Bacteria.pdf

Kingdom Eubacteria  Bacteria - Bacteria are prokaryotes - Single-celled organisms that lack membrane-bound organelles - These organisms have lived on Earth for over 3.5 billion years - Most are 1-2 µm (micrometres) long - Scientists have identified and named roughly 30...

Kingdom Eubacteria  Bacteria - Bacteria are prokaryotes - Single-celled organisms that lack membrane-bound organelles - These organisms have lived on Earth for over 3.5 billion years - Most are 1-2 µm (micrometres) long - Scientists have identified and named roughly 30,000 kinds of bacteria Structure  Structure - Cell wall and plasma membrane surround cytoplasm containing free-floating ribosomes - Single loop of DNA in the nucleoid region - Also contain genetic material in a plasmid - Small loop of DNA that contains a small number of genes not essential for cell function  Structure - Have a flagella to help them move about - Small hair-like pili help them attach to surfaces & other bacteria - Cell walls are made up of peptidoglycan - Strong & rigid - Some also have a sticky capsule outer layer - Reduces water loss, resists high temps, helps keep out antibiotics  Classifying Bacteria Bacteria are classified on 3 characteristics: 1. Their shape & colony shape 2. Structure of their cell wall 3. Sources of food and metabolism  Shape of Bacteria Bacteria can be classified into three different groups based on their shape. Bacteria can be: - Spherical (cocci) - Rod shaped (bacilli) - Spiral/other (spirilla)  Shape of Colony Bacteria are unicellular but some cells like to stick together. Diplo - cells are arranged in pairs Staphylo - arranged in clusters (like grapes) Strepto - arranged in a chain  Cell Wall Structure - Scientists determine the thickness of the bacterial cell wall through a process called Gram staining. - They will use a purple stain to see how thick the walls are - A thick cell wall will retain the purple stain and is known as gram positive bacteria - Thin cell walls will not retain the purple and are known as gram negative bacteria  Metabolism - Autotrophic Bacteria make their own food from simple inorganic chemicals (substances such as carbon dioxide, water, minerals) - Heterotrophic Bacteria get their nutrients from organic chemicals (containing carbon - ex. Other living organisms) Cyanobacteria – photosynthetic autotroph Heterotrophic Escherichia coli  Oxygen? Some bacteria are obligate aerobes that require oxygen. Some bacteria are facultative aerobes that can survive without oxygen by performing anaerobic respiration, or fermentation. Some bacteria are obligate anaerobes that cannot live in an environment where oxygen is present.  Reproduction Binary fission: asexual reproduction where a parent cell divides to produce two identical daughter cells Copying errors result in mutations and increased genetic diversity  Reproduction Conjugation: a form of sexual reproduction in which two cells join to exchange genetic information a plasmid is transferred DNA from plasmid loop can integrate into the main DNA loop  Reproduction Transformation: A bacterial cell picks up a loose fragment of DNA from its surroundings. If the DNA came from a different species this is called horizontal gene transfer. Surviving Unfavorable Conditions - Some bacteria produce endospores - Endospores are highly resistant structures that form around the chromosomes when cells are under stress - This unique strategy allows bacteria to survive unfavorable conditions such as: - High temperatures - Irradiation - Strong acids - Disinfectants  Good Bacteria? Not all bacteria is harmful to humans Decomposers (some recycle nutrients, such as nitrogen) Producers (photosynthetic bacteria produce oxygen) Food production (cheese, yogurt, soy sauce, and chocolate) Production of vitamins K and B12 in the large intestine Production of medicine (antibiotics) Genetic engineering (insulin, human growth hormone)  Bad Bacteria Infectious bacteria are called pathogens and are responsible for many diseases Including: cholera, diphtheria, Lyme disease, pertussis, tetanus, leprosy, typhoid fever, strep throat, salmonella poisoning, tuberculosis, and many more!