Bacteria & Viruses

Living or Non-living

Bacteria

Prokaryotes = unicellular organisms with no nucleus

General characteristics Cell membrane surrounded by a thick, protective

cell wall Genetic material contained on a single strand of

circular DNA – plasmid Lack mitochondria, chloroplasts and other

membrane bound structures

Two New Kingdoms Archaebacteria or “ancient

bacteria” Live in extreme environments Cell wall lacks peptidoglycan Cell membrane contains lipids

not found in any other organism

Many cannot survive in the presence of oxygen

Eubacteria or “true bacteria” Thick, rigid cell walls of

peptidoglycan Cell wall surrounds a cell

membrane Diverse

Types of Bacteria

Round or spherical = coccus (cocci)

Rod shaped = bacillus (bacilli)

Spiral or corkscrew shaped = spirillum (spirilla)

Named for shape and arrangement of bacteria ex. Staphylococcus or Streptococcus

Reproduction in Bacteria

Binary fission – splits into two daughter cells

Conjugation – part of the genetic information from one cell is transferred to another through a bridge connecting both cells

Transformation – pick up bits and pieces of DNA from other bacteria allowing them to pick up new traits

Protective behavior

Bacteria can make endospores

Protective capsules

Allow bacteria to remain dormant until appropriate conditions exist

Can remain dormant for years

Harmful Bacteria

Infect other foods and cause illness

Infect other organisms Pathogenic Treated with antibiotics Antibiotic resistance

Helpful Bacteria

Biotechnology Insulin production Gene splicing Recombinant DNA

Useful in a variety of products Certain cheeses Yogurt – active cultures Sauerkraut

Part of metabolism Example: aids in digestion

Viruses

Tiny “particle” made of genetic material and protein that can invade and replicate within a living host.

General structure Protein coat called a

“capsid” Protein coat “tricks” host

cells into letting the virus in

Nucleic acid core

Viruses

Viruses are species specific

Types of Viruses – classified according to nucleic acid content DNA viruses RNA viruses Retroviruses

Viruses

TMV – tobacco mosaic virus first discovered by Wendell Stanley.

Bacteriophage is a virus that infects bacteria.

Viral Reproduction

Can only reproduce when they invade or infect a host cell.

Lytic cycle Injects its genetic material

into a host Immediately takes over the

cells metabolic functions Hosts DNA is used to make

viral DNA & the host cell makes new viral genes and proteins until it bursts.

5 Step Process

Viral Reproduction

Retroviruses Contain RNA

Make DNA copies of their RNA genes and then insert them into the host cells chromosomes

Remain dormant, then become active Direct production of new viruses and kills the host cell Example: HIV which causes AIDS

Bacterial Disease in Humans Pathogens = disease causing

agents Pasteur – “germ theory of

disease” Some bacteria damage

cells and tissues by breaking them down to use for food Mycobacterium

tuberculosis Some bacteria release

toxins that interfere with the normal activities of the host. Diptheria Streptococcus bacterium

Scarlet fever

Preventing Bacterial Disease

Antibiotics Block growth and

reproduction of bacteria Bacterial resistance to

antibiotics

Vaccines – stimulate the body’s immune system Weakened or killed strain

of the disease Stimulates the body to form

antibodies

Bacterial Disease in Animals

Many bacteria can affect both animals and humans

Requires special precautions to protect livestock from infection

Example: Bacillus anthracis or “anthrax”

Diseases Caused by Bacteria

Lyme disease Tetanus Tuberculosis Diptheria Bacterial meningitis Strep throat Tooth decay

Controlling Bacteria

Sterilization by heat Food storage and processing

Refrigeration slows down bacterial growth Boiling, frying or steaming foods Preserving foods

Disinfectants = chemical solutions that kill pathogenic bacteria Concern with overuse - resistance

Viral Diseases in Humans and Animals

Viruses produce disease by disrupting the body’s normal equilibrium

Attack and destroy specific cells in the body. Poliovirus – attacks the nervous system

Some viruses cause infected cells to change their patterns of growth and development. Some cancers

Diseases Caused by Viruses Common cold Influenza Small pox Warts AIDS Chickenpox Measles Hepatitis A, B and C West Nile Virus Polio

Viroids and Prions – virus-like particles

Viroids – cause disease in plant Single stranded RNA

molecules with no surrounding capsid

Infect cells by making them synthesize new viroids

Disrupt plant metabolism and stunt plant growth

Viroids and Prions

Prions – cause disease in animals

First discovered in sheep but also found in other animals including humans

Cause disease by forming protein clumps which interfere with normal protein production

Particles contain no DNA or RNA, only proteins Prions = “protein infectious particles”