Oxford Tutorial Notes Contains all the information you need for your 5 minute presentation on each of the 3 topics for Bio 130 Tutorial!

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Published on 16 Oct 2011
School
University of Waterloo
Department
Biology
Course
BIOL130
Professor
Phagocytosis
What mechanisms do professional phagocytes have to kill bacteria and how do some bacteria
get around them?
Phagocytosis is the process where materials are taken into the cell
It is also known as “cell-eating” because that’s what the process resembles
In this process, the phagocyte, such as macrophages or neutrophils (which are types of
white blood cells in mammals) recognize invading organisms (such as pathogens) as well
as damaged or dying cells and debris
Once recognized, receptors on the surface of the phagocyte bind to the receptor sites
on the invading organism which initiates the phagocytic process
Through actin polymerization, folds in the cell membrane known as pseudopodia
(literally “false feet”) stretch and envelop the material, forming a vacuole, or
phagosome, which then pinches off on the inside of the cell membrane as the folds of
the cell membrane fuse back together
Once inside the cell, a lysosome containing lysosomal enzymes from the Golgi Complex
fuses with the phagosome, forming a phagolysosome
Here, there are a few different ways in which the material can be digested or destroyed:
o They may be destroyed by lysosomal enzymes when the lysosome fuses with the
phagosome
o Since the lysosome has a low pH, the acidic environment may kill the bacteria
o Oxygen free radicals generated within the lumen of the phagosome may also kill
the bacteria
However, this isn’t always the case; some bacteria have ways of hijacking the
phagocytic process to survive
I’ll mention 3 different examples or cases:
o Bacteria responsible for tuberculosis (mycobacterium tuberculosis) is taken into
the cytoplasm as usual, but inhibits the fusion of the lysosome with the
phagosome that’s enclosing the bacteria. Instead, the bacteria multiplies within
the cell
o Bacteria responsible for Q fever (Coxiella burnetii) is also taken into the cell and
becomes enclosed in a phagosome, but although the lysosome fuses with the
phagosome, neither the acidic environment of the phagolysosome nor the
lysosomal enzymes are able to destroy the bacteria
o Bacteria responsible for meningitis (Listeria monocytogenes), on the other hand,
produces proteins that destroy the integrity of the lysosomal membrane, which
allows the bacteria to escape to the cell’s cytosol
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Document Summary

Phagocytosis is the process where materials are taken into the cell. It is also known as cell-eating because that"s what the process resembles. In this process, the phagocyte, such as macrophages or neutrophils (which are types of white blood cells in mammals) recognize invading organisms (such as pathogens) as well as damaged or dying cells and debris. Once recognized, receptors on the surface of the phagocyte bind to the receptor sites on the invading organism which initiates the phagocytic process. Once inside the cell, a lysosome containing lysosomal enzymes from the golgi complex fuses with the phagosome, forming a phagolysosome. However, this isn"t always the case; some bacteria have ways of hijacking the phagocytic process to survive. I"ll mention 3 different examples or cases: bacteria responsible for tuberculosis (mycobacterium tuberculosis) is taken into the cytoplasm as usual, but inhibits the fusion of the lysosome with the phagosome that"s enclosing the bacteria.