“Prokaryotes”

- single-celled organisms that do not have membrane-bound organelles

Bacteria versus ArchaeaBacteria Both Archaea

-live everywhere

-can cause diseases

-cell wall contains peptidoglycan

-small (1-10 M)-prokaryotic-single celled -DNA as a single circular chromosome-no membrane-bound organelles-both reproduce asexually via binary fission

-Both extremophiles & mesophiles (moderate T)

-do not cause diseases

-cell wall does not contain peptidoglycan

• Archaea are rather difficult to study…– Won’t grow in a Petri dish…

Live in volcanic hot springs…

And acid mine drainage…

Archaea

• Differ from bacteria in their biochemistry and metabolism– Phospholipid composition (ether-linked lipids)– Cell wall composition (some contain

pseudomurein)– Metabolism: use a wide variety of food

sources (autotrophic or heterotrophic)

Bacteria

Classified by Shape:

1. spherical: coccus or cocci, ex. strep throat

2. rod-shaped: bacillus or bacilli, ex. E. coli

3. spiral: spirillium or spirilla, ex. Treponema pallidium, the cause of syphilis

Classified by Respiration:

1) obligate aerobes: must have oxygen

ex. Mycobacterium tuberculosis

2) obligate anaerobes – can only grow in the absence of oxygen

ex. deep soil bacteria, deep marine bacteria, Treponema pallidium

3) facultative anaerobes – can live in both oxygen – rich and oxygen – deprived conditions, ex. E. coli

• under anaerobic conditions (no oxygen) bacteria will undergo anaerobic respiration, producing ethanol or lactic acid and energy

Classified by Nutrition1) heterotrophic

- most bacteria, obtain nutrients from other organisms

i) parasitic: detrimental to host

ii) saprophytic: decompose dead organic matter

iii) symbiotic: contribute to host’s well-being

2. autotrophic

- produce own food

i) photosynthetic: produce sugars using light energy

ii) chemosynthetic: produce sugars using chemical reactions

General Structure of a Bacterium

cilia

Bacterial Reproduction

• there are two types of bacterial reproduction

1) Binary Fission

- creates two identical

daugther cells

- asexual

2) Conjugation- exchange of genetic information between two

bacterial cells

- involves the copy and donation of a circular plasmid through a pilus

- sexual

- cause of large-scale antibiotic resistance!

plasmid

pilus

bacterial chromosome

A sneaky alternative: endospores

• during times of unfavourable environmental conditions some bacteria can form highly resistant endospores

- dormant forms where the genetic material is protected by a thick wall

- once bad times pass the bacteria will re- emerge, ready for binary fission

Being Homo sapiens centered, we tend to define bacteria as helpful or harmful to us…

Helpful Bacteria

1) Bacteria in medicine:- can make things for us: ex. engineered

bacteria make human growth hormone and insulin

2) Bacteria in industry:- make bioplastics: fully degradable plastics

(take 6 months as opposed to 400 years to degrade!)

3) Bacteria as decomposers

- can be used in bioremediation to clean up oil spills, clear our waste water, etc. by converting harmful substances to less harmful ones

4) Bacteria as food makersex.1 Cheese– originally it was the action of bacteria

producing acid that caused the separation of a curd from the milk

ex. 2 Chocolate – without bacteria we would not have chocolate!!!

5) Bacteria in and on our bodies

Harmful Bacteria

1) Harmful to the industry

- bacteria can cause degradation of desired products

ex. Pasteur was originally hired by a wine maker to figure out why what should be wine was coming out as vinegar…

2) harmful to our health

- there are many many many pathogenic (disease-causing) bacteria and we suffer losses from them every year

humans vs. microbes:Antibiotic Resistance

• the overuse of antibiotics over the last decades has lead to a rise in antibiotic resistant bacteria, i.e. bacteria that do not react to antibiotics

• done by selecting and then unintentionally breeding resistant bacteria

• we perform a similar experiment in our bodies when we do not follow instructions for our antibiotics

1) low doses and not enough exposure selects bacteria that are resistant

2) given time the resistant bacteria take over

How do hand sanitizers work?

• the alcohol in the sanitizer causes

lysis of bacterial cells

(and yours also, btw)

Penicillin InhibitsStaphylococcus aureus

Note that growth of the bacteria Staphylococcus aureus is inhibited in the area surrounding the invading penicillin-

secreting Penicillium mold colony.