Chapter 19Viruses and Bacteria

Viruses• Viruses are NOT cells!

• A virus is made up of:

1.Nucleic acid

(RNA or DNA)

2. Protein coat

What is a virus?

• Made of nucleic acid (DNA OR RNA), protein coat (capsid) and sometimes lipids

• MUST enter living cells in order to reproduce

• Very small

• Range from a few to 100s of genes Bacteriophage = virus that

infects bacteria

Viruses: Living or Non-living?

• No cell membrane or other living cell components

• Host cells required for reproduction

• Do not metabolize or respond to stimuli

• BUT, they do have genetic info and can change over time

Virus Infection: Lytic vs. Lysogenic Cycles

• Lytic Cycle: virus enters cell, makes copies of itself, and causes the cell to “lyse” or burst

• Lysogenic Cycle: virus integrates into host cell DNA and viral genetic info is copied along with host cell’s DNA

Lytic Cycle

The viral infection that rapidly kills the host cell is the lytic cycle.

Lytic Cycle of a Cold or Influenza

Virus

The cold or flu virus infects cells lining of the nose and throat, reproducing more cold viruses and destroying body cells.

• What are the two things all viruses have?

• Are viruses living or non-living?

• What are the two ways viruses infect a living host cell?

• What are the two ways viruses can reproduce?

Review Lytic and Lysogenic Cycles…

Retrovirus• A virus that contains

RNA instead of DNA

• Human Immunodeficiency Virus (HIV) is a retrovirus

• HIV causes AIDS

ENVELOPE

RNA

CAPSID

HIV Virus and Immune System

The thymus gland by the heart and the bone marrow produce the white blood cells that protect us from infection.

HIV attacks the T cell of the immune system.

Retroviruses• When enter cells, produce

DNA copy of RNA then integrate into host cell

• Can remain dormant until replicate and burst open cell

• “Retro” because genetic info is copied backwards RNA => DNA

• Destroys helper T cells–Makes getting other diseases really easy

• Transmitted by blood, breast feeding, sexually, and other bodily fluids• Can happen to anyone!

Mouth sores common to AIDS patients

Viruses as Parasites

• Take advantage of host cell’s respiration, nutrition and other cellular functions

• Depends entirely on another organism for its existence

Types of Viral Diseases

• Must know – Names– Symptoms– Transmission

West Nile

• Symptoms– Fever– Headache– Body ache

• Transmitted by – infected mosquitoes

Chicken Pox

• Symptoms– Fever and weakness– Red, itchy rash

• Transmitted by– Direct contact– Droplet inhalation

Common Cold

• Symptoms– Sneezing– Sore throat– Fever– Muscle and headaches

• Transmitted by– Direct contact– Droplet inhalation

Warts/HPV

• Symptoms– Noncancerous growths on

skin; can become cancerous

• Transmitted by– Direct contact– Sex

Hepatitis

• Symptoms– Jaundice– Fatigue– Abdominal pain– Diarrhea and nausea

• Transmitted by– Human waste, contaminated

food and water (Hep A)– Contact w/ bodily fluids (B & C)

Herpes

• Symptoms– Blister like sores (can

actually be on any part of the body)

– Fever– Fatigue

• Transmitted by– Direct contact– Sex

Measles

• Symptoms– High fever– Sore throat– Rash– Swollen eyelids

• Transmitted by– Droplet inhalation

Polio

• Symptoms– Fever– Headache– Muscle weakness– Difficulty swallowing

• Transmitted by– Droplet inhalation

Smallpox

• Symptoms– High fever– Fatigue– Rash

• Transmitted by– Contact– Droplet inhalation

Virus Prevention

• Vaccination – Injection of weakened or dead pathogen

• Hygiene– Wash your hands!

• Safe sex– Use condoms or other prophylactic contraceptives

• Abstinence – Only method that is 100% effective against

transmission of sexually transmitted viruses

BacteriaBacteria are small PROKARYOTIC cells.

They have a cell wall and DNA.

Some bacteria are beneficial and some are pathogenic. *Pathogenic = disease causing

Bacteria

• Used as a common name to describe prokaryotes

• Usually range from 1-5 micrometers!

• Divided into two kingdoms: eubacteria and archaebacteria

Staphylococcus epidermidis

Eubacteria• Largest bacterial Kingdom• Wide range; many lifestyles,

live almost anywhere• Usually have cell wall for

shape and protection - cell wall contains peptidoglycan

• Have cell membrane- sometimes an extra membrane outside of it as well

Escherichia coli

Archaebacteria

• Look similar to eubacteria under microscope but chemically different

• No peptidoglycan & different membrane lipids

• DNA more like eukaryotes (Share a more recent common ancestor)

• Live in extreme/harsh environments

How Are Bacteria Identified?

Identified by:– Shape– Movement techniques – Way of obtaining energy– Oxygen Needs– Mode of Reproduction

Shape

• Rod-shape: Bacilli

• Spherical shape: Cocci

• Spiral and corkscrew: Spirilla

Movement

• Not all prokaryotes can move

• Ones that move– Propelled by flagella (whiplike structures for

movement)– Lash, snake or spiral– Glide along layer of slime

Escherichia coli

Metabolic Diversity: Heterotrophs vs. Autotrophs

• Most are heterotrophic!• If autotrophic:

– Some are photoautotrophs (similar to plants)– Some are chemoautotrophs (make organic molecules

from CO2

• If heterotrophic:– Most are chemoheterotrophs (Take in organic

molecules for energy and carbon supply)– Humans are chemoheterotrophs, too!– Some are photoheterorophs (photosynthetic but need

organic compounds for carbon source)

Oxygen Needs

• Facultative anaerobes– Can survive with or without oxygen

• Obligate anaerobes– Must live in the absence of oxygen

• Obligate aerobes– Require constant supply of oxygen to live

Growth and Reproduction• Conjugation

– Hollow bridge forms between two cells and genes move from one cell to the other; increases genetic diversity

– IS a sexual process (NOT REPRODUCTION – does not produce gametes)

• Binary Fission– Grows to where it

doubles in size then replicates DNA and divides in half

Bacteria’s Importance

• Producers• Nitrogen Fixation• Human Uses

– Food and beverage production– Industry– Drug and chemical production– Live in our intestines; provide vitamins– Biotechnology

• Decomposers– Recycle nutrients in ecosystem– Sewage treatment

Bacterial Diseases

Two ways bacteria causes diseases:

1. Break down organism’s cells for food

2. Release toxins that affect the organism’s body

Examples of Bacterial Diseases

• Streptococcus– Symptoms – fever, sore throat, swollen glands

• Diphtheria– Symptoms – sore throat, low grade fever

***Both cause disease by releasing TOXINS

Circulatory SystemBacteria can infect the heart valves and the lining of the ventricles.

The circulatory system brings oxygen and nutrients to all body cells.

Left ventricle

Beneficial Bacteria in the Digestive System

Bacteria like E. coli make digestive enzymes and vitamin K in the large intestine.

Nervous SystemBrain

Spinal cord

Spinal& peripheral nerves

The nervous system responds to changes in the external and internal environment. It is “the communicator”.

Nervous System Infections

Both bacteria and viruses can infect the brain causing such diseases as meningitis and encephalitis.

Nerve cells or Neurons

Controlling Bacteria• Food storage and processing• Disinfectants

– Chemical solutions that kill bacteria

• Sterilization– Method to control growth of bacteria by heat

• Vaccines– Weakened or killed pathogens– Sometimes prompts body to produce immunity

• Antibiotics– Block growth of bacteria

Comparing VIRUSES and BACTERIA

1.Which is a virus?2.Which is a bacteria?3.Which is living?4.Which is non-living?

A. B.

Kingdoms

• LIST THE 6 KINGDOMS

• GIVE 2 DETAILS FOR EACH ONE….EX:– prokaryotic or eukaryotic?– autotroph or heterotroph?– cell wall or no cell wall?– unicellular or multicellular?

• What kingdom is a virus in?