La Vie en Rose : on the pink tones of the waters in lakes populated by halophilic and halotolerant microorganisms Francisco Javier Martn-Gil, Pablo Martn-Ramos, Jess Martn-Gil and Mara del Carmen Ramos-Snchez

La Vie en Rose: on the pink tones of the waters in lakes populated by halophilic and halotolerant microorganisms Francisco Javier Martn-Gil1, Pablo Martn-Ramos2, Jess Martn-Gil1 and Mara del Carmen Ramos-Snchez3 1.Department of Agricultural and Forestry Engineering, University of Valladolid, Campus at Palencia, Palencia, Spain 2.Department of Agricultural and Environmental Science, University of Zaragoza, Campus at Huesca, Huesca, Spain. 3.Microbiology Laboratory in Rio Hortega Universitary Hospital, Valladolid, Spain Abstract There are three groups of microorganisms that live and grow in hypersaline (>15% NaCl) lakes: the halophilic Archaea and the halotolerant Bacteria and algae. In order to grow and reproduce in such high-saltenvironments,theseorganismshavemadebasicbiochemicaladaptationsintheir proteins,nucleicacids,lipidsandosmoregulationmechanisms.Thepinktonesofthewatersin lakes populated by halophilic and halotolerant microorganisms are reviewed in this paper. One of the most spectacular Nature phenomena are the pink lakes. Among the most beautifulpinklakesare:LakeHillier,locatedinthemainislandoftheRecherche Archipelago,Australia;LakeRetbainSenegal;LakeMasazir(orMasazirgol)notfar fromtheQaradadistrictofBaku,Azerbaijan;SalinadeTorrevieja-LaMata,in Alicante, Spain; Dusty Rose Lake in British Columbia, Canada; and Laguna Colorada in Colombia. Initially, the pigmentation of the waters of the lakes mentioned above was referred to the carotenoids produced by microalgae such as Dunaliella salina. D. salina is a type of halophile green micro-algae especially found in sea salt fields and in the pits or the salt crystallizers.Itischaracterizedbyaccumulatinginhypersalineenvironments[1]and nitrogen limitation [2] high concentrations of -carotene, raising 14% of their dry mass. Undertheseconditions andwithlightintensitiesofthe orderof195E.m-2s-1, the red pigment exceed to chlorophyll content a 20:1 ratio and is responsible for color change (in water with normal salinity, D. salina is as green as other chlorophytes). Today we know that although D. salina produce -carotene in a high salt environment, Archaea such as Halobacterium, not Dunaliella, are responsible for the red and pink coloring of salt lakes.[3]. Occasionally, orange patches of Dunaliella colonies will crop up.TheredandpinkpigmentsarebacteriorhodopsinproducedbyArchaebacteria (Halobacteriumsalinarum,HalobacteriumhalobiumorHalobacteriumcutirubrum)or rubredoxinsandrubrerythrinsfromsulfate-reducingBacteriaasDesulfohalobium retbaense. Dunaliella salinaHalobacterium salinarumDesulfohalobium retbaense Dunaliella,HalobacteriumandDesulfohalobiumareallmicroorganismsthatcan survive in waters of extreme salinity. The survival is gained because of its adaptations in order to cope with the high salt concentrations [4]. These adaptations are: modifying thesequencesofitsproteins,recruitingproteinsfromdifferentsourceswithdifferent functions, as well as lateral gene transfer from other halophilic organisms. Lake Hillier, Western Australia Of special interest is the case of halophilic Archaea and further of halotolerant Bacteria which in turn may range from obligate aerobes to photoautotrophs to anaerobic sulfate-reducers bacteria.HalobacteriumsalinarumisanextremelyhalophilicmarineGram-negativeobligate aerobic archaeon. This microorganism is not a bacterium, but rather a member of the domain Archaea. It is found in hypersaline lakes, and salterns. As these salterns reach theminimumsalinitylimitsforextremehalophiles,theirwatersbecomepurpleor reddishcolorduetothehighdensitiesofhalophilicArchaea.Halobacteriahavea purplemembrane,becausetheyhaveapigmentrhodopsintypecalled bacteriorhodopsin,whichreactswithlighttoformaprotongradientacrossthe membrane,allowingsynthesisofATP,theonlyexampleknowninthenatureofa photophosphorylation without chlorophyll. The ability of H. salinarum to survive at such highsaltconcentrationshasbeenachievedbymeansofacquiredgenesthrougha deep and intense cooperation with another microbe [5]. Methanogens sometimes live and work together with other bacteria and archaea that produce hydrogen and carbon dioxide that they consume. It's not difficult to imagine a next step, in which one of the two symbiotic partners is taken up by the other and gets stripped of its genes. LakeRetbaowesitscolortothepresenceofhighconcentrations(385g/L)of halotolerantanaerobicsulfate-reducersbacteriumDesulfohalobiumretbaense,which canutilizeH2andalimitedrangeoforganicsubstrates,whichareincompletely oxidizedtoacetateandCO2,forgrowth.D.retbaenseisthefirstdescribed hydrogenotrophicanaerobeabletogrowatsalinitiesabove10%.Intheircytoplasm, multiprotein complexes containing red/pink colored rubredoxins and rubrerythrins have been described [6].

Lake Retba, Senegal In SW Spain, in the Alicante area, two salt seeps, the Salina de Torrevieja and La Mata deLaSalina,arethelargestsaltlakesinEurope.Thepink-purplecolorofthe TorreviejalagooniscausedbypigmentsofHalobacteriumbacteriaandSalinibacter ruber (bacteria similar in protein structure to the family Halobacteriaceae). The colour is also caused by the microalga Dunaliella salina, which is responsible for the bright red colour of the lake seen at certain times of the year. The Artemiasalina brine shrimp, which lives in the lake, is also red because it feeds on the bacteria.

Salina de Torrevieja, Alicante, Spain Lake Masazir, overlooking the Caspian Sea, is another pink lake located not far from theQaradadistrictofBaku,thecapital of Azerbaijan.Large volumes of chloride and sulphateareconcentratedinioncompositionofthewater.Athermophilicstrainof Dunaliella bardawil Masazir CCAP 19/38 isolated from the lake has been patented [7]. Lake Masazir, Baku, Azerbaijan The strong red-brown color of Laguna Colorada shallow, 10 kilometer (6 mile) long lake is derived from algae that thrive in its salty water. Occasionally the lake has green and rose phases as well because different algae display different colors. The red and rose colours are due to microalgae Dunaliella salina [8]. Perfectly contrasted, the salt lake is dotted with large white pools caused by massive borax deposits on the lake's surface. Laguna Colorada. Colombia Very different case from the previous ones is the appearance of the Dusty Rose Lake in British Columbia, Canada: water color of this lake (which is not salty at all, and not contain algae) comes from the surrounding pink-purplish rocks which, during the warm season,arecarriedasparticlesbythemeltingglaciersdirectlyintothelake. Rhodochrositeandcobaltoandolomitemineralsarealsoevidentinthepinky/purple rocks surrounding the lake. The water feeding the lake is said to have a lavender hue.

Dusty Rose Lake in British Columbia, Canada The recapitulation of the above information has led to the search for pink hypersaline lagoonsinordertocharacterizeitsmicrobiologicalandmineralcompositionfor comparison with those of the lakes previously mentioned. The first to be studied will be the Chaguneta de Chiosu, in the mountains of Asturias, Spain Chaguneta de Chiosu. Puerto del Rasn. Asturias, Spain References 1.Gmez,P.;Barriga,A.;CifuentesA.;Gonzlez,M.(2003).Effectofsalinityonthe quantity and quality of carotenoids accumulated by Dunaliella salina (strain CONC-007) and Dunaliella bardawil (strain ATCC 30861). Biol. Res. 36: 185-192. 2. Borowitzka,M.;Borowitzka,L.;Kessly,D.(1990).Effectsofsalinityincreaseon carotenoidaccumulationinthegreenalgaDunaliellasalina.J.Appl.Phycol.2:111-119. 3.Oren, A. (2005). "A hundred years of Dunaliella research: 1905-2005". Saline Systems 1:2. DOI:10.1186/1746-1448-1-2. PMC 1224875. PMID 16176593. 4.Litchfield,C.D.(1998).Survivalstrategiesformicroorganismsinhypersaline environmentsandtheirrelevancetolifeonearlyMars.Meteoritics&Planetary Science, 33, 813-819. 5.Nelson-Sathi,S.;Dagan,T.;Landan,G.;J anssen,A.;Steel,M.:McInerneyJ .O.; Deppenmeier,U.;Martin,W.F.(2012).Acquisitionof1,000eubacterialgenes physiologically transformed a methanogen at the origin of Haloarchaea, Proceedings of theNationalAcademyofSciences,109(50)20537-20542.DOI:10.1073/pnas. 1209119109. 6.Spring,Setal.(2010).CompletegenomesequenceofDesulfohalobiumretbaense type strain (HR100T). Standards in Genomic Sciences, 2: 38-48. 7.http://www.eapo.org/ru/publications/bulletin/ea201301/HTML/017565.html 8.http://bo.geoview.info/rea_laguna_colorada_the_red_colour_is_caused_by_microalgae_dunaliella_salina_%C2%A9gs,43328868p