Methane-oxidizing bacteria could play a greater role than previously thought in preventing the release of climate-damaging methane from lakes, researchers from Bremen report. They also show who is behind the process and how it works.\u00a0<\/p>\n\n\n\n
Meth\u00adane is a po\u00adtent green\u00adhouse gas fre\u00adquently pro\u00adduced in the sea and in fresh wa\u00adter. Lakes in par\u00adtic\u00adu\u00adlar re\u00adlease large quant\u00adit\u00adies of this cli\u00admate-killer. For\u00adtu\u00adnately, however, there are mi\u00adcroor\u00adgan\u00adisms that coun\u00adter\u00adact this: They are able to util\u00adize meth\u00adane to grow and gen\u00ader\u00adate en\u00adergy, thus pre\u00advent\u00ading it from be\u00ading re\u00adleased into the at\u00admo\u00adsphere. These mi\u00adcroor\u00adgan\u00adisms, known as meth\u00adan\u00ado\u00adtrophs, are there\u00adfore re\u00adgarded as an im\u00adport\u00adant “bio\u00adlo\u00adgical meth\u00adane fil\u00adter”.<\/p>\n\n\n\n
Meth\u00adan\u00ado\u00adtrophs com\u00adprise vari\u00adous groups of mi\u00adcroor\u00adgan\u00adisms, and many ques\u00adtions about their way of life have yet to be answered. A study by re\u00adsearch\u00aders from the Max Planck In\u00adsti\u00adtute for Mar\u00adine Mi\u00adcro\u00adbi\u00ado\u00adlogy in Bre\u00admen, Ger\u00admany, and the Swiss Eawag, which has now been pub\u00adlished in the journal Nature Com\u00admu\u00adnic\u00ada\u00adtions, shows the as\u00adton\u00adish\u00ading abil\u00adit\u00adies of some of these or\u00adgan\u00adisms and their pre\u00advi\u00adously over\u00adlooked role for our cli\u00admate.<\/p>\n\n\n\n
For their study, the re\u00adsearch\u00aders around Sina Schorn and Jana Milucka from the Max Planck In\u00adsti\u00adtute in Bre\u00admen traveled to Lake Zug in Switzer\u00adland. This lake is al\u00admost 200 meters deep and per\u00adman\u00adently oxy\u00adgen-free from a depth of around 120 meters. Nev\u00ader\u00adthe\u00adless, the oxy\u00adgen-free wa\u00adter con\u00adtains so-called aer\u00adobic meth\u00adane-ox\u00adid\u00adiz\u00ading bac\u00adteria (MOB for short). These, as their name im\u00adplies, are es\u00adsen\u00adtially de\u00adpend\u00adent on oxy\u00adgen. Whether and how they can break down meth\u00adane in the oxy\u00adgen-free wa\u00adter was un\u00adclear un\u00adtil now.<\/p>\n\n\n\n
Milucka and Schorn’s team there\u00adfore de\u00adcided to take a closer look at the activ\u00adity of these mi\u00adcroor\u00adgan\u00adisms. For their study, they used meth\u00adane mo\u00adlecules (CH4) that were labeled with \u201cheavy\u201d car\u00adbon atoms (13C in\u00adstead of 12C). These were ad\u00added to nat\u00adural lake wa\u00adter samples con\u00adtain\u00ading the in\u00adhab\u00adit\u00ading mi\u00adcroor\u00adgan\u00adisms. Sub\u00adsequently, the sci\u00adent\u00adists fol\u00adlowed the path of the heavy car\u00adbon in in\u00addi\u00advidual cells us\u00ading spe\u00adcial in\u00adstru\u00adments (known as NanoSIMS). This al\u00adlowed them to ob\u00adserve how the bac\u00adteria con\u00advert the meth\u00adane into car\u00adbon di\u00adox\u00adide, which is also a po\u00adtent green\u00adhouse gas but less cli\u00admate-dam\u00adaging than meth\u00adane. Part of the car\u00adbon was also in\u00adcor\u00adpor\u00adated dir\u00adectly into the bac\u00adterial cells. This re\u00advealed which cells in the bac\u00adterial com\u00admunity were act\u00adive and which were not. Us\u00ading mod\u00adern meth\u00adods such as meta\u00adge\u00adn\u00adom\u00adics and meta\u00adtran\u00adscrip\u00adtom\u00adics, they also in\u00advest\u00adig\u00adated which meta\u00adbolic path\u00adways the bac\u00adteria used.<\/p>\n\n\n\n
\u201cOur res\u00adults show that aer\u00adobic MOB re\u00admain act\u00adive also in oxy\u00adgen-free wa\u00adter,\u201d says Sina Schorn, who is now a re\u00adsearcher at the Uni\u00adversity of Gothen\u00adburg. \u201cHowever, this only ap\u00adplies to a cer\u00adtain group of MOB, eas\u00adily re\u00adcog\u00adniz\u00adable by their dis\u00adtinct\u00adive rod-shaped cells. To our sur\u00adprise, these cells were equally act\u00adive un\u00adder oxic and an\u00adoxic con\u00addi\u00adtions, i.e. with and without oxy\u00adgen. Thus, if we meas\u00adure lower rates of meth\u00adane ox\u00adid\u00ada\u00adtion in an\u00adoxic wa\u00adters, it is prob\u00adably be\u00adcause there are fewer of these spe\u00adcial rod-shaped cells and not be\u00adcause the bac\u00adteria are less act\u00adive.\u201d<\/p>\n\n\n\n
The Max Planck re\u00adsearch\u00aders en\u00adcountered an\u00adother sur\u00adprise when they took a closer look at the meta\u00adbolic cap\u00adab\u00adil\u00adit\u00adies of this group of bac\u00adteria. “Based on the genes present, we were able to de\u00adterm\u00adine how the bac\u00adteria re\u00adspond when oxy\u00adgen be\u00adcomes scarce,” ex\u00adplains Jana Milucka, head of the Green\u00adhouse Gases Re\u00adsearch Group at the Max Planck In\u00adsti\u00adtute in Bre\u00admen. “We found genes that are used for a spe\u00adcial type of meth\u00adane-based fer\u00adment\u00ada\u00adtion.” While this pro\u00adcess had already been demon\u00adstrated for MOB cul\u00adtures in the labor\u00adat\u00adory, it had not yet been stud\u00adied in the en\u00advir\u00adon\u00adment. The re\u00adsearch\u00aders also dis\u00adcovered sev\u00aderal genes for de\u00adni\u00adtri\u00adfic\u00ada\u00adtion, which likely al\u00adlow the bac\u00adteria to use ni\u00adtrate in\u00adstead of oxy\u00adgen to gen\u00ader\u00adate en\u00adergy.<\/p>\n\n\n\n
The fer\u00adment\u00ada\u00adtion pro\u00adcess, in par\u00adtic\u00adu\u00adlar, is in\u00adter\u00adest\u00ading. “If the MOB per\u00adform fer\u00adment\u00ada\u00adtion, they likely re\u00adlease sub\u00adstances that other bac\u00adteria can use for growth. This means the car\u00adbon con\u00adtained in the meth\u00adane is re\u00adtained in the lake for a longer period of time and does not reach the at\u00admo\u00adsphere. This rep\u00adres\u00adents a sink for meth\u00adane car\u00adbon in an\u00adoxic en\u00advir\u00adon\u00adments that is typ\u00adic\u00adally not ac\u00adcoun\u00adted for, which we will need to in\u00adclude in our fu\u00adture cal\u00adcu\u00adla\u00adtions,” says Milucka.<\/p>\n\n\n\n
In this study, the Bre\u00admen re\u00adsearch\u00aders ex\u00adplain who breaks down meth\u00adane in oxy\u00adgen-free hab\u00adit\u00adats and how this de\u00adgrad\u00ada\u00adtion takes place. They show that meth\u00adane-ox\u00adid\u00adiz\u00ading bac\u00adteria are sur\u00adpris\u00adingly im\u00adport\u00adant to keep the re\u00adlease of meth\u00adane from these hab\u00adit\u00adats to the at\u00admo\u00adsphere in check.<\/p>\n\n\n\n
\u201cMeth\u00adane is a po\u00adtent green\u00adhouse gas that is re\u00adspons\u00adible for about a third of the cur\u00adrent global rise in tem\u00adper\u00adat\u00adure,\u201d says Schorn, ex\u00adplain\u00ading the sig\u00adni\u00adfic\u00adance of the res\u00adults now pub\u00adlished. \u201cMeth\u00adane ox\u00adid\u00ada\u00adtion by mi\u00adcroor\u00adgan\u00adisms is the only bio\u00adlo\u00adgical sink for meth\u00adane. Their activ\u00adity is there\u00adfore cru\u00adcial for con\u00adtrolling meth\u00adane emis\u00adsions into the at\u00admo\u00adsphere and thus for reg\u00adu\u00adlat\u00ading the global cli\u00admate. Given the cur\u00adrent and pre\u00addicted in\u00adcrease in an\u00adoxic con\u00addi\u00adtions in tem\u00adper\u00adate lakes, the im\u00adport\u00adance of MOB for meth\u00adane de\u00adgrad\u00ada\u00adtion in lakes is ex\u00adpec\u00adted to grow. Our res\u00adults sug\u00adgest that MOB will make a sig\u00adni\u00adfic\u00adant con\u00adtri\u00adbu\u00adtion to green\u00adhouse gas mit\u00adig\u00ada\u00adtion and car\u00adbon stor\u00adage in the fu\u00adture.\u201d<\/p>\n\n\n\n