To investigate the basis for this discrepancy, photosynthate utilization was characterized in Dunaliella tertiolecta Butcher grown at three different growth rates in N-limited chemostats. Pb was measured throughout a 2 min to 24 h time course and showed clear growth-rate-dependent differences in lifetimes of newly fixed carbon. 14C pulse-chase experiments revealed
differences in patterns of carbon utilization between growth rates. At high growth rate, the majority of 14C was initially fixed into polysaccharide and lipid, but the relative contribution of each labeled PD0325901 chemical structure biochemical pool to the total label changed over 24 h. In fast-growing cells, labeled polysaccharides decreased 50%, while labeled lipids increased over the first 4 h. At check details low growth rate, 14C was initially
incorporated primarily into protein, but the contribution of labeled protein to the total label increased over the next 24 h. Together, time-resolved measurements of Pb and cellular NAD and NADP content suggest an enhanced role for alternative dissipation pathways at very low growth rate. Findings of this study contribute to an integrated understanding of growth-rate-dependent shifts in metabolic processes from photosynthesis to net growth. “
“Benthic microalgae (BMA) are important primary producers in intertidal and shallow subtidal sediments, serving as a vital 上海皓元 food resource for heterotrophs. BMA also release extracellular polymeric secretions that inhibit resuspension of sediments. Key ecological parameters such as abundance, productivity, and species composition of BMA each contribute to the character of these roles. Our primary objectives were to (i) assess the importance of biotic disturbance to the structure of sedimentary microalgal communities and (ii) identify principal modes of recolonization. We employed field comparative studies to test whether deposit feeding
by two invertebrates (Leptosynapta tenuis and Balanoglossus aurantiacus) caused removal of BMA, and manipulative experiments to assess rates and mechanisms of recolonization. Both deposit feeders were determined to significantly reduce BMA biomass via ingestion; however, little change in community composition was observed. Recovery of these disturbed patches was followed over the period of intertidal exposure. We distinguished between potential recolonization methods of migration and regrowth by monitoring fecal coils incubated naturally on underlying sediments (regrowth + migration treatment), hydrogen-peroxide-treated coils incubated on ambient sediment (migration only), and coils that were incubated on 0.2 μm filters and thereby isolated from underlying sediment (regrowth only).