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A long strand of DNA shows RNA polymerase bound to a promoter upstream of gene A. Many various shapes are attached to the promoter and RNA polymerase. These are transcription factors and mediator proteins. These also bind to distant regions of DNA called distal control elements and activators. This requires DNA to bend (so the distant regions can reach the promoter). This bending is due to a DNA bending protein.
In eukaryotes, an enhancer is a DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements. Activators bound to the distal control elements interact with mediator proteins and transcription factors. Two different genes may have the same promoter but different distal control elements, enabling differential gene expression.

Dna-level control

In eukaryotes, the DNA molecules or associated histones can be chemically modified in such a way as to influence transcription; this is called epigenetic regulation . Methylation of certain cytosine nucleotides in DNA in response to environmental factors has been shown to influence use of such DNA for transcription, with DNA methylation commonly correlating to lowered levels of gene expression. Additionally, in response to environmental factors, histone proteins for packaging DNA can also be chemically modified in multiple ways, including acetylation and deacetylation, influencing the packaging state of DNA and thus affecting the availability of loosely wound DNA for transcription. These chemical modifications can sometimes be maintained through multiple rounds of cell division, making at least some of these epigenetic changes heritable.

  • What stops or allows transcription to proceed when attenuation is operating?
  • What determines the state of a riboswitch?
  • Describe the function of an enhancer.
  • Describe two mechanisms of epigenetic regulation in eukaryotes.

Resolution

Although Mark survived his bout with necrotizing fasciitis, he would now have to undergo a skin-grafting surgery, followed by long-term physical therapy. Based on the amount of muscle mass he lost, it is unlikely that his leg will return to full strength, but his physical therapist is optimistic that he will regain some use of his leg.

Laboratory testing revealed the causative agent of Mark’s infection was a strain of group A streptococcus (Group A strep). As required by law, Mark’s case was reported to the state health department and ultimately to the Centers for Disease Control and Prevention (CDC). At the CDC, the strain of group A strep isolated from Mark was analyzed more thoroughly for methicillin resistance.

Methicillin resistance is genetically encoded and is becoming more common in group A strep through horizontal gene transfer. In necrotizing fasciitis, blood flow to the infected area is typically limited because of the action of various genetically encoded bacterial toxins. This is why there is typically little to no bleeding as a result of the incision test. Unfortunately, these bacterial toxins limit the effectiveness of intravenous antibiotics in clearing infection from the skin and underlying tissue, meaning that antibiotic resistance alone does not explain the ineffectiveness of Mark’s treatment. Nevertheless, intravenous antibiotic therapy was warranted to help minimize the possible outcome of sepsis, which is a common outcome of necrotizing fasciitis. Through genomic analysis by the CDC of the strain isolated from Mark, several of the important virulence genes were shown to be encoded on prophages, indicating that transduction is important in the horizontal gene transfer of these genes from one bacterial cell to another.

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Key concepts and summary

  • Gene expression is a tightly regulated process.
  • Gene expression in prokaryotes is largely regulated at the point of transcription. Gene expression in eukaryotes is additionally regulated post-transcriptionally.
  • Prokaryotic structural genes of related function are often organized into operons , all controlled by transcription from a single promoter. The regulatory region of an operon includes the promoter itself and the region surrounding the promoter to which transcription factors can bind to influence transcription.
  • Although some operons are constitutively expressed , most are subject to regulation through the use of transcription factors (repressors and activators). A repressor binds to an operator , a DNA sequence within the regulatory region between the RNA polymerase binding site in the promoter and first structural gene, thereby physically blocking transcription of these operons. An activator binds within the regulatory region of an operon, helping RNA polymerase bind to the promoter, thereby enhancing the transcription of this operon. An inducer influences transcription through interacting with a repressor or activator.
  • The trp operon is a classic example of a repressible operon . When tryptophan accumulates, tryptophan binds to a repressor, which then binds to the operator, preventing further transcription.
  • The lac operon is a classic example an inducible operon . When lactose is present in the cell, it is converted to allolactose. Allolactose acts as an inducer, binding to the repressor and preventing the repressor from binding to the operator. This allows transcription of the structural genes.
  • The lac operon is also subject to activation. When glucose levels are depleted, some cellular ATP is converted into cAMP, which binds to the catabolite activator protein (CAP) . The cAMP-CAP complex activates transcription of the lac operon. When glucose levels are high, its presence prevents transcription of the lac operon and other operons by catabolite repression .
  • Small intracellular molecules called alarmones are made in response to various environmental stresses, allowing bacteria to control the transcription of a group of operons, called a regulon.
  • Bacteria have the ability to change which σ factor of RNA polymerase they use in response to environmental conditions to quickly and globally change which regulons are transcribed.
  • Prokaryotes have regulatory mechanisms, including attenuation and the use of riboswitches , to simultaneously control the completion of transcription and translation from that transcript. These mechanisms work through the formation of stem loops in the 5’ end of an mRNA molecule currently being synthesized.
  • There are additional points of regulation of gene expression in prokaryotes and eukaryotes. In eukaryotes, epigenetic regulation by chemical modification of DNA or histones, and regulation of RNA processing are two methods.

Fill in the blank

The DNA sequence, to which repressors may bind, that lies between the promoter and the first structural gene is called the ________.

operator

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The prevention of expression of operons encoding substrate use pathways for substrates other than glucose when glucose is present is called _______.

catabolite repression

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Short answer

What are two ways that bacteria can influence the transcription of multiple different operons simultaneously in response to a particular environmental condition?

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Questions & Answers

a.o.a can u please tell me five name of Gram +be bacteria
Tahira Reply
a.o.a...please send me five name of Gram +ve bacteria
Tahira
a.o.a...please send me five name of Gram +ve bacteria
Tahira
a.o.a...please send me five name of Gram +ve bacteria
Tahira
staphylococcus ,streptococcus,lactobacillus,mycobacterium,clostridium, bacillus,enterococcus.
Nadiya
thank u so much
Tahira
1. Staphylococci 2. Mycobacterium tuberculosis 3. Bacillus anthrasis 4. Chlostridium 5. Diplococci
praveen
gram -ve mn knsy hn
Tahira
pseudomonas
Nadiya
wo bhi 5 hon
Tahira
salmonella,proteus,shigella,neisseria
Nadiya
wo bhi 5 hon
Tahira
Nadiya ap kia krti hn?
Tahira
bsc microbiology final year
Nadiya
1. Neisseria gonohorreae 2. E.coli 3. Salmonella typhi 4. Klebsiella pneumonia 5. Shigella dysenteriae
praveen
1. Neisseria gonohorreae 2. E.coli 3. Salmonella typhi 4. Klebsiella pneumonia 5. Shigella dysenteriae
praveen
1. Neisseria gonohorreae 2. E.coli 3. Salmonella typhi 4. Klebsiella pneumonia 5. Shigella dysenteriae
praveen
MSc zoolgy. 1st semester
Tahira
B.Sc microbiology 1st year
praveen
good
Tahira
mn vu sy hoon and u?
Tahira
davv
Nadiya
Vijaya College,R.V.Road,Basavangudi Bangalore-560004
praveen
oh!! bht khub
Nadiya
hi
Nouman
how are u
Nouman
thank u friend
Nouman
please define classification of bacteria
Nouman
calssification of bacteria are of 3 types: ●.on the basis of shap:1.spirilla 2.bacilli 3.cocci ●in the basis of gram stain : 1.gram -ve 2.gram +ve ●on the basis of oxygen demand: 1.aerobic 2.anaerobic.
Nadiya
detail se please
Nouman
paresention hai iseley
Nouman
jo bacteria hote hai pehle to woh 3 tarha se unka classification kiya jata hai .pehle y ki shape kya hai ....lakin shape hum tab hi define kar payenge jab hum unhe pehchanenge ki bacteria ko kaise jane ki woh kaise hote hai or unka classification kaise hota hai
Nadiya
to hum gram staining karte hai
Nadiya
gram staining ek aaisi technique hoti hai jise hun 2 large group m devide karte hai
Nadiya
or differenciate karte hai bacteria ko
Nadiya
based on thir diff. cell wall constituents
Nadiya
gram staining ko 2 procedure mai distinguish between kiya gaya hai
Nadiya
gram positive and gram negative
Nadiya
phir
Nouman
gram +ve and gram -ve groups by colouring these cells red or violet colour.
Nadiya
red jo cells hogi woh pink bhi ho sakti h because stains ki wajah se uski quantity ki wajah se
Nadiya
gram positive bact.stain violet due to presence a thick layer of a peptidoglycon in theri cell walls are stained with.. or gram -ve bact.stain red .which is attribute to a thinner peptidoglycan wall.
Nadiya
ab hum unhe identify karenge microscope mai
Nadiya
then fir hum identify karte karte hum shape dekhenge
Nadiya
gram positive cocci or rod shaped k honge .or garm negative cocci or rods or spirochaetes honge .......lakin inke colour ki wajah se hum pehchanenge ki red or pink aaya to gram negative .or agar violet aaya to positive
Nadiya
ok?
Nadiya
fir
Nouman
or bhi types k hote hai bacteria jaise sphirical "cocci",rod "bacilli",spiral"spirilla",comma shape k jo honge woh"vibrio",or corkscrew shape k jo honge woh "spirochaetes.
Nadiya
fir
Nouman
or oxygen k basis pr dekhenge agar apan to woh :aerobic jo o2 ki presence m honge or anaerobic jo honge woh without oxygen ki presence mai servive karenge .sabhi micro organisms banate h energy cellular respiration k through. lakin aerobic and anaerobic k basis pr bhi diffrenciate hote hai yeh .
Nadiya
Streptococcus Staphylococcus Corynebacterium Clostridium
Srinivas
yeh 3no calssification batadiye detail mai ab aap net p or seach kar le
Nadiya
fir
Nouman
ok thank u so much
Nouman
کتنے پیارے اور چھوٹے سے خواب ہیں آپ کے ۔ الله پاک آپ کے سپنے سچ اور پورے کرے ۔ آمین ۔۔۔۔۔۔۔۔۔۔۔💝
Nouman
my pleasure!
Nadiya
acha ji ap ho kaha se
Nouman
Hyderabad
Srinivas
telangana
Srinivas
Can hiv virus survive in mosquitoes?
Mad
hiv virus cannot survive in mosquitoes.
Nadiya
Lol
Number
What,s the correct answer?
Nadiya
:-)
Nadiya
We will also know?what's the right answer !
Nadiya
Good going people
Number
Ok tell me all the conditions where a gram positive organism appears wrongly as gram negative organism in microscopy
Number
Staphylococcus Listria 2.Streptomyces 3. Streptococcus 4. Clostridium 5. Propionibacteriu
Basem
We know answer!
Lovely
ok
Basem
but you tell me first :can hiv virus survivr in mosquitoes? i dont know what's the correct answer !
Nadiya
No it can't.... Coz retroviruses require CDt4 receptors for replication which aren't found in mosquitoes
Number
Samjhi?
Number
yaaaa .......jazakallah !
Nadiya
well done doc.!
Nadiya
Good
Number
scale up fermentation ? define plz !
Nadiya
U can find all these answers easily on Web. Discuss something which is unique
Number
what is the gram negative
Xaviery Reply
what is enzyme immobilizatio ?
Nadiya Reply
the process of decreasing the rate of enzyme activity.
Edward
shukriya edward knevy .thnks .
Nadiya
sorry thi one is about enzyme inhibition
Edward
enzyme immobization is imprisonment of enzyme in a matrix.
Edward
i am confused
Nadiya
about what
Edward
ok .....i understood ur last one msg .
Nadiya
thanks .
Nadiya
Hallow
Chimo
my pleasure
Edward
can you helpe me please 🤗🤗
Chimo
?
Nadiya
but why
Nadiya
imuhhe patta nhi aapka ki aap kon ho to mai kaise no. send karu aapko or kyu karu ? wajaah to bataaa .
Nadiya
mujhe pata nhi
Nadiya
I want to learn microbiology
rakesh
this app is very benifit to learn microbiology .
Nadiya
Man Topics for Microbiology
rakesh
Please tell me
rakesh
first.u clear ur basic concept in microbiology .
Nadiya
Secondly what should you do
Nancy
u can start ur studies in book by dubey and maheshwari author.
Nadiya
what is primary and secondary screening ?
Nadiya Reply
which scope in the field of dmlt corse ? snd plz explain your experiences with me !
Nadiya
Country?
Number
india
Nadiya
Depends on place
Number
your birth place ?
Nadiya
whats your profession ?
Nadiya
scope of microbiolgy?
Nadiya
Clinical microbiologist
Number
M a doctor
Number
Dmlt isn't that good in india
Number
Bakwas hai
Number
but why ?
Nadiya
whats ur counter plz give m answer ?
Nadiya
Coz i know
Number
Saturation
Number
oh .i get it.
Nadiya
but what choose i ?in this field?
Nadiya
Hmm
Number
Wats ur basic qualification
Number
Good evening all
Ngozi
microbiology
Nadiya
evening
Dennis
good evening 2 u
Nadiya
What microbiology?
Number
bsc final year in micro.......
Nadiya
Do msc n PhD then.... Its better than dmlt n ll
Number
but i dont do this
Nadiya
what Cadillac
Topcy
number@......u r a doctor ?
Nadiya
really
Nadiya
plz explain the defination of scale up of fermentation ?
Nadiya
how do micro biology aids pharmacy
Dennis Reply
please check Google.
Nadiya
bcz very interested topic are able in goggle site
Nadiya
I'm Jeremiah what are the step that involved Gram staining
Jeremiah Reply
place slide with heat fixed smear on staining
Nadiya
smear with crystal violet and let stand for 1 min
Nadiya
and then after 1 min gently wash rinse with tap water...than smear the grams idone and stand for 1 min
Nadiya
again rinse with tap water.then,rhe smear will appear as a purple circle on the slide
Nadiya
then ,decolarize 95%with ethyl alcohol and acetone .till the slide slightly and apply tge alcohol deop by drop for 5 to 10 sec.
Nadiya
and then the alcohol until runs the almost clear .carefully not to over decolorization
Nadiya
immideatly rinse with water.
Nadiya
view the smear using a light microscope under oil immersion
Nadiya
and then complete 😊
Nadiya
.
Nadiya
what is the relation between aspergillus and vinegar.
Asad
can anyone send me the procedure of using autoclave.
Asad
yeh i will....but i can send a site on google !then u can read easily and understand it the procedure of autoclave ? ok .
Nadiya
***google autoclave procedure.
Nadiya
and u write in google site ......procedure of using an autoclave
Nadiya
can anyone send me the calculation and formula for spread plate technique cfu/ml
Ankita
@Nadiya... I think u have missed the last step of gram staining after decolonization with alcohol we have to counter stain it with either basic fucshin Or Saffranin.
Ankita
yaa ofcourse ...thank u so much ankitaa.
Nadiya
hi asghar
Nadiya
who are u ? and where are u live from ?
Nadiya
Ideally we should use 5 second technique while making one slide of Grams stain
Number
what is scale up of fermentation ?
Nadiya
the most commonly used microorganisms in alcohol fermentation is?
Shaikh Reply
Saccharomyces cerevisiae
Online
saccharomyses
Nadiya
Yeast is the most commonly used microorganism for ethanol productionby fermentation. ... Besides S. cerevisiae, other examples of yeastsused for ethanol production are Schizosaccharomyces pombe, Kluyveromyces lactis, Candida spp., Pichia spp that are able to ferment...
bazi
Ethanol fermentation using the hydrolysate obtained after the saccharification of biomass is the last step in lignocellulosic bioethanol production process. The hydrolysate contains large amount of fermentable sugars that can be directly used by the ethanologenic microorganisms. Yeast is the most co
Najeebul
saccharomyces
Nadiya
yeast
Nadiya
yeast
Veronica
A.o.a aspergillus aur vinegar ka kia relation he.?
Asad
Hmm
Number
what is difference between primary host and secondary host ?
Edward
what is primary screening and secondary screening ....hmm?
Nadiya
primary and secondry host ...best example of female anaPhilis .and disease -maleria !
Nadiya
i am asking about difference not example
Edward
Primary host- the host in which the adult parasite lives, and reproduces sexually. Secondary host- the host in which the immature forms of parasite lives
bazi
primary host -the host in which the adult parasite lives ,and reproduces sexually.and the second host -host in which the immature forms of parasite lives. okyyyy?
Nadiya
synthesis of DNA from a single strand of RNA
Veronica Reply
In this initially , a single stranded RNA is taken into a eppendorff tube as a template for synthesis of Double stranded DNA and dNTPs are added along with reverse transcriptase enzyme . All should be placed in buffered solution. Then above mixture is run on RTPCR machine.
Ravikumar
In which initially double stranded RNA- DNA hybrid is formed and later multiple copies of Double stranded DNA is Formed in number of cycles.
Ravikumar
exactly
Nadiya
what is a virus?
abdulwali Reply
What is DNA transcription
abdulwali
virus is not a bacteria ...it is present in our body fluid .the protein are not composed and work in a proper manner the virus present quikly .
Nadiya
i refer a book name .u find ur question answers .12 or 11th book
Nadiya
DNA trancription is a process the imfirmation are transfer into dna to dna and dna to rna is called dna transcription
Nadiya
in other words,dna transcription ,:in thich a particular segment of dna is copied into rnaand especially mRNA by the enzyme rna polymerase .
Nadiya
why most virus are of RNA genome?
Mika Reply
Good Question❓
MALESELA
its due to their fastidious nature.
Kwame
enlist types of bacteria on tha basis of arrangement of tha flagella
Mihir Reply
monotrichous:vibrio cholerae, amphitrichous,lophotrichous,and last peritrichous.
Nadiya
econom emportance of bacteria
Japhet Reply
We can get agar which is used in microbiological media
Kashif
cause disease
Mika
industrial use.
Nadiya
what is microbiology
Anil Reply
what is bacteriology
Anil
vaccine chapter notes give me
Ambika
In bacteria
Kashif
the study of bacteria
Zaajid
microbiology the study of small living thinks that can not seen by the eye
Zaajid
Only micro organism can be studied in microbiology
Kashif
no some of microbiology study of smll living things that cn not be sen by the eye
Zaajid
kashif qamar do you known micro micro means small
Zaajid
Ya but microbiology is a broad term which is not only for small but in this there are some alge and funji that canbbe studied here
Kashif
ya!!! I have a qz what is different btn virulence and virus
Kurwa
so this means, it is the study of microorganisms and their importance.
Kwame
virulence means their level of infection or how infectious a viron is. virus is an intracellular obligates or fastidious organism(parasites) that cannot be filtered with a biological filter and cause harm to it host.
Kwame
so what brought about the study of microbiology
anawuje
Hi guys what is life.... Basic definition require
Kashif
life is the situation of an living organism to survive in a certain condition as host or parasite also life it include commonly living organism that have ability to survive bt life do not include dead organism .
Kurwa
hello explain ways in which gene expression is controlled in a eukaryotic cell...
Cotilda
gene expression how? please come clear!
Kwame
please what does a lady with G6PD result "Partial Defect" signifies?
Kwame
please what is nosocomia infection
Kwabena
nosocomia infection is the infection that are obtained from the hospital or the environment eg TB
Timothy
what is the microbiology
Moha
i think study of all microbes or micro oraganisms
abdul
The branch of that deals with micro organisms
Katta
Koch postulate
Suraju
study of microorganisms
Mika
microbilogy is a study of microbes and microorganisms ...we cannot seen with the naked eyes.
Nadiya
and they can cause many types of diseases .they are benificial and harmful......overall ..microbiology is the study of micro organinsm
Nadiya
study of bacteria is called becteriology.
Nadiya
What is the name of the bacteria cell that stop the replication of DNA
adebisi Reply
onyii
Chisom
Hi this s saroja from hyd
Katipogu
ESBL ARTICLE
Katipogu
What s the reference book for Esbl
Katipogu
hello. who likes microbs? :)
Bahadir
is there any injectable vit. B cmplex?! hi there to all group chatter...
Josearnel
what is the reference book of this course?
Syarifa Reply
Do u want an undergraduate book or a postgraduate book
Number
please what does a woman with G6PD result' Partial Defect means?
Kwame
Evans this ll mean that the person has theG6PD is small in the blood and can still not take drugs with sulphur content
rita
Evans this ll mean that the G6PD defeat is small in the blood and can still not take drugs with sulphur content
rita
wow
Blessing
have Miss a lot can I get a teacher to teach me
Blessing
undergraduate book, please! @number seven
Syarifa
antigen and antibody reaction chapter notes
Ambika
what will happen if the person should take a drug with sulphur content
ignatius
@syarifa u can consult jawetz, levinsons, ananth narayan or a new book recommended by konemans... Medical microbiology by Apurbo shankar shastry
Number
A.h Patel
Nadiya
pelzar
Nadiya

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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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