Astrobiology Field Reports: Sampling Microbial Muck

Ateam of scientists and astronauts ventured to Canada's Pavilion Lakethissummer to study the lake's odd bacterial life and practice techniquesthat mayone day be used to seek out life on other worlds. Here, AstrobiologyMagazine'sHenry Bortman sends his last field report from the project:

July5, 2010

Onmy last day with folks from PavilionLake Research Project, I went on a road trip to the Cariboo Plateau lakes withAllyson Brady, the acting principal investigator for PLRP 2010; EricCollins, apost-doctoral fellow; and Jennifer Hansen, a laboratory assistant. Allthree areor have beenconnected with Greg Slater?s group at McMaster University. Slater, whohas beena leading member of the PLRP team for several years, was home this yearwith anewborn son.

TheCariboo Plateaulakesare a group of small lakes that dot the landscape in a region nearPavilionLake. The three we visited are quite unlike Pavilion, however: They?reshallow,highlyalkaline (think baking soda dissolved in water, so everythingit splatterson, your clothes, your hands, your face, turns slimy when wet, andcrusty whendry), and they?re surrounded by noxious, sucking mud that makesentering andexiting them in a canoe a serious challenge.

Themud containsa large amount of microbialslime, a mix of living organisms and the rotting cellularcarcasses of deadones. I didn?t quite get clear on which of the two, the living or thedead, wasresponsible for the general stench. There was something disturbinglyfamiliarabout the smell.

Ittook me a while to identify it, but it finally clicked: Old Bay gonebad. (Forthose of you who?ve never dined along the Maryland coast, Old Bay is aspicemixture liberally used to flavor the state crustacean, the blue crab.Havinggrown up in Maryland, I?ve always been a fan of crab ? la Old Bay, butaftervisiting theCariboo Plateau, I may reconsider.)

Theday began with a protracted effort to lash the 10-foot-long canoe totheuncooperatively small roof rack of a rented SUV. We rewarded oursuccess with astop at the Cordial Restaurant in Clinton, British Columbia, apparentlyaninitiation rite for PLRP visitors to the Cariboo Plateau.

TheCordial is known for its pancakes. Very large, very thick pancakes. Youhavetwo choices: eat the whole thing, or face public humiliation. I wascautionedthe night before to eat a light dinner, advice which I ignored (therewas fruitcobbler for dessert). Nevertheless, I did finish my pancake. Withbacon. Justfor the record.

Firstup was a lake unofficially dubbed ?Probe? Lake (researchers lost ascientific probe there some years back). After a ride down a twistingone-lanedirt logging road, the canoe juddering somewhat uncertainlyon the roof, we arrived. The challenge at Probe Lake is thequarter-mileportage from the road to the canoe-launching point along the shore.Once you?rethere, though, the mud barrier surrounding the lake is relativelynarrow.

Here,Brady and Hansen paddled out in the canoe to collect lake water.MeanwhileCollins waded out into the muck and scooped up a few choice gobs ofslime,sealing them into various-sized jars and tubes for later distributiontoanalytical laboratories. His sampling tool, affectionately called MatSampler3000 (a reference to the rubbery mat-like structures built by somemicrobes),was a six-foot-long hollow PVC pipe.

Lashedto one end of the pipe with electrical tape was a cutoff Nalgenebottle, holesdrilled in its bottom. Brady explained later that they had foundits component parts in a basement some years ago. ?It does what itneeds to do,? she said. You gotta love the duct-tape culture of fieldscience.

Thissame basic scenario, two people heading out into the lake in the canoeforwater samples while the third person stayed near shore and scooped upslime,was repeated at lakes number two and three. But each lake had itsparticularcharm.

Lakenumber two, referred to as Deer Lake, is much closer to the road thanProbeLake, so minimal portage is required. But it wins the prize hands-downforwidest mud apron.

Lastyear, the PLRP team built a walkway there of downed tree limbs, hauledto thelakeshore from the nearby woods, so that they can get the canoe closeenough tothe water to have any hope of paddling it though the muck. This year,the waterlevel of the lake was lower than last year, so the walkway had to beextendedseveral feet.

Employingthe word ?paddling? to describe the propulsion of the canoe through themud isa bit misleading.

Whathappened was this: Brady and Hansen got in the canoe with paddles,whileCollins stood at the end of the makeshift walkway, one hand on thestern, theother outstretched for balance. Brady and Hansen plunged their paddlesinto themuck and pushed with all their might, while Collins gave an extralittle shovefrom the edge of the walkway, the total effort moving the canoe perhapsa fewinches.

ThenBrady and Hansen struggled to extract their paddles from the viscousmuck,trying to avoid, in the process, pulling their boat back towards shore.(Youknow, that pesky action-reaction thing.) This went on for about tenminutes,although after the first two rounds the canoe was out of Collins?sreach, soBrady and Hansen had to traverse the last few feet on their own.

Finally,Brady and Hansen went sailing off into clear water, all 15 cm of it,whileCollins squatted on the end of the walkway, scooping up handfuls ofmud,sniffing each handful in turn (the particular mix of noxious gassesgiven offby each handful holds clues to which types of microbes reside within),andoccasionally stuffing a handful into a collection jar.

Hedid this, by the way, not in knee-high boots like a normal, sensibleperson,but in sandals. He did wear the requisite purple nitrile gloves,but that was to protectthe microbes from being contaminated by him, not the otherway around.

Whenwe finished up at Deer Lake, I asked Brady what the particulardistinguishing characteristic was of the third lake, officially namedGoodenough Lake,. ?Bugs,? she said. I?ll leave that to yourimagination.Suffice it to say that a week later I was still nursing a scab from theworstof my mosquito bites.

Isuppose you want to know why they go to all this trouble. Here?s theCliff?sNotes version. The Cariboo Lakes help put Pavilion Lake in contextbecause, asBrady said, ?The [Cariboo] mats are full of carbonate,? as are the microbialitestructures at Pavilion Lake. But unlike at Pavilion Lake, inthe CaribooPlateau lakes, ?they?re not forming microbialites. Either there?s amissingfactor, or something?s inhibiting them.?

Bradyand Hansen are interested in how the water chemistry of various lakesaffectsthe microbial communities that live there, which in turn may determinewhetheror not microbialites form. They are also hoping to pinpoint biomarkers,chemical signatures that can be used as unambiguous indicators ofbiology atwork. That work is focused on carbon isotopes and lipids. Collins isconductinga broad-scale DNA analysis of the microbial populations in Pavilion andothernearby lakes.

Asa parting image, picture this scene: Collins and I are sitting in afilthycanoe on Deer Lake, invery shallow water, the surface of the stinking microbialmats mere inches below us. I?m paddling around, gently so asnot to stir uptoo much muck, which would interfere with his sampling efforts, andhe?sleaning over the edge of the canoe, on the lookout.

Everyonce in a while, he gets excited because he?s seen a glob of green gunk(itmostly ranges from dirty pink to brown). So I plunge my paddle into themuck tohold the canoe steady while he scoops up the green stuff with the MatSampler3000.

Inthis idyllic setting I ask him, ?Which do you like better, collectingor takingstuff back to the lab and analyzing it??

?Ireally like collecting,? he says with a grin. ?But the problem is, ifyou?rejust collecting, you never actually find out any answers.?

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