Learning Target: Bacteria: The Good, the Bad, & the Ugly

Learning Target: Bacteria: The Good, the Bad, & the Ugly

I Can…Describe how bacteria play both beneficial and negative roles in organisms and the ecosystemI Will…• Explain how normal flora bacteria are

beneficial in symbiotic relationships with host organisms

• List examples of how bacteria are used to produce food products

• List examples of how bacteria benefit the ecosystem

• Describe examples of pathogenic bacteria • List reasons for the evolution of antibiotic

resistant bacteria


Bacteria:• Single-celled prokaryotic organism (ALIVE)• No nucleus or membrane-bound organelles• Has a cell wall, but no chloroplast• Not an animal, not a plant

• 3 basic shapes• Sphere (cocci)• Rod (bacilli)• Spiral (spirilla)

• Environment• Aerobes – oxygen• Anaerobes – CO2

• Facultative aerobes -w/ or w/o O2


Bacteria:• Reproduce by:• Binary fission (Similar to mitosis)• Conjugation• Exchange of genetic material

through pili


Bacteria:• Alive single celled organism• Reproduces by binary fission / conjugation• Invades cells or releases toxin• Treated with antibiotics

Virus:• Not alive protein capsid around nucleic acid• Cannot reproduce – needs host cell• Lytic cycle destroys cells• Treat symptoms while immune system

defeats virus


Normal flora – beneficial bacteria that exist on and in other organisms without harm • Often symbiotic (both life-forms benefit)• Animal digestive tracts• Helps breakdown indigestible

material so nutrients can be absorbed

• Synthesize vitamins to be absorbed• Keeps pathogenic organisms away

(fill a niche)• e.g. E. coli in intestines• e.g. Staph epidermidis on skin


Beneficial bacteria – Provides food and services for organisms and ecosystem• Fermentation – chemical breakdown of

organic material (food) to add flavor and characteristics

• Probiotics in foods assist immune and digestive system health

Yogurt Cheese PicklesSoy sauce Alcohol Vinegar


Ecosystem benefits – • Cyanobacteria produce oxygen (Blue-

green algae)• Recycle Carbon (decompose organic

material)• Nitrogen fixing (converts atmospheric

nitrogen into ammonia to be absorbed by plants)• Legumes (peanuts) • Mutualistic


Ecosystem benefits – • Bioremediation – process of using

microbes to breakdown pollutants such as oil spills • Polluted water and beaches

• Biodegradable – ability of bacteria to breakdown a substance• Plastics• Landfills


Opportunistic Pathogens – Good bacteria gone Bad• Bacteria which are Normal flora and

beneficial under certain conditions and environments

• BUT• Change the environment or conditions

and may become pathogenic• e.g. E. coli• Normal and beneficial in intestines• Leading cause of urinary tract

infections


Pathogens – Disease causing• Prior to medical revolution• Most deaths caused by bacterial infections• Sterile technique (disinfection)• Antibiotics• Alexander Fleming• 1928 [1940s]


Bacterial Pathogens Two ways bacteria can cause disease• Invading and attacking cells (alters form

& function)• Release toxins (poisons)• Stimulates immune response• Inflammation


Antibiotics – Wonder Drug• Kills bacteria• Prevents reproduction• Affects formation of cell wall

Why do antibiotics kill bacteria and not our cells?


Antibiotic ResistanceResistance – result of natural selection• Bacteria who are resistant and not killed

by antibiotic survive and reproduce - passing on the resistant genes

• Conjugation can exchange genetic material that carries instructions for resistance


Antibiotic ResistanceCauses:• Overuse – creates selective pressure

favoring resistant bacteria over nonresistant


Antibiotic ResistanceCauses:• Underuse - only destroys the weakest

bacteria but not all leaving bacteria not initially killed alive to reproduce passing on some resistance


Antibiotic ResistanceCauses:• Misuse – Not effective on viral infection

(WHY?)• Agricultural feed overuse

Why does evolution happen so quickly in bacteria?

Documents

Learning Target: Bacteria: The Good, the Bad, & the Ugly