Conjugation in Bacteria

hi everyone and welcome to biology professor today we're talking about genetic recombination and bacteria bacterial cells have this really cool ability to obtain extra DNA through various mechanisms that can give them extra functionality what this means is they can pull DNA from different places using a few different mechanisms and the DNA may enable them to be resistant to some type of antibiotic it may enable them to gain a virulent factor so something that allows them to establish or maintain an infection of a host or it can give them the ability to couse toxins these are all examples of ways that bacteria can benefit from genetic recombination the three types of genetic recombination are called transformation conjugation and transduction I have videos on all three of these types so you can check those out in this video we are talking about conjugation conjugation is made possible by a plasmid that is extra chromosomal DNA so what this means is it is circular DNA that is separate from the actual bacterias chromosomal DNA in particular this plasmid is called a conjugated plasmid you might also hear it referred to as a fertility the reason that this plasmid makes conjugation possible is because in addition to any other genes that it may encode so genes for antibiotic resistance for a virulence factor it also encodes genes for something called a sex Phyllis and it is this sex palace which enables conjugation to happen the actual definition of conjugation is the transfer of genetic material from one bacterial cell to another bacterial cell by direct cell to cell contact that direct cell to cell contact is made possible by the sex LS for example if you have a bacteria here that has this conjugative or fertility plasmid this is called an f-plus cell with fertility plasmid encodes genes for effects fellas this is basically a cellular structure that allows the f+ valve to connect with an f-minus cell so a cell that does not already have this classman then the conjugated plasmid is able to transfer a copy of itself from the f+ fell to the f- cell in a process of conjugation now that we have talked about the basics of conjugation let's look at the mechanism and a little bit more detail here we start with our F plus cell that has the fertility class names here drawn in red and then s minus L which lacks with agility plasmids both of these cells have chromosomal DNA as well and remember that the fertility plasmid codes for the sex LS it is the sex palace that enabled the direct cell to cell contact needed for conjugation to occur here we have our F plus cell which is our donor cell it contains this fertility plasma that is capable of replicating itself and then the copy of a fertility plasmid goes through the sex palace and enters the recipient cell's cytoplasm the result of this is you have our original f plus cell it still has its fertility plasmid but now that recipient cell has a copy of the fertility cotton as well so now it is also considered an F plus L so it is capable of repeating this process which is one of the possibilities that may occur next where you get this newly made positive cell basically starting this process over again also remember that the fertility plasma contains not only the DNA necessary to make the sex fellas it also can contain other genes that can give the cells something something different in it and happy for other genes required to help them survive an unfriendly environment genes that confer resistance to some sort of antibiotic so for exists for example this new at plug valve now that is gained this plasmid it might be resistant to streptomycin which means that it's infecting a human host streptomycin is no longer going to work to be able to share that infection so in addition to this possibility of this cell continuing to share these genes with other at- cells through the process of conjugation something else can happen as well that's drawn here this is when we have chromosomal DNA it has actually allowed the fertility plasmid DNA to integrate into the chromosome so if the fertility partment integrate in the bacterial chromosome so now we have one unit of DNA this cell is called an H F our cell hf r stands for high frequency of recombination these cells are capable of doing something interesting where they still have this DNA from the original fertility positive so they can still form FX Phillips to connect from the HR cell which we will draw is newly integrated chromosome this X plus allows the age of our cell to connect to an F - cell this F minus L I've drawn its chromosomal DNA and blue simply so we can distinguish between the original chromosomal DNA of this valve and black the fertility plasmid DNA that's still in red as it's been throughout and then the chromosomal DNA of this new recipient at - cell what happens at this point is the fertility plasmid DNA replicate so that the DNA from both the red DNA the fertility plasmid DNA as well as the chromosomal DNA Francis aja our cell is able to copy itself and then move in - yep - cell what we get at this point the result is we still have this HFR cell that has its chromosomal DNA and then the integrative fertility plasmid DNA but we also have this at - cell has undergone recombination between its original chromosome and some of the chromosomal DNA that it got from the HFR cell what this looks like is it still has its original chromosomal DNA and blue but it's picked up some of the chromosomal DNA it was copied from the HFR cell it came through sex tell us what we get here is a recombinant cell it's still enough - cell it doesn't have any of this red DNA that came from the fertility - but it still has acquired extra genes which means that if this cell has any kind of extra DNA already incorporated into its chromosome originally it's now been integrated into the chromosome of this F - cell again this means that that might have cell while it's not capable of further conjugation on its own it's missing utility plasmid DNA it still may have acquired additional functionality in the hormone virulence factors or antibiotic resistance or toxins that it can now produce simply because it's gained this extra DNA so this is how the process of conjugation works to give bacterial cells these additional genes

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Keywords: AP Biology, Hfr cell, Mcat, Bacterial Conjugation, Conjugation, fertility plasmid, MCAT Review, biology, MCAT Biology, Microbiology (Field Of Study), biology 101, conjugative plasmid, Microbiology, Mcat Review, Biology Professor, sex pilus, plasmid, Mcat Biology, HGT, horizontal gene transfer

Id: YycVGqBs1p0

Length: 9min 36sec (576 seconds)

Published: Tue Feb 04 2014