Tiny Bubbles Tell All

Plant responses to low [CO2] of the past

During the Last Glacial Maximum (LGM; 18,000-20,000 yr ago) and previous glacial periods, atmospheric [CO(2)] dropped to 180-190 ppm, which is among the lowest concentrations that occurred during the evolution of land plants. Modern atmospheric CO(2) concentrations ([CO(2)]) are more than twice those of the LGM and 45% higher than pre-industrial concentrations. Since CO(2) is the carbon source for photosynthesis, lower carbon availability during glacial periods likely had a major impact on plant productivity and evolution. From the studies highlighted here, it is clear that the influence of low [CO(2)] transcends several scales, ranging from physiological effects on individual plants to changes in ecosystem functioning, and may have even influenced the development of early human cultures (via the timing of agriculture). Through low-[CO(2)] studies, we have determined a baseline for plant response to minimal [CO(2)] that occurred during the evolution of land plants. Moreover, an increased understanding of plant responses to low [CO(2)] contributes to our knowledge of how natural global change factors in the past may continue to influence plant responses to future anthropogenic changes. Future work, however, should focus more on the evolutionary responses of plants to changing [CO(2)] in order to account for the potentially large effects of genetic change.

Isolation of a novel acidiphilic methanogen from an acidic peat bog

Acidic peatlands are among the largest natural sources of atmospheric methane and harbour a large diversity of methanogenic Archaea. Despite the ubiquity of methanogens in these peatlands, indigenous methanogens capable of growth at acidic pH values have resisted culture and isolation; these recalcitrant methanogens include members of an uncultured family-level clade in the Methanomicrobiales prevalent in many acidic peat bogs in the Northern Hemisphere. However, we recently succeeded in obtaining a mixed enrichment culture of a member of this clade. Here we describe its isolation and initial characterization. We demonstrate that the optimum pH for methanogenesis by this organism is lower than that of any previously described methanogen.