December 4

http://www.bionewsonline.com/y/what_is_rhizobia.htm

Free web - needs Web site evaluation sheet

• Rhizobia from the Greek words Riza which means Root and Bios which means Life
• Soil bacteria
• Fix nitrogen when they become situation in the root nodules of legumes

 

 

http://school.eb.com/search?ct=&query=Rhizobium&x=0&y=0

    Multimedia = cool!

 

http://www.bionewsonline.com/y/what_is_rhizobia.htm

·         “Rhizobiales, a probably-monophyletic group of proteobacteria”

o   Proteobacteria (http://www.earthlife.net/prokaryotes/proteo.html)

§  Second largest group of bacteria

§  Phylum = 1534 species or 32.3% of bacteria

§  Gram negative

o   Monophyletic (Britannica)

§  All from “a single ancestral stock”

·         Example of mutualism

o   Mutual dependence

 

 

Merriam-Webster

·         capitalized : the genus of Rhizobiaceae comprising small heterotrophic soil bacteria capable of forming symbiotic nodules on the roots of leguminous plants and of there becoming bacteroids that fix atmospheric nitrogen

Britannica

·         “Nitrogen Budget” "

·         atmosphere." Encyclopædia Britannica. 2007. Encyclopædia Britannica Online School Edition. 6 Dec.  2007  <http://school.eb.com/eb/article-261440>.

o   Turns nitrogen (N₂) into compounds that have ammonium (NH⁺), nitrite (NO₂^-), and nitrate (NO₃^-)

o   This is called nitrification or nitrogen fixing

o   The Rhizobium on nodules of  legume roots help convert diatomic nitrogen gas to ammonia

 

·         History:

·         "microbiology." Encyclopædia Britannica. 2007. Encyclopædia Britannica Online School Edition. 6 Dec.  2007  <http://school.eb.com/eb/article-216182>.

o   Soil microbiologists:

§  Martinus W. Beijerinck (1851–1931), a Dutchman

§  Sergey N. Winogradsky (1856–1953), a Russian

o   Discovery of relationship between bacteria and legumes in legume nodules was made in 1888 by other scientists

 

·         "nitrogen fixation." Encyclopædia Britannica. 2007. Encyclopædia Britannica Online School Edition. 6 Dec.  2007  <http://school.eb.com/eb/article-9055949>.

o   “Mutualistic (symbiotic) bacteria” versus free living, non-symbiotic bacteria

o   Process

§  Go into root hairs of plants

§  “Multiply and stimulate the formation of root nodules”

§  In nodules, convert “free nitrogen (“which is a relatively inert gas plentiful in air”) to nitrates”

§  The plant uses the nitrates to grow

http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Undef&id=379&lvl=3&lin=f&keep=1&srchmode=1&unlock

Bacteria à

Proteobacteria à

Alphaproteobacteria à

 Rhizobiales à

Rhizobiaceaeà

 Rhizobium

Weir, B. S. (2006) The current taxonomy of rhizobia. New Zealand rhizobia website. http://www.rhizobia.co.nz/taxonomy/rhizobia.html. Last updated: 11th June, 2007.

·         Rhizobium is the genus/genera

o   Right now it has 16 species

·         Named

 

http://edis.ifas.ufl.edu/AG152

·         Fast growing

·         Produces acid

http://filebox.vt.edu/users/chagedor/biol_4684/Microbes/rhizobium.html

·         Aerobic – needs oxygen to make ATP usually, but some can function with less oxygen

·         Rod shaped

·         Does not form spores meaning it reproduces differently…

·         “Mobile by a single polar flagellum or two to six peritrichous flagella”

o   Polar flagellum

·         Uses carbohydrates and amino compounds

·         “Legumes are herbaceous woody plants that produce seeds in pods; examples of legumes include peas, beans, alfalfa, vetches, clovers, lupines, trefoils, locust, and mimosa”

·         Because their relationship is symbiotic, rhizobia benefit from nutrients provided by the plant’s roots cells.

·         Lives mostly in the soil at about 25-30 degree C

http://www.springerlink.com/content/hv3j367102n45w52/

·         Anaerobic growth with nitrogen

·         Autotrophic

 

Tallack, Peter. The Science Book. Sterling Company, Inc., 2006. 16 Dec. 2007 <books.google.com>.

• Even the early Greeks knew that soil which had recently grown beans was better for crops
• The real discovery of Rhizobia was in 1886 by German Agricultural chemists Hermann Hellriegel and Hermann Willfarth
• They noted it as the bacteria that fixes nitrogen
• Symbiotic relationship: rhizobia get energy source and carbon-based molecules while the plant gets nitrogen
• Each year, rhizobia produces about 200 million tons of fixed nitrogen.
•  

 

 

 

Classification – Aerobic/Anaerobic; Formal scientific name (anything interesting about name?)

·         Aerobic

·          

Gram stain – Is the bacteria gram – or gram +

·         Gram negative

o   Means…

Structure – shape; cell wall; internal structures; flagella present? Spore forming (endospores)?

·         Rod shaped

·         Flagella (two types)

·         Non-spore forming

Habitat – where would you find this bacterium?

·         In the dirt

o   Plant roots

***Nutritional Requirements –Autotrophic? Chemoautotrophic?

***Reproduction – Description of its asexual and sexual reproductive strategies

***History – When discovered; interesting historical information dealing with your bacteria.

Beneficial properties – How is this bacteria helpful to humans, other animals, plants, fungus, protista?

DUH

Problems associated with the loss of bacteria in the environment?

Interesting or unusual facts about your bacteria.

Recent scientific and/or medical research dealing with this bacteria?