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A cell contains host chromosome (large loop of DNA), F plasmid (small loop of DNA) and a pilus (projection out of the cell). The F plasmid is inserted into the host chromosome to become Hfr male (donor). When the plasmid is removed from the host chromosome, genes from the chromosome (such as lac) may move from the chromosome to the plasmid. In this case the cell becomes an F’ cell.
(a) The F plasmid can occasionally integrate into the bacterial chromosome, producing an Hfr cell. (b) Imprecise excision of the F plasmid from the chromosome of an Hfr cell may lead to the production of an F’ plasmid that carries chromosomal DNA adjacent to the integration site. This F’ plasmid can be transferred to an F cell by conjugation.
a) Diagram showing one cell with multiple genes on its chromosome as well as an integrated F plasmid. This cell begins copying and transferring its entire genome but conjugation ends before the entire chromosome is transferred. B) A sample plasmid showing the variety of genes on the plasmid. Some sample genes include: argG, pabB, metA, argR, polA, and oriC. Numbers in the center of the plasmid indicate the location of genes; these numbers show a plasmid of 1000bp total.
(a) An Hfr cell may attempt to transfer the entire bacterial chromosome to an F cell, treating the chromosome like an extremely large F plasmid. However, contact between cells during conjugation is temporary. Chromosomal genes closest to the integration site (gene 1) that are first displaced during rolling circle replication will be transferred more quickly than genes far away from the integration site (gene 4). Hence, they are more likely to be recombined into the recipient F cell’s chromosome. (b) The time it takes for a gene to be transferred, as detected by recombination into the F cell’s chromosome, can be used to generate a map of the bacterial genome, such as this genomic map of E. coli . Note that it takes approximately 100 minutes for the entire genome (4.6 Mbp) of an Hfr strain of E. coli to be transferred by conjugation.

Consequences and applications of conjugation

Plasmids are an important type of extrachromosomal DNA element in bacteria and, in those cells that harbor them, are considered to be part of the bacterial genome. From a clinical perspective, plasmid s often code for genes involved in virulence. For example, genes encoding proteins that make a bacterial cell resistant to a particular antibiotic are encoded on R plasmids . R plasmids, in addition to their genes for antimicrobial resistance, contain genes that control conjugation and transfer of the plasmid. R plasmids are able to transfer between cells of the same species and between cells of different species. Single R plasmids commonly contain multiple genes conferring resistance to multiple antibiotics.

Genes required for the production of various toxins and molecules important for colonization during infection may also be found encoded on plasmids. For example, verotoxin-producing strains of E. coli ( VTEC ) appear to have acquired the genes encoding the Shiga toxin from its gram-negative relative Shigella dysenteriae through the acquisition of a large plasmid encoding this toxin. VTEC causes severe diarrheal disease that may result in hemolytic uremic syndrome (HUS), which may be lead to kidney failure and death.

In nonclinical settings, bacterial genes that encode metabolic enzymes needed to degrade specialized atypical compounds like polycyclic aromatic hydrocarbons (PAHs) are also frequently encoded on plasmids. Additionally, certain plasmids have the ability to move from bacterial cells to other cell types, like those of plants and animals, through mechanisms distinct from conjugation. Such mechanisms and their use in genetic engineering are covered in Modern Applications of Microbial Genetics .

Questions & Answers

what is elements
Erneet Reply
an Element is a substance that can not be further decomposed by ordinary chemical means.
can i get notes of biochemistry
Sneha Reply
yep why not
what is microbiology?
Gayanjali Reply
what is malaria
bios- life/living things micro- small things that cannot be seen with the naked eye In other words the study of living things that cannot be seen with the naked eye but with the help of a microscope
logos- science
it is 10 to the power minus 6 biology which studies life forms on those scales including metabolism , physiology, nutrition requirements
what are prokarytes
A prokaryotic is a unicellular organanism that lacks a membrane bound nucleus ,mitochondria or other any membrane bound organelle. .......
in prokaryotic nucleus is not developed and cell organelles are absent
how is one who is feeling blockage in the chest with mucus be diagnosed
Essy Reply
be talking sepitol every morning
is that all?
What is prions
Sangeeta Reply
is tuberculosis a viral infection?
hildar Reply
No. It is a Bacterial Infection.
what are zn staining
Evelyn Reply
full meaning zeil neelson staining
By using zn stain we diagnose / examine acid fast bacilli .
explain hw bacteria grows
Kanyago Reply
Hw does bacteria grow?
Binary fission
three successive phase comes in bacteria growth i.e lag phase/adaptation phase ,log phase/exponential phase ,death phase when it is in fermentation process .
introduction to virology
Dongyile Reply
is the study of virus
study of virus which can be seen by using electron microscope i.e below 1micron in size . It requires a host cell to multiply own number to proliferate itself .
what are some five benefits of studying microbiology
Joyce Reply
please I'm waiting for answers
microbio is very important! 1.) microbes thought to have evolved into our cells 2.) they keep us healthy 3.) they can cause disease and illness 4.) good for bioremediation 5.) show evolution in real time(observable) 6.) make the earth a liveable place (make more o2 than plants)
What fields are interesting to study when you are doing your postgraduate degree
what is mean by killed vaccine?
Nasira Reply
Heat or formaldehyde inactivated live strain
what is an antimicrobial
Denis Reply
what are eukaryotes
Oenen Reply
a eukaryote is an organism whose cells contain complex structures enclosed within membranes .
has a nucleus. prokaryotes don't have a true nucleus.
they are micro-organisms with complex structure or have a nuclear membrane
It has true nucleus
how many protons,electrons and neutrons are there in a matter
Y'NOTS Reply
this would depend what matter you're looking at, on top of other variables such as isotopes and isomers. can we have a better picture of what you're trying to identify
Practice MCQ 4

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