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12.11.2009 Hid­den Treas­ures

Hidden treasures in subterranean sulfidic springs

Sci­ent­ists of the Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy and the Pennsylvania State Uni­versity ex­plore mi­croor­gan­isms in sub­ter­ranean sulf­idic springs of the largest lime­stone cave sys­tem in Italy, le Grotte di Frasassi.
The show cave of „Le Grotte di Frasassi“ (source: http://​www.itali­ae­asy.se)
 
Hidden treasures in subterranean sulfidic springs

Scientists of the Max Planck Institute for Marine Microbiology and the Pennsylvania State University explore microorganisms in subterranean sulfidic springs of the largest limestone cave system in Italy, le Grotte di Frasassi. The physically and geochemically isolated microbial populations in the sulfidic cave ecosystem provide an opportunity to study early Earth microbial evolution and biogeochemistry.

Tour­ists walk through a long tun­nel and pause in sus­pense be­hind a massive metal door be­fore their views ex­pand across the stun­ning, over 200 meter high main dome of “Grotta Grande del Vento”, the Big Wind Cave. Dur­ing the next hour, they gaze in awe at the gi­ant stalac­tites and stalag­mites as the tour guide ex­plains many of the mys­ter­ies of the dark and cold un­der­world in one of the largest caves in the world. But the gorge of Frasassi in Genga (Ancona), loc­ated in the heart of the Nat­ural Park of Gola della Rossa and Frasassi, holds also other secrets than the 1.5 km long tour­ist pas­sage. With the sub­ter­ranean cave sys­tem ex­tend­ing over 30 km on eight dif­fer­ent geo­lo­gical levels, there is plenty more to ex­plore.

In May and Septem­ber 2009, a group of re­search­ers around Dr. Lubos Pole­recky from the Max Planck In­sti­tute (MPI) for Mar­ine Mi­cro­bi­o­logy in Bre­men, Ger­many, vis­ited the Frasassi caves. They joined their col­leagues from the Pennsylvania State Uni­versity to in­vest­ig­ate a pos­sible in­volve­ment of mi­croor­gan­isms in the cave form­a­tion. With the aid of pro­fes­sional cavers and the local geo­lo­gists Dr. Sandro Montanari and Si­mone Cerioni, the sci­ent­ists squeezed them­selves and their equip­ment through nar­row holes and pas­sages into parts of the cave far bey­ond those ac­cess­ible for tour­ists. The MPI sci­ent­ists are col­lab­or­at­ing on this pro­ject with Amer­ican geo­mic­ro­bi­o­lo­gists led by Dr. Jen­nifer Macalady, who have been in­vest­ig­at­ing the mi­croor­gan­isms liv­ing in the dark and sulf­idic sub­sur­face world of the Frasassi cave since 2004. The goal of the sci­ent­ists is to un­der­stand the role of bac­teria in this ex­treme eco­sys­tem, where light is ab­sent, oxy­gen is scarce, and hy­dro­gen sulf­ide is plen­ti­ful (see more info in box).
While the group of sci­ent­ists around Dr. Macalady fo­cuses on study­ing the mi­cro­bial eco­logy in sulf­idic springs in­side the caves, Dr. Pole­recky and his col­leagues from the MPI in Bre­men also in­vest­ig­ate the col­our­ful bac­terial com­munit­ies grow­ing just out­side the caves, where the sulf­idic springs enter the sun­lit world. “We were very lucky with the tim­ing of this fieldtrip. At one sulf­idic spring, we spent two weeks in­vest­ig­at­ing the beau­ti­fully col­oured mats of dif­fer­ent pho­to­trophic bac­teria. Un­for­tu­nately, the lush col­ours and boom­ing activ­ity of our 'mi­cro­bial para­dise' dis­ap­peared a day after the spring gradu­ally dried out”, said Dr. Lubos Pole­recky. One pool was col­oured pink be­cause of a thick film of purple sul­fur bac­teria, an­other was dark green be­cause of cy­anobac­teria. The dif­fer­ent col­ours de­rive from dif­fer­ent pig­ments in­side the cells of pho­to­trophic bac­teria. Or­gan­isms with light har­vest­ing pig­ments build bio­mass from car­bon di­ox­ide us­ing light en­ergy, sim­ilar to what plants do. However, bac­teria liv­ing in il­lu­min­ated sulf­idic wa­ters like these were here long-long be­fore the plants. These pho­to­trophic mi­croor­gan­isms are cap­able of an­oxy­genic pho­to­syn­thesis; in­stead of wa­ter, which is used in oxy­genic pho­to­syn­thesis, they use sulf­ide to gain elec­trons for the re­duc­tion of car­bon di­ox­ide.

Ju­dith Klatt, an­other re­searcher at the MPI in Bre­men, de­term­ines the activ­ity of the purple sul­fur bac­teria un­der dif­fer­ent con­di­tions. “It must be a para­dise for sul­fur ox­id­iz­ing bac­teria”, she stated. Dur­ing fur­ther in­vest­ig­a­tions in the sun­lit sulf­idic pools, the re­searches found spe­ci­mens of fil­a­ment­ous chemo­li­tho­trophs and pho­to­li­tho­trophs ar­ranged in pe­cu­liar pat­terns. “We want to un­der­stand how the bac­teria find their niche in this en­vir­on­mental set­ting and whether they in­ter­act with each other in a com­pet­it­ive or co­oper­at­ive way”, ex­plains Dr. Pole­recky. Pre­lim­in­ary meas­ure­ments with a diver op­er­ated mo­tor­ized mi­cro­sensor sys­tem and hy­per­spec­tral ima­ging by Stefan Häusler, an­other MPI sci­ent­ist, already gave in­ter­est­ing in­sights into the life­style of the cy­anobac­teria there. These bac­teria seem to out­com­pete other pho­to­trophs by be­ing able to carry out sim­ul­tan­eously an­oxy­genic and oxy­genic pho­to­syn­thesis.

“This eco­sys­tem is so ex­cit­ing! Set­tings sim­ilar to these prob­ably ex­is­ted on early Earth 2.8 bil­lion years ago, when cy­anobac­teria began dom­in­at­ing our planet, gen­er­at­ing vast amounts of oxy­gen which even­tu­ally gave raise to the evol­u­tion of much more di­verse forms of life, in­clud­ing ours. Here we hope to find out some of the mech­an­isms how this might have happened”, con­cludes Lubos Pole­recky. Back at the en­trance to the caves, the tour­ists do not sus­pect any of this. In­stead, they sip on the 'stinky wa­ter' they have just col­lec­ted from the spring, ex­actly as vis­it­ors to this re­gion have been do­ing since the times of the Ro­mans.

Susanne Borgwardt

For fur­ther in­form­a­tion please con­tact:
Dr. Lubos Pole­recky, Tel: 0421 2028-834, lpole­rec@mpi-bre­men.de

or the MPI press of­ficers:
Dr. Man­fred Schlösser, Tel: 0421 2028-704, mschloes@mpi-bre­men.de
Dr. Susanne Borgwardt, Tel: 0421 2028-704, sborgwar@mpi-bre­men.de

Par­ti­cip­at­ing in­sti­tu­tions:

Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy, Celsi­usstrasse 1, 28359 Bre­men, Ger­many

The Pennsylvania State Uni­versity, De­part­ment of Geosciences, 210 Deike Build­ing, Uni­versity Park, PA 16802, USA

Os­ser­vatorio Geo­lo­gico di Coldi­gioco, Frontale di Apiro, Italy
Judith Klatt
Ju­dith Klatt enters the sulf­idic caves through a small hole in the rocks (source: Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy and Pennsylvania State Uni­versity)
Höhlenforscher
Sci­ent­ists of the Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy and re­search­ers from the Pennsylvania State Uni­versity at work in one of the hid­den caves (source: Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy and Pennsylvania State Uni­versity)
purple sulfur bacteria
Purple sul­fur bac­teria in a pool of the sulf­idic spring (source: Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy and Pennsylvania State Uni­versity)
green cyanobacteria and white sulfur bacteria
Sulf­ide ox­id­izers para­dise: thick mats of chemolito­trophic and pho­to­trophic sulf­ide ox­id­iz­ing bac­teria near the exit of the sulf­idic spring emer­ging from the Frasassi cave sys­tem (source: Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy and Pennsylvania State Uni­versity)
microsensor system
A port­able mi­cro­sensor sys­tem (DOMS) used for the study of bac­terial activ­ity in the sulf­idic springs (source: Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy)

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