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Resolution

Within 24 hours, the results of the diagnostic test analysis of Alex’s stool sample revealed that it was positive for heat-labile enterotoxin (LT) , heat-stabile enterotoxin (ST) , and colonization factor (CF) , confirming the hospital physician’s suspicion of ETEC . During a follow-up with Alex’s family physician, this physician noted that Alex’s symptoms were not resolving quickly and he was experiencing discomfort that was preventing him from returning to classes. The family physician prescribed Alex a course of ciprofloxacin to resolve his symptoms. Fortunately, the ciprofloxacin resolved Alex’s symptoms within a few days.

Alex likely got his infection from ingesting contaminated food or water. Emerging industrialized countries like Mexico are still developing sanitation practices that prevent the contamination of water with fecal material. Travelers in such countries should avoid the ingestion of undercooked foods, especially meats, seafood, vegetables, and unpasteurized dairy products. They should also avoid use of water that has not been treated; this includes drinking water, ice cubes, and even water used for brushing teeth. Using bottled water for these purposes is a good alternative. Good hygiene (handwashing) can also aid the prevention of an ETEC infection. Alex had not been careful about his food or water consumption, which led to his illness.

Alex’s symptoms were very similar to those of cholera , caused by the gram-negative bacterium Vibrio cholerae , which also produces a toxin similar to ST and LT. At some point in the evolutionary history of ETEC , a nonpathogenic strain of E. coli similar to those typically found in the gut may have acquired the genes encoding the ST and LT toxins from V. cholerae . The fact that the genes encoding those toxins are encoded on extrachromosomal plasmids in ETEC supports the idea that these genes were acquired by E. coli and are likely maintained in bacterial populations through horizontal gene transfer.

Go back to the previous Clinical Focus box.

Viral genomes

Viral genomes exhibit significant diversity in structure. Some viruses have genomes that consist of DNA as their genetic material. This DNA may be single stranded, as exemplified by human parvoviruses , or double stranded, as seen in the herpesviruses and poxviruses . Additionally, although all cellular life uses DNA as its genetic material, some viral genomes are made of either single-stranded or double-stranded RNA molecules, as we have discussed. Viral genomes are typically smaller than most bacterial genomes, encoding only a few genes, because they rely on their hosts to carry out many of the functions required for their replication . The diversity of viral genome structures and their implications for viral replication life cycles are discussed in more detail in The Viral Life Cycle .

  • Why do viral genomes vary widely among viruses?

Genome size matters

There is great variation in size of genomes among different organisms. Most eukaryotes maintain multiple chromosomes; humans, for example have 23 pairs, giving them 46 chromosomes. Despite being large at 3 billion base pairs, the human genome is far from the largest genome. Plants often maintain very large genomes, up to 150 billion base pairs, and commonly are polyploid, having multiple copies of each chromosome.

The size of bacterial genomes also varies considerably, although they tend to be smaller than eukaryotic genomes ( [link] ). Some bacterial genomes may be as small as only 112,000 base pairs. Often, the size of a bacterium’s genome directly relates to how much the bacterium depends on its host for survival. When a bacterium relies on the host cell to carry out certain functions, it loses the genes encoding the abilities to carry out those functions itself. These types of bacterial endosymbionts are reminiscent of the prokaryotic origins of mitochondria and chloroplasts.

From a clinical perspective, obligate intracellular pathogens also tend to have small genomes (some around 1 million base pairs). Because host cells supply most of their nutrients, they tend to have a reduced number of genes encoding metabolic functions. Due to their small sizes, the genomes of organisms like Mycoplasma genitalium (580,000 base pairs), Chlamydia trachomatis (1.0 million), Rickettsia prowazekii (1.1 million), and Treponema pallidum (1.1 million) were some of the earlier bacterial genomes sequenced. Respectively, these pathogens cause urethritis and pelvic inflammation, chlamydia, typhus, and syphilis.

Whereas obligate intracellular pathogens have unusually small genomes, other bacteria with a great variety of metabolic and enzymatic capabilities have unusually large bacterial genomes. Pseudomonas aeruginosa , for example, is a bacterium commonly found in the environment and is able to grow on a wide range of substrates. Its genome contains 6.3 million base pairs, giving it a high metabolic ability and the ability to produce virulence factors that cause several types of opportunistic infections .

Interestingly, there has been significant variability in genome size in viruses as well, ranging from 3,500 base pairs to 2.5 million base pairs, significantly exceeding the size of many bacterial genomes. The great variation observed in viral genome sizes further contributes to the great diversity of viral genome characteristics already discussed.

 A graph showing genome sizes. Viruses have genomes that range from 1.7x10 to the 2nd bp to 2.5x10 to the 6th bp. Bacteria have genomes that range in size from 10 to the 5th to 10 to the 7th. One example is E. coli which ranges from 4.6 to 5.6 x 10 to the 6th bp. Fungi have genomes that range from 10 to the 6th to 10 to the 8th bp. Saccharomyces cerevisiae (yeast) has a genome of 1.2 x 10 to the 7th bp. Plants and animals have genomes that range from 10 to the 6th to 10 to the 11th bp. Mammals range from 10 to the 9th to 10 to the 10th bp. Humans have a genome of 3 x  10 to the 9th.
There is great variability as well as overlap among the genome sizes of various groups of organisms and viruses.

Key concepts and summary

  • The entire genetic content of a cell is its genome .
  • Genes code for proteins, or stable RNA molecules, each of which carries out a specific function in the cell.
  • Although the genotype that a cell possesses remains constant, expression of genes is dependent on environmental conditions.
  • A phenotype is the observable characteristics of a cell (or organism) at a given point in time and results from the complement of genes currently being used.
  • The majority of genetic material is organized into chromosomes that contain the DNA that controls cellular activities.
  • Prokaryotes are typically haploid, usually having a single circular chromosome found in the nucleoid. Eukaryotes are diploid; DNA is organized into multiple linear chromosomes found in the nucleus.
  • Supercoiling and DNA packaging using DNA binding proteins allows lengthy molecules to fit inside a cell. Eukaryotes and archaea use histone proteins, and bacteria use different proteins with similar function.
  • Prokaryotic and eukaryotic genomes both contain noncoding DNA , the function of which is not well understood. Some noncoding DNA appears to participate in the formation of small noncoding RNA molecules that influence gene expression; some appears to play a role in maintaining chromosomal structure and in DNA packaging.
  • Extrachromosomal DNA in eukaryotes includes the chromosomes found within organelles of prokaryotic origin (mitochondria and chloroplasts) that evolved by endosymbiosis. Some viruses may also maintain themselves extrachromosomally.
  • Extrachromosomal DNA in prokaryotes is commonly maintained as plasmids that encode a few nonessential genes that may be helpful under specific conditions. Plasmids can be spread through a bacterial community by horizontal gene transfer.
  • Viral genomes show extensive variation and may be composed of either RNA or DNA, and may be either double or single stranded.

True/false

Within an organism, phenotypes may change while genotypes remain constant.

True

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Noncoding DNA has no biological purpose.

False

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Fill in the blank

Plasmids are typically transferred among members of a bacterial community by ________ gene transfer.

horizontal

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Short answer

What are some differences in chromosomal structures between prokaryotes and eukaryotes?

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How do prokaryotes and eukaryotes manage to fit their lengthy DNA inside of cells? Why is this necessary?

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What are some functions of noncoding DNA?

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In the chromatin of eukaryotic cells, which regions of the chromosome would you expect to be more compact: the regions that contain genes being actively copied into RNA or those that contain inactive genes?

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Questions & Answers

can i use the graph of bacterial growth for my master's thesis?
Christoph Reply
facultative anaerobic bavteria gives uniform turdibity in nutrient broth why?
Princess Reply
oils and waxes are not sterilized in autoclave
Princess
what is the function of paraffin
Muhammad
@ MAHI because they can grow all over the media from surface to the bottom as they can utilize oxygen or conduct fermentation in its absence.
Online
2.@MAHI Autoclave uses steam under pressure. The steam cannot penetrate through oil and wax. Thus, dry heat sterilization is preferred than autoclave .
Online
thnku
Nadiya
how nutirent agar can converted into blood agar
Princess
thank you
Princess
take a nutrient agar ........and add 5ml blood and put in it ...........!
Nadiya
nutrient agar +blood 5ml+ distilled water =blood agar .
Nadiya
mixed wellllll
Nadiya
what are the five predisposing factors of opportunistic infections
Asher Reply
1. long term exposure to diseases, that the body immunity weakens.
prosper
2. Nature Of some diseases to weaken body immunity such as, AIDS.
prosper
3. Use of immuno-suppresive drugs.
prosper
anyone... need a hand here 🙋😞
prosper
Low immune is the major cause eg for kaposis sarcoma
Davismith
suitable conditions e.g temp,
Muhammad
what os gnormal flora
kifayat Reply
morphological and genetic classification of bacteria
Potter Reply
what is the morphogical
Bupe
h
Sudhir
morphologycal is defined as relating to the branch of biology that deals with the form of living organisms,and with relationship between their structures.
Nadiya
relating to the form or structure of things .
Nadiya
what is the meaning of lessions
oluwa
i am frim Afghanistan.
wahidullah Reply
iam from iraq
Haidar
and i'm from pakistan
Muhammad
Nice
Amina
what's about the qualification
Muhammad
Hlo
Asiya
Hmm
Number
Almustafa Muhammad from Nigeria
Mujtafa
am ustaz Abdulsalam from Ghana
ustaz
am Bupe Chifita from Zambia
Bupe
what is microbiology
Bupe
is the study of invisible micro organism
Mujtafa
microbiology is the study of very too small organisms which we can't see with naked eyes ......in other words ....study of microorganism is called microbiology.
Nadiya
Hello! How Can Microorganisms Be Isolated From The Skin?.. 5 ways if possible. (briefly)
prosper
from skin swabbing is the prefer method worldwide
Muhammad
thanks Muhammad Nauman very much!
prosper
hi
Meek
hi Meek
prosper
are there any other ways pals?
prosper
hi prosper
Meek
hello Meek Mild.
prosper
Any question or ideas, Meek?😊
prosper
and if a patient have any blister or abscess on the skin then first cut the blister or abscess. inside material is taking by syringe.
Muhammad
in case of fingernail or toenails simply cut a small piece of nail and culture on the appropriate media at a required temperature and time
Muhammad
Again, thanks Mr. Muhammad! I appreciate the help.
prosper
you welcom prosper 😊
Muhammad
what are the media use for skin swab?
Sieh-Mlanwin
blood and macckonkey mostly usededia for skin bacteria
Muhammad
used media*
Muhammad
@ SIEH mostly fungal infection occurs in skin so SDA ( Sabouraud Dextrose Agar) or MEA ( Malt extract agar) are common.
Online
thanks
Sieh-Mlanwin
Microbiologicam source of vitamins
Bachi Reply
what do you mean?
Md
that's example?
Md
hi everyone
Muhammad
such as. c/s media
Md
hmm hlw
Md
just tell me about that ?
Md
where are u from
Muhammad
history of Bactolagy?
Piyush Reply
ask me any question you want on microbiology
Norbuqaari Reply
what is scale up fermenter ? and whict bectetia is benifited in industrial microbilogy ?
Nadiya
can u explain to me wts the meaning of autoclave,and how it doing and ,wt r the equipment to need to do it?
chandi
stem heat under pressure
Nadiya
thnks
chandi
autoclave is a steam heat under pressure .it is use to sterilize the equipment, agar ,petridish broth liquid and many more things....to kill the microbes.......free from microbes
Nadiya
nadiya Scale up studies refers to the act of using results obtained from laboratory studies for designing a prototype and a pilot plant process. do you agree or
Norbuqaari
bectetia is benifited in industrial microbilogy is lactobacilli
Norbuqaari
and
Nadiya
chandi. strong heated container used for chemical reactions and other processes using high pressures and temperatures, e.g. steam sterilization.
Norbuqaari
another
Norbuqaari
who is father of microbiology?
Norbuqaari
anton van leoven hook
chandi
antonie van leeuwenhoek
chandi
thanks
Norbuqaari
what is microbial taxonomy
Ini
what is normal flora
kifayat
normal flora contains the microorganisms which lives on and in our body but can not cause diseases easily....e.g staph. aureus lives on our body they dont cause disease in normal conditions whenever our skin is injured by any cut or wound then they enter into the body and cause diseases
Muhammad
two types of normal flora .... one is the resident normal flora and the other is transient normal flora.....resident normal flora is reside on our body in every condition but transient normal flora changes with the conditions
Muhammad
what is the method used for anaerobic bacteria to grow in the lab other then the candle jar method?
Muhammad
Why those beans water smell
Asiya
wow
Sebewu
hahahaha
Kwame
Asiya Ibrahim please beans water how? please come clear!
Kwame
what is the purpose of gam staining
Norbuqaari Reply
the purpose of gram staining is to differentiate and classified bacteria and other microbes !
Nadiya
the purpose of gram staining is to differentiate between gram negative bacteria and gram positive bacteria
Leah
thanks Nadiya... Thank you Leah Kalasya..Safari njema!
prosper
remember me in yr prayers norbuqaari ! 🙂
Nadiya
what is the virus?
Norbuqaari Reply
an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.
chandi
chandi sheeth thanks alot
Norbuqaari
😊😊😊
chandi
what is bacteria
Ibrahim Reply
a member of a large group of unicellular microorganisms which have cell walls but lack organelles and on organised nucleus and ,including some which can cause disease
Nadiya
what is a germ
Ibrahim
a microorganisms,speciallay one which causes disease .
Nadiya
bacteria are a type of biological cells. They are unicellular. Bacteria were among the first life forms appear on the earth. they have a number of shapes, typically a few micrometers in length. They are present in of its habitata on earth.
isha
What is Auto clave?
Lovely
Autoclave is a pressure chamber used to sterilize equipments
praveen
hi
Lovely
n
vijaya
hii
chandi
what is a Laminar air flow?
isha
Laminar airflow cabinet is a carefully enclosed bench designed to prevent contamination of semiconductor wafers, biological samples or any particle sensitive materials
praveen
Praveen Deepi.... thnq....
isha
what bacteria causes malaria
Silas
female anaphilis mosquitos!
Nadiya
malaria isn`t caused by a bacteria rather by a digenetic parasite named Plasmodium.
Online
plasmodium sp
SRUTHI
its caused by a plasmodium germ....
Cotilda
Malariya cycle
Mohit
malariya cycle is
xasan
what is sterilization.
Shujjat
process of removing of microorganisms
SRUTHI
May anyone cite some few examples of Gram negative bacteria.😕
prosper
tnx shrutti
Shujjat
 Escherichia coli, Pseudomonas aeruginosa, Neisseria gonorrhoeae, Chlamydia trachomatis, and Yersinia pestis.
rohit
prokeryot and eukoryot ?
Shujjat
can anyone describe for me some roles played by lipids?
Cotilda
short description on C-reactive proteins plz
WINFRED
lipids regulate membrane permeability, lipids are storage compounds, triglycerides serve as reserve energy of the body, lipids are the important compounds of cell membrane structure in eucaryotic cell, lipids serve as source of fat soluble vitamins....
isha
what is dry heat
Shahid
C-reactiv proteins is a blood test marker inflammation in the body. It called CRP also. It's produced in the lever and it's level is measured by testing the blood. It is classified as an acute phase reachant, which mean that it's levels will rise in response to inflammation.
isha
what is stlization
Shahid
dry heat is used to kill the microorganisms.using of flame is an example for dry heat
SRUTHI
what is pasteurization
SRUTHI
what is mothed of dry heat
Shahid
the process of making something free from bacteria or other living microorganisms.
Nadiya
is called sterilization.
Nadiya
incineration
SRUTHI
buring
SRUTHI
incineration is a waste treatment process that involves the combustion of organic substance contain in waste material .this method also burns any organisms yo ash!
Nadiya
pasteurization is a process to kill or to finish the pathogenic microorganisms in milk or fruit juice (liquid food) by heat treatment... less than 100 degree Celsius....or 212 degree Fahrenheit temperature...
isha
pasteurization is a process of heating ,and then rapidly cooling ,liquid or food in order to kill microbes that may expedite their spoilage or cause disease .and .....French scientists who invented the process of pasteurization was Louis pasteur.
Nadiya
is the single celled organisms that can existance independent or dependent living
Norbuqaari
i think it dependent
chandi
what caused the expansion of the wound
Blessing Reply
Robert Koch ka Pura naam kya h?
isha Reply
the theory of Koch,'s Postulation are: 1_Any disease must found microorganism 2_Microorganism can grow it outside pure culture 3_ Pure culture can inoculated to susceptible host and can cause typical disease. 4_ Microorganism can reisolated from inoculated disease from susceptible host.
Algur
ok
Kwame
that good
Ifeoma
please I want a detailed explanation to " G6PD result being Partial Defect" of a young lady.
Kwame
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

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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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