Chapter 23 & 24 Bacteria and Viruses Edited by: R. LeBlanc (2/2007) Anton Leeuwonhoek (1 st to see bacterial cells) E Coli Bacteria

100 µm20 µm0.5 µm um = 1,000,000th of a meter; meters (a micron) The cells in figure on the right are magnified 16,600 times. Why is it important for you to properly clean and disinfect a puncture wound? How small are bacteria?

Bacteria Rocky Mountain Spotted Fever (caused by bacteria in a tick bite) Streptococcus bacteria

Facts About Bacteria Most metabolically diverse of 6 Kingdoms Classified into two kingdoms: –Archaebacteria (live in extreme habitats) –Eubacteria (most common form of bacteria) live in a wide array of habitats some are heterotrophic (obtain energy from living organisms) some live as saprobes (feed on dead organic material) some are photosynthetic autotrophs (obtain their energy from light; Cyanobacteria) some are chemosynthetic autotrophs (obtain energy from inorganic compounds)

Characteristics of Bacteria

Facts About Bacteria Smallest & Simplest living things. Found in three shapes: –Round (coccus) –Spiral (spirillum) –Rod-shaped (bacillus)

in-text, p. 356 coccusbacillus spirillum

Facts About Bacteria Also classified by their arrangements. Some exist alone, most are grouped together: Diplo - paired cells Staphylo - clustered cells Strepto - cells in chains

Different examples of bacterial infections Match the picture with the bacterial infection: A) LEPROSY B) LYME DISEASE C) PINK EYE D) ATHELETES FEET

MRSA Bacterial Infection How would you classify this type of bacteria? –Staphylococcus (or staph) How is this infection spread? –It is spread by physical contact with someone (or object) who has MRSA. –It can enter open cuts or wounds. Can be prevented by washing your hands

Facts About Bacteria Contains cell wall made of sugars and amino acids Cause half of all human diseases. Prokaryotes (they have no membrane bound nucleus). Obligate aerobes - Need oxygen to survive Obligate anaerobes - Killed in presence of oxygen Ex. Syphilis Reproduce asexually - Chromosome is copied and cell splits into two (binary fission) Reproduce sexually - Transfer of genetic information to another cell through pili (conjugation).

Bacterial Identification BC A F E D ANSWERS: A) SPIRILLUM B) DIPLOBACILLUS C) STREPTOCOCCUS D) DIPLOCOCCUS E) STAPHYLOCOCCUS F) STREPTOBACILLUS

Facts about Bacteria Endospores - Hard outer covering resistant to drying out, heat, and chemicals produced during unfavorable conditions. Ex. Botulism, tetanus Antibiotics effectively kill many types of bacteria. Examples of bacterial diseases: –Tuberculosis, Pneumonia, Strep Throat, Diphtheria, Tetanus, Gonorrhea, Syphilis, Botulism, Scarlet Fever, Lyme DiseaseStrep Throat DiphtheriaScarlet Fever

stain with purple dye stain with iodine wash with alcohol counterstain with safranin Proper Gram Staining Procedures: 1.Collect bacterial sample and carefully heat-fix cells to microscope slide. 2.Add Crystal Violet, a purple dye, to the bacterial sample turning all cells purple. 3.Then add iodine, a binding agent, that causes the purple dye to stick to the gram positive bacterial cells. 4.Use an alcohol wash to rinse off the purple dye from the gram negative cells making them neutral in color. 5.Last, counter-stain the bacterial sample with safranin, a pink dye, that will stick to the gram negative cells turning them pink. Gram Positive: bacteria cells purple. Gram Negative: bacteria cells pink with counter stain.

The Proper Techniques Used in Gram Staining Bacteria

Economic Importance of Bacteria Used to make cheese, pickles, yogurt, vinegar, beer, and wine through fermentation. Recycle nutrients by breaking down dead organisms & wastes.

Economic Importance of Bacteria Nitrogen Fixation Cycle –Certain nitrogen fixing plants are used: Beans peas –Converts nitrogen in the air into nitrogen compounds for the soil. –Nitrogen in soil helps most plants grow.

Nitrogen fixing plant with corn plant

Economic Importance of Bacteria Replenish the oxygen supply in the atmosphere & help eliminate carbon dioxide. Some produce antibiotics that kill other bacteria.

Viruses, Viruses, and Viruses

Fig. 22.2, p µm bacteriophageruptured bacterial cell How small are viruses?

Virus Facts Cause diseases like measles, mumps, flu, colds, chicken pox, rabies, polio & AIDS.measlesmumps chicken poxrabiespolio Smaller than bacteria Nonliving Do not carry out respiration, grow, move or take in energy. Consist only of an inner core of nucleic acid (DNA or RNA) and a protein coat.

A Closer Look At Viruses

Fig , p. 364 viral RNA protein subunits of coat 18-nm diameter, 250-nm length 80-nm diameter lipid envelope; proteins span the envelope, line its inner surface, and spike out above it viral RNA reverse transcriptase viral coat (proteins) nm diameter DNA protein coat sheath base plate tail fiber 65-nm diameter head, 225-nm total length

Virus Structure

Chapter 24 Parts of a Virus

The Nucleic Acid Core Contains the genetic material. Some have DNA, others RNA. Contains coded instructions for making copies of the virus.

The Protein Coat Arrangement of the protein coat give viruses different shapes.

Chapter 24 Lytic Cycle

The Lytic Cycle 1) Attachment The virus attaches itself to a specific receptor site on the plasma membrane of the host cell. Most can only infect certain cells. Ex: Polio virus only infects human nerve cells (see the picture above).

The Lytic Cycle 2) Entry Some act like syringes and inject their nucleic acid through host cell’s plasma membrane. Others attach to the plasma membrane and enter through endocytosis.

The Lytic Cycle 3) Replication Virus takes over the host’s DNA. The viral nucleic acid instructs the host to make new viral proteins & nucleic acid.

The Lytic Cycle 4) Assembly / Formation New viral parts are assembled into complete viruses, identical to the original virus.

The Lytic Cycle 5) Lysis and release During lysis, the viral nucleic acid instructs the host cell’s ribosomes to make a “suicide enzyme”. This destroys the host cell’s plasma membrane & releases new viruses to infect other cells.

The Lytic Cycle Typical lytic cycle takes about 90 minutes. About 200 new viruses are released from each infected host cell during the lytic cycle. Host cell is destroyed during the lytic cycle. A cell lysis by the flu virus Notice all the separate flu virus particles that will now infect other cells.

Chapter 24 Lysogenic Cycle

The Lysogenic Cycle Does not destroy or interfere with normal functioning of host cell. The viral nucleic acid becomes part of the host cell’s DNA (Provirus). When the host cell’s DNA replicates, it also makes a copy of the provirus.

The Lysogenic Cycle Can continue undetected for many years. Ex. HIV The provirus can suddenly enter the lytic cycle at any time, and the host cell is then destroyed. Ex. Herpes As a result, every copy of the host cell has a copy of the provirus in its DNA.

The Lysogenic Cycle Examples of lysogenic viruses: –HIV (seen in the picture) –Herpes –Hepatitis B –Chicken pox

Chapter 24 AIDS (Acquired Immunodeficiency Syndrome)

Summarizing The