Shewanella is the sole genus included in the marine bacteria family Shewanellaceae. Some species within it were formerly classed as Alteromonas. Shewanella consists of facultatively anaerobic Gram-negative rods, most of which are found in extreme aquatic habitats where the temperature is very low and the pressure is very high.{{Cite book|title=Endotoxins : Structure, function and recognition|date=2010|publisher=Springer Verlag|others=Wang, Xiaoyuan., Quinn, Peter J.|isbn=978-9048190782|location=Dordrecht|oclc=663096120}} Shewanella bacteria are a normal component of the surface flora of fish and are implicated in fish spoilage.Adams and Moss, Food Microbiology, third edition 2008, pp 26, 138, 140, Shewanella chilikensis, a species of the genus Shewanella commonly found in the marine sponges of Saint Martin's Island of the Bay of Bengal, Bangladesh.{{Cite journal|date=2021-12-15|title=Identification of marine sponge-associated bacteria of the Saint Martin's island of the Bay of Bengal emphasizing on the prevention of motile Aeromonas septicemia in Labeo rohita|url=https://www.sciencedirect.com/science/article/abs/pii/S004484862100819X|journal=Aquaculture|language=en|volume=545|pages=737156|doi=10.1016/j.aquaculture.2021.737156|issn=0044-8486|last1=Paul|first1=Sulav Indra|last2=Rahman|first2=Md. Mahbubur|last3=Salam|first3=Mohammad Abdus|last4=Khan|first4=Md. Arifur Rahman|last5=Islam|first5=Md. Tofazzal|bibcode=2021Aquac.54537156P |url-access=subscription}}

Shewanella oneidensis MR-1 is a widely used laboratory model to study anaerobic respiration of metals and other anaerobic extracellular electron acceptors, and for teaching about microbial electrogenesis and microbial fuel cells.{{Cite journal|last1=Gorby|first1=Yuri A.|last2=Yanina|first2=Svetlana|last3=McLean|first3=Jeffrey S.|last4=Rosso|first4=Kevin M.|last5=Moyles|first5=Dianne|last6=Dohnalkova|first6=Alice|last7=Beveridge|first7=Terry J.|last8=Chang|first8=In Seop|last9=Kim|first9=Byung Hong|date=2006-07-25|title=Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms|journal=Proceedings of the National Academy of Sciences|language=en|volume=103|issue=30|pages=11358–11363|doi=10.1073/pnas.0604517103|issn=0027-8424|pmid=16849424|pmc=1544091|bibcode=2006PNAS..10311358G|doi-access=free}}

Biochemical characteristics of ''Shewanella'' species

Colony, morphological, physiological, and biochemical characteristics of Shewanella species are shown in the Table below.

class="wikitable"

! Test type

! Test

! Characteristics

rowspan="4" |Colony characters

|Size

|Small, Medium

Type

|Round

Color

|Brownish, Pinkish

Shape

|Convex

Morphological characters

|Shape

|Rod

rowspan="2" |Physiological characters

|Motility

Growth at 6.5% NaCl

rowspan="12" |Biochemical characters

|Gram's staining

|–

Oxidase

Catalase

Oxidative-Fermentative

|Fermentative

Motility

Methyl Red

|–

Voges-Proskauer

|–

Indole

|–

H₂S Production

Urease

Nitrate reductase

|–

β-Galactosidase

rowspan="6" |Hydrolysis of

|Gelatin

|–

Aesculin

Casein

Tween 40

Tween 60

Tween 80

rowspan="13" |Acid production from

|Glycerol

|–

Galactose

|–

D-Glucose

D-Fructose

D-Mannose

Mannitol

N-Acetylglucosamine

Amygdalin

Maltose

D-Melibiose

D-Trehalose

Glycogen

D-Turanose

Note: + = Positive; – =Negative

Metabolism

Currently known Shewanella species are heterotrophic facultative anaerobes.Serres, [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1482980/ Genomic Analysis of Carbon Source Metabolism of Shewanella oneidensis MR-1: Predictions versus Experiments], Journal of Bacteriology, July 2006 In the absence of oxygen, members of this genus possess capabilities allowing the use of a variety of other electron acceptors for respiration. These include thiosulfate, sulfite, or elemental sulfur,Burns, [http://aem.asm.org/content/75/16/5209.full Anaerobic Respiration of Elemental Sulfur and Thiosulfate by Shewanella oneidensis MR-1 Requires psrA, a Homolog of the phsA Gene of Salmonella enterica Serovar Typhimurium LT2], Applied and Environmental Microbiology, 19 June 2009 as well as fumarate.Pinchuk et al., [https://www.ncbi.nlm.nih.gov/pubmed/21965410 Pyruvate and lactate metabolism by Shewanella oneidensis MR-1 under fermentation, oxygen limitation, and fumarate respiration conditions.], Applied and Environmental Microbiology December 2011 Marine species have demonstrated an ability to use arsenic as an electron acceptor as well.Saltikov et al.,

[http://www.cell.com/biophysj/fulltext/S0006-3495(14)03228-7, Expression Dynamics of Arsenic Respiration and Detoxification in Shewanella sp. Strain ANA-3], Journal of Bacteriology, Nov 2005 Some members of this species, most notably Shewanella oneidensis, have the ability to respire through a wide range of metal species, including manganese, chromium, uranium, and iron.Tiedje, [https://www.nature.com/articles/nbt1102-1093#ref2, Shewanella—the environmentally versatile genome], Nature Biotechnology

Reduction of iron and manganese through Shewanella respiration has been shown to involve extracellular electron transfer through the employment of bacterial nanowires, extensions of the outer membrane.Pirbadian et al., [http://www.cell.com/biophysj/fulltext/S0006-3495(14)03228-7, Bacterial Nanowires of Shewanella Oneidensis MR-1 are Outer Membrane and Periplasmic Extensions of the Extracellular Electron Transport Components], Biophysical Journal, Volume 108, Jan 2015

=Applications=

The discovery of some of the respiratory capabilities possessed by members of this genus has opened the door to possible applications for these bacteria. The metal-reducing capabilities can potentially be applied to bioremediation of uranium-contaminated groundwater,Newsome, [http://www.sciencedirect.com/science/article/pii/S0009254113004907 The biogeochemistry and bioremediation of uranium and other priority radionuclides], Chemical Geology, Volume 363, pp 164-184, 10 Jan 2014,

with the reduced form of uranium produced being easier to remove from water than the more soluble uranium oxide. Scientists researching the creation of microbial fuel cells, designs that use bacteria to induce a current, have also made use of the metal reducing capabilities some species of Shewanella possess as a part of their metabolic repertoire.Hoffman et al., [https://link.springer.com/article/10.1007/s10800-013-0550-5 Dual-chambered bio-batteries using immobilized mediator electrodes], Journal of Applied Electrochemistry, Vol 43, Issue 7, pp 629–636, 27 Apr 2013

Significance

One of the roles that the genus Shewanella has in the environment is bioremediation.{{Cite journal|last=Dikow|first=Rebecca B.|date=2011-05-12|title=Genome-level homology and phylogeny of Shewanella (Gammaproteobacteria: lteromonadales: Shewanellaceae)|journal=BMC Genomics|volume=12|pages=237|doi=10.1186/1471-2164-12-237|pmid=21569439|pmc=3107185|issn=1471-2164 |doi-access=free }} Shewanella species have great metabolic versatility; they can reduce various electron acceptors. Some of the electron acceptors they use are toxic substances and heavy metals, which often become less toxic after being reduced. Examples of metals that Shewanella are capable of reducing and degrading include uranium, chromium, and iron.{{Cite book|title=The third domain : the untold story of archaea and the future of biotechnology|pages=247|last=Tim.|first=Friend|date=2007|publisher=Joseph Henry Press|isbn=978-0309102377|location=Washington, D.C.|oclc=228173040|url-access=registration|url=https://archive.org/details/thirddomainun00frie}} Its ability to decrease toxicity of various substances makes Shewanella a useful tool for bioremediation. Specifically, Shewanella oneidensis strain MR-1 is often used to clean up contaminated nuclear weapon manufacturing sites.

Shewanella also contributes to the biogeochemical circulation of minerals. Members of this genus are widely distributed in aquatic habitats, from the deep sea to the shallow Antarctic Ocean. Its diverse habitats, coupled to its ability to reduce a variety of metals, makes the genus critical for the cycling of minerals. For instance, under aerobic conditions, various species of Shewanella are capable of oxidizing manganese.{{Cite journal|last1=Wright|first1=Mitchell H.|last2=Farooqui|first2=Saad M.|last3=White|first3=Alan R.|last4=Greene|first4=Anthony C.|date=2016-08-15|title=Production of Manganese Oxide Nanoparticles by Shewanella Species|journal=Applied and Environmental Microbiology|volume=82|issue=17|pages=5402–5409|doi=10.1128/AEM.00663-16|issn=0099-2240|pmc=4988204|pmid=27342559|bibcode=2016ApEnM..82.5402W}} When conditions are changed, the same species can reduce the manganese oxide products. Hence, since Shewanella can both oxidize and reduce manganese, it is critical to the cycling of manganese.

References

External links

[http://www.genomesonline.org/search.cgi?colcol=all&goldstamp=ALL&gen_type=ALL&org_name1=genus&gensp=Shewanella&org_domain=ALL&org_status=ALL&size2=ALL&org_size=Kb&gen_gc=ALL&phylogeny2=ALL&gen_institution=ALL&gen_funding=ALL&gen_data=ALL&cont=ALL&gen_country=ALL&gen_pheno=ALL&gen_eco=ALL&gen_disease=ALL&gen_relevance=ALL&gen_avail=ALL&selection=submit+search Shewanella Genome Projects] (from [http://www.genomesonline.org Genomes OnLine Database])
[http://img.jgi.doe.gov/cgi-bin/pub/main.cgi?section=TaxonList&page=lineageMicrobes&genus=Shewanella Comparative Analysis of Shewanella Genomes] (at DOE's IMG system)

Category:Alteromonadales

Category:Bacteria genera

Shewanella