Shewanella oneidensis
A Microbial Biorealm page on the genus Shewanella oneidensis
Classification
Higher order taxa
Bacteria; Proteobacteria; Gammaproteobacteria; Alteromonadales; Shewanellaceae; Shewanella; Shewanella oneidensis MR-1
Species
Shewanella oneidensis
Description and significance
Shewanella oneidensis is a Gram-negative anaerobic bacteria which is predominantly found in deep sea anaerobic habitats; but can also reside in soil and sedentary habitats. There is a presence of lipoproteins/cytochromes (MtrC and OmcA) on the outer membrane of Shewanella oneidensis. These cytochromes have been of particular interest in the field of research due to their potential of bioremediation of heavy metals. The entire genome of Shewanella oneidensis was sequenced by The Institute for Genomic Research (TIGR) in Rockville, Maryland and La Jolla, California.
Genome structure
Shewanella oneidensis MR-1 has 4,566 genes in its entire genome which was completed in September , 2002. Of the total 4,566 genes; 4,324 are protein encoding genes. There are a total of 4,969,803 nucleotides present in the genome of Shewanella oneidensis MR-1, and the GC base concentration is 45 percent. All the genes are compacted into a single circular chromosome. Shewanella oneidensis MR-1 also has a circular plasmid present in its cytoplasm known as pMR-1. This plasmid has 184 genes of which 149 are protein encoding genes.
Cell structure and metabolism
Shewanella oneidensis has outer membrane cytochromes (MtrC and OmcA) which reduce Fe(III) during anaerobic respiration; it does this by coupling oxidation of organic carbon to electron acceptors such as Fe(III), oxygen, nitrate, and other metals. Shewanella oneidensis has the ability to produce pilus like structures when its immediate environment is low in electron acceptor concentration (metals). These pili help the organism to locate and reduce metals. The main central metabolic pathway for Shewanella oneidensis MR-1 is the serine isocitrate lyase pathway in which formaldehyde made from pyruvate is reacted with glycine to produce serine.
Ecology
Shewanella oneidensis forms biofilms in soil and sediment environments when there is an abundance of electron acceptors.
Application to Biotechnology
Due to its ability to reduce heavy metals in the environment via cytochromes present on the outer membrane Shewanella oneidensis has been the target of bioremediation research.
Current Research
1) Atomic Force Microscopy was used to observe if a bond forms between a hematite (Fe203) thin film. This technique revealed that there was a specific interaction between the cytochrome of Shewanella oneidensis and the hematite film.
2) Cytochromes of Shewanella oneidensis were radiolabelled in order to determine if they were lipoproteins in the outer membrane. Upon comparison of this wild-type with the mutant which didn’t have outer membrane cytochromes it was determined in the radiolabelled wild-type that lipoproteins were present [4].
3) The knocking out of the gene SO1377 was compared to a wild-type strain and it was observed that the mutant had a depleted growth rate in aerobic conditions but not in anaerobic conditions.
References
1) "Microbe." Chapter 18, pg. 370. Moselio Schaechter, John L. Ingraham, Frederick C. Neidhardt. ASM Press, American Society for Microbiology, Washington, DC 20036.
2)“Polyphasic taxonomy of the genus Shewanella and description of Shewanella oneidensis sp. Nov.” K Venkateswaran, DP Moser, ME Dollhopf, DP Lies, DA Saffarini, BJ MacGregor, DB Ringelberg, DC White, M Nishijima, H Sano, J Burghardt, E Stackebrandt and KH Nealson Center for Great Lakes Studies, University of Wisconsin-Milwaukee, Milwaukee, WI 53204, USA
3)“Specific bonds between an iron oxide surface and outer membrane cytochromes MtrC and OmcA from Shewanella oneidensis MR-1.” Lower BH, Shi L, Droubay TC, Lower SK. Pacific Northwest National Laboratory. 275 Mendenhall Laboratory, Columbus, Ohio
4)“The outer membrane of cytochromes of Shewanella oneidensis MR-1 are lipoproteins.” Lower BH, Kennedy DW, Mottaz HM, Marshall MJ, Hill EA, Zachara JM. Microbiology Group, Pacific Northwest National Laboratory, Richland, WA. NCBI database [info@ncbi.nlm.nih.gov]
5)“c-Type cytochrome-dependent formation of U(IV) nanoparticles by Shewanella oneidensis.” Marshall MJ, Shi L, Kennedy DW, Lai B, Wang Z. Biological sciences division, Pacific Northwest National Laboratory, Richland, WA.
Edited by student Gurpreet Dhillon; Professors: Rachel Larsen and Kit Pogliano
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