1. Bacteria – again!

2. Learning Goal
We are learning about the helpful and harmful bacteria in our world.

3. Harmful & Helpful Bacteria
bacteria can be both harmful and helpful to humans
Cholera is an acute intestinal infection caused by a bacterium that can be picked up through contaminated water and food.

4. Article on High Risk of Cholera
Harmful Bacteria
pathogen: a biological agent that causes disease inside the host organism
pathogenic bacteria interfere with cell function, and/or produce toxins
Ex. cholera, leprosy, typhoid fever, strep throat, salmonella and tuberculosis  
Cholera is an acute intestinal infection caused by a bacterium that can be picked up through contaminated water and food.
Article on High Risk of Cholera

5. Infection and Disease Cont’d…
antibiotics can often kill unwanted bacteria
Penicillin killed the bacterium on the left by weakening its cell wall

6. Infection and Disease Cont’d…
the overuse of antibiotics can cause bacteria to adapt and become resistant, making them less effective

7. Helpful Bacteria
many bacteria are decomposers and recycle nutrients vital to the biogeochemical cycles (e.g. carbon cycle)
A saprophyte or saprotroph is an organism which gets its energy from dead organic matter. This may be decaying pieces of plants or animals. 

8. Helpful Bacteria Cont’d…
soil bacteria convert atmospheric nitrogen into more usable forms for plants
A saprophyte or saprotroph is an organism which gets its energy from dead organic matter. This may be decaying pieces of plants or animals. 

9. Helpful Bacteria Cont’d…
photosynthetic bacteria are the major producers in marine ecosystems and are therefore major producers of atmospheric oxygen
A saprophyte or saprotroph is an organism which gets its energy from dead organic matter. This may be decaying pieces of plants or animals. 

10. Helpful Bacteria Cont’d…
bacteria in the intestines of animals help cellulose digestion in cattle and produce some vitamins in our digestive systems
A saprophyte or saprotroph is an organism which gets its energy from dead organic matter. This may be decaying pieces of plants or animals. 

11. Helpful Bacteria Cont’d…
bacteria is used in the production of cheese, yogurt, soy sauce and chocolate
genetic engineers have modified some bacteria to produce medically valuable compounds (ex. insulin and human growth hormone)
antibiotics produced by bacteria can be used to kill other unwanted microorganisms
The most common usage for bacteria in food preparation is with dairy fermentations.
Yogurt and cheeses have been made for centuries using bacteria. The ancients may not have known exactly what kind of bacteria that was needed or if what was needed was, indeed, bacteria. All they knew was that the previous batch was required to make a new one. Many people lack the ability to break down and absorb lactose, the sugar molecule in milk. As a result, it enters the gut, producing acid and gas, causing pain and diarrhea. Fermented milk products metabolize lactose into lactic acid, which is more tolerable for many people
Making cheese and yoghurt are also processes that depend upon micro-organisms - in this case bacteria.
The souring of milk is a fermentation process, as it takes place better when oxygen is absent.
Fresh milk contains sugars and some bacteria.
The bacteria feed on the sugars in the milk.
The main sugar in milk is called lactose.
Lactose is converted into lactic acid by bacterial fermentation, the increased acidity sours and thickens the milk.

12. Learning Goal
We are learning about the helpful and harmful bacteria in our world.

13. Homework: 2.1 Question 8 on page 53
if conditions are unfavourable, bacteria may form endospores until conditions improve
after the DNA replicates, a thick, resistant cell wall forms around one of the chromosomes
the one daughter cell will die, but the protected cell can withstand the harsh conditions
the endospore offers protection to the bacterial chromosome under harsh dry conditions