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Transformation

Frederick Griffith was the first to demonstrate the process of transformation . In 1928, he showed that live, nonpathogenic Streptococcus pneumoniae bacteria could be transformed into pathogenic bacteria through exposure to a heat-killed pathogenic strain. He concluded that some sort of agent, which he called the “transforming principle,” had been passed from the dead pathogenic bacteria to the live, nonpathogenic bacteria. In 1944, Oswald Avery (1877–1955), Colin MacLeod (1909–1972), and Maclyn McCarty (1911–2005) demonstrated that the transforming principle was DNA (see Using Microorganisms to Discover the Secrets of Life ).

In transformation , the prokaryote takes up naked DNA found in its environment and that is derived from other cells that have lysed on death and released their contents, including their genome, into the environment. Many bacteria are naturally competent, meaning that they actively bind to environmental DNA, transport it across their cell envelopes into their cytoplasm, and make it single stranded. Typically, double-stranded foreign DNA within cells is destroyed by nucleases as a defense against viral infection. However, these nucleases are usually ineffective against single-stranded DNA, so this single-stranded DNA within the cell has the opportunity to recombine into the bacterial genome. A molecule of DNA that contains fragments of DNA from different organisms is called recombinant DNA . (Recombinant DNA will be discussed in more detail in Microbes and the Tools of Genetic Engineering .) If the bacterium incorporates the new DNA into its own genome through recombination, the bacterial cell may gain new phenotypic properties. For example, if a nonpathogenic bacterium takes up DNA for a toxin gene from a pathogen and then incorporates it into its chromosome, it, too, may become pathogenic. Plasmid DNA may also be taken up by competent bacteria and confer new properties to the cell. Overall, transformation in nature is a relatively inefficient process because environmental DNA levels are low because of the activity of nucleases that are also released during cellular lysis. Additionally, genetic recombination is inefficient at incorporating new DNA sequences into the genome.

In nature, bacterial transformation is an important mechanism for the acquisition of genetic elements encoding virulence factor s and antibiotic resistance . Genes encoding resistance to antimicrobial compounds have been shown to be widespread in nature, even in environments not influenced by humans. These genes, which allow microbes living in mixed communities to compete for limited resources, can be transferred within a population by transformation, as well as by the other processes of HGT. In the laboratory, we can exploit the natural process of bacterial transformation for genetic engineering to make a wide variety of medicinal products, as discussed in Microbes and the Tools of Genetic Engineering .

Questions & Answers

what is arabinose operon and it's stucture
Pooja Reply
The L-arabinose operon, also called the ara or araBAD operon, is an operon required for the breakdown of the five-carbon sugar, L-arabinose, in Escherichia coli
Tharra
kya hum operon ko divide kar skate hain
Kartik
reactions if viruses to physical and chemical agents?
VICTOR Reply
All viruses contain the following two components: 1) a nucleic acid genome and 2) a protein capsid that covers the genome. Together this is called the nucleocapsid. In addition, many animal viruses contain a 3) lipid envelope. The entire intact virus is called the virion.
Asali
assume you have performed a gram stain on a sample of pus from a patients urethra. you see red, nucleated cells and purple rods. what can you conclude
Petty Reply
bacteria
ABUBAKAR
Study of micro organisation which we cannot see with naked eye...
shyam Reply
Despite their bad reputation, microbes are mostly beneficial or have a neutral effect on our lives. Microbiology is the scientific study of these microorganisms. Microorganisms are those organisms that are too small to see with the naked eye and include things like bacteria, fungi, and viruses.
Asali
yes
Dhirender
not 'things'...'organisms' like bacterias, viruses and fungi
Sinmi
simi, it's not bacterias but bacteria which is the plural form of the word while bacterium is the singular of it
Richard
bacterium is obvio in a singular form but plural of bacterium is bacterias
Sinmi
Richard is right it's bacterium which is the singular form and plural is bacteria. *Bacterias* doesn't exist.
Aakriti
what is microbiology?
Sandeep Reply
what is microbiology
Glory
is the study of small microorganisms that can't be viewed by our naked eyes under a microscope
Nabukwasi
it's the study of microbes their classification, diversity, their cellular structure and processes, their applications and interaction with other organisms.
Chaitanya
what is EMP pathway
rajesh
which organism is implicated in meningoencephalitis
Peter Reply
Herpes virus
Carlos
Yeah
Laxmi
which mold is called dairy mold?
Gopinath
mushroomm
Top
Geotrichum candidum
Gopinath
hi
bio
Hlw
Laxmi
which infectious agent is the smallest
Sinmi
spore or virus
Anushree
prion ....it is a single protein in a misfolded form..there is also a theory based on it
Sinmi
yup...m sry
Anushree
yes it can be turned as a virus
Sinmi
which gram positive bacteria is responsible for food poisoning?
Sinmi
prion is not a living organism yet it is infectoois why
Jeevan
prions are virus like organism. and it is a misfolded protein that may cause disease to us.
Tharra
Clostridium perfringens, B.cereus
Sneha
Who is the father of the biology
Dhirender
I have one more question. . that who is the father of botany and medicine? ? can any one tell
Dhirender
define polar bond in simple way
Rashmi Reply
when there is formation of positive and negative poles i.e. one atom is +ve and other is -ve which further results in the dipole moment. Such bond is know as polar bond. It is a convalent bond only.
Aakriti
Hi everyone, is these site only about microbiology? I want a site which I can download articles on hematological and biochemical profile
Peter Reply
I think it is only about micro biology.
Kimberly
so whats happening
Michael
I am about to enter school and am going for MCB
Olugbenga Reply
What is DNA damage and repair
Sree Reply
removal of nucleotide bases from DNA is damage n addition or insertion of bases in DNA is repair.
Rashmi
replication is a term related to generation of new DNA from a parental DNA.
Rashmi
role of microorganism as pathogens
Parteek Reply
to live inside the host body, reproduction n destroy the immune system of host body.
Rashmi
what is replication
rajesh
please give me ans
rajesh
replication is a term related to generation of new DNA from parental DNA.
Rashmi
difference between endotoxin and exotoxin
Binkheir Reply
toxins released inside the cell or a body is endotoxin n toxins released outside the cell or a body is exotoxin.
Rashmi
Generally, exotoxins are produced by gram positive bacteria and endotoxins are the integral part of the cell wall of gram negative bacteria. But some gram negative bacteria can also produced exotoxins such as E.coli.
Aakriti
Yeah u r ryt aakarti exotoxins screted by gram postive bacteria nd secreted by cell surface and they are secondary metabolites ....On the other hand endotoxin released by gram negtive bacteria nd released inside the cell (lipopolysaccharide) ..
Bharat
Heat stable lipopolysaccharides to be exact.
Aakriti
yup..
Bharat
please I want the names of bacteria and the diseases they cause.
Ibrahim Reply
there are many we classify it according to their shapes gram negative or gram positive
Tharra
so u may refer the book u guess or by when u want I can do a list for you and send u here
Tharra
😊
Tharra
please do a list for me
Ibrahim
I have the lost but it's too much to type ..
Tharra
MSc entrance prepare books and questions LA etha base pani irukum..
Guhan Reply
kushal always prescott is the imp book to follow.search some objective mcqs books based on your syllabus
deepthi Reply
I want to clear entrance of ms university so I have no more idea so my preparation is based on my bachlor studies.
Kushal
what are the opportunistic infection in aids stage
Kalkak
certain cancer or pneumonia 🤔
Kushal
Practice MCQ 4

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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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