( ( The methanogens ) ( ( are ( ( characterized ( by ( ( their ability ) ( to ( harvest energy ) ) ) ) ) ( by ( ( converting ( ( H2 and ) CO2 ) ) ( into ( methane gas ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS methanogens)) (VP (VBP are) (VP (VBN characterized) (PP (IN by) (NP (NP (PRP$ their) (NN ability)) (PP (TO to) (NP (NN harvest) (NN energy))))) (PP (IN by) (S (VP (VBG converting) (NP (NNP H2) (CC and) (NNP CO2)) (PP (IN into) (NP (NN methane) (NN gas)))))))) (. .)))
The methanogens are characterized by their ability to harvest energy by converting H2 and CO2 into methane gas.
(ROOT (S (NP (NP (NNS Gases)) (PP (JJ such) (IN as) (NP (NN co2) (CC and) (NN methane)))) (VP (MD can) (VP (NN trap) (NP (NP (JJ thermal) (NN energy)) (PP (IN in) (NP (NP (NN earth) (POS 's)) (NN atmosphere)))) (PP (IN before) (S (VP (VBG radiating) (NP (PRP it)) (PP (IN into) (NP (NN space)))))))) (. .)))