{"id":76636,"date":"2021-11-11T02:55:00","date_gmt":"2021-11-11T01:55:00","guid":{"rendered":"https:\/\/www.sonnenseite.com\/?p=76636"},"modified":"2021-11-10T09:56:03","modified_gmt":"2021-11-10T08:56:03","slug":"a-natural-co2-sink-thanks-to-symbiotic-bacteria","status":"publish","type":"post","link":"https:\/\/www.sonnenseite.com\/en\/science\/a-natural-co2-sink-thanks-to-symbiotic-bacteria\/","title":{"rendered":"A nat\u00adural CO2-sink thanks to sym\u00adbi\u00adotic bac\u00adteria"},"content":{"rendered":"\n

Like many land plants, seagrasses live in sym\u00adbi\u00adosis with ni\u00adtro\u00adgen-fix\u00ading bac\u00adteria<\/p>\n\n\n\n

Seagrasses cover large swathes of shallow coastal seas, where they provide a vital habitat. They also remove large amounts of carbon dioxide (CO2<\/sub>) from the atmosphere and store it in the ecosystem. However, seagrasses need nutrients to thrive, particularly nitrogen. Up to now, researchers have assumed that the plants take up the nitrogen primarily from the surrounding seawater and sediment. However, in many of the regions where seagrasses are most successful there is little nitrogen to be found. Researchers of the Max Planck Institute for Marine Microbiology in Bremen now show that seagrass in the Mediterranean Sea lives in symbiosis with bacteria that reside in their roots and provide the nitrogen necessary for growth. Such symbioses were previously only known from land plants. The study was published in the journal Nature.<\/p>\n\n\n\n

Seagrasses are wide\u00adspread in shal\u00adlow coastal re\u00adgions of both tem\u00adper\u00adate and trop\u00adical seas, cov\u00ader\u00ading up to 600,000 square kilo\u00admet\u00aders, which is roughly the area of France. They form the basis of the en\u00adtire eco\u00adsys\u00adtem, which is home to nu\u00admer\u00adous or\u00adgan\u00adisms, some of them en\u00addangered spe\u00adcies such as turtles, seahorses and manatees, and nurs\u00adery ground for many eco\u00adnom\u00adic\u00adally im\u00adport\u00adant fish spe\u00adcies. Moreover, seagrasses pro\u00adtect coast\u00adlines from erosion by storm surges and se\u00adquester mil\u00adlions of tons of car\u00adbon di\u00adox\u00adide every year, which is stored in the eco\u00adsys\u00adtem as so-called \u201cblue car\u00adbon\u201d for long peri\u00adods of time.<\/p>\n\n\n\n

Lush life despite a lack of nutrients<\/strong><\/p>\n\n\n\n

The hab\u00aditat of many seagrasses is poor in nu\u00adtri\u00adents, such as ni\u00adtro\u00adgen, for much of the year. Al\u00adthough ni\u00adtro\u00adgen is abund\u00adant in the sea in its ele\u00admental form (N2<\/sub>), seagrasses can\u00adnot use it in this form. How can the plants still thrive? It is thanks to their now dis\u00adcovered mi\u00adcro\u00adscopic part\u00adners: Bac\u00adterial sym\u00adbionts liv\u00ading within the plants roots that con\u00advert N2<\/sub> gas into a form that the plants can use. Wiebke Mohr and her col\u00adleagues from the Max Planck In\u00adsti\u00adtute for Mar\u00adine Mi\u00adcro\u00adbi\u00ado\u00adlogy in Bre\u00admen, Ger\u00admany, Hy\u00addra Mar\u00adine Sci\u00adences in B\u00fchl, Ger\u00admany, and the Swiss Wa\u00adter Re\u00adsearch In\u00adsti\u00adtute Eawag now de\u00adscribe how this in\u00adtim\u00adate re\u00adla\u00adtion\u00adship between seagrass and bac\u00adteria works.<\/p>\n\n\n\n

Harmony in the roots<\/strong><\/p>\n\n\n\n

\u201cIt was as\u00adsumed that the so-called fixed-ni\u00adtro\u00adgen for the seagrasses comes from bac\u00adteria that live around <\/em>their roots in the sea\u00adfloor,\u201d Mohr ex\u00adplains. \u201cWe now show that the re\u00adla\u00adtion\u00adship is much closer: The bac\u00adteria live inside<\/em> the roots of the seagrass. This is the first time that such an in\u00adtim\u00adate sym\u00adbi\u00adosis has been shown in seagrasses. It was pre\u00advi\u00adously only known from land plants, es\u00adpe\u00adcially ag\u00adri\u00adcul\u00adtur\u00adally im\u00adport\u00adant spe\u00adcies such as legumes, wheat and sugar cane.\u201d These, too, have sym\u00adbi\u00adotic bac\u00adteria, to which they sup\u00adply car\u00adbo\u00adhydrates and other nu\u00adtri\u00adents in re\u00adturn for fixed ni\u00adtro\u00adgen. A very sim\u00adilar ex\u00adchange of meta\u00adbolic products also oc\u00adcurs between the seagrass and its sym\u00adbiont.<\/p>\n\n\n\n

\"\u00a9
\u00a9 Wiebke Mohr \/Max Planck Institute for Marine Microbiology | A part of Fetovaia Bay, in which most samples of this study were retrieved.<\/figcaption><\/figure><\/div>\n\n\n\n

The bac\u00adteria that live in the seagrass roots are a new dis\u00adcov\u00adery. Mohr and her team named them Celerinatantimonas neptuna<\/em>, after their host, the nep\u00adtune grass (Posidonia<\/em>). Re\u00adl\u00adat\u00adives of C. neptuna <\/em>have pre\u00advi\u00adously been found in as\u00adso\u00adci\u00adation with sea\u00adweeds. \u201cWhen the seagrasses moved from land to sea about 100 mil\u00adlion years ago, they prob\u00adably ad\u00adop\u00adted the bac\u00adteria from the sea\u00adweeds,\u201d Mohr spec\u00adu\u00adlates. \u201cThey vir\u00adtu\u00adally copied the sys\u00adtem that was highly suc\u00adcess\u00adful on land and then, in or\u00adder to sur\u00advive in the nu\u00adtri\u00adent-poor sea\u00adwa\u00adter, ac\u00adquired a mar\u00adine sym\u00adbiont.\u201d The cur\u00adrent study looked at seagrasses of the genus Posidonia <\/em>in the Medi\u00adter\u00adranean Sea. However, such sym\u00adbi\u00adoses may also oc\u00adcur else\u00adwhere. \u201cGe\u00adnetic ana\u00adlyses sug\u00adgest that sim\u00adilar sym\u00adbi\u00adoses also ex\u00adist on trop\u00adical seagrasses and in salt marshes,\u201d says Mohr. \u201cThis way, these flower\u00ading plants man\u00adage to col\u00adon\u00adize a wide vari\u00adety of seem\u00adingly nu\u00adtri\u00adent-poor hab\u00adit\u00adats, both in the wa\u00adter and on land.\u201d<\/p>\n\n\n\n

Going with the seasons<\/strong><\/p>\n\n\n\n

As the sea\u00adsons change, the amount of nu\u00adtri\u00adents present in coastal wa\u00adter var\u00adies. In winter and spring, the nu\u00adtri\u00adents present in the wa\u00adter and sed\u00adi\u00adment seem suf\u00adfi\u00adcient for the seagrasses. \u201cAt that time, we do find scattered sym\u00adbionts in the roots of the plants, but they are prob\u00adably not very act\u00adive,\u201d says Mohr. In sum\u00admer, when sun\u00adlight in\u00adcreases and more and more al\u00adgae grow and con\u00adsume the few avail\u00adable nu\u00adtri\u00adents, ni\u00adtro\u00adgen quickly be\u00adcomes scarce. Then the sym\u00adbionts take over. They dir\u00adectly sup\u00adply the seagrasses with the ni\u00adtro\u00adgen they need. This is how seagrasses can reach their largest growth in sum\u00admer, when nu\u00adtri\u00adents are most scarce in the en\u00advir\u00adon\u00adment.<\/p>\n\n\n\n

\"\u00a9
\u00a9 Daniela Tienken\/Soeren Ahmerkamp \/Max Planck Institute for Marine Microbiology | The symbiosis under the microscope: On the left a cross-section through a seagrass root, on the right a fluorescence image of the bacteria (in pink) inside the seagrass root.<\/figcaption><\/figure><\/div>\n\n\n\n

Many different methods for a clear picture<\/strong><\/p>\n\n\n\n

The present study bridges the en\u00adtire eco\u00adsys\u00adtem, from seagrass pro\u00adductiv\u00adity to the sym\u00adbionts that live in their roots and ul\u00adti\u00admately fuel the sys\u00adtem. To ac\u00adcom\u00adplish this, the re\u00adsearch\u00aders used a vari\u00adety of dif\u00adfer\u00adent meth\u00adods to un\u00adder\u00adstand the sym\u00adbi\u00adosis as fully as pos\u00adsible: Oxy\u00adgen meas\u00adure\u00adments car\u00adried out in the wa\u00adters of the Medi\u00adter\u00adranean Sea re\u00advealed the pro\u00adductiv\u00adity of the seagrass meadow. Mi\u00adcro\u00adscopy tech\u00adniques, in which in\u00addi\u00advidual bac\u00adterial spe\u00adcies are color-labeled (known as FISH), helped to visu\u00adal\u00adize the bac\u00adteria in and between the root cells of the seagrass. In the NanoSIMS, a state-of-the-art mass spec\u00adtro\u00admeter, they showed the activ\u00adity of the in\u00addi\u00advidual bac\u00adteria. Ge\u00adn\u00adomic and tran\u00adscrip\u00adtomic ana\u00adlyses re\u00advealed which genes are prob\u00adably par\u00adtic\u00adu\u00adlarly im\u00adport\u00adant for the in\u00adter\u00adac\u00adtion and that these path\u00adways are heav\u00adily used. As a res\u00adult, the re\u00adsearch\u00aders suc\u00adceeded in provid\u00ading a sound and de\u00adtailed de\u00adscrip\u00adtion of this amaz\u00ading col\u00adlab\u00ador\u00ada\u00adtion. \u201cOur next step is to study these new bac\u00adteria in more de\u00adtail,\u201d says Mohr. \u201cWe want to isol\u00adate them in the labor\u00adat\u00adory to fur\u00adther in\u00advest\u00adig\u00adate how the sym\u00adbi\u00adosis works and how it de\u00adveloped. It will cer\u00adtainly also be ex\u00adcit\u00ading to search for com\u00adpar\u00adable sys\u00adtems in other re\u00adgions and hab\u00adit\u00adats.\u201d<\/p>\n\n\n\n