Leptospira

Taxobox
color = lightgrey
name = "Leptospira"

image_width = 240px
image_caption = Scanning electron micrograph of "Leptospira interrogans".
regnum = Monera
phylum = Spirochaetes
classis = Spirochaetes
ordo = Spirochaetales
familia = Leptospiraceae
genus = "Leptospira"
genus_authority = Noguchi 1917
subdivision_ranks = Species
subdivision = "L. alexanderi" "L. biflexa" "L. broomii" "L. borgpetersenii" "L. fainei" "L. inadai" "L. interrogans" "L. kirschneri" "L. licerasiae" "L. meyeri" "L. noguchii" "L. santarosai" "L. weilii" "L. wolbachii" "L. kmetyi" "L. wolffii"

"L. genomospecies 1 "L. genomospecies 3 "L. genomospecies 4 "L. genomospecies 5

"Leptospira" (from the Greek "leptos", meaning fine or thin, and the Latin "spira", meaning coil) [cite web | title = leptospirosis | work = American Heritage Dictionary of the English Language: Fourth Edition | publisher = Bartleby.com | date = 2000 | url = http://www.bartleby.com/61/66/L0126650.html | accessdate = 2007-05-13 ] is a genus of spirochaete bacteria, including a small number of pathogenic and saprophytic species.cite book | author = Ryan KJ; Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | publisher = McGraw Hill | year = 2004 | id = ISBN 0-8385-8529-9 ] "Leptospira" was first observed in 1907 in kidney tissue slices of a leptospirosis victim who was described as having died of "yellow fever." [Stimson AM (1907). "Note on an organism found in yellow-fever tissue." "Public Health Reports" 22:541.]

Taxonomy

"Leptospira", together with the genera "Leptonema" and "Turneria", is a member of the family Leptospiraceae. The genus "Leptospira" is divided into 20 species based on DNA hybridization studies.cite journal |author=Brenner DJ, Kaufmann AF, Sulzer KR, Steigerwalt AG, Rogers FC, Weyant RS |title=Further determination of DNA relatedness between serogroups and serovars in the family Leptospiraceae with a proposal for Leptospira alexanderi sp. nov. and four new Leptospira genomospecies |journal=Int. J. Syst. Bacteriol. |volume=49 Pt 2 |issue= |pages=839–58 |year=1999 |pmid=10319510 |doi=] cite journal |author=Bharti AR, Nally JE, Ricaldi JN, Matthias MA, Diaz MM, Lovett MA, Levett PN, Gilman RH, Willig MR, Gotuzzo E, Vinetz JM |title=Leptospirosis: a zoonotic disease of global importance |journal=The Lancet infectious diseases |volume=3 |issue=12 |pages=757–71 |year=2003 |pmid=14652202 |doi=]

"'Pathogenic "Leptospira""':"Leptospira interrogans":"Leptospira kirschneri":"Leptospira noguchii":"Leptospira alexanderi":"Leptospira weilii":"Leptospira" genomospecies 1 :"Leptospira borgpetersenii":"Leptospira santarosai":"Leptospira kmetyi" [Slack, A. T., Khairani-Bejo, S., Symonds, M. L., Dohnt, M. F., Galloway, R. L., Steigerwalt, A. G., Bahaman, A. R., Craig, S., Harrower, B. J. & other authors (2008). Leptospira kmetyi sp. nov., isolated from an environmental source in Malaysia. Int J Syst Evol Microbiol In Press.]

Intermediates or opportunistic "Leptospira"

Non-pathogenic "Leptospira"

:"Leptospira biflexa":"Leptospira meyeri":"Leptospira wolbachii":"Leptospira" genomospecies 3:"Leptospira" genomospecies 4:"Leptospira" genomospecies 5

frame|">Evolutionary relationships of the 20 recognized species of "Leptospira"
The evolutionary history was inferred using the Minimum Evolution method [Rzhetsky A & Nei M (1992) A simple method for estimating and testing minimum evolution trees. Molecular Biology and Evolution 9:945-967 ] . The bootstrap consensus tree inferred from 1000 replicates is taken to represent the evolutionary history of the taxa analyzed [Felsenstein J (1985) Confidence limits on phylogenies: An approach using the bootstrap. Evolution 39:783-791] . Branches corresponding to partitions reproduced in less than 50% bootstrap replicates are collapsed. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are shown next to the branches. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site [Tamura, K., Nei, M. & Kumar S. (2004) Prospects for inferring very large phylogenies by using the neighbor-joining method. PNAS 101:11030-11035. ] . The ME tree was searched using the Close-Neighbor-Interchange (CNI) algorithm at a search level of 1 [Nei M & Kumar S (2000) Molecular Evolution and Phylogenetics. Oxford University Press, New York] . The Neighbor-joining algorithm was used to generate the initial tree. Codon positions included were 1st+2nd+3rd+Noncoding [Saitou N & Nei M (1987) The neighbor-joining method: A new method for reconstructing phylogenetic trees. Molecular Biology and Evolution 4:406-425] . All positions containing gaps and missing data were eliminated from the dataset (Complete deletion option). There were a total of 1254 positions in the final dataset. Phylogenetic analyses were conducted in MEGA4 [Tamura K, Dudley J, Nei M & Kumar S (2007) MEGA4: Molecular Evolutionary Genetics Analysis (MEGA) software version 4.0. Molecular Biology and Evolution 10.1093/molbev/msm092] .

Members of "Leptospira" are also grouped into serovars according to their antigenic relatedness. There are currently over 200 recognized serovars. A few serovars are found in more than one species of "Leptospira".

At its 2002 meeting, the Committee on the Taxonomy of Leptospira of the International Union of Microbiological Societies approved the following nomenclature for serovars of Leptospira. Genus and species must of course be italicized, with the serovar name not italicized and with an upper case first letter.

:"Genus species" serovar Serovar_name

For example:

*"Leptospira interrogans" serovar Australis
*"Leptospira biflexa" serovar Patoc

Morphology

Although over 200 serovars of "Leptospira" have been described, all members of the genus have similar morphology. "Leptospira" are spiral-shaped bacteria that are 6-20 μm long and 0.1 μm in diameter with a wavelength of about 0.5 μm.cite journal |author=Levett PN |title=Leptospirosis |journal=Clin. Microbiol. Rev. |volume=14 |issue=2 |pages=296–326 |year=2001 |pmid=11292640 |doi=10.1128/CMR.14.2.296-326.2001] One or both ends of the spirochete are usually hooked. Because they are so thin, live "Leptospira" are best observed by darkfield microscopy.

The bacteria have a number of degrees of freedom; when ready to proliferate via binary fission, the bacterium noticeably bends in the place of the future split.

Cellular structure

"Leptospira" have a Gram-negative-like cell envelope consisting of a cytoplasmic and outer membrane. However, the peptidoglycan layer is associated with the cytoplasmic rather than the outer membrane, an arrangement that is unique to spirochetes. The two flagella of "Leptospira" extend from the cytoplasmic membrane at the ends of the bacteria into the periplasmic space and are necessary for the motility of "Leptospira".cite journal |author=Picardeau M, Brenot A, Saint Girons I |title=First evidence for gene replacement in "Leptospira spp." Inactivation of "L. biflexa flaB" results in non-motile mutants deficient in endoflagella |journal=Mol. Microbiol. |volume=40 |issue=1 |pages=189–99 |year=2001 |pmid=11298286 |doi=]

The outer membrane of "Leptospira", like those of most other Gram-negative bacteria, contains lipopolysaccharide (LPS). Differences in the highly immunogenic LPS structure account for the numerous serovars of "Leptospira".. Consequently, immunity is serovar specific; current leptospiral vaccines, which consist of one or several serovars of "Leptospira" endemic in the population to be immunized, protect only against the serovars contained in the vaccine preparation. Leptospiral LPS has low endotoxin activity.. An unusual feature of leptospiral LPS is that it activates host cells via TLR2 rather than TLR4.cite journal |author=Werts C, Tapping RI, Mathison JC, Chuang TH, Kravchenko V, Saint Girons I, Haake DA, Godowski PJ, Hayashi F, Ozinsky A, Underhill DM, Kirschning CJ, Wagner H, Aderem A, Tobias PS, Ulevitch RJ |title=Leptospiral lipopolysaccharide activates cells through a TLR2-dependent mechanism |journal=Nat. Immunol. |volume=2 |issue=4 |pages=346–52 |year=2001 |pmid=11276206 |doi=10.1038/86354] The unique structure of the lipid A portion of the LPS molecule may account for this observation.cite journal |author=Que-Gewirth NL, Ribeiro AA, Kalb SR, Cotter RJ, Bulach DM, Adler B, Girons IS, Werts C, Raetz CR |title=A methylated phosphate group and four amide-linked acyl chains in "Leptospira interrogans" lipid A. The membrane anchor of an unusual lipopolysaccharide that activates TLR2 |journal=J. Biol. Chem. |volume=279 |issue=24 |pages=25420–9 |year=2004 |pmid=15044492 |doi=10.1074/jbc.M400598200] Finally, the LPS O antigen content of "L. interrogans" differs in an acutely infected versus a chronically infected animal.cite journal |author=Nally JE, Chow E, Fishbein MC, Blanco DR, Lovett MA |title=Changes in lipopolysaccharide O antigen distinguish acute versus chronic "Leptospira interrogans" infections |journal=Infect. Immun. |volume=73 |issue=6 |pages=3251–60 |year=2005 |pmid=15908349 |doi=10.1128/IAI.73.6.3251-3260.2005] The role of O antigen changes in the establishment or maintenance of acute or chronic infection, if any, is unknown.

Habitat

"Leptospira", both pathogenic and saprophytic, can occupy diverse environments, habitats and life cycles; these bacteria are found throughout the world, except in Antarctica.cite book | author = Madigan M; Martinko J (editors). | title = Brock Biology of Microorganisms | edition = 11th ed. | publisher = Prentice Hall | year = 2005 | id = ISBN 0-13-144329-1 ] High humidity and neutral (6.9-7.4) pH are essential for their survival in the environment, with stagnant water reservoirs - bogs, shallow lakes, ponds, puddles, etc. - being the natural habitat for the bacteria.

Nutrition

"Leptospira" are typically cultivated at 30 °C in Ellinghausen-McCullough-Johnson-Harris (EMJH) medium, which can be supplemented with 0.2-1% rabbit serum to enhance growth of fastidious strains.cite journal |author=Johnson RC, Harris VG |title=Differentiation of pathogenic and saprophytic letospires. I. Growth at low temperatures |journal=J. Bacteriol. |volume=94 |issue=1 |pages=27–31 |year=1967 |pmid=6027998 |doi=] Growth of pathogenic "Leptospira" in an artificial nutrient environment such as EMJH becomes noticeable in 4-7 days; growth of saprophytic strains occur within 2-3 days. The minimal growth temperature of pathogenic species is 13-15 °C. Because the minimal growth temperature of the saprophytes is 5-10 °C, the ability of "Leptospira" to grow at 13 °C can be used to distinguish saprophytic from pathogenic "Leptospira" species. The optimal pH for growth of "Leptospira" is 7.2-7.6.

Like most bacteria, "Leptospira" require iron for growth.cite journal |author=Faine S |title=Iron as a growth requirement for pathogenic "Leptospira" |journal=J. Gen. Microbiol. |volume=20 |issue=2 |pages=246–51 |year=1959 |pmid=13654718 |doi=] "L. interrogans" and "L. biflexa" have the ability to acquire iron in different forms.cite journal |author=Louvel H, Bommezzadri S, Zidane N, Boursaux-Eude C, Creno S, Magnier A, Rouy Z, Médigue C, Saint Girons I, Bouchier C, Picardeau M |title=Comparative and functional genomic analyses of iron transport and regulation in "Leptospira" spp |journal=J. Bacteriol. |volume=188 |issue=22 |pages=7893–904 |year=2006 |pmid=16980464 |doi=10.1128/JB.00711-06] A TonB-dependent receptor required for utilization of the ferrous form of the iron has been identified in "L. biflexa", and an ortholog of the receptor is encoded in the genome of "L. interrogans". "L. interrogans" can also obtain iron from heme, which is bound to most of the iron in the human body. The HbpA hemin-binding protein, which may be involved in the uptake of hemin, has been identified on the surface of "L. interrogans"cite journal |author=Asuthkar S, Velineni S, Stadlmann J, Altmann F, Sritharan M |title=Expression and characterization of an iron-regulated hemin-binding protein, HbpA, from "Leptospira interrogans" serovar Lai |journal=Infect. Immun. |volume=75 |issue=9 |pages=4582–91 |year=2007 |pmid=17576761 |doi=10.1128/IAI.00324-07] Although other pathogenic species of "Leptospira" and "L. biflexa" lack HbpA, yet another hemin-binding protein, LipL41, may account for their ability to use hemin as a source of iron. Although they do not secrete siderophores, "L. biflexa" and "L. interrogans" may be capable of obtaining iron from siderophores secreted by other microorganisms.

Genome

The genome of pathogenic "Leptospira" consists of two chromosomes. The size of the genomes of "L. interrogans" serovars Copenhageni and Lai is approximately 4.6 Mb.cite journal |author=Ren SX, Fu G, Jiang XG, Zeng R, Miao YG, Xu H, Zhang YX, Xiong H, Lu G, Lu LF, Jiang HQ, Jia J, Tu YF, Jiang JX, Gu WY, Zhang YQ, Cai Z, Sheng HH, Yin HF, Zhang Y, Zhu GF, Wan M, Huang HL, Qian Z, Wang SY, Ma W, Yao ZJ, Shen Y, Qiang BQ, Xia QC, Guo XK, Danchin A, Saint Girons I, Somerville RL, Wen YM, Shi MH, Chen Z, Xu JG, Zhao GP |title=Unique physiological and pathogenic features of Leptospira interrogans revealed by whole-genome sequencing |journal=Nature |volume=422 |issue=6934 |pages=888–93 |year=2003 |pmid=12712204 |doi=10.1038/nature01597] cite journal |author=Nascimento AL, Ko AI, Martins EA, Monteiro-Vitorello CB, Ho PL, Haake DA, Verjovski-Almeida S, Hartskeerl RA, Marques MV, Oliveira MC, Menck CF, Leite LC, Carrer H, Coutinho LL, Degrave WM, Dellagostin OA, El-Dorry H, Ferro ES, Ferro MI, Furlan LR, Gamberini M, Giglioti EA, Góes-Neto A, Goldman GH, Goldman MH, Harakava R, Jerônimo SM, Junqueira-de-Azevedo IL, Kimura ET, Kuramae EE, Lemos EG, Lemos MV, Marino CL, Nunes LR, de Oliveira RC, Pereira GG, Reis MS, Schriefer A, Siqueira WJ, Sommer P, Tsai SM, Simpson AJ, Ferro JA, Camargo LE, Kitajima JP, Setubal JC, Van Sluys MA |title=Comparative genomics of two Leptospira interrogans serovars reveals novel insights into physiology and pathogenesis |journal=J. Bacteriol. |volume=186 |issue=7 |pages=2164–72 |year=2004 |pmid=15028702 |doi=] However, the genome of "L. borgpetersenii" serovar Hardjo is only 3.9 Mb in size with a large number of pseudogenes, gene fragments, and insertion sequences relative to the genomes of "L. interrogans."cite journal |author=Bulach DM, Zuerner RL, Wilson P, Seemann T, McGrath A, Cullen PA, Davis J, Johnson M, Kuczek E, Alt DP, Peterson-Burch B, Coppel RL, Rood JI, Davies JK, Adler B |title=Genome reduction in Leptospira borgpetersenii reflects limited transmission potential |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=103 |issue=39 |pages=14560–5 |year=2006 |pmid=16973745 |doi=10.1073/pnas.0603979103] "L. borgpetersenii" serovar Hardjo is usually transmitted by direct exposure to infected tissues, whereas "L. interrogans" is often acquired from water or soil contaminated by the urine of carrier animals harboring "Leptospira" in their kidneys. The high number of defective genes and insertion sequences in "L. borgpetersenii" Hardjo together with the poor survival outside of the host and difference in transmission patterns compared to "L. interrogans" suggest that "L. borgpetersenii" is undergoing insertion-sequence mediated genomic decay, with ongoing loss of genes necessary for survival outside of the host animal.

ee also

*Leptospirosis

References

External links

* [http://microbewiki.kenyon.edu/index.php/Leptospira "Leptospira" page at Kenyon College MicrobeWiki.]
* [http://www.pasteur.fr/recherche/Leptospira/Leptospira.html Pasteur Institute - "Leptospira" Molecular Genetics Server]

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