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Human Health and Disease
Bacteria
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
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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Gram-positive Bacteria
Possess a thick peptide layer which retains a stain called
crystal violet. Appear purple when viewed under a
microscope.
Types of bacteria
Gram-negative Bacteria
• have a thin peptide layer, take up the pink stain, and appear pink when viewed under a microscope.
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
• Toxins-Some 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.