This is based on several characteristics for each strain and each character is given equal weightage. Since a large array of microbiologists study the characteristics of organisms (morphological, physiological, biochemical, genetical, molecular), sometimes, it is difficult to assign an organism based on all the characters because a character may be important to a particular microbiologist may not be that important to another, hence, different taxonomists may arrive at very different groupings. General Methods of Classifying Bacteria : (iv) Important part of the Earth’s nitrogen cycle. (iii) Nitrogen-fixing bacteria change N 2 into usable ammonia (NH 3). (ii) 80% of atmosphere is N 2, but plants can’t use nitrogen gas. (i) Rhizobium is Gram negative and live in legume root nodules. (ii) Iron-oxidizing bacteria found in freshwater ponds use iron salts for energy.

(i) Gram negative bacteria that obtain energy from minerals. coli that lives in the intestinal tract making vitamin K and helping break down food. (ii) Can live in aerobic and anaerobic environments. (ii) Subdivided into Enteric bacteria, Chemoautotrophic bacteria, & Nitrogen- fixing bacteria. (i) Largest and most diverse bacterial group. (iv) May be free-living, parasitic, or live symbiotically with another organism. (iii) Some are aerobic (require oxygen) others are anaerobic. (ii) Have flagella at each end so move in a corkscrew motion. (ix) After eutrophication, the cyanobacteria die, decompose, and use up all the oxygen for fish. (viii) Anabaena that lives on nitrates and phosphates in water can overpopulate and cause “population blooms” or eutrophication. (vii) First bacteria to re-enter devastated areas. Oscillatoria) and have specialized cells called heterocyst that fix nitrogen. (v) May be red, yellow, green, brown, black, or blue-green. (iv) Contain pigments called phycocyanin (red and blue) and chlorophyll a (green).

(ii) Carry on photosynthesis and make oxygen. (ix) Can be identified by Gram staining (gram positive or gram negative). (viii) Subdivided into 4 phyla – Cyanobacteria (blue-green bacteria), Spirochetes, Gram-positive, and Proteobacteria. (vii) Can be aerobic (require oxygen) or anaerobic (don’t need oxygen). (vi) Most are heterotrophic (can’t make their own food). (v) Bacteria in grapelike clusters are called staphylococci. (iv) Bacteria occurring in chains are called strepto – bacilli or cocci. (iii) Bacteria can occur in pairs (diplo – bacilli or cocci). (ii) Come in 3 basic shapes - cocci (spheres), bacilli (rod shaped), spirilla (corkscrew shape). (ii) Found in hot springs in Yellowstone National Park, in volcanic vents on land, and in cracks on the ocean floor that leak scalding acidic water. (i) Live in extremely hot (110☌) and acidic (pH 2) water. (iii) Use salt to help generate ATP (energy). (ii) Found in the Dead Sea, Great Salt Lake, etc. (v) Produce marsh gas or intestinal gas (methane). (iv) Break down cellulose for herbivores (cows). (iii) Found in swamps, marshes, sewage treatment plants, digestive tracts of animals. (ii) Obtain energy by changing H 2 and CO 2 gas into methane gas. (i) Live in anaerobic environments (no oxygen).

(iii) Subdivided into 3 groups based on their habitat - methanogens, thermoacidophiles, and extreme halophiles. (i) Found in harsh environments (undersea volcanic vents, acidic hot springs, salty water). (xxii) Classified by their structure, motility (ability to move), molecular composition, and reaction to stains (Gram stain). (xxi) Once grouped together in the kingdom Monera. (xx) Grouped into 2 kingdoms – Eubacteria (true bacteria) and Archaebacteria (ancient bacteria). (xix) Classified by their structure, motility (ability to move), molecular composition, and reaction to stains (Gram stain). (xviii) Some can form protective endospores around the DNA when conditions become unfavorable may stay inactive several years and then re-activate when conditions favorable.

Diagrams of bacteria shapes rod shaped