3 Domains

Archaea constitute third Domain Archaea seem more closely related to Domain Eukarya than to bacteria contain unique genetic sequences in their rRNA have unique membrane lipids & cell wall construction live in the most extreme habitats in nature, extremophiles adapted to heat, salt, acid pH, pressure & atmosphere includes: methane producers, hyperthermophiles, extreme halophiles, and sulfur reducers

Bacteria Image Source:http://www.qub.ac.uk/afs/vs/vsd9.html Bacteria are often maligned as the causes of human and animal disease (like this one, Leptospira, which causes serious disease in livestock). However, certain bacteria, the actinomycetes, produce antibiotics such as streptomycin and nocardicin; others live symbiotically in the guts of animals (including humans) or elsewhere in their bodies, or on the roots of certain plants, converting nitrogen into a usable form. Bacteria put the tang in yogurt and the sour in sourdough bread; bacteria help to break down dead organic matter; bacteria make up the base of the food web in many environments. Bacteria are of such immense importance because of their extreme flexibility, capacity for rapid growth and reproduction, and great age - the oldest fossils known, nearly 3.5 billion years old, are fossils of bacteria-like organisms. Image Source:http://www.ucmp.berkeley.edu/bacteria/bacteria.html

Bacterial Structure Very small cell Lack membrane bound organelles Ribosomes Lack nuclear membrane DNA circular Nucleoid Biochemical processes in cytoplasm Plasmids –loops of DNA Image Source: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookDiversity_2.html Note the nucleoid region (n) where DNA is located as well as the electron dense areas of the cytoplasm (dark areas) on these two cells of Neisseria gonorrhoeae. Bacteria lack a nuclear membrane and membrane-bound organelles. Biochemical processes that normally occur in a choloroplast or mitochondrion of eukaryotes will take place in the cytoplasm of prokaryotes. Bacterial DNA is circular and arrayed in a region of the cell known as the nucleoid. Scattered within bacterial cytoplasm are numerous small loops of DNA known as plasmids. Bacterial genes are organized in by gene systems known as operons.

A Typical Bacteria Cell Image Source: Biggs, Alton, Kathleen Gregg, Whitney Crispen Hagins, and Chris Kapicka. Biology: The Dynamics of Life. Columbus: Glencoe/McGraw Hill, 2002. Inside Story: A Typical Bacteria Cell P.503 Bacteria live in hypotonic environment, higher concentration of water molecules outside the cell than inside which causes the water to continuously enter the bacteria cell. The cell wall protects the bacteria from bursting by osmotic pressure. Scientists use a bacterium’s need to maintain its cell wall to destroy bacteria that cause disease.

BINARY FISSION Asexual Reproduction Copies chromosome DOUBLING THEIR NUMBERS EVERY 20 MINUTES Image Source: Pearson Education Inc as Benjamin Cummings Publishers 1. MOST BACTERIA reproduce by a process called BINARY FISSION. 2. BINARY FISSION IS A PROCESS IN WHICH THE CHROMOSOMES REPLICATE, AFTER WHICH THE CELL DIVIDES. 3. BINARY FISSION IS A TYPE OF ASEXUAL REPRODUCTION. 4. Under ideal conditions, bacteria divide (reproduce) rapidly, DOUBLING THEIR NUMBERS EVERY 20 MINUTES. 5. ALL BACTERIA ARE HAPLOID AND CONTAIN ABOUT 1/1000 AS MUCH DNA AS ORDINARY EUKARYOTIC CELLS.  MOST BACTERIA'S DNA IS A SINGLE DOUBLE STRAND THAT ATTACHES TO THE CELL MEMBRANE AND REPLICATES JUST BEFORE THE CELL DIVIDES Their small size, ability to rapidly reproduce (E. coli can reproduce by binary fission every 15 minutes), and diverse habitats/modes of existence make monerans the most abundant and diversified kingdom on Earth. Bacteria occur in almost every environment on Earth, from the bottom of the ocean floor, deep inside solid rock, to the cooling jackets of nuclear reactors.

Bacterial Shapes

Cocci

Bacilli

Spirilla

Cell Wall Gram + Gram - Gram Staining Image Source: http://129.109.136.65/microbook/ch002.htm The cell membrane is surrounded by a cell wall in all bacteria except one group, the Mollicutes, which includes pathogens such as the mycoplasmas. The composition of the cell wall varies among species and is an important character for identifying and classifying bacteria. In this diagram, the bacterium has a fairly thick cell wall made of peptidoglycan (carbohydrate polymers cross-linked by proteins); such bacteria retain a purple color when stained with a dye known as crystal violet, and are known as Gram-positive (after the Danish bacteriologist who developed this staining procedure). Other bacteria have double cell walls, with a thin inner wall of peptidoglycan and an outer wall of carbohydrates, proteins, and lipids. Such bacteria do not stain purple with crystal violet and are known as Gram-negative. Cell Wall

The Gram Stain Reaction Based on the difference in the chemical composition of bacterial cell walls. Gram + have a thick peptidoglycan layer. Gram – have a thinner peptidoglycan layer surrounded by outer lipid-containing layers.

Gram Staining Image Source: http://sps.k12.ar.us/massengale/images/clip0081.jpg In this diagram, the bacterium has a fairly thick cell wall made of peptidoglycan (carbohydrate polymers cross-linked by proteins); such bacteria retain a purple color when stained with a dye known as crystal violet, and are known as Gram-positive (after the Danish bacteriologist who developed this staining procedure). Other bacteria have double cell walls, with a thin inner wall of peptidoglycan and an outer wall of carbohydrates, proteins, and lipids. Such bacteria do not stain purple with crystal violet and are known as Gram-negative.

Data Name of Bacteria Shape Color Gram + or Gram -

Discussion What was the purpose of doing this lab? List 3 characteristics of bacteria cells. Compare and contrast gram positive and gram negative bacteria.