What are other macronutrients cells need in smaller amounts?
P, S, K, Mg
What are the two types of media?
defined and complex
What can culture media be in terms of growth
nonselective, selective, semi0selective and differential
what is selective media
inhibit growth of organisms other than the one being sought
what is differential media
contain a substance that certain bacteria change in a recognizable way
What is the benefit for differential media
media for rapid screening and ID of microorganisms use certain dyes and organic compounds that fluoresce under UV or produce distinctive
What is enrichment?
helps to grow a detectable population of cells from a very low initial level
What are enrichment techniques used for ?
recover injured microorganisms
What does selective enrichment do?
furthers the growth of the target while suppressing the competing microflora with temperature, antimicrobials, salts, acids, and metals
What does nitrobacter do?
oxidize NO2- to NO3- by the enzyme nitrite oxidoreductase with electrons
What is nitrobacter used for?
isolated using a multistep serial enrichment technique because
what is the purpose of isolation?
obtain isolated colonies. so that pure cultures of the target organism will be available for the identification tests
Why do preenrichment?
to allow the stressed target organism to resuscitate in either a non-selective or moderately selective medium
how much growth occurs during preenrichment?
very little
What are conventional microbiology procedures known by
-nature labor-intensive and time-consuming
what are the three areas of major improvement that have been achieved
1) sample preparation
2) separation and concentration of target cells
3) end detection
What is the countable range for plates?
25-250
what is dry rehydration method
petrifilms are ready-made culture medium systems
two plastic films coated with standard method nutrients , a water-soluble gelling agent, and a tetrazolium indicator that helps to enumerate colonies
what is spiral plater
special count grid, which relates the area of the plate to the sample volume
What does MPN stand for
Most probable number count
Which is the only agar media-based diagnostic kit system
enterotube II
what is the most widely used dehydrated media minikit
API
What is API 20E
has 20 small elongated wells with dehydrated media housed in a plastic panel
What do microtiter plates contain?
dehydrated media with different C, N, P, S substrates
What happens during incubation with microtiter plates
microorganisms oxidize substrates in the plates wells and simultaneously reduce colorless tetrazolium dye to a colored product
what are novel methodological developments
-improved soil dispersion protocol
-using dilute media
-replacing agar with gellan gum as a solidifying agent
-very long incubation times
-careful inspection of plates for barely visible colonies
-dilution-to-extinct approach that helps to isolate and protect slow-growing organisms
