Bacteria Part 1:History

Bacteria Fossil evidence suggests bacteria have been around for over 3.5 billion years. In comparison humans have been around roughly 1 million years. Most abundant form of life on Earth

Time Machine Close your eyes and try to imagine travelling back in time 4 billion years. What does the world look like around you? What is the atmosphere like? Are there plants or animals?

Ancient Earth At the time when the first bacteria would have been created the planet was highly acidic, very saline,extremely hot with an atmosphere containing mostly C02 and Nitrogen. There were no plants, animals, oceans or oxygen present.

Bacterial Evolution Autotrophic bacteria carried out photosynthesis and converted CO2 into Oxygen. These bacteria are partially responsible for the current, oxygen rich atmosphere that we currently have.

Bacteria Part 2: Structure

Introduction Members of the Monera kingdom are all bacteria. most abundant, most ancient, most simple of all organisms over 4500 different kinds of bacteria they are important constituents of the atmosphere, soil, water.

Bacteria Structure Unicellular, procaryotes lack organelles DNA is free in the cytoplasm (no nuclear membrane) 1 m in size capsule flagella ribosome DNA cell wall cell membrane

External Structures: Capsule Gel like coating on the outside of the cell helps cells attach to their environment protection from being eaten by other microbes capsule

Streptococcus mutans Bacteria that causes tooth decay secretes the capsule in the presence of sugar and sticks to teeth this causes plaque to form on the teeth resulting in tooth decay

Flagella Help bacteria to move spirrilum and rod shaped bacteria have flagella, spherical shaped bacteria lack flagella need flagella to move around to look for nutrients

Cell Wall: Peptidoglycan Chemically different than plant cell walls made up of cellulose A matrix of sugar crosslinked with amino acids function: helps keep the shape of cell, and protects the cell from swelling or breaking.

Cell Wall Gram Positive: Gram Negative: E. coli cells Staphylococcus cells Gram Negative: E. coli cells 2 different types of cell walls: Gram Positive - contain a thick layer of peptidoglycan that absorbs stain. Gram Negative - contains a thin layer of peptidoglycan that does not absorb stain.

Cell Membrane Bi-lipid layer with protein channels retains the cytoplasm in the cell is the barrier between the internal and exterior environment important in the transport of molecules into and out of the cell Protein channel Lipids

Ribosomes Ribosomes are the protein synthesizing factories of the cell.

Endospore Endospores are highly resistant resting structures produced within cells Spores are resistant to heat, radiation, chemicals, and dessication Spores that were dormant for thousands of years in the great tomes of the Egyption Pharohs were able to germinate and grow when placed in appropriate medium.

Bacteria Part 3: Classification

The Different Types of Bacteria Bacteria are extremely diverse and therefore live in many different environments and play many different roles.

Shapes of Bacteria Shapes Round: coccus Rod: bacillus Spiral: spirillus

Metabolism based Classification Aerobic bacteria: use oxygen to carry on respiration which produces energy. MOST bacteria are aerobic. Facultative Anaerobic bacteria: bacteria that can produce energy with or without oxygen. This is called fermentation. Obligate Anaerobes: bacteria can only produce their energy in an oxygen-free environment. This process is also called fermentation.

Nutrition Based Classification Autotrophic Bacteria Obtain energy from inorganic (non-living) sources. 2 types photosynthetic bacteria: contain chlorophyll in the cell membrane (not held in a plastid).These are the blue-green or cyanobacteria. Chemoautotrophic bacteria: energy comes from inorganic molecules such as nitrogen, sulfur, hydrogen and iron compounds. Oscillatoria Sulfur bacteria

Heterotrophic Bacteria Obtain energy from organic (living) sources. These bacteria play a leading role in the breakdown and decomposition of organic molecules. Thus are key players in the biological recycling of nutrients. Rhizobacterium on clover stem

2 type of Heterotrophic bacteria Saprobes: feed on dead plant and animal matter. They secrete digestive enzymes onto the organic matter which digest the food into small particles. This food can then be absorbed by the bacteria. Gives soil its characteristic smell Mutant bacteria: able to breakdown inorganic material such as nylon, plastic, herbicides and pesticides.

Examples: meningitis, pneumonia, tuberculosis. Parasites: These bacteria live on or in living organisms and may cause disease. Examples: meningitis, pneumonia, tuberculosis. Bacteria causing pneumonia and meningitis Listeria: bacteria which causes food poisoning Staphylococcus: cause toxic shock syndrome

Tuberculosis Lung tissue infected with pink, rod shaped Mycobacterium tuberculosis

Uses of Bacteria Lactobacillus: used in dairy foods to change glucose into lactose. Used in making foods like sauerkraut, yogurt,cheeses, vinegar. Use bacteria to make food for cattle (silage) which helps increase milk production. Used as herbicides and pesticides. Backgound image: Lactobacillus

Uses of Bacteria Some bacteria are used in industry to clean up wastes, chemical spills of PCBs, gas and oil. The bacteria can digest toxic chemicals and turn them into harmless products. As long as toxic materials remain, the bacteria will continue to digest them. Once the contaminate is gone the bacteria have no food source and will die. Perfect cleaning mechanism. Backgound image: Lactobacillus

Reproduction Mostly by asexual reproduction Binary Fission- a form of asexual reproduction where a parent cell divides into two identical cells. Under ideal conditions, lots of food, proper temperature and lots of space, bacteria divide every 20 minutes and in 24 hours a single bacterial cell could produce 2 million kg of bacterial cells.

Binary Fission

Sexual Reproduction . Genetic recombination is responsible for generating diversity within bacterial populations. It is defined as the combining of genetic material from two individuals into the genome of a single individual. Three processes named transformation, transduction, and conjugation are responsible for bacteria’s genetic recombination( sexual reproduction).

Transformation living cells take up DNA from their environment. A foreign allele is incorporated into a bacterial chromosome by replacing the native allele. Thus the transformed cell now has a chromosome containing DNA from two different cells.

Transduction In transduction, viruses that infect bacteria or ‘phages’ are responsible for this ‘gene transfer’. Bacterial DNA found in the phage is transferred to the new host and is incorporated into the host genome.

Transduction

Conjugation "Conjugation is the direct transfer of genetic material between two bacterial cells that are temporarily joined"(Biology Campbell 3rd edition 1993). Animation Conjugation resembles sexual reproduction, in that the two bacteria join (mate) and exchange genes. Conjugation is a ‘one way’ transfer of DNA. The DNA donor uses appendages called sex pili to attach to the recipient. This is followed by the formation of a cytoplasmic bridge for which DNA can be transferred through, and promote recombination.

Conjugation

Assignment Complete work sheet- both sides Clay Activity- model a bacterium and go through the steps of binary fission and conjugation. Book- Page 531, Think Creatively # 28