viruses and bacteria chapters 19 & 27. bacteria small less organized viruses even smaller...
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Viruses and BacteriaChapters 19 & 27
Bacteria Small Less organized Viruses Even smaller Simpler Lacking structure Metabolic
machinery
Tobacco mosaic virus
Viral structure Protein coat surrounds nucleic
acids Nucleic acid (DNA or RNA) Linear, circular, single or double
stranded
Viral structure RNA genome: Flu, measles, AIDS, SARS DNA genome: Herpes, small pox, mono, hepatitis
B
Helical Rodlike in appearance Isometric Spherical shaped
Viral structure
Virus
Virus
Bacteriophages
Bacteriophages
Viral structure Capsid: Protein sheath surrounds nucleic acid core Few different proteins-repeated Envelope: Surrounds the capsid Made of proteins, lipids, and glycoproteins Derived from host cell’s membrane
Virus host range All organisms are affected by viruses Host range: Cells suitable for a virus Viruses replicate in only a few types of
cells Examples: HIV affects certain WBC Hepatitis affects the liver Common cold virus infect lining of
upper respiratory tract
Virus host range Rabies virus has a broad host
range Infects several species Some viruses lay dormant for
years HIV or herpes Some do not cause any problems
Viral replication Not considered organisms Unable to reproduce
independently Lack ribosomes Enzymes for protein synthesis Obligate intracellular parasites
General viral replication Enter host cells Reproduce Viruses replicate Host’s genetic machinery Their genes are translated into
proteins
Transcriptionand manufactureof capsid proteins
Self-assembly of new virus particles and their exit from the cell
Entry anduncoating
Fig. 19-4VIRUS1
2
3
DNA
Capsid
4
Replication
HOST CELL
Viral DNA
mRNA
Capsidproteins
Viral DNA
Viral replication Phage replication 1. Lytic cycle 2. Lysogenic cycle
Viral replication Lytic cycle: Virus kills infected host cell when
replicating Virulent virus: Virus multiplies within the host Eventually rupturing the host
Bacteriophages
Virulent viruses
Lysogenic viruses Incorporate viral nucleic acid into
genome of the host cell Does not kill host Prophage: Viral nucleic acid is part of the
host genome
Lysogenic Virus Transformation: Genetic alteration of a cell’s
genome by introducing foreign DNA
Phage conversion: Foreign DNA is from the virus
Lysogenic Virus Prophage genes can make toxins Makes bacteria more serious Diphtheria, botulism and scarlet
fever
Scarlet fever
Animal Virus Replication Viruses cause illnesses in animals Classified according to genome RNA or DNA Many have envelopes
(glycoproteins)
Animal Virus Replication Bind to cell membrane at receptors Enter cell Viral RNA used as template Makes more viral RNA Combines with capsid Exits host (buds) Encased in envelope derived from host
Fig. 19-7
Capsid
RNA
Envelope (withglycoproteins)
Capsid and viral genomeenter the cell
HOST CELL
Viral genome (RNA)
Template
mRNA
ER
Glyco-proteins
Capsidproteins Copy of
genome (RNA)
New virus
Influenza
Varicella virus
Shingles
Epstein Barr virus
Polio virus
HIV
HIV Retrovirus (“backwards”) Transcribes an RNA template into
a DNA Reverse transcriptase Provirus New integrated viral DNA Does not leave host
Fig. 19-8aGlycoprotein
Reversetranscriptase HIV
RNA (twoidenticalstrands)
Capsid
Viral envelope
HOST CELL
Reversetranscriptase
Viral RNA
RNA-DNAhybrid
DNA
NUCLEUS
Provirus
ChromosomalDNA
RNA genomefor thenext viralgeneration
mRNA
New virus
HIV Human immunodeficiency virus 1981 T-4 cells (CD4 cells) Lymphocytes Unable to fight off other diseases Maybe asymptomatic for 10 years AIDS (acquired immunodeficiency
syndrome)
Fig. 19-8b
HIVMembrane ofwhite blood cell
HIV entering a cell
0.25 µm
New HIV leaving a cell
HIV Symptoms Fatigue Weight loss Lymphadenopathy (swollen lymph
glands) Neurological disease
HIV Opportunistic infections Candidiasis (yeast) Pneumocystis carinii pneumonia Kaposi sarcoma TB
HIV
HIV Transmission Blood Transfusion or shared needles Intercourse Mother to fetus
Hepatitis B Infection of the liver Jaundice Decreased liver function Contact through bodily fluids
Ebola virus
Ebola virus Hemorrhagic fever Africa Fever, joint pain Internal & external bleeding
SARS (severe acute respiratory syndrome)
SARS Respiratory infection Coronavirus 2003 China
Vaccines Inactive version of pathogen Causes immune system to form
antibodies Hepatitis MMR, Polio, Rotavirus Smallpox Diphtheria (Td)
Emerging virus Virus that starts in one organism Passes on to another Disease progresses SARS, Ebola and HIV West Nile
Emerging virus Mutations Increased transmission (global) Other animals Bats SARS Chickens Avain flu Epidemics Pandemics
Virus Viruses appear to cause certain human
cancers. Hepatitis B virus associated with liver cancer. Epstein-Barr virus Linked to several types of cancer in parts of
Africa, notably Burkitt’s lymphoma. Papilloma viruses are associated with cervical
cancers. HTLV-1 retrovirus causes a type of adult
leukemia.
Plant Viruses Horizontal transmittance Viruses enter damaged plants Vertical transmittance Inherits a virus from a parent Travel easily through the plant Brown spots Stunt growth
Viroids Small circular RNA molecules Replicate in host plants Stunt growth of plants
Prions
Infectious proteins Infect animals Neurological disease (encephalopathy) Mad cow disease
Prokaryotes
Prokaryotes Resemble first organisms on earth Most abundant (over 5000 kinds) Understanding prokaryotes help
understand disease, genetics and ecology
Bacteria structure Shapes Bacilli: rod shaped Cocci: spheres Spirochetes: spiral shaped Bacilli & cocci - form colonies Spirochetes swim alone
Prokaryote structure Cell wall Maintains shape Keeps cell from swelling &
rupturing Peptidoglycan: Polysaccharides with polypeptide
links
Gram staining helps classify bacteria
Gram + (purple color) Simpler Thick complex network of
Peptidoglycan Around the outside of the cell
Prokaryote structure
Prokaryote structure Gram – (red color) Peptidoglycan is a thin layer Sandwiched between two plasma
membrane layers Harder to treat with antibiotics
that affect cell wall synthesis
Cell wall
Gram stain
Gram stain
Prokaryote structure Internal structure Internal membranes Cellular respiration Plasmids Small independently replicating
circles of DNA
Plasmid
Flagella Made of proteins Anchored to cell wall Spin-pull bacteria through water
Prokaryote structure
Prokaryote structure Pili Hair like structure Located on some prokaryotes Help bacteria attach to structures
Prokaryote structure Ribosomes Only organelle Smaller than eukaryotes Tetracycline and chloramphenicol
are antibiotics Affect bacteria ribosomes Kills
Prokaryote structure Endospores Thick-walled structure Surrounds genome & a small part
of the cytoplasm Protects in harsh environments Develops new generations later
Variation Mutations Genetic recombination CDC
Variation Mutations Rapidly divide UV, radiation, chemicals enhance
mutations Change to respond to
environment Resistance to antibiotics
Variation Transformation Foreign DNA is added to the bacterial
DNA Transduction Phages carry genetic information from
cell to cell. Conjugation Genetic info is transferred between 2
bacteria that are joined
Staphylococcus aureus
Staphylococcus aureus
Streptococcus
Bacillus anthracis (Anthrax)
Lyme disease
Tuberculosis Mycobacterium tubericulosis Respiratory disease Increase in incidence due to AIDS Increased incidence of drug
resistance TB skin test (PPD)
Prokaryotes Benefits Chemical recycling Decomposers Fixation Photosynthesis fix CO2
Nitrogen fixation Reduce N2 (from atmosphere) to NH3
Prokaryotes Symbiotic relationships Plants give bacteria sugars Bacteria give plants usable nitrogen Cows-bacteria in gut Helps digest cellulose Humans-E. Coli in large intestine Produces vit B12 & K
Nutrition Photoautotrophs Sun for energy CO2 for carbon Chemoautotrophs Energy from ammonia, sulfur or
iron CO2 for carbon
Nutrition Photoheterotrophs Sun for energy Organic molecules for source of
carbon Chemoheterotrophs Obtain carbon & energy from
organic molecules Decomposers and most pathogens
Prokaryotes Oldest form of live (3.5 billion
years ago) 1 billion years before eukaryotes 1970-1980’s two groups Archaebacteria (Archaea) Bacteria
Prokaryotes Large diversity among themselves Based on many criteria such as
amino acid sequences Refer to book to see differences