the diversity of viruses, bacteria, and fungi. eukaryotic cells (10–100 µm) prokaryotic cells...
TRANSCRIPT
The Diversity of Viruses, Bacteria, and
Fungi
Eukaryotic cells(10–100 µm)
Prokaryotic cells(0.2–10 µm)
cyanobacterium
Viruses (0.05–0.2 µm)
Escherichia coli
Staphylococcus1 µm
Viruses
Defining Characteristics
A virus is a noncellular infectious agent. Viruses are major pathogens and infect virtually all living organisms from animals to bacteria.
The two defining characteristics of a viruses are: A viral particle consists of a protein coat wrapped
around a nucleic acid core (the Genome). A virus CANNOT reproduce itself. Its
reproduction is dependent upon the host cell.
glycoproteins
proteincoat
envelope(lipid bilayer)
spikes
coreproteins
reversetranscriptase
genetic material(viral RNA) coated with protein
viral RNA
protein subunits of coat
helical virus
polyhedral virus
DNA
protein coat
sheath
base plate
tail fiber
complex virus
rabies virus herpes virus
bacteriophage
tobaccomosaic plant virusmeasles virus
Copyright © 2005 Pearson Prentice Hall, Inc.
Ebola virus particles
Treating Viral Infections
Because viruses use the host cell machinery in order to reproduce, the illnesses that they cause are difficult to treat.
Viruses also have high mutation rates, which makes it inevitable that when a population of viruses is being treated with an antiviral drug, a mutation will arise that will result in resistance to the drug.
Prokaryotes (Bacteria)
Characteristics of Prokaryotes Prokaryotes are microscopic (too small to be
seen without a microscope) Most abundant organisms on earth. Metabolically diverse Do not contain membrane bound nuclei or
organelles Usually have a single chromosome Most contain a cell wall Reproduce by fission Come in three basic morphologies
Prokaryotic Cell Morphology
coccus bacillus
spirillum
The Prokaryotic Cell
bacterial flagellum pilus
capsule
cell wall
plasma membrane
cytoplasm
DNA
ribosomes in cytoplasm
The Cell Wall A semi-rigid structure that helps the cell maintain its
shape and resist rupturing. Composed of peptidoglycan molecules The cell wall is often enclosed by a glycocalyx or a
sticky mesh composed of polypeptides, polysaccharides, or both. It helps the cell attach to surfaces such as teeth and mucous membranes and protect against phagocytosis. When highly organized and firmly attached it forms a
capsule When less organized and loosely attached it forms a slime
layer.
Endospores
When some rod-shaped bacteria encounter inhospitable conditions, they form protective structures called Endospores.
An Endospore forms inside of a bacterium and contains genetic material and a few enzymes encased within a thick protective coat.
Endospores are resistant to extreme environmental conditions.
endospore
bacterium
Two Kinds of Prokaryotes Archaebacteria – the bacteria that live under
extreme conditions. Divided into 3 categories Extreme Halophiles – live in high salt
environments Methanogens – Produce methane gas and live in
oxygen free environments such as the gut and swamps
Extreme Thermophiles – live in extremely high temperatures (> 80°C).
Eubacteria – the most common bacteria. Can be divided into two sub-groups: Gram-positive Gram-negative
The Gram Stain
A staining technique called the Gram stain is commonly used in identification of bacterial species. Expose to a purple dye and then iodine Wash with alcohol Counterstain
Gram-positive cells stain purple Gram-negative cells stain pink
Bacillus subtilis Gram positive
E. coli Gram negative
Eubacteria
Photoautotrophs – Cyanobacteria: aerobic cells that engage in photosynthesis. Some convert nitrogen gas to ammonia for use in biosynthesis.
Chemoautotrophs – derive energy by combining oxygen with inorganic molecules such as sulfur, ammonia, and nitrite.
Chemoheterotrophs – derive energy by breaking down organic compounds .
Prokaryotic Growth and Reproduction
Growth is measured by the increase in the number of cells in a population.
Under ideal conditions cell division can occur in as little 10 to 30 minutes in some bacteria and as long as 15 hours in other bacteria.
Prokaryotic cells reproduce by a mechanism called Fission.
parent DNA molecule
DNA copy
DNA replication completed
DNA replication begins
Bacterium before DNA replication bacterial
chromosome
Membrane growth moves DNA
molecules apart
New membrane and cell-wall material
deposited
Cytoplasm divided in two
Bacteria and Human Health: Good Bacteria
Some bacteria are beneficial to other organisms Lactobacillus used to make pickles, yogurt,
sauerkraut, and buttermilk. Actinomyces used as a source of antibiotics Various bacterial components are used in
vaccines Escherichia coli makes vitamin K and compounds
that help us digest milk.
Bad Bacteria:Pathogens
Pathogens are bacteria or parasites that threaten our health and well-being.
They synthesize toxins that cause disease symptoms. Some E. coli strains cause diarrhea Clostridium botulinum causes botulism, C. tetani causes
tetanus Borrelia burgdorferi causes Lyme disease Streptococcus variants cause pneumonia and strep throat. Treponema pallidum – syphilis Neisseria gonorrhoeae - gonorrhea
Fungi
Fungi
Fungi obtain their nutrients from other organisms.
Fungi propagate by spores. Most fungi can reproduce both sexually and
asexually.
Fungi and Us
Fungi attack plants that are important to people.
Fungi cause human diseases. Fungi can produce toxins. Many antibiotics are derived from fungi. Fungi make important contributions to gastronomy.
Wine and beer are made using yeasts Yeasts make bread rise Research details of both….
• Firm cell walls (generally of “chitin”)
• “Spores” as reproductive bodies
• Unique chromosomes and nuclei
• Includes molds, yeasts, rusts, and mushrooms
hyphae - the vegetative bodies of most fungi, constructed of tiny filaments mycelium -an interwoven mat of hyphae
Human hair
Fungal hypha