Bacteria

Bacteria Tyler Kreshover ·  All bacteria are Prokaryotes (unicellular organisms that lack a nucleus). ·  Bacteria is classified into two groups: The Eubacteria and The Archaebacteria 1.   Eubacteria ·  Live everywhere: Fresh water, salt water, on land, within the human body…. ·  Usually have a cell wall that protects the cell from injury and determines its shape ·  The cell walls of a Eubacteria contain peptidoglycan, a carbohydrate ·  Some Eubacteria have a second membrane, outside the cell membrane that makes them especially resistant to damage 2.   Archaebacteria ·  Archaebacteria lack the peptidoglycan of Eubacteria and also have different lipids ·  The DNA sequences of key Archaebacteria genes are more like those of Eukaryotes than those of Eubacteria ·  They can live in extremely harsh environments ·  One group of Archaebacteria is the Methanogens; Prokaryotes that produce methane gas and live in oxygen free environments ·  Prokaryotes are identified by characteristics such as shape, the chemical nature of their cell walls, the way they move, and the way the obtain energy 3.   Shape ·  Rod Shaped Prokaryotes are called Bacilli ·  Spherical Prokaryotes are called Cocci ·  Spiral and Corkscrew shaped Prokaryotes are called Spirilla 4.   Cell Walls ·  Two different kinds of cell walls are found in Eubacteria. To tell them apart scientists use a method called Gram staining to tell them apart (two dyes; one violet and one red) ·  When the violet stain is applied it stains the polytidoglycan cell walls. ·  Gram-Positive bacteria have thick peptidoglycan walls that retain the dark color of the violet stain after being washed out by alcohol ·  Gram-Negative bacteria have much thinner walls inside an outer lipid layer. Alcohol dissolves the stain out of it, leaving it a faded red/ pink color 5.   Movement ·  You can also classify Prokaryotes whether they move and how they do it   ·   Some do not move at all ·  Others are propelled by flagella (whip-like structures used for movement) ·  Others lash, snake or spiral forward ·  Still some glide slowly along a layer of slime-like material they secrete ·  Most Prokaryotes are Heterotrophs, meaning that they their energy by consuming organic molecules made by other organisms ·  Others are Autotrophs that make their own food from inorganic molecules 6.   Heterotrophs ·  Prokaryotes that must take in organic molecules for both energy and a supply of carbon are called Chemoheterotrophs ·  Organisms that are photosynthetic, using sunlight for energy, but also take in organic compounds as a carbon source are called Photoheterotrophs 7.   Autotrophs ·  Photoautotrophs use light energy to convert carbon-dioxide and water to carbon compounds and oxygen in a process similar to that used by green plants ·  Chemoautotrophs like photoautotrophs make organic make organic carbon molecules from carbon dioxide. Unlike photoautotrophs, they do not require light as a source of energy; instead they use energy directly from chemical reactions involving ammonia, hydrogen sulfide, nitrites, sulfur, or iron. 8.   Releasing Energy ·  Organisms that require a constant supply of oxygen in order to live are called Obligate Aerobes ·  Some bacteria do not require oxygen and can be killed by it. These are called Obligate Anaerobes. ·  Facultative Anaerobes can survive with or without oxygen 9.   Binary Fission- When a bacterium has grown so that it has nearly doubled in size, it replicates its DNA and divides in half producing two identical “daughter” cells. 10.   Conjugation- A hollow bridge forms between two bacterial cells and genes move from one cell to the other. 11.   Spore Formation- When conditions aren’t right for a bacterium to reproduce they can form structures called spores that can remain dominant for months or even years while waiting for more favorable conditions. 1.   Bacteria are vital to maintaining the living world. Some are producers that capture energy by photosynthesis. Others are decomposers that break down the nutrients in dead matter and the atmosphere. Still other bacteria have human uses involved in medicine, cleaning up oil spills, and food.
 * I.   **** Classifying Prokaryotes **
 * II.   **** Identifying Prokaryotes **
 * III.   **** Metabolic Diversity (Obtaining Energy) **
 * IV.   **** Growth and Reproduction **
 * V.   **** Importance of Bacteria **