Refuge from predation, the benefit of living in an extreme acidic environment?

Organisms living in extreme habitats require costly adaptations to cope with these conditions. Among the suggested potential benefits that trade off these costs is refuge from predation. To study these interactions in extreme environments, samples were taken in the cave Cueva de Villa Luz, Tabasco, Mexico, where more than 32 subterranean springs, some H(2)S rich, rise from the floor. Hydrogen sulfide gas plus oxygen is absorbed by freshwater, and oxidation forms concentrated sulfuric acid. Snottites, whitish hollow mucous tubes, hang from the ceiling of the cave. Fluid drops from these snottites were recorded as having pH values of 0-3. We report the discovery of a new species of nematode that thrives in the highly acidic environment of the snottite. Micro CT scan of snottites reveals a complex interaction between the acidic snottite, nematodes, and abundant nematode-eating mites. The nematode adaptation to low pH probably protects them against mite predation, for which nematodes are most likely the most important source of carbon in this sulfur-driven ecosystem.

Sugar cane bagasse as feedstock for second generation ethanol production: part I: diluted acid pretreatment optimization

Tons of sugar cane bagasse are produced in Brazil as waste of the sugar and ethanol industries. This lignocellulosic material is a potential source for second-generation ethanol production. Diluted acid hydrolysis is one of the most efficient pretreatments for hemicellulosic solubilization. The hydrolysate obtained is rich in xylose, which can be converted to ethanol by Pichia stipitis. This work used a statistical approach and the severity factor to investigate the effects of factors associated with the diluted acid hydrolysis process (acid concentration, solid:liquid ratio and time of exposure) on various response variables (xylose concentration, hydrolysis yield, inhibitor concentration and hydrolysate fermentability). The severity factor had a strong influence on the generation of inhibitors. The statistical analysis was useful for determining the effects of the individual factors and their interactions on the response variables. An acid concentration of 1.09 percent (vv), an S:L ratio of 1:2.8 (g:ml), and an exposure time of 27 min were established and validated as the optimum pretreatment conditions for the generation of hydrolysates with high xylose concentration and low contents of inhibitors. In such conditions, hydrolysate with 50 g/l of xylose was obtained.