Biology II

Bacteria

• The invention of the microscope opened our eyes to the hidden, living world around us.

• Microscopic life covers nearly every square centimeter of earth

Prokaryotes

• The smallest and most common microorganisms

• Unicellular organisms that lack a nucleus and a membrane bound organelles

• Mainly Bacteria

• Prokaryotes can be divided into two very different groups– Eubacteria– Archaebacteria

Eubacteria

• Include a wide range of organisms with different lifestyles

• Eubacteria live almost everywhere• Largest Prokaryote Domain• Cell membrane around cytoplasm• Some have an extra cell wall on the outside to

resist damage

Archaebacteria

• Lack the same carbohydrates of eubacteria and also have different membrane lipids

• Also, the DNA sequences of key archaebacterial genes are more like those of eukaryotes than those of eubacteria

• Many archaebacteria live in extremely harsh environments

Identifying Prokaryotes

• Prokaryotes are identified by characteristics such as: – shape– the chemical nature of their cell walls– the way they move– the way they obtain energy

Shapes

• Bacilli – Rod shaped• Cocci – Spherical Shaped• Spirilla – spiral and corkscrew shaped

Cell Walls

• Eubacteria – Have peptidoglycan• Archaebacteria – Don’t have peptidoglycan

Movement

• Flagella• Lash, snake or spiral forward• They do not move at all

Metabolic Diversity

• No characteristic of prokaryotes illustrates their diversity better than the way they obtain energy

Heterotrophs

• Must take inorganic molecules for both energy and a supply of carbon– Chemoheterotrophs: must take in organic

molecules for energy– Photo heterotrophs: Use sunlight for energy but

need organic compounds for a carbon source

Autotrophs

• Chemoautotrophs: perform chemosynthesis to make carbon from carbon dioxide. Does not require sunlight

• Photoautotrophs: Use light to convert carbon dioxide and water into carbon compounds and oxygen gas

Getting Energy

• Bacteria need a constant supply of energy– Obligate aerobes- Require costant supply of

oxygen– Obligate anaerobes- Need no oxygen, for some

oxygen will kill it– Facultative anaerobes- Survive with or without

oxygen

Releasing Energy

• Like all organisms, bacteria need a constant supply of energy

• This energy is released by the process of cellular respiration or fermentation or both

Growth and Reproduction

• Bacteria can grow really fast• Types of Reproduction– Binary fission– Conjugation– Spore formation

Binary Fission

• When a bacterium has grown so that it has nearly doubled in size, it replicated its DNA and divided in half producing 2 identical daughter cells

Conjugation

• Many bacteria are also able to exchange genetic information by a process called conjugation

• This transfer of genetic information increases genetic diversity

Spore Formation

• When growth conditions become unfavorable, many bacteria form structures called spores

Endospore

• A type of spore formed when a bacterium produces a thick internal wall that encloses a thick internal wall that encloses its DNA and a portion of its cytoplasm

Importance of Bacteria

• Decomposers– Break down dead matter

• Nitrogen Fixers– Converts nitrogen into a form plants use

Decomposers

• As decomposers, bacteria help the ecosystem recycle nutrients, therefore maintaining equilibrium in the environment.

Human Uses of Bacteria

• Used in food and beverage production• Industries: petroleum, water, mining, drugs• Inside of us (symbiosis)– E. Coli

• Drug Research

Helpful Bacteria

• Bacteria help the body digest food and produce certain vitamins

• Some bacteria fight off diseases• Helps break down all the dead plant and

animal remains making nutrients for the soil