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.