Diazotrophs are bacteria and archaea that Nitrogen fixation fix atmospheric nitrogen gas into a more usable form such as ammonia . ref name Postgate98 cite book author Postgate, J year 1998 title Nitrogen Fixation, 3rd Edition publisher Cambridge University Press, Cambridge UK ref A diazotroph is an organism that is able to grow without external sources of fixed nitrogen. Examples of organisms that do this are rhizobia and Frankia in symbiosis and Azospirillum . All diazotrophs contain iron molybdenum nitrogenase systems. Two of the most studied systems are those of Klebsiella pneumoniae and Azotobacter vinelandii . These systems are used because of their genetic tractability and their fast growth. ref name DK94 cite journal author Dixon R and Kahn D year 2004 title Genetic regulation of biological nitrogen fixation journal Nat Rev Microbiol volume 2 issue 8 pages 621 31 doi 10.1038 nrmicro954 pmid 15263897 ref Types of diazotrophs Diazotrophs are scattered across bacterial taxonomic groups mostly in the Bacteria but also a couple of Archaea . Even within a species that can fix nitrogen there may be strains that do not fix nitrogen. ref name Postgate98 Fixation is shut off when other sources of nitrogen are available, and, for many species, when oxygen is at high partial pressure. Bacteria have different ways of dealing with the debilitating effects of oxygen on nitrogenases, listed below. Free living diazotrophs Anaerobes these are obligate anaerobes that cannot tolerate oxygen even if they are not fixing nitrogen. They live in habitats low in oxygen, such as soils and decaying vegetable matter. Clostridium is an example. Sulphate reducing bacteria are important in ocean sediments e.g. Desulfovibrio , and some Archean methanogens fix nitrogen in muds and animal intestines. ref name Postgate98 Facultative anaerobes these species can grow either with or without oxygen, but they only fix nitrogen anaerobically. Often, they respire oxygen as rapidly as it is supplied, ... more details
Unreferenced type bacteria auto yes date December 2009 Taxobox color lightgrey name Oxalobacteraceae regnum Bacteria phylum Proteobacteria classis Beta Proteobacteria ordo Burkholderiales familia Oxalobacteraceae subdivision ranks Genera subdivision Collimonas br Duganella br Herbaspirillum br Herminiimonas br Janthinospirillum br Massilia bacterium Massilia br Naxibacter br Oxalobacter br Oxalicibacterium br Telluria The Oxalobacteraceae are a family of bacteria , included in the order Burkholderiales . Like all Proteobacteria , Oxalobacteraceae are gram negative . The Family includes strict Anaerobic organism aerobes , strict Aerobic organism anaerobes , and also Diazotroph nitrogen xing diazotrophs members. The cells are curved, vibroid or straight rod shaped. References Garrity, George M. Brenner, Don J. Krieg, Noel R. Staley, James T. eds. 2005 . Bergey s Manual of Systematic Bacteriology, Volume Two The Proteobacteria, Part C The Alpha , Beta , Delta , and Epsilonproteobacteria. New York, New York Springer. pp. 354 361. ISBN 978 0 387 24145 6. Category Burkholderiales Proteobacteria stub de Oxalobacteraceae es Oxalobacteraceae fr Oxalobacteraceae it Oxalobacteraceae ... more details
italic title Expert subject Microbiology date November 2008 Taxobox color lightgrey name Azotobacter regnum Bacterium Bacteria phylum Proteobacteria classis Gamma Proteobacteria ordo Pseudomonadales familia Pseudomonadaceae genus Azotobacter species A. vinelandii binomial Azotobacter vinelandii binomial authority Jacob Goodale Lipman Lipman ref cite book title Review of American Chemical Research volume 10 year 1904 editor William A. Noyes page http books.google.com books?id LAoSAAAAIAAJ&pg PA75 v onepage&q&f false 75 ref Azotobacter vinelandii is diazotroph that can fix nitrogen while grown aerobic organism aerobically . It is a genomics genetically tractable system that is used to study nitrogen fixation . These bacteria are easily cultured and grown. It is a free living N sub 2 sub fixer which is known to produce many phytohormone s and vitamin s in the soil. The nitrogenase enzyme holoenzyme of Azotobacter vinelandii has been characterised via x ray crystallography in both Adenosine diphosphate ADP tetrafluoroaluminate bound ref Schindelin, H., Kisker, C., Schlessman, J.L., Howard, J.B., Rees, D.C. 1997 Structure of ADP x AIF4 stabilized nitrogenase complex and its implications for signal transduction. Nature 387 370 376 ref and Mg Adenosine triphosphate ATP bound ref Chiu, H., Peters, J.W., Lanzilotta, W.N., Ryle, M.J., Seefeldt, L.C., Howard, J.B., Rees, D.C. 2001 MgATP Bound and nucleotide free structures of a nitrogenase protein complex between the Leu 127 Delta Fe protein and the MoFe protein. Biochemistry 40 641 650 ref states. The enzyme possesses molybdenum iron sulfido cluster Cofactor biochemistry cofactors FeMoCo as active site s, each bearing 2 pseudo cubic iron sulfido structures. References reflist External links http www.azotobacter.org Azotobacter vinelandii Genome Project http www.micron.ac.uk organisms Avi.html Current research on Azotobacter vinelandii at the Norwich Research Park Category Pseudomonadales Proteobacteria stub es Azotobacter vin ... more details
unreferenced date July 2009 File Centaurea maculosa.jpg thumb Centaurea maculosa , an example of pioneer species Pioneer species are species which Colonisation biology colonize previously uncolonized land, usually leading to ecological succession . They are the first organisms to start the chain of events leading to a livable biosphere or ecosystem . Since uncolonized land may have thin, poor quality soils with few nutrients, pioneer species are often hearty plants with adaptations such as long roots, root nodes containing Diazotroph nitrogen fixing bacteria , and leaves that employ transpiration . Pioneer species will die creating plant litter , and break down as leaf mold after some time, making new soil for secondary succession see below , and nutrients for small fish and aquatic plant s in adjacent bodies of water. Pioneer flora Pioneer species are often Poaceae grass es such as Ammophila Poaceae marram grass , which grows on sand dunes . In more rocky and damp conditions, they are usually lichen , and small ephemeral bunchgrass es and wildflower s in crevices. The plants, or anything that has the system of a plant, will be specially adapted to the extremes that may be experienced, and once they have modified the environment may be out competed by less specific plants, eventually leading to a climax community . Examples of the plants and organisms that colonize such areas are Barren rock blue green bacteria , lichen Barren sand Leymus Lyme grass Leymus arenarius , Agropyron Sea couch grass Agropyron pungens , Ammophila Poaceae Marram grass Ammophila breviligulata Salt water green algae , Zostera Marine eel grass Zostera Zostera spp. , Pickleweed Salicornia virginica , and Spartina Cordgrass hybrid Spartina townsendii and Spartina anglica . Clear water algae , mosses , Vallisneria Freshwater eel grass Vallisneria americana . Pioneer fauna Pioneering fauna are not responsible for initial colonisation of an area, but will colonize an area only flora and fungi previ ... more details
orphan date February 2010 The nif gene is the gene responsible for the coding of protein s related and associated with the nitrogen fixation fixation of atmospheric nitrogen into a form of nitrogen available to plants. These genes are found in nitrogen fixing bacteria and cyanobacteria . References http www.biology online.org dictionary Nif gene Nif gene definition from Biology Online.org Nif genes hae both positive and negative regulators. Some of nf genes are Nif A, D, L,K, F,H S,U,Y,W,Z The nif genes are genes encoding enzymes involved in the fixation of atmospheric nitrogen. The primary enzyme encoded by the nif genes is the nitrogenase complex which is in charge of converting atmospheric nitrogen N2 To other nitrogen forms such as ammonia which the plant can use for various purposes. Besides the nitrogenase enzyme, the nif genes also encode a number of regulatory proteins involved in nitrogen fixation. The nif genes are found in both free living nitrogen fixing bacteria and in symbiotic bacteria in various plants. The expression of the nif genes is induced as a response to low concentrations of fixed nitrogen and oxygen concentrations the low oxygen concentrations are actively maintained in the root environment . 4,6,7,8 . Examples from nature The expression and regulation of nif genes while sharing common features in all or most of the nitrogen fixing organisms in nature, have distinct characters and qualities differed from one diazotroph to another. Examples of nif genes structure and regulation in different diazotrophs Klebsiella pneumoniae a free living anaerobic nitrogen fixing bacteria. It contains a total of 20 nif genes located on the bacteria s chromosome in a 24kb region. nifH, nifK and nifD encode the nitrogenase s subunits, while nifE, nifN, nifU, nifS, nifV, nifW, nifX, nifB and nifQ encode proteins involved the assembly and incorporation of the Fe and Mo into the nitrogenase s subunits. nifF and nifJ encode proteins related to electron transfer ta ... more details
with a protein such as Leghemoglobin . ref name postgate Microorganisms that fix nitrogen Diazotroph ... strains are also capable of diazotroph ic growth. Genome sequencing has provided a large amount of information ... more details
Taxobox image Klebsiella pneumoniae 01.png image width 240px image caption K. pneumoniae on a MacConkey agar MacConkey agar plate . regnum Bacteria phylum Proteobacteria classis Gamma Proteobacteria ordo Enterobacteriaceae Enterobacteriales familia Enterobacteriaceae genus Klebsiella species K. pneumoniae binomial Klebsiella pneumoniae binomial authority Schroeter 1886 br Trevisan 1887 Klebsiella pneumoniae is a Gram negative , non motile , Bacterial capsule encapsulated , lactose fermentation biochemistry fermenting , facultative anaerobic , rod shaped bacterium found in the normal flora of the mouth, skin, and intestines. ref name Sherris cite book author Ryan KJ Ray CG editors title Sherris Medical Microbiology edition 4th publisher McGraw Hill year 2004 isbn 0838585299 ref It is clinically the most important member of the Klebsiella genus of Enterobacteriaceae it is closely related to Klebsiella oxytoca K. oxytoca from which it is distinguished by being indole test indole negative and by its ability to grow on both melezitose and 3 hydroxybutyrate . It naturally occurs in the soil, and about 30 of strains can nitrogen fixation fix nitrogen in anaerobic conditions. ref name Postgate 1998 cite book author Postgate J year 1998 title Nitrogen fixation, 3rd ed. publisher Cambridge University Press ref As a free living diazotroph , its nitrogen fixation system has been much studied. Members of the Klebsiella genus typically express 2 types of antigens on their cell surface. The first, O antigen, is a component of the lipopolysaccharide LPS , of which 9 varieties exist. The second is K antigen, a capsular polysaccharide with more than 80 varieties. ref cite journal author Podschun R, Ullman U title Klebsiella spp. as Nosocomial Pathogens Epidemiology, Taxonomy, Typing Methods, and Pathogenicity Factors journal Clinical Microbiology Reviews volume 11 issue 4 pages 589 603 year 1998 pmid 9767057 pmc 88898 ref Both contribute to pathogenicity and form the basis for serogr ... more details
Encyclopedia
top
