Pathology

Is defined as the scientific study of the nature of disease and its causes, processes, development, and consequences.

A pathogen is a disease causing agent, such as bacteria, virusus, fungi or parasites.

Before the doctors told us of the danger of a kissI considered kissing you nothing short of bliss

But now I know the danger and I sit and sigh and moan --Six billion small bacteria, and I thought we were alone.

Bacteriasingular: bacterium / plural: bacteria

▪microscopic Prokaryotes

▸LACK CELL NUCLEUS

▪Until recently, bacteria were placed into one Kingdom -Kingdom Monera, hence sometimes bacteria are referred to as Monerans

- Kingdom Eubacteria

- Kingdom Archaebacteria

What is Bacteria??I love my

bacteria!!!!

Kingdom MonaraIs actually two kingdoms:

1. Eubacteria (true bacteria) – Tend to be smaller

– more similar to eukaryotes then archaebacteria

– Classified according to their mode of getting nutrients, mechanism of movement, and their shape

– Cell wall made of peptidoglycan

Kingdom Monara

2. Archaebacteria (Ancient Bacteria) – Tend to be larger– tend to live in extreme environments -

sometimes they are called "Extremophiles"– Cell walls with out peptidoglycan

– Halophiles - salt lovers– Methanogens - produce methane as a by-product– Thermoacidophiles - love hot, acidid environments

DiversityReactivity with Oxygen

▪Obligate Aerobes - require oxygen for respiration, need oxygen to grow and survive

▪Obligate Anaerobes - must avoid oxygen, they will die in its presence

▪Facultative Anaerobes - can use oxygen when it is available, but can also do without it

HeterotrophsMetabolic

▪Heterotrophs- get energy by consuming organic molecules made by other organisms

▸Chemoheterotrophs- an organism that gets “nourishment from others and from using chemicals”

▸Photoheterotrophs- an organism that gets “nourishment from others and from using light”

-Ex. Live at surface of lakes, streams

and oceans.

Autotrophs

▪ Autotrophs- make their own food from inorganic molecules

▸ Chemoautotrophs- an organism that gets “nourishment for itself using chemicals”

▸ Photoautotrophs- an organism that gets “nourishment for itself using light”

Diversity

▪ Cocci - sphere

▪ Bacilli - rods

▪ Spirilla - spirals

▪ Staph - in clusters

▪ Strep - in chains

Cell SHAPE:

DiversityHelp bacteria survive in hostile environments

▪capsules (slime layers) - help evade immune system and adhere to surfaces

▪pili – hair-like projections

▪endospores - bacteria become dormant until conditions (environment) become favorable

DiversityMovement

▪flagella - one or more tail-like structures

▪chemotaxis - response to chemicals

▪phototaxis - response to light

▪magnetotaxis - response to magnetic field

Kingdom Eubacteria

Gram Stainstains bacteria to identify the types of cells walls.

▪Bacterial species with walls containing small amounts of peptidoglycan are Gram-negative. (appear pink)

▪Bacteria with walls containing

relatively large amounts of peptidoglycan are Gram- positive. (appear purple)

Gram-Negative & Gram-Positive

Reproduction

▪ Binary fission - one cell splits into two cells, offspring are genetically identical to parent

▪ Conjugation - a form of sexual reproduction where bacteria exchange genetic information before dividing, offspring have new genes (and new traits)

▪ Transformation - bacteria incorporate genes from dead bacteria

▪ Transduction - viruses insert new genes into bacterial cells. This method is used in biotechnology to create bacteria that produce valuable products such as insulin

Bacteria: Friend or Foe?

Saccharomyces cerevisiae a.k.a.

baker's yeast. Wanted for

making bread rise.

Lactobacillus acidophilus

turns milk into yogurt.

Escherichia coli live in your gut and

help you digest food

Friend: helpful bacteria

1. Decomposers – eat dead organisms

2. Help digest food as well as produce vitamins

3. Help plants absorb nutrients

4. Nitrogen- Fixing bacteria : fix nitrogen so plants can absorb

5. Food – Milk, Cheese, Yogurt

6. Clean oil spills (purify water)

7. Antibiotics – bacteria fighting bacteria

Foe: harmful bacteria

• Streptococcus lactis : strep throat, related bacteria causes necrotizing fasciitis

• Staphylococcus aureas found on skin, responsible for minor infections (like on cuts/scratches)

• Bacillus subtilis common lab bacteria, easy to grown, unharmful

• Bacillus tetani causes tetanus (lockjaw)• Bacillus botulism causes botulism (food poisoning)Bacillus

pestis causes Black Plague• Bacillus anthracis: anthrax Mycoplasm is very very tiny,

cause of pneumonia• Rickettsia rickettsi link between bacteria and viruses, can't

reproduce outside host, causes Rocky Mountain Spotted Fever

• Escherichia coli: E. Coli - common bacteria of the digestive tract, also causes food poisoning

Fighting Back!

Bacteria Review

Virus = virion

1. Living characteristics of viruses:• They reproduce at a fantastic rate, but only in living host

cells. • They can mutate.

2. Nonliving characteristics of viruses • They are acellular, that is, they contain no cytoplasm or

cellular organelles. • They carry out no metabolism on their own and must

replicate using the host cell's metabolic machinery. In other words, viruses don't grow and divide. Instead, new viral components are synthesized and assembled within the infected host cell.

• They possess DNA or RNA but never both.

Therefore not alive!!!

Structure of a virus

• A virus particle, or virion, consists of the following:

• Nucleic acid - Set of genetic instructions, either DNA or RNA, either single-stranded or double-stranded

• Coat of protein - Surrounds the DNA or RNA to protect it • Lipid membrane - Surrounds the protein coat (found only

in some viruses, including influenza; these types of viruses are called enveloped viruses as opposed to naked viruses)

What are viruses?

SpecificityTo host cells

▪Viruses are specific to their hosts. ▸They can only attack specific cells

–Rabies, for instance, can be passed from animal to human. HIV is a virus that seems specific to humans.

▸The common cold is a virus that specifically attacks cells of the respiratory track (hence the coughing and sneezing and sniffling).

▸Other viruses attack other types of cells. –HIV virus specifically attacks white blood cells.

Bacteriophageviruses that infect bacteria

▪have a protein "tail" attached to the capsid (protein coat that envelopes the genetic material), which is used to infect the host bacteria.

▪Viruses cannot reproduce on their own, and must infect a host cell in order to create more viruses.

Replicationuse their own genetic material and the host cell's machinery

▪1. Penetration - surface proteins bind to host, and release genetic material (RNA or DNA) into the cytoplasm

▪2. Replication - the viral genetic material is copied

▪3. Transcription - the genetic material is used as a blueprint, for the cell to make messenger RNA which is used to make viral proteins

▪3. Protein synthesis - occurs in the cytoplasm (ribosomes), viral proteins are made

▪4. Viral Assembly - the viral genetic material (from replication) is surrounded by the newly made viral proteins

▪5. Release - viruses emerge from the cell by "budding" from the cell membrane or bursting out of the cell (this causes the cell's death)

Lytic and Lysogenic

▪ Lysogenic Pathway - the virus stays within the cell until certain environmental triggers cause it to enter the lytic cycle

▪ Lytic Pathway - rapid replication of the virus, ending in cell lysis (or death). More phages are released to infect other cells

Lytic cycle • The virus reproduces

itself using the host cell's chemical machinery.

• The red spiral lines in the drawing indicate the virus's genetic material.

• The orange portion is the outer shell that protects it.

Animation of the Lytic Life Cycle of a Bacteriophage

Animation of the Lysogenic Life Cycle of a Temperate Bacteriophage

How Do Viruses Work??

Human Immunodefiency Virus (HIV) - causes AIDS

• Retrovirus - RNA inside a protein coat

• HIV infects one particular type of immune system cell, called the CD4+T cell, also know as a T-helper cell – FX in the body’s immune response.

• Once infected, the T-helper cell turns into a HIV-replicating cell.

• There are typically 1 million T-cells per one milliliter of blood. HIV will slowly reduce the number of T-cells until the person develops

AIDS.

The Medical Mechanics of HIV

Statistics

• Between 36.7 and 45.3 million people are infected with the HIV virus worldwide as of November 2005, with as many as 25.8 million of those cases in sub-Saharan Africa.

• Additionally, another 4.9 million new HIV infections occurred in 2005, which represents almost 14,000 new cases per day.