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Learning objectives

  • Identify and describe culture media for the growth of bacteria, including examples of all-purpose media, enriched, selective, differential, defined, and enrichment media

The study of microorganisms is greatly facilitated if we are able to culture them, that is, to keep reproducing populations alive under laboratory conditions. Culturing many microorganisms is challenging because of highly specific nutritional and environmental requirements and the diversity of these requirements among different species.

Nutritional requirements

The number of available media to grow bacteria is considerable. Some media are considered general all-purpose media and support growth of a large variety of organisms. A prime example of an all-purpose medium is tryptic soy broth (TSB) . Specialized media are used in the identification of bacteria and are supplemented with dyes, pH indicators, or antibiotics. One type, enriched media , contains growth factors, vitamins, and other essential nutrients to promote the growth of fastidious organisms , organisms that cannot make certain nutrients and require them to be added to the medium. When the complete chemical composition of a medium is known, it is called a chemically defined medium . For example, in EZ medium , all individual chemical components are identified and the exact amounts of each is known. In complex media , which contain extracts and digests of yeasts, meat, or plants, the precise chemical composition of the medium is not known. Amounts of individual components are undetermined and variable. Nutrient broth, tryptic soy broth, and brain heart infusion , are all examples of complex media.

Media that inhibit the growth of unwanted microorganisms and support the growth of the organism of interest by supplying nutrients and reducing competition are called selective media . An example of a selective medium is MacConkey agar . It contains bile salts and crystal violet, which interfere with the growth of many gram-positive bacteria and favor the growth of gram-negative bacteria , particularly the Enterobacteriaceae . These species are commonly named enterics, reside in the intestine, and are adapted to the presence of bile salts. The enrichment culture s foster the preferential growth of a desired microorganism that represents a fraction of the organisms present in an inoculum. For example, if we want to isolate bacteria that break down crude oil, hydrocarbonoclastic bacteria , sequential subculturing in a medium that supplies carbon only in the form of crude oil will enrich the cultures with oil-eating bacteria. The differential media make it easy to distinguish colonies of different bacteria by a change in the color of the colonies or the color of the medium. Color changes are the result of end products created by interaction of bacterial enzymes with differential substrates in the medium or, in the case of hemolytic reactions, the lysis of red blood cells in the medium. In [link] , the differential fermentation of lactose can be observed on MacConkey agar. The lactose fermenters produce acid, which turns the medium and the colonies of strong fermenters hot pink. The medium is supplemented with the pH indicator neutral red, which turns to hot pink at low pH. Selective and differential media can be combined and play an important role in the identification of bacteria by biochemical methods.

Questions & Answers

what is the size of virus
Beatrice Reply
What is the difference between TVC and Bioburden test
Mohamed
?
Mohamed
structure of bacteria and 10 types
Jennifer Reply
what is accidental host?
Domingo Reply
what is endomembrane system
Ikpi Reply
what is human anatomy
Ikpi
okay. Go ahead and ask
Blessing Reply
Industrial microbiology mcq
mohamed
Okay. What's your question?
Blessing
life arises from living matter or live organism.
Swami Reply
yes
sildra
I think live matter arises from non living matter
sildra
I dont think so...can u explain with an example
Manya
living maters made by non living matters
sildra
non living matters like stones? rocks?
Manya
eno
sildra
no
sildra
then?
Manya
cells are made by C N O minerals etc
sildra
I mentioned these as non living maters
sildra
that's all
sildra
cells are made up of those things but they originate from living things..
Manya
ok
sildra
Ok..good chat:-)
Manya
where are you from
sildra
thanks
sildra
India...u?
Manya
Tamil nadu
sildra
I am from Maharashtra
Manya
what about your studies
sildra
completed bsc.. preparing for msc entrance...wbu?
Manya
same
sildra
are you microbiologist
sildra
yes i am
Manya
good
sildra
what s the scope for micro in ur state?
Manya
did you find your college to higher studies
sildra
have to give an entrance exam for every college here...so lets c
Manya
food industries, medical lab, vaccine industries ,etc
sildra
hoping for pune University...wbu?
Manya
great!
Manya
is that centeral University right
sildra
what is your namr
sildra
hello
Udhaya
Hi
Maruf
Family kindly help me with this question? 1) Shortlist the configurative measurements of the following human anatomical ranges of÷ - Blood ( haemeglobin) in both male and female - Haematocytes in both male and female - Hepatocytes in both male and female - Lymphocyte / T. Lymphocytes in both male
Gifted
My names are Gift Mwale and am a Zambian. Kindly help me with this research which goes like this... 1) Shortlist the configurative measurements of the following human anatomical ranges of ÷ - Blood ( haemeglobin) in both male and female - Hepatocytes in both male and female - Haematocytes in both
Gifted
please what is the full meaning for TCDS
UDEME
from a single cell
Freedom
tcds means transcranial direct current stimulation...in this small electric currents are given to brain( specific parts) to help increase brain performance or to help with depression.. current should be in range 0.5-2.0mA
Manya
what's underlying disease relating unsanitary diet microorganism with the highest rate of epidemology solution and efficacy leading molecules elucidated structural solutions
feven
please can anybody talk about brain tumour and its cure.
BELLO Reply
enlargement of the thyroid gland resulting in over production of hormone.
Kamal Reply
What can u say on Thyroid Cancer?
Abdulkareem
Please, talk about the thyroid cancer.
BELLO
explain the Grave's disease
John Reply
what is cell
Avi Reply
is unit of life
Kamaluddeen
Ok
mohamed
who is an industrial microbiologist
Cynthia Reply
I want to know the biochemical composition of bacteria
Josh Reply
It contains peptidoglcon, DNA nd RNA
Asiya
what are Carrier protein
Ikpi
bacteriophage disadvantage
Momina Reply
disease due to __________ abnormalities are termed primary immunodeficiencies
Tayee Reply
Some primary immunodeficiencies are due to a defect of a single cellular or humoral component of the immune system.
Prince
Examples of primary immunodeficiencies include: chronic granulomatous disease, X-linked agammaglobulinemia, selective IgA deficiency etc
Prince
thank you
Nana
explain microbial mutation
Emerald
what is mutation
Cynthia Reply
alteration in genetic makeup
UDEME

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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