Some Trees 'Farm' Bacteria to Help Supply Nutrients
Post Last Edit by dauswq at 2-8-2010 17:56http://www.sciencedaily.com/images/2010/07/100729172332.jpgNew research finds that some trees, such as oak (above) and beech, that grow in nutrient-poor forest soil may get what they need by cultivating specific root microbes to create compounds they require (Credit: iStockphoto)
ScienceDaily (July 30, 2010) — Some trees growing in nutrient-poor forest soil may get what they need by cultivating specific root microbes to create compounds they require. These microbes are exceptionally efficient at turning inorganic minerals into nutrients that the trees can use. Researchers from France report their findings in the July 2010 issue of the journal Applied and Environmental Microbiology.
"In acidic forest soils, availability of inorganic nutrients is a tree-growth-limiting factor. A hypothesis to explain sustainable forest development proposes that tree roots select soil microbes involved in central biogeochemical processes, such as mineral weathering, that may contribute to nutrient mobilization and tree nutrition," says Stéphane Uroz, an author on the study.
Certain microbes are efficient at breaking down inorganic minerals into nutrients. This process, called mineral weathering, is especially important in acidic forest soils where tree growth can be limited by access to these nutrients. Mineral-weathering bacteria can release necessary nutrients such as iron from soil minerals. This gives trees with increased concentrations of mineral-weathering microbes an advantage over other trees.
Distinct impacts of the tree species on the soil bacterial community structure have been previously reported, suggesting that the composition and activity of soil bacterial communities depend on tree physiology and notably on its impact on the soil physicochemical properties and nutrient cycling. However, no study has ever addressed the question of the impact of tree species on the structure of forest soil bacterial communities involved in mineral weathering.
"This question regarding the impact of tree species on the functional diversity of the bacterial communities remains a major issue in forestry, especially in the context of today's climate change, which will give rise to a shift in the spatial distribution of forest tree species," says Uroz.
The researchers took soil samples from the root areas of beech, oak and Norway spruce trees and cultured them to determine the bacterial populations. They observed heightened levels of mineral-weathering bacteria in the samples near the roots of oak and beech trees compared to surrounding soil samples. This difference was not seen in the Norway spruce samples.
"Our results suggest that certain tree species have developed indirect strategies for mineral weathering in nutrient-poor soils, which lie in the selection of bacterial communities with efficient mineral weathering potentials," says Uroz. mineral weathering - boleh bantutkn tumbesaran pokok:D Byk je bacteria yang baik :$ Reply 3# bacteria82
off topic:
bacteria82 sakat org tak?:lol: Reply 3# bacteria82
in fact
dlm artikel diberitahu kelebihan bacteria - mineral weathering
seingat aku
ada bacteria yg urai N2 dr pokok kekacang
sekaligus mengimbangkn kandungan N2 di atmosphere..
lupa lak nama bacteria tu..(bukan mod kuman ya:lol:) Reply 5# dauswq
A'ah, simbiosis.. Tak ingat gak bacteria ape.. Reply 5# dauswq
nama bacteria tu Rhizobium kan? :$
The current taxonomy of rhizobia
The species listed here are all of the most current validly published names for the rhizobia, which currently consists of 76 species found in 13 genera. Rhizobia are nitrogen-fixing bacteria that form root nodules on legume plants. Most of these bacterial species are in the Rhizobiacae family in the alpha-proteobacteria and are in either the Rhizobium, Mesorhizobium, Ensifer, or Bradyrhizobium genera. However recent research has shown that there are many other rhizobial species in addition to these. In some cases these new species have arisen through lateral gene transfer of symbiotic genes.
Taxonomy is a complicated and ever-changing discipline of science, the list below is not "official" by any means, and it is merely my compilation and interpretation of the literature. An alternative list is maintained by the "ICSP Subcommittee on the taxonomy of Rhizobium and Agrobacterium".
It is important to note that there are other non-rhizobial species present in these genera. For example in the Rhizobium genus, there is Rhizobium radiobacter — formerly known as Agrobacterium tumefaciens. However these species are not listed here, as the 'Agrobacteria' do not form nitrogen fixing symbiotic root nodules (unless they contain a symbiotic plasmid – see Velazquez et. al. 2005). I have another page about these bacteria that could be confused with 'true' rhizobia.
To see all of the currently valid members of a genus, including non-rhizobial species, click on the name of the genus in the text after each title. This will take you to the LPSN website.
This page was compiled from my own research; a paper by J.G. Howieson and J. Brockwell presented at the 14th Australian Nitrogen Fixation Conference, and the NCBI and LPSN websites.
This page is updated regularly. If you know of any additions or corrections please email me. I do try to keep up, but I am working on different projects now. I have added a changelog so you can see difference between updates: change log
If you wish you can cite this page as:
Weir, B.S. (2009) The current taxonomy of rhizobia. New Zealand rhizobia website. http://www.rhizobia.co.nz/taxonomy/rhizobia.html. Last updated: 14th September, 2009. (check green box above for latest update date)
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