Cell Vulnerabilites

1/24/2014

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Vulnerability

• What is vulnerability?

• Vulnerability means “the inability to withstand the effects of a hostile environment”

• All cells are exposed to the environment somehow

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Living things

• Living things have certain basic characteristics/requirements

• Living things:

– Require energy

– Require water in its liquid form

– Require chemical nutrients

– Must be able to reproduce

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Cellular life

• Most life on Earth is microbial, which means _______________________.

• Macro-life is easier to see, but makes up only a small portion of the total living mass of life on Earth!

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Natural Selection

• Means that individuals that are best able to survive in an environment (because of their genetics) are the ones that are most likely to survive – and thus pass on their genes

• Individuals that are weaker – or MORE VULNERABLE - are less likely to survive and reproduce

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Vulnerability

• Changes in the environment means a change in what “most fit” means

• This can be devastating to species

• Most species that have ever existed are extinct!!

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Reproduction

• The Earth’s environment is constantly changing

• For life to continue, living things must reproduce quickly enough to ensure survival

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Other vulnerabilities

• Cells are vulnerable to environmental change – and to attack by other livings

• Because Living things have to compete for resources, the competition is usually fatal

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Cells and viruses

• Most life is in the oceans

• Every day, about 1 in 5 ocean microbes are killed by viruses

• Viruses require a host to reproduce, they cannot reproduce without taking over a living cell

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Viruses

1/27/2014

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Introduction - Cells

• Cells are like factories for making proteins

• DNA is the instructions for how to make these proteins

• What if the cell could be taken over, so instead of making the proteins it’s supposed to make, it’s tricked into making something else?

• That’s what viruses do!

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Lytic cycle

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Lytic cycle

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Where do viruses live?

• Many found free-living in the environment (oceans, soils, bodies of water, etc.) – these are usually not harmful to humans, usually they just prey on bacteria

• Others are found in a “host” species • For example, “Swine-influenza” viruses live in pigs • Other viruses are found in bats, rodents,

mosquitoes, ticks, etc. • Every known species – including humans – are

hosts to viruses

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Where do Viruses live?

• Usually only able to infect one or two kinds of cells in their hosts (you have tens of thousands of cell types!)

• A virus is not vulnerable to the immune system of its host – for example, Swine Influenza lives very happily inside of a pig

• But they often are highly vulnerable to the environments outside their hosts, so they are usually only found in their host

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How viruses infect us

• Sometimes – by accident – they are able to cross the “species barrier” and survive in a new host

• Their new host may be highly vulnerable to the virus! (swine flu, bird flu, etc.)

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An introduction to some common viruses

You are not directly responsible for this – but I thought it would be

interesting!

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Other viruses

• Influenza – a family of viruses that cause “flu-like” symptoms in humans

• Magnification here is 500,000 times!

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Influenza – many versions of this

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Influenza is spread by…

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Rhinovirus

• Rhino = nose

• This is the virus that causes the common cold

• Colder temperatures INCREASE your vulnerability to this virus!!

• Spread just like influenza – can be spread with influenza!

An nm is a

nanometer, and is a billionth of a

meter! 21

Herpes

Other versions of Herpes include the viruses that cause chicken pox, Epstein-Barr and Shingles. Nearly 2 in 3 people have these viruses! So we are a “host species” for these in a sense, since they live in us but *most* people are not vulnerable to them

These sores are an additional

VULNERABILITY because other bacteria/viruses

can invade through these openings

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Human Immunodeficiency Virus

• The Virus that causes AIDS

• Crossed species barrier to humans in c. 1915, possibly much earlier

• Destroys immune system, making humans totally vulnerable to all other kinds of infecting organisms

False color – green HIV virus particles emerging from a human immune system

cell, a process which destroys the cell 23

Ebola virus

A gruesome kiler, and a microbiologist’s nightmare! 24

Egyptian fruit bat – host for Ebola?

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Viruses and where they infect

• Viruses can’t attack all cells in a body – only certain cells are actually vulnerable to any particular virus

• Rhinovirus – attacks cells in lining of upper respiratory system

• Influenza – attack cells in lining of respiratory tract

• Herpes – attacks cells in and immediately below skin

• HIV – attacks immune system cells in blood and lymph

• Ebola – attacks and destroys the integument

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Virus wrap-up

• With the exception of Ebola, none of the other viruses mentioned actually kill – but they do make you more vulnerable to other diseases or other invading organisms

• Some scientists call some viruses “smart” or “dumb” based on how fast – or if – they kill their host

• A cure for these is a chemical that the virus is vulnerable to, but for most of these…

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