Unit 9 Bacteria and Viruses

What are the characteristics of Bacteria?

• Smallest and simplest living thing

• Have no organelles, including no nucleus (meaning it’s a prokaryote, remember?!?)

• Genetic material is in a simple circular chromosome

• They do have cell calls that protect them from outside pressure.

• They can be transmitted through air, water, human contact, contaminated food

Bacteria shapes

• Coccus: are round

• Bacillus: rod shaped

• Spirillum: spirals

Arrangements

• Diplo:Pairs

• Staphylo: clusters

• Strepto: Chains

Feeding Requirements

• Some are heterotrophs and live as parasites.

• Some feed on dead material, called saprobes.

• Some are photosynthetic and are autotrophs

Types of Metabolism

• Obligate anaerobes- killed in presence of oxygen.

• Obligate aerobes: require oxygen to live• Facultative aerobes: can live with or without

oxygen.

Reproduction Adaptations

Bacteria

Endospores

• They are hard outer covering produced during harsh environmental conditions

• Resistant to drying out and boiling.

• Metabolism slows down inside the endospore while in the extreme environment.

• Bacteria resumes growing when conditions are more favorable.

Toxin Production

• As an endospore begins to grow, some bacteria produce poisons.

• Some of these toxins are deadly. These toxins can also kill off other bacteria that are helpful

• Examples: Botulism (food poisoning); tetanus (lock jaw)

Tooth decay

Lyme disease

Tetanus

Tuberculosis

Salmonella food poisoning

Pneumonia

Cholera

Streptococcus mutans

Borrelia burgdorferi

Clostridium tetani

Mycobacterium tuberculosis

Salmonella enteritidis

Streptococcus pneumoniae

Vibrio cholerae

Regular dental hygiene

Protection from tick bites

Current tetanus vaccination

Vaccination

Proper food-handling practices

Maintaining good health

Clean water supplies

Disease Pathogen Prevention

Section 19-2

Common Diseases Caused by Bacteria

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Binary Fission• Reproduce asexually by

splitting in half after copying DNA

• This is a fast process.• Why will these bacteria

stop reproducing?– Run out of food– Dry up– Poisoned by own waste

Conjugation

• Sexual reproduction that transfers all or part of the DNA between 2 bacteria.

• The sex pilli structure is used to transfer DNA.

• When threatened the bacteria will choose to reproduce in this method.

• **Conjugation is what makes bacteria resistant to changes, mainly because this is when mutations would occur in the DNA to cause these beneficial changes.

Helpful Uses

• Nitrogen Fixation-some bacteria convert nitrogen gas into nitrates in the soil which is necessary for plant growth.

• Saprobes: break down organic food/material

Helpful Uses

• Food: food flavors are produced by fermentation and bacterial wastes. b. vinegar, yogurt, butter, cheese, pickles, buttermilk

• Some bacteria even produce antibiotics that kill other bacteria

• ONLY ANTIBIOTICS CAN KILL BACTERIA!!!!

Harmful Bacteria- • Pneumonia-inflammation of lungs(can be

from a bacteria, virus, or fungus).

• Conjunctivitis “Pink Eye ”

• Infects outermost layer of eye(Conjunctiva)

• can be viral(cold) or bacterial(staph or strep), or allergies

• Contagious

Harmful Bacteria- Leprosy

• Skin lesions , nerve damage

• Mycobacterium

• Difficult to transmit; Leper colonies not neccessary

• 100 cases a year in U.S.(south, Ca, Hawaii)

• Have medicine now

Harmful Bacteria- Digestive1. Stomach Virus (24 hour)- most of time it is not a virus but a

bacteria from food poisoning.

2. Botulism- Food poisoning- Clostridium botulinum; endospore,

a. infants- don’t give homemade honey ; canning (boil at high temp)

b. Pasteurization- heating process to prevent contamination of milk.

3. Salmonella enterocolitis- infection in small intestine by

Salmonella bacteria. Any food can have it.

Lyme Disease-Harmful Bacteria

• Borrelia burgdorferi- transferred by a deer tick

• Skin rash, inflammation, flu-like symptoms

Harmful Bacteria- Anthrax

• Bacillus anthracis

• Spore-forming

• Occurs in cattle, sheep, humans

• Inhale it or handle contaminated animal products

• Symptoms show within 7 days

Harmful Bacteria-Skin1. Diaper Rash- bacteria from feces

2. Scarlet Fever- skin rash- group A streptococci

3. Acne- oil blocks & bacteria grow

Harmful Bacteria- Respiratory

1. Strep Throat- infection of pharynx with Streptococcus. Spread-nasal or saliva

2. Sinusitis- inflammation of sinuses(hollow spaces within the bones around your nose)

3. Pertussis- Whooping Cough-like cold except coughing spells. Bordetella pertussis

Viruses

Characteristics of Viruses

• Tiny, non-living particles• Do not respire, move or grow• Cannot reproduce on their own• Most reproduce inside of a host cell.• They can cause people to have infections that

can last 7-10 days.• Viruses are not given Latin names; named for

– Disease caused– Organ infected– Region detected in

Viral Structure

• Consist of 2 basic parts:– 1. nucleic acid– 2. protein coat

• Capsid: protein coat containing inner core of DNA and RNA

• They may have tail fibers and projections as structures to aid in attachment

• Some have an extra outer layer called an envelope.

Viral recognition and attachment

• Virus must recognize specific receptor site on host cell

• Part of virus matches site on host• Lands on host and “locks in”• Attachment is specific: virus can enter and

reproduce in only a few types of cells

Ex. HIV- WBC

Ex. Flu- Respiratory tract

Ex: tobacco mosaic virus- tobacco plant

Ex. T4 Bacteriophage- virus that infects bacteria

Examples of Viruses

• Influenza (bird flu; swine flu)

• HIV

• West Nile

• ebola

Compare and contrast

• Viruses vs. Living organisms

Viral Reproduction

• Viruses MUST reproduce inside a host cell.

• They are classified as intracellular parasites.

• Method of entry into host cell depends on the virus.

• 2 main types of viral reproduction:– 1. lytic cycle– 2. lysogenic cycle

Lytic Cycle

• Viral DNA takes over host nucleus, produces new viruses, the cell fills with new viruses, at the end the cell bursts and dies!

Lytic Cycle continued

• Attachment: virus attaches to cell surface.

• Entry: injects DNA, takes over host nucleus

• Replication: reproduces virus parts

• Assembly: puts virus parts together into mature viruses

• Lysis and release: cell splits open releasing viruses that can infect others.

Lysogenic Cycle• Virus attacks cells, but does not kill immediately.• Viral DNA is mixed with host DNA like lytic cycle.• Does not immediately begin to reproduce, the host may

function normally while viruses stay dormant.• Provirus can pop out at any time and begin reproducing.• Example: herpes-cold sores, fever blisters

Steps of Lysogenic cycle

• Attachment: attaches to cell surface

• Entry: DNA enters bacterial cell

• Integration: DNA integrates into bacterial DNA

• Replication: replicates when bacterial DNA replicates.