Human Health and Disease
Bacteria and Viruses
Bacteria:
Characteristics:
•Prokaryotic
•Kingdom Monera
•Single-celled organism with no
membrane-bound organelles
•Reproduce asexually
•Components: Cell wall, Cell
membrane, cytosol, ribosomes and
DNA plasmids. Some have cilia or
flagella for movement
Types of bacteria
Gram-positive Bacteria
Possess a thick peptide layer
which retains a stain called
crystal violet. Appear purple
when viewed under a
microscope.
Gram-negative Bacteria
• have a thin peptide layer, take up the
pink stain, and appear pink when
viewed under a microscope.
Shapes of bacteria: Bacillus (rod-shaped), Cocci
(round), Spirillum (corkscrew-shaped)
Bacillus:
Example: Anthrax
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Cocci:
Example: streptococcus (causes strep throat)
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Spirillum/Spirochetes:
Example: Treponema pallidum- causes syphilis
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How Bacteria Cause Disease
• Metabolizing the host– Heterotrophic bacteria obtain nutrients by
secreting enzymes that break down organic
structures and absorb them
– If the environment is your throat or lungs, this
can cause serious problems!
• Ex.
– Tuberculosis bacteria settle into the lungs and use human
tissue as their nutrients
– Propionibacterium acnes causes acne
• ToxinsSome bacteria secrete chemical
compounds into their environment
which are poisonous to eukaryotic
cells (toxic)
– Ex. Diptheria grows in the throat,
but the toxins attack the heart,
nerve, liver and kidneys
– Food poisoning occurs when
humans eat food where bacteria
have grown and produced toxins
What can you do?
• Protect your food:
– Heat
– Freeze
– Dry
Evolution of Antibiotic Resistance:
• Forty or fifty years ago, thanks to antibiotics, scientists
thought medicine had all but eradicated infectious
agents as a major health threat.
• More recently, an upsurge of infectious disease is a
problem we have unwittingly created for ourselves b/c:
– rapid, frequent, and relatively cheap international travel allows
diseases to leap from continent to continent
– Many people have inadequate sanitation and lack of clean
drinking water
– We have overused the "miracle drugs“ to treat such diseases to
the point that they lose their potency
• Whenever antibiotics wage war on microorganisms, a few of
the enemy are able to survive the drug.
• Because microbes are always mutating, some random
mutation eventually will protect against the drug.
• Antibiotics used only when needed and as directed usually
overwhelm the bugs.
• Too much antibiotic use selects for more resistant
mutants.
• When patients cut short the full course of drugs, the resistant
strains have a chance to multiply and spread.