Bacteria by liz daleybacteria.jpg

Diagnostic Characteristics
Bacteria is one of the Prokaryotic Domains or Monera branches. The other Prokaryotic Domain is Archaea. Bacteria are normally unicellular, meaning they are single celled. They lack a nucleus, a nuclear envelope, and membrane enclosed organelles. The cell walls of these organisms contain peptidoglycan, which is the combination of polymers and modified sugars, cross linked by short polypeptide chains. Until relatively recently, bacteria and archaea were thought to be a lot more closely related to each other than they really are. Due to their discovered differences, they were broken down into two different domains. However, there are still things like "archabactera" and "eubacteria" that show their relatedness. A difference between bacteria and archaea is that bacteria contain one RNA polymerase which archaea contain three. RNA polymerase is an enzyme used during transcription to connect the basic building blocks of RNA. A huge difference between domain Bacteria and the other two domains is that during the process of translation for protein synthesis, the first amino acid to begin the polypeptide chain is fornylmethionine, a descendent from our commonly known initiator amino acid, methionine. The two amino acids are coded by the same codon, AUG. Some bacteria that infect humans and cause harm can be treated with antibiotics, which kill the harmful bacteria. However, some bacteria are resistant to antibiotics.

There are no specific habitats for bacteria. They dominate the biosphere and can be located anywhere from the soil to a hand of a human. One of the necessary requirements for survival of bacteria is water and nutrition. Ultimately, the location of bacteria depends on the species. All bacteria are either anaerobic or aerobic, so depending on the classification of that, they can live with or without oxygen. There are some bacteria known as facultative anaerobes who prefer to live with oxygen, but are able to survive without it. The only limitation on where a bacteria can survive is that they can not survive in extreme conditions.

Major Types
1. Proteobacteria – Bacteria in this division are gram-negative meaning their cell walls are more structurally complex and contain less peptidoglycan. Peptidoglycan is polymers and modified sugars attached by short polypeptide chains. This group contains photoautotrophs, which use photosynthesis, heterotrophs, which eat other bacteria or the waste of other bacteria, and chemoautotrophs, which need carbon dioxide. Also, both anaerobic and aerobic species are categorized in this group. There are five subgroups including Alpha, Beta, Gamma, Delta, and Epsilion Proteobacteria. These five subgroups are determined mainly by RNA sequences. Also, there are two methods of locomotion in proteobacteria including flagella (a hairlike extremity used to propell a bacteria), and bacterial gliding (flagella are not used, but a bacteria can still move itself).

2. Chlamydias – This type of bacteria includes parasites. Parasites can only survive in the cells of animals and are usually after energy sources, like ATP for example. These bacteria have gram-negative walls and lack peptidoglycan. An example of this is Chlamydia trachomatis which is the most common cause of blindness. The three Chlamydia species include: a human pathogen, a species that affects swine, and another species that affects only mice and hamsters.

3. Spirochete – The bacteria in this group are helical heterotrophs, meaning that they are in a similar shape to the double helix of DNA. Due to the helical shape, these bacteria move in a corkscrew like motion. One example of this is Borrelia burgdorferi which causes Lyme disease. Spirochetes also have endocellular flagella, usually about two to two hundred depending on the species of the organism. Borrelia burgdorferi, spirochete is the cause of Lyme disease.


4. Gram-Positive Bacteria – These bacteria have a simple cell wall structure and contain a large amount of peptidogylcan. One subgroup is actinomycetes, which form colonies with chains of cells. This subgroup helps to decompose organica material in the soil. Another subgroup is mycoplasmas. In this subgroup is the only bacteria that lacks a cell wall and are also the smallest of all known cells.
These gram positive bacteria are stained purple for their peptidoglycan in their cell walls
These gram positive bacteria are stained purple for their peptidoglycan in their cell walls

5. Cyanobacteria – These are commonly known as photoautotrophs, meaning they perform photosynthesis. They are most usually found where there is a great supply of water. Cyanobacteria are referred to as photosynthetic because they live in the water and are able to manufacture their own food. All cyanobacteria are unicellular, and despite the fact that they lack flagella, many cyanobacteria are still able to move. Because cyanobacteria are photosynthetic and acquatic, they are often called "blue-green algae" because of their blue-green appearance. This lake is full of cyanobacteria which is easily distinguishable by its bluish green color. Cyanobacteria can be single-celled or colonial. When cyanobacteria takes on a colonial form, there are three distinct cell types: vegetative cells (photosynthetic, form in favorable conditions), climate-resistant spores (form in harsh environment), and thick-walled heterocysts (have enzyme to do nitrogen fixation).

This lake is full of cyanobacteria which is easily distinguishable by its bluish green color
This lake is full of cyanobacteria which is easily distinguishable by its bluish green color

The Gram stain is named after the 19th century Danish bacteriologist who developed it.
  • The bacterial cells are first stained with a purple dye called crystal violet.
  • Then the preparation is treated with alcohol or acetone.
  • This washes the stain out of Gram-negative cells.
  • To see them now requires the use of a counterstain of a different color (e.g., the pink of safranin).
  • Bacteria that are not decolorized by the alcohol/acetone wash are Gram-positive

Transport of Materials
Bacteria uses active transportation, which goes against the concentration gradient and requires ATP, to move substances in and out of the cells. Nutrients like carbon dioxide are absorbed through the cell wall. Depending on the type of bacteria will tell which types of materials it takes in and gives off. Photoautotrophs take in carbon dioxide and give off oxygen. Chemoautotrophs also need carbon dioxide.

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Binary fission in bacteria

Bacteria reproduce using binary fission, which simply means “division in half.” During this process, DNA is synthesized almost continuously. The population of bacteria can almost double in around twenty minutes and generation time is usually measured in 1-3 hours. This is a form of asexual reproduction, meaning there is only one parent cell. Because bacteria don’t do meiosis or mitosis, they still transfer genes, just in different ways including transformation, conjugation, and transduction. In transformation, the transfer of genes is completed by the sharing of genes from surrounding environments. Conjugation is the direct transfer of genes from one bacterium to another. During transduction, phages, viruses that infect bacteria, carry genes from one bacterium to another. The rates of these transfers can be sped up in the presense of the right temperature, pH, nutrient levels, and salt concentrations. Genetic variation is caused by mutations.

Environmental Adaptations
Bacteria descended from Archaea a very long time ago. Huge amounts of bacteria can be created in only twenty minutes, which allows for each cell to adapt to its environment very quickly. Mutations and resistance form over time which allows for the bacteria to become genetically modified and also means that each new bacterium will have to adapt to lesser and lesser environmental changes. Bacteria are great at adapting to its environment. An example of this is how bacteria are able to become resistant to their environment is how they are able to adapt to survive antibiotics. Bacteria that at first were susceptible to drugs became more and more resistant to those drugs to be able to survive in their environment. In addition, bacteria are able to react to a major environmental change by quickly repressing or expressing a large amount of genes.

Review Questions
1. Explain the anatomy of a bacteria.
2. Explain why and how Bacteria are able to mutate as well as adapt to new environments so quickly and why this is a problem when it comes to disease and medicine.
3. Describe the method used by bacteria to transport materials.
4. What does bacteria use to share genes? Describe the different processes and variables in speed.
5. Explain the Gram Stain and how it worked.