bacteria

Archaebacteria and Eubacteria

Bacteria are of immense importance because of their rapid growth, reproduction, and mutation rates, as well as, their ability to exist under adverse conditions.

The oldest fossils known, nearly 3.5 billion years old, are fossils of bacteria-like organisms.

Bacteria can be autotrophs or hetertrophs.

Those that are classified as autotrophs are either photosynthetic, obtaining energy from  sunlight or chemosynthetic, breaking down inorganic substances for energy .

Bacteria classified as heterotrophs derive energy from breaking down complex organic compounds in the environment.  This includes saprobes, bacteria that feed on decaying material and organic wastes, as well as those that live as parasites, absorbing nutrients from living organisms.

Depending on the species, bacteria can be aerobic which means they require oxygen to live

                                                or

anaerobic which means oxygen is deadly to them.  

Archaebacteria 

Methanogens

                These Archebacteria are anaerobes. They make methane (natural gas) as a waste product. They are found in swamp sediments, sewage, and in buried landfills. In the future, they could be used to produce methane as a byproduct of sewage treatment or landfill operation.

Halophiles

                These are salt-loving Archaebacteria that grow in places like the Great Salt Lake of Utah or salt ponds on the edge of San Francisco Bay. Large numbers of certain halophiles can turn these waters a dark pink. Pink halophiles contain a pigment very similar to the rhodopsin in the human retina. They use this visual pigment for a type of photosynthesis that does not produce oxygen. Halophiles are aerobes, however, and perform aerobic respiration.

Thermophiles

                These are Archaebacteria from hot springs and other high temperature environments. Some can grow above the boiling temperature of water. They are anaerobes, performing anaerobic respiration.

Thermophiles are interesting because they contain genes for heat-stable enzymes that may be of great value in industry and medicine. An example is taq polymerase, the gene for which was isolated from a collection of Thermus aquaticus in a Yellowstone Park hot spring. Taq polymerase is used to make large numbers of copies of DNA sequences in a DNA sample. It is invaluable to medicine, biotechnology, and biological research. Annual sales of taq polymerase are roughly half a billion dollars.

Eubacteria

Cyanobacteria

                This is a group of bacteria that includes some that are single cells and some that are chains of cells. You may have seen them as "green slime" in your aquarium or in a pond.

Cyanobacteria can do "modern photosynthesis", which is the kind that makes oxygen from water. All plants do this kind of photosynthesis and inherited the ability from the cyanobacteria.

Bacteria are often maligned as the causes of human and animal disease.  However, certain bacteria, the actinomycetes, produce antibiotics such as streptomycin and nocardicin.

Other Bacteria live symbiotically in the guts of animals or elsewhere in their bodies.

For example, bacteria in your gut produce vitamin K which is essential to blood clot formation.

Still other Bacteria live on the roots of certain plants, converting nitrogen into a usable form.

Bacteria put the tang in yogurt and the sour in sourdough bread.

Saprobes help to break down dead organic matter.

Bacteria make up the base of the food web in many environments.

Bacteria are prokaryotic and unicellular.

Bacteria have cell walls.

Bacteria have circular DNA called plasmids

Bacteria can be anaerobes or aerobes.

 Bacteria are heterotrophs or autotrophs.

Bacteria are awesome!

Bacteria can reproduce sexually by conjugation or asexually by binary fission.

Endospore

Bacteria can survive unfavorable conditions by producing an endospore.

Shapes of Bacteria

Penicillin kills bacteria by making holes in their cell walls.  Unfortunately, many bacteria have developed resistance to this antibiotic.

The Gram stain, which divides most clinically significant bacteria into two main groups, is the first step in bacterial identification. 

Bacteria stained purple are Gram + - their cell walls have thick petidoglycan and  teichoic acid.

Bacteria stained pink are Gram – their cell walls have have thin peptidoglycan and  lipopolysaccharides with no teichoic acid.

The Gram stain has four steps:

1. crystal violet, the primary stain: followed by

2. iodine, which acts as a mordant by forming a crystal violet-iodine complex, then

3. alcohol, which decolorizes, followed by

4. safranin, the counterstain.

Is this gram stain positive or negative? 
Identify the bacteria.

Gram staining tests the bacterial cell wall's ability to retain crystal violet dye during solvent treatment.

Safranin is added as a mordant to form the crystal violet/safranin complex in order to render the dye impossible to remove.

Ethyl-alcohol solvent acts as a decolorizer and dissolves the lipid layer from gram-negative cells. This enhances leaching of the primary stain from the cells into the surrounding solvent.

 Ethyl-alcohol will dehydrate the thicker gram-positive cell walls, closing the pores as the cell wall shrinks. 

For this reason, the diffusion of the crystal violet-safranin staining is inhibited, so the bacteria remain stained.