Pseudomonas stutzeri is a Gram-negative soil bacterium that is motile, has a single polar flagellum, and is classified as bacillus, or rod-shaped.[1][2] While this bacterium was first isolated from human spinal fluid,[3] it has since been found in many different environments due to its various characteristics and metabolic capabilities.[4] P. stutzeri is an opportunistic pathogen in clinical settings, although infections are rare.[3] Based on 16S rRNA analysis, this bacterium has been placed in the P. stutzeri group, to which it lends its name.[5]
P. stutzeri is most easily differentiated from the other Pseudomonas spp. in that it does not produce fluorescent pigments.[6] P. mendocina, P. alcaligenes, P. pseudoalcaligenes, and P. balearica are classified within the same branch of pseudomonads as P. stutzeri based on 16S rRNA sequences and other phylogenetic markers.[6] Of this group, P. stutzeri is most closely related to P. balearica and they can be differentiated not only by the 16S rRNA sequences, but also by the ability of P. stutzeri to grow above 42 °C.[7] P. stutzeri has been isolated in many different locations, and since each strain is a little different based on where it was isolated, the P. stutzeri group contains many genomovars.[6] This means that the many strains of P. stutzeri can be considered genospecies, which are organisms that can only be differentiated based on their nucleic acid composition.[8]
Burri and Stutzer first described P. stutzeri in 1895 and named the bacterium Bacillus denitrificans II.[9] In 1902, Itersonion developed an enrichment culture for P. stutzeri, which was later described by van Niel and Allen in 1952.[10] The enrichment medium is a mineral medium with 2% nitrate and tartrate (or malate, succinate, malonate, citrate, ethanol, or acetate) used under anaerobic conditions at 37 °C.[10] The organism has been isolated from a wide variety of places such as human spinal fluid, straw, manure, soil, and canal water.[10]
Pseudomonas stutzeri is a Gram-negative, rod-shaped, non-spore-forming bacterium that is typically 1–3 micrometres long and 0.5–0.8 micrometres wide.[10] It tests positive for both the catalase and oxidase tests.[11][12] P. stutzeri grows optimally at a temperature of about 35 °C, making it a mesophilic organism, although it can grow at temperatures as low as 4 °C[6] and as high as 44 °C.[12] When grown on a lysogeny broth (LB) medium at 32 °C, this bacterium has a doubling time of about 53 minutes.[13] As the temperature is decreased to approximately 28 °C, the doubling time gets longer and can become as high as 72 minutes.[13] On an asparagine (Asn) minimal medium, however, P. stutzeri has a typical doubling time of about 34 minutes.[13] Despite the differences in doubling time between the two media, P. stutzeri reaches its stationary phase around 10–11 hours after being inoculated, or introduced, into both media.[13] P. stutzeri grows best in media containing 2% NaCl although it can tolerate a salinity (NaCl content) ranging of 1–5%.[14] This bacterium prefers a neutral [[pH] (pH7), but it can grow at a pH as high as 9.[10] P. stutzeri possesses both type IV pili and a polar flagellum, both of which help it to be motile.[10][15]
All Pseudomonas bacteria were originally thought to be incapable of fixing nitrogen.[16] Several Pseudomonas species, including P. stutzeri, however, have since been discovered that have demonstrated the ability to fix nitrogen.[16] Sequencing the genome of the P. stutzeri strain DSM4166 revealed some genes for nitrogen fixation, along with 42 genes that coded for major parts of a denitrification complex.[16] Scientists hypothesize that the genes needed to fix nitrogen were acquired by these particular bacterial species through lateral gene transfer.[16] Similar to other bacteria within the Pseudomonas genus, P. stutzeri strains are heterotrophic organisms that are capable of reducing metals and degrading compounds such as hydrocarbons.[17] Unlike other bacteria within the genus, however, P. stutzeri strains are not fluorescent.[18]
P. stutzeri strains are capable of growing on several various types of media because they can use different electron donors and acceptors to fuel their metabolisms.[17] The bacterium frequently utilizes organic compounds as its electron donors, some of which include: glucose, lactate, acetate, succinate, pyruvate, sucrose and fumarate.[17] As an electron acceptor, P. stutzeri will either use oxygen, if it is in aerobic conditions, or nitrate, if it is in anaerobic conditions.[12] While the bacterium has been shown to grow on solid media (such as gelatin and agar), liquid media (such as nitrate or nitrite-free media), and even potatoes, it shows optimal growth on peptone or yeast agar.[10] When in aerobic environments, P. stutzeri can even grow on more complex media such as lysogeny and Reasoner's 2A (R2A) broths,[17] with the latter of the two being significantly useful in selecting for specific microbes due to its lack of abundant nutrients.[19] Each of the assorted media produce their own slight variations in the phenotypes of the P. stutzeri colonies that result from growth.[10] Some of these variations include changes in surface film or mucus production, changes in texture (such as addition of ridges), or changes in shape (such as circular to polygon-like).[10]
While the microbial colonies of P. stutzeri can alter based on what medium the bacterium is grown on, there are conserved, distinguishable characteristics that are apparent in almost every colony of this species.[10] When examined on solid media, this bacterium has dry, rigid colonies that cling together so tightly it is often easier to remove an entire colony, if needed, rather than just a piece of one.[10] The color of the colonies is usually brown, although it can deviate with a change in media.[12] The shape of each colony mimics that of a crater because the exterior edges are raised, forming a depression in the center.[10] The edges of each colony project outwards often allowing colonies to come into contact with one another.[10]
P. stutzeri is a facultative anaerobe that utilizes respiratory metabolism with terminal electron acceptors such as oxygen and nitrogen.[6] When grown anaerobically, organisms within the genus Pseudomonas are considered to be model organisms for studying denitrification.[20] Strains tested by Stainer and coworkers were able to grow and utilize the following substrates: gluconate, D-glucose, D-maltose, starch, glycerol, acetate, butyrate, isobutyrate, isovalerate, propionate, fumarate, glutarate, glycolate, glyoxylate, DL-3-hydroxybutyrate, itaconate, DL-lactate, DL-malate, malonate, oxaloacetate, 2-oxoglutarate, pyruvate, succinate, D-alanine, D-asparagine, L-glutamate, L-glutamine, L-isoleucine, and L-proline and hydrolysis of L-alanine-para-nitroanilide.[6] D-maltose, starch, and ethylene glycol are carbon sources that are not commonly utilized by other pseudomonads as shown by Stainer et al.
Some strains of P. stutzeri are known to use thiosulfate as an inorganic energy source.[6] In 1999, Sorokin et al. isolated and described seven strains of P. stutzeri that were able to use nitrite, nitrate, or nitrous oxide as electron acceptors in the oxidation of thiosulfate to tetrathionate under anaerobic conditions.[21] The oxidation of thiosulfate to tetrathionate cannot support autotrophic growth as it only yields one electron, therefore strains that perform this are obligate heterotrophs.[21] Thiosulfate oxidation can occur in the presence or absence of oxygen, although it occurs much slower under anaerobic conditions.[6]
In 1998, Metcalf and Wolfe enriched for and isolated a P. stutzeri strain WM88 that could oxidize reduced phosphorus compounds, such as phosphite and hypophosphite, to phosphate.[22] To enrich for a hypophosphite-utilizing organism, a 0.4% glucose-MOPS medium containing 0.5 mM hypophosphite was used as the sole phosphorus source with inoculum from a variety of soil and water environments.[22] Specifically, strain WM88 can use phosphite as its sole phosphorus source when grown in succinate-MOPS medium.[22] When grown anaerobically, the researchers showed P. stutzeri is unable to perform hypophosphite oxidation with nitrate as its electron acceptor.[22] However, phosphite oxidation is unaffected under similar conditions.[22]
In 1913, a strain of P. stutzeri was one of the first microorganisms to be identified as a degrader of alkanes.[23] There is not much information in the literature about other aliphatic hydrocarbon degrading strains of P. stutzeri, however strain KC has been studied extensively due to its potential biotechnological applications.[6] Strain KC was isolated from an aquifer and it is able to transform carbon tetrachloride to carbon dioxide, formate, and other less dangerous products.[6] Carbon tetrachloride can be a pollutant in soils and groundwater,[6] and according to the Center for Disease Control and Prevention (CDC) it is able to cause kidney damage and even death in individuals exposed to it for long periods of time.[24] For biotechnological purposes, strain KC can mineralize carbon tetrachloride, which is useful for in situremediation of aquifers contaminated with carbon tetrachloride.[6]
Aromatic compounds, such as benzene, are considered to be environmental pollutants despite their natural prevalence in nature.[6] Strain P16 of P. stutzeri is a polycyclic aromatic hydrocarbon (PAH) degrading bacterium[6] that was isolated from creosote-contaminated soil via a phenanthrene enrichment culture.[25] As the sole carbon and energy source, strain P16 is able to grow using phenanthrene, fluorene, naphthalene, and methylnaphthalenes.[26] In conjunction with the anionic surfactant Tergitol NP10 and phenanthrene, strain P16 has been proposed to be a model for looking at the effects of surfactants on non-aqueous hydrocarbon bioavailability.[6]
The inclusion of this bacterium into the Pseudomonas genus was confirmed by DNA-DNA hybridization and similarity comparisons of the rRNA sequences.[27] Four rrn operons and an origin of replication site have been identified in P. stutzeri.[27] Strains of P. stutzeri are divided into separate genomic groups called genomovars.[27] The genomovar concept was used for P. stutzeri to distinguish genotypically similar strains.[6] Two strains of P. stutzeri can be classified in a single genomovar if DNA-DNA similarity is at least 70% similar.[6] Seven genomovars have been characterized and their genome sizes range from 3.75 to 4.64 Mbp.[27] These differences in genomovar genomes are believed to have been caused by chromosomal rearrangements during its evolution.[27]
The GC content of the genomes of P. stutzeri strains falls between 60 – 66 mol%.[16][28] P. stutzeri strain DSM4166 is a strain that has been studied and shown specifically to have exactly 61.74% GC content in its circular chromosome.[16] While this strain appears to have no plasmid in coordination with its chromosome, it is thought that the strain has 59 tRNA genes and 4 rRNA operons.[16] When doing global genome comparisons between multiple P. stutzeri strains, it has been found that many of the genomic regions of this bacterium's genome are conserved between varying strains.[17] One of the strains that has been found to vary is strain RCH2.[17] This strain has an extra 244 genes which are believed to aid the bacterium in chemotaxis and in the formation of both a pilus and the pyruvate/ 2-oxoglutarate complex.[17] When this strain was sequenced, it was found to have a 4.6 Mb circular chromosome and three plasmids.[17]
A comparative genomic and phylogenomic study analyzed 494 complete genomes from the entire Pseudomonas genus, with 19 of the being classified within the wider P. stutzeri evolutionary group.[28] These 19 P. stutzeri genomes encoded between 3342 and 4524 (average: 4086) proteins each, with 2080 of them being shared among all members of the group (core proteins).[28]
Originally, P. stutzeri strains were misidentified with other species in similar growth environments due to the limitations of phenotypically similar bacteria of Pseudomonas.[6] P. stutzeri is found widely in the environment and occupies a diverse range of ecological niches including being found to be an opportunistic pathogen in humans.[6] The habitats and ecology of P. stutzeri are diverse not only because of its ability to grow organotrophically or anaerobically using oxidative metabolism, but also because of its chemolithotrophic properties, its resistance to metals, the wide sources of nitrogen it can use, and the range of temperatures that support its growth.[6]
P. stutzeri genes have been found in the rhizosphere region of soil implying the relevance of this bacterium as a nitrogen fixer.[29] This bacterium has been isolated from oil-contaminated soil and marine water/sediment samples.[6] While most Pseudomonas strains that have been isolated from marine environments are eventually transferred to another genus after classification, P. stutzeri is one of the few strains that has not.[6] This strain meets the requirements of being able to tolerate NaCl and it is found in water columns in the Pacific Ocean and sediments in the Mediterranean.[6] These marine strains have many ecological roles including naphthalene degradation, sulfur oxidation, and most importantly denitrification and diazotrophy (nitrogen fixation).[6] There is also evidence of P. stutzeri in wastewater treatment plants.[6] ZoBell, AN10, NF13, MT-1, and HTA208 are the most significant strains isolated from marine environments and have been found in places such as water columns in the Pacific-ocean, polluted Mediterranean marine sediments, Galapagos rifts near hydrothermal vent at depths of 2500 meters, and Mariana trench samples at 11 000 meters.[6] Several other P. stutzeri strains have even been found in other locations such as manure, pond water, straw and humus samples.[11]
Several strains of Pseudomonas stutzeri have been found to behave as opportunistic pathogens in humans.[3] It was not until 1973, however, that P. stutzeri's ability to cause infection started to become a topic of discussion within scientific literature.[30] The first known infection was observed in combination with a permanent tibial fracture that required surgery.[30] Since that initial infection, P. stutzeri has been able to cause infections within individuals that have a variety of illnesses, including: endocarditis, infections of the bone, eye, skin or urinary tract, meningitis, pneumonia, arthritis, and several others.[3] Some patients even have health conditions as serious as tumors, infected joint cavities and collapsed lungs.[11] Within those infected, P. stutzeri strains have been isolated from the blood, feces, cerebral spinal fluid, ears, eyes, and organ systems (such as respiratory and urinary).[11] When strains of this bacterium are discovered within infected patients they are often accompanied by other pathogenic microbes.[11]
While P. stutzeri has caused numerous infections since it has been discovered, it has caused few deaths, giving it a much lower virulence rating in relation to other Pseudomonas species, such as Pseudomonas aeruginosa.[6] Despite its lack of major virulence, however, this bacterium still poses a threat to human health because it contains a variety of antibiotic resistance mechanisms.[3] In fact, P. stutzeri has so many resistance mechanisms that antibiotic-resistant P. stutzeri strains have been discovered and isolated for almost every antibiotic family except fluoroquinolones.[31] Some of the more-studied resistance mechanisms include: utilization of beta-lactamases, which are able to cleave penicillins, cephalosporins, and other antibiotic classes, and ability to vary lipopolysaccharide and outer membrane protein components.[32] In order to gain resistance to fluoroquinolones, mutations in the gyrA (gyrase gene) and parC(topoisomerase IV gene) are often needed, mutations which are not as common.[31] Only one strain of P. stutzeri, strain 13, has been found to have mutations that allow it to be resistant to fluoroquinolones.[31] The reason P. stutzeri strains are less of a concern for major antibiotic resistance as compared to other Pseudomonas strains, like P. aeruginosa, is likely due to the fact the strains are less common in clinical settings and thus less frequently exposed to antibiotics.[31]
Some strains of P. stutzeri are capable of associating with pollutants and toxic metals, such as biocides and oil derivatives, in such a way that allows the bacterium to promote the degradation of these substances.[6] Other strains of this bacterium have metabolic capabilities, such as metal cycling, that allow for the preservation of essential metals, such as copper and iron, and the degradation of toxic metals, such as uranium and lead.[6] One specific strain of P. stutzeri, strain RCH2, is currently being studied as a potential tool for the bioremediation of soil and water supplies since it has shown an ability to reduce hexavalent chromium concentrations in areas where this pollutant is high.[17] Several other P. stutzeri strains, such as strain A15, have demonstrated an ability to reduce atmospheric nitrogen so they are being explored as agents to help increase plant growth.[33] These strains are specifically being studied for use in rice plants because they have been shown to naturally infect and inhabit the roots of these plants.[33] By living within the roots, P. stutzeri is able to supply the plants directly with the reduced nitrogen compounds they produce.[6]
Several different strains of P. stutzeri have been found to be competent for natural genetic transformation.[34] The frequency of transformation between individuals of the same P. stutzeri strain is typically high.[34] Between individuals of different strains, or between P. stutzeri strains and other Pseudomonas species, however, the frequency of transformation is usually greatly reduced.[34] The complete genome sequence of a highly transformable P. stutzeri strain, strain 28a24, has been determined and is available for observation.[35]
Pseudomonas stutzeri is a Gram-negative soil bacterium that is motile, has a single polar flagellum, and is classified as bacillus, or rod-shaped. While this bacterium was first isolated from human spinal fluid, it has since been found in many different environments due to its various characteristics and metabolic capabilities. P. stutzeri is an opportunistic pathogen in clinical settings, although infections are rare. Based on 16S rRNA analysis, this bacterium has been placed in the P. stutzeri group, to which it lends its name.
Pseudomonas stutzeri on sugukonda Pseudomonadaceae kuuluv bakter. See on oportunistik patogeen, mis on eriti tuntud oma denitrifitseerimisvõime poolest ja teda kasutatakse selle uurimisel mudelorganismina. P. stutzeri't kirjeldati esmakordselt 1895. aastal. Katsed näitasid, et bakter kuulub DNA-rRNA hübridisatsiooni järgi perekonda Pseudomonas. 1966. aastal tehti kindlaks, et P. stutzeri võib toituda väga mitmekülgselt ning kasutada süsinikuallikatena ka selliseid ühendeid, mida teised perekonda Pseudomonas kuuluvad bakterid ei kasuta. Osa P. stutzeri tüvedest toodab ka siderofoore.[1]
Katsetega on kindlaks tehtud P. stutzeri fülogeneetiline kuuluvus. Kasutatud on nii DNA-DNA hübridisatsiooni võrdlemist, DNA-rRNA hübridisatsiooni, GC-protsenti, 16S rRNA järjestuse analüüsimist, Grami järgi värvimist kui palju muud.[1]
Bakterit saab isoleerida kahel viisil. Kasutada võib diferentsiaalsöötme meetodit. Sellega tagatakse söötmel sobivad tingimused elamiseks vaid P. stutzeri'le ning teised ei saa sellise söötme peal kasvada. See viis võeti esmakordselt kasutusele 1902. aastal. Kasvatades rakke anaeroobsetes tingimustes sellisel söötmeagaril, mis sisaldab 2% nitraati ja tartraati (C4H4O62-) (selle asemel võib olla ka malaat, suktsinaat, tsitraat, etnool või atsetaat), muutub domineerivaks liigiks P. stutzeri. Bakter suudab kasvada ka sellisel söötmel, kus on energiaallikateks kas ainult ammoonium või nitraat, teised kasvufaktorid ei ole vajalikud.[1]
Teine võimalus on kõik proovis olnud bakterid läbi analüüsida ja jõuda lõpuks P. stutzeri'ni. Seda võib teha 16S rRNA järjestusel põhineva meetodi abil. 1998. aastal loodi sellised PCR-praimerid, mis olid spetsiifilised kõigile tol ajal teada olnud P. stutzeri tüvedele. Samas kasutati meetodit vaid selleks, et oma tulemusi üle kontrollida. P. stutzeri puhul on võimalik kontrollida ka denitrifitseerimisgeenide nirS ja nosZ olemasolu. Lisaks nifH geeni, mille abil saab analüüsida just neid baktereid, kes suudavad risosfääris elades õhulämmastikku siduda. [1]
P. stutzeri on kepikujuline pulkbakter, kes kuulub gramnegatiivsete bakterite hulka. Tema rakud on üldiselt üks kuni kolm mikromeetrit pikad ning 0,5 mikromeetrit laiad. Suuremal osal P. stutzeri tüvedest on olemas liikumisvõime, eriti levinud on see mullas elavate tüvede seas. Liikumist võimaldab üks polaarne vibur, harvemini esineb kaks lateraalset viburit. Kui tüvel AN11 katsetati viburi tekkimist, siis 38%-l tuli 1 polaarne vibur, 31%-l tekkis(id) ka lisavibur(id) ning ülejäänutel vibur puudus. [1]
P. stutzeri teeb huvitavaks tema kolooniate eripärane kuju ning konsistents. Alles isoleeritud kolooniad, mis on veel värsked, tunduvad olevat kortsulise struktuuri ja punakaspruuni värvusega. Tavaliselt on kolooniad siiski kõvad ja üsna kuivad, sellepärast on neid ka lihtne substraadilt eemaldada. Kolooniate välisäärt võib kirjeldada kui puuoksa, sest kolooniate ääred on samamoodi hargnenud. Samas võib kolooniate kuju muutuda. Kui laboritingimustes toimub kolooniate pidev edasikülvamine või ümberkülvamine, võivad P. stutzeri kolooniad muutuda kahvatukollasteks ning kolooniate ääred ühtlaselt siledaks. Tavaline temperatuur P. stutzeri laboris kasvatamiseks on 30 °C. Kui hoida rakke 24 tundi 4 °C juures, muutuvad kolooniad struktuurilt taas kortsuliseks. [1]
P. stutzeri kasvutemperatuur on 4 kuni 45 °C, kuid kasv ekstreemsetes oludes on kõigi tüvede puhul pärsitud. Süvaookeanist isoleeritud tüved taluvad kasvu 2 °C juures ja 100 MPa rõhu all. Suurem osa eelistab kasvada temperatuuril 40 kuni 41 °C, mõned üksikud tüved eelistavad 43 °C. Üldiseks optimumiks loetakse 35 °C. pH taluvuse vahemik on samuti suur, kuid seni pole avastatud tüve, mis suudaks kasvada pH 4,5 või sellest väiksema juures. P. stutzeri kasvab hästi õhuhapniku käes, kuid kasvatades rakke eesmärgil siduda lämmastikku, tuleb neid hoida mikroaerofiilidele sobilikes tingimustes. Kõik tüved kasvavad, kui substraadiks on glükonaat, D-glükoos, D-maltoos, tärklis, glütserool, atsetaat, butaraat, isopürovaat, propionaat, fomaraat, glutaraat, glükolaat, DL-3-hüdroputüraat, DL-laktaat, DL-malaat, oksaalatsetaat, püruvaat, suktsinaat, A-alaniin, A-asparagiin, L-glutamaat, L-glutamiin, L-isoleutsiin või L-proliin. [1]
Kõigil P. stutzeri tüvedel on üks tsirkulaarne kromosoom. Genoomi suurus on 3,75 kuni 4,64 Mb. Eri tüvede genoomide suurus võib erineda kuni 20%. Bakteri geenide hulgast on leitud replikatsiooni alguspunkti lähedat neli rrn-operoni. Teiste bakteriliikide puhul asuvad rrn-operonid pigem replikatsiooni alguspunktist kaugemal. Tõenäoliselt arenes sellest bakterist eraldi liik genoomi suuruse ja eriskummalise paigutuse tõttu. P. stutzeri plasmiide uuriti kokku kahekümnel tüvel, millest pooltel need esinesid, ühel tüvel enamasti üks kuni neli. Kõikidest leitud plasmiididest olid 72% väiksemad kui 50 kb, üks jäi vahemikku 50 kuni 95 kb ning üks oli suurem kui 95 kb. Ükski tüvedest ei jaganud täpselt samasuguseid plasmiide. Kümnest plasmiididega tüvest olid seitse isoleeritud reostunud aladelt. NCBI (The National Center for Biotechnology Information) andmebaasis on kümne P. stutzeri tüve genoomid täielikult ning 21 tüve genoomid osaliselt sekveneeritud. [1]
Selle protsessi eesmärgiks on kasutada õhulämmastikku elektroni aktseptorina, et läbi viia bioenergeetilisi protsesse anaeroobses, mikroanaeroobses või väga harva ka aeroobsetes tingimustes. Denitrifikatsiooni ensümaatiline elektronide ülekanne on otseselt seotud ATP tootmisega. Elektronide ümberpaigutumine kutsub esile prootongradiendi, millest saabki sünteesida ATP'-d. P. stutzeri denitrifitseerimise rada on stabiilne ning ta on üks kõige aktiivsemaid denitrifitseerijaid bakterite hulgas. Sel põhjusel on ta ka võetud denitrifitseerimise uurimisel mudelorganismiks.[2]
Oma suure geneetilise ja füsioloogilise vastuvõtlikkuse pärast saab P. stutrzeri tüvesid saab kasutada keskkonnatehnoloogias. Paljud tüved võivad lagundada inimtegevuse reoaineid ning sellega mängivad nad olulist rolli reostuste likvideerimisel. P. stutzeri tüved taluvad väga erinevaid keskkonnatingimusi ja see teeb nende kasutamise võimalikuks peaaegu igas kohas. Bioloogias ja biotehnoloogias pakuvad erilist huvi tüved AG259 ja RS34. [1]
AG259 on P. stutzeri tüvi, mis isoleeriti USA Utah' osariigi hõbedakaevandusest. Tema hõbedaresistentsuse kohta ei ole palju teada, kuid usutakse, et selle tagab geen pKK1. Arvatakse, et see geen tagab bakterile mehhanismi, millega saab toota raku sees hõbedast ja sulfiidist komplekse. Hilisemates uuringutes on näidatud, et bakter suudab oma periplasmasse koguda ka hõbedal baseeruvaid kristalle. Need võivad olla kuni 200 nm suured ning kas kolm- või kuusnurksed. Samuti suudab AG259 koguda endasse suurtes kogustes germaaniumit, vaske, pliid ja tsinki. Sellest tulenevalt pakub tüvi suurt huvi tehnoloogiates, mille eesmärgiks on katta pinnad orgaanilise metalliga. [3]
RS34 on tsingi suhtes resistentne ning see on eraldatud India New Delhi tööstuste reostatud alalt. Bakter kogub enda morfoloogiat muutes oma välismembraani suurtes kogustes tsinki. Selline mehhanism on ainulaadne ega sarnane ühegi teise seni teadaoleva teise mehhanismiga. RS34 seda rada on kasutatud, et eemaldada tsinki lahustest ja kaevandusmaakidest.[4]
Kõik elusolendid vajavad mingil määral metalle, et tagada organismi normaalne talitlus. Ehkki nende mõju võib-olla toksiline. Bakterid neutraliseerivad enda jaoks metalle eri süsteemide abil. P. stutzeri'l on kolm siderofoori, mis tagavad talle koobalti, nikli, vase ja raua saamise ilma kahjustusteta. Samas on paljud P. stutzeri tüved resistentsed ka alumiiniumi, plii, germaaniumi, mangaani, plutooniumi, seleeni, hõbeda, titaani ja paljude teiste metallide suhtes. Seni on leitud, et kõik resistentsussüsteemid on geenide kodeeritud ja need geenid asuvad enamasti plasmiidides. Enim uuritud on P. stutzeri hõbedaresistentsust. [1]
Benseenituum on looduses väga levinud, kuid tegu on keskkonda saastava ühendiga. Perekonnas Pseudomonas on aromaatsete ühendite lagundamine levinud võime ning see on teadusele pikka aega selge olnud. P. stutzeri suudab lagundada mono- ja dihalogeene, Br-, Cl-, I- või F-bensoaate, 4-hüdroksübensoaati, benseensulfonaati, 4-metüülbenseensulfonaati, kresooli, naftaleeni (tüvi AN10), fenooli, toluaati, tolueeni ja salitsülaati. [5]
P. stutzeri on antibiootikumide suhtes palju tundlikum kui Pseudomonas aeruginosa. Põhjus arvatakse olevat tema väheses kokkupuutes eri antibiootikumidega ning harv esinemine haiglates. Suurema antibiootikumitaluvusega P. stutzeri on leitud HIV-positiivsete inimeste proovidest. Ühtlasi on leitud, et tegelikult on bakteril palju mehhanisme antibiootikumide resistentsuse jaoks, kuna iga antibiootikumi perekonna suhtes on leitud mõnel P. stutzeri tüvel resistentsus. Seni on kirjeldatud kahte mehhanismi: välismembraani valkude ja lipopolüsahhariidide varieerumine ja β-laktaamide olemasolu, mis hüdrolüüsivad looduslikke ja poolsünteetilisel penitsilliinil põhinevaid antibiootikume.
Kõik seni uuritud tüved on olnud tuntumatest antibiootikumidest resistentsed gentamütsiini, kanamütsiini ja tetratsükliini suhtes. Mõnel tüvel on leitud resistentsust ka rifampitsiidi, penitsilliini ja amoksüliini suhtes. [1]
1973. aastal dokumenteeriti esimene P. stutzeri põhjustatud infektsioon. Pärast seda juhtumit on esinenud veel mõni luu-, liigese-, silma- või nahainfektsioon. Seni teatakse vaid kahte P. stutzeri põhjustatud infektsiooni, mis on lõppenud surmaga. Kummagi juhtumi puhul ei ole selge, kas surma tegelik põhjus oli infektsioon või mõni teine haigus. P. stutzeri infektsioonid on patsientidel esinenud pärast operatsiooni või mõne suurema trauma järel. Haiglas läbi viidud uuringus koguti proove nii patsientide verest, uriinist, hingamisteedest kui ka haavadest. Eraldi proove võeti ka HI-viirust põdevatelt inimestelt. Tulemused näitasid, et kõikides proovides esinenud Pseudomonas'e perekonna esindajatest moodustas P. stutzeri 1,8% HIV patsientidel ning 2% teistel haigetel. Tulemustest selgus, et kõige rohkem P. stutzeri’t sisaldasid uriiniproovid. Selle põhjal võib P. stutzeri’t lugeda oportunistlikuks patogeeniks, kuid mitte täielikult patogeenseks bakteriks. [6]
Kõik seni uuritud P. stutzeri tüved on biotsiidide vastu resistentsed ning paljud suudavad neid ka lagundada. Biotsiide kasutatakse laialdaselt nii põllumajanduses, tööstustes kui ka kliinilistes asutustes. Inimtegevuse tagajärjel paisatakse loodusesse igal aastal rohkem kui 14 miljonit kilogrammi biotsiide ning selle tagajärjeks võib-olla reostus. Nii P. stutzeri, teiste selle perekonna esindajate kui ülejäänud reoaineid lagundavatel bakterite ökoloogilises tähtsus on loodust puhastada. P. stutzeri eeliseks on võime elada nii maapinnas, magevees kui ka merevees. Tööstuslike jääkide lagundamisel pakuvad teadlastele suuremat huvi P. stutzeri tüved 5MP1 ja AK61. [1]
Pseudomonas stutzeri on sugukonda Pseudomonadaceae kuuluv bakter. See on oportunistik patogeen, mis on eriti tuntud oma denitrifitseerimisvõime poolest ja teda kasutatakse selle uurimisel mudelorganismina. P. stutzeri't kirjeldati esmakordselt 1895. aastal. Katsed näitasid, et bakter kuulub DNA-rRNA hübridisatsiooni järgi perekonda Pseudomonas. 1966. aastal tehti kindlaks, et P. stutzeri võib toituda väga mitmekülgselt ning kasutada süsinikuallikatena ka selliseid ühendeid, mida teised perekonda Pseudomonas kuuluvad bakterid ei kasuta. Osa P. stutzeri tüvedest toodab ka siderofoore.
Pseudomonas stutzeri là một vi khuẩn hình roi gram âm di động lần đầu được cô lập từ chất lưu xương sống người.[1][2]. Dựa trên phân tích 16S rRNA, P. stutzeri đã được đặt vào nhóm P. stutzeri, nhóm mà nó cho mượn tên.[3]
Các nghiên cứu về trình tự 16S rRNA cho thấy chúng tương đồng với các loài như P.mendocinia, P.alcaligenes, P.pseudoalcaligenes và P.balearica.
•Tế bào có hình que, dài 1 đến 3μm, rộng 0.5 μm.
•Khuẩn lạc có hình dạng không kiên định khi được phân lập trực tiếp, khuẩn lạc có dạng sần, khô, bám chặc với nhau. P.stutzeri có gram âm, hình que, di chuyển bằng một cực của tiên mao.
•Nó không có sắc tố và có khả năng loại nitơ từ NO3- giải phóng N2.
•P.stutzeri có thể tăng trưởng trong môi trường amylase, maltose và tinh bột nhưng không phát triển trong gelatinase.
•Vi khuẩn hiếu khí, phân bố rộng rãi trong các vùng địa lý nhưng được tìm thấy chủ yếu trong đất và nước. Nhiều dòng được phân lập từ các mẫu bệnh lý. Chúng có khả năng chuyển hóa, làm giảm các chất độc cho môi trường và các hợp chất có trọng lượng phân tử cao như polyethylene glycols.
Pseudomonas stutzeri là loại vi khuẩn khử nitrate, không phát quỳnh quang. Gần đây nhiều nhà khoa học đang chú ý đến khả năng chuyển hóa chuyên biệt của nó:
•Một vài dòng có thể chuyển hóa các hợp chất thơm như naphthalene và mathylnapthalenes Hai hợp chất thơm này hiện diện nhiều trong dầu thô, là chất có tiềm năng gây độc.
•P.stutzeri được đề cập như một hệ thống khử nitrate vì nó có khả năng là giảm nitrate chuyển khí N2.
•Một số loài có khả năng biến đổi tự nhiên, là đối tượng thích hợp cho các nghiên cứu về sự biến đổi gen trong môi trường. P.stutzeri được phân lập từ động vật, môi trường bệnh viện và các mẫu bệnh ở người.
•Ớ Việt Nam ta, các chủng vi khuẩn địa phương khử đạm mạnh, phù hợp với điều kiện sinh thái địa phương có thể ứng dụng vào xử lý môi trương nước đã được các nhà khoa học nghiên cứu, đặc biệt gần đây nhất là đề tài phân lập vi khuẩn Pseudomomas stutzeri có khả năng khử đạm mạnh trong nước thải ao cá tra ở Đồng Bằng Sông Cửu Long và ứng dụng nó vào xử lý nước thải. (Pseudomonas stutzeri có khả năng làm giảm hàm lượng nitrogen, amoni, … trong nước ở những nuôi cá tra, basa,… tăng hiệu quả kinh tế, cải thiện cuộc sống cho người dân.)
•Việc nghiên cứu ứng dụng những vi sinh vật có tiềm năng sinh học khử được các hợp chất chứa nitơ vô cơ là rất cần thiết, điển hình là vi khuẩn Pseudomonas stutzeri là loài có tính đa dạng cao và phân bố ở vùng địa lý rộng. Vi khuẩn Pseudomonas stutzeri. Vi khuẩn Pseudomonas stutzeri có khả năng khử đạm, quá trình này làm giảm tác hại ô nhiễm môi trường. Hiện nay, vi khuẩn này đã và đang được nhiều nhà khoa học nghiên cứu, nhưng ở tại Việt Nam những nghiên cứu và ứng dụng về loài vi khuẩn này còn rất nhiều hạn chế. Vì vậy, thực hiện đề cương niên luận sinh học về "Pseudomonas stutzeri khử đạm trong môi trường nước" là điều cần thiết.
Pseudomonas stutzeri là một vi khuẩn hình roi gram âm di động lần đầu được cô lập từ chất lưu xương sống người.. Dựa trên phân tích 16S rRNA, P. stutzeri đã được đặt vào nhóm P. stutzeri, nhóm mà nó cho mượn tên.
Các nghiên cứu về trình tự 16S rRNA cho thấy chúng tương đồng với các loài như P.mendocinia, P.alcaligenes, P.pseudoalcaligenes và P.balearica.
Bacillus denitrificans II Burri and Stutzer 1895
Bacterium stutzeri Lehmann and Neumann 1896
Bacillus nitrogenes Migula 1900
Bacillus stutzeri Chester 1901
Achromobacter sewerinii Bergey, et al. 1923
Achromobacter stutzeri Bergey, et al. 1930
Pseudomonas stanieri Mandel 1966
Pseudomonas perfectomarina corrig. (ex ZoBell and Upham 1944) Baumann, et al. 1983
Pseudomonas chloritidismutans Wolterink, et al. 2002
シュードモナス・スタッツェリ(Pseudomonas stutzeri)とは、シュードモナス属のグラム陰性細菌である。ヒトの脳脊髄液から単離された[1][2]。
脱窒菌である[3]。発症はまれだが、ヒトに対して日和見感染の病原性を持つ[4]。2000年に行われたシュードモナス属細菌の16S rRNA系統解析により、シュードモナス属の分類群の中にP. stutzeriグループが設けられ、P. stutzeriはそのグループの代表種に位置づけられた[5]。
Pseudomonas stutzeriは、単一の極鞭毛を持つグラム陰性桿菌である。単一の極鞭毛を持ち、運動性を有する。細胞の大きさはおおよそ1-3μm×0.5μmである。コロニーは円盤型で、中心からしわが放射状に広がっている。
Pseudomonas stutzeriは様々な環境に生息しており、その代謝特性も非常に多種多様である。また、代謝特性の多様性は、系統学的に同じとされる菌株間でも観察される。
Pseudomonas stutzeriは炭素源として有機物を摂取ことができる従属栄養微生物であり、大気中の二酸化炭素を使うことができる独立栄養微生物でもある。
P. stutzeriには脱窒菌株と窒素固定菌株がいる。脱窒菌株は電子受容体として酸素ではなく硝酸塩を利用することができる。この場合、硝酸塩は細胞内で亜硝酸塩、酸化窒素、亜酸化窒素、最終的に窒素ガスへと段階的に変換される。窒素固定菌株は米の根に生息し、米と共生している。いくつかの窒素固定菌株は、窒素ガス以外に窒素源がない環境で米を生長させることが確認されている。
エネルギー(電子)源としてチオ硫酸塩を用いる菌株も存在する。また、一部の菌株は、リン酸源がない環境でリン酸塩または次亜リン酸塩を酸化する。鉱山や重金属汚染された土壌など、重金属が高濃度で残留する環境で重金属耐性菌株が単離されている。今までに銀、亜鉛、ニッケルイオン、並びに亜テルル酸、亜セレン酸への耐性菌株が確認されている。
これらの菌株は農業技術に利用できる。また、バイオレメディエーションや排水処理に利用できる菌株もある。
Pseudomonas stutzeriの3菌株のゲノムシークエンシングが完了している。ゲノムサイズは最も大きかったもので4,547,930bpで、他の2菌株はこれより少し小さい程度だった。これら3菌株はプラスミドを持たない。
ゲノムシークエンシングされた3菌株のうち2菌株から脱窒活性の遺伝子が見つかった。33個の遺伝子からなる30kbpのクラスター領域があり、窒素酸化物還元酵素およびそれの組み立てと電子の供与に関わる遺伝子をコードしている。このクラスターに含まれていない遺伝子もP. stutzeriの脱窒過程に関わっていると考えられている。
P. stutzeriは、環境中から同種および異種のプラスミドDNAを取り込み、自身のゲノムに統合する自然形質転換[ 英: natural transformation ]をすることができる。この能力は多様な環境に適応することを可能にし、P. stutzeriは世界中の幅広い環境中から見出せる。
ゲノムシークエンシングされた3菌株は安息香酸とカテコールを分解する遺伝子を持つ。また、化学走化性に関わる遺伝子も発見されている。
Pseudomonas stutzeriは稀にヒトに日和見感染する。P. stutzeriを含む多くのシュードモナス属細菌は皮膚感染する(壊疽性膿瘡[ 英: ecthyma gangrenosum ])。また、人工骨の埋め込み施術後にP. stutzeri感染することもある。P. stutzeriの感染症の治療は、患者が死亡した2例を除いてすべて抗生物質により成功している。ただし、死亡した2例において、死亡原因がP. stutzeriの感染によるものか、他の要因によるものかははっきりしていない。
土壌、特にcordgrass(Spartina属（英語版）の多年生イネ科植物)、大麦、小麦、米などの植物の根圏に生息している。海水および海水中の堆積物からも見出される。マリアナ海溝の熱水噴出孔にも生息している[6]。
Pseudomonas stutzeriとP. fluorescensは細胞膜で四塩化炭素[注釈 1]を還元し、二酸化炭素と非揮発性物質に分解する[7]。このため、四塩化炭素のバイオレメディエーションへの利用が研究されている。
KC株は四塩化炭素のバイオレメディエーションへの利用が有望視されている株の一つであり、帯水層から単離された。KC株は四塩化炭素を最終的に二酸化炭素、ギ酸、非揮発性物質に変換する。揮発性の塩化炭化水素を分解する生物により産生される非揮発性物質は一般に代謝されるか環境中に蓄積する[8][9][10][11]。また、他の四塩化炭素分解性の脱窒微生物の大部分は、同等もしくはより高い残留性を持つクロロフォルムの環境中の蓄積を引き起こすのに対して、KC株はクロロフォルムを生産しない[12][13][14]。
KC株が迅速に四塩化炭素を分解するためには、500Daの小因子が必要である。この小因子は、栄養素としての鉄分Fe3+が不足している条件において、対数増殖期に分泌される。また、四塩化炭素の分解経路には酸素は用いられないが、小因子は酸素の利用と脱窒により産生される[15]。小因子が与えられている条件では、四塩化炭素を分解しない生物も分解活性を示す[16]。
ATCC 17588
CCUG 11256
CFBP 2443
CIP 103022
DSM 5190
JCM 5965
LMG 11199
NBRC 14165
NCCB 76042
VKM B-975
