INTENSE NATURAL SELECTION ON BODY SIZE AND WING AND TAIL ASYMMETRY IN CLIFF SWALLOWS DURING SEVERE WEATHER.

Extreme climatic disturbances provide excellent opportunities to study natural selection in wild populations because they may cause measurable directional shifts in character traits. Insectivorous cliff swallows (Petrochelidon pyrrhonota) in the northern Great Plains must often endure periods of cold weather in late spring that reduce food availability, and if cold spells last four or more days, mortality due to starvation may result. We analyzed morphological shifts associated with viability selection, and how patterns of bilateral symmetry were affected by survival selection, during a four-day period of cold weather in 1992 and a six-day period in 1996 in southwestern Nebraska.

Oxidation of hydrogen sulfide by flocculated Thiobaccillus denitrificans in a continuous culture.

In a continuous fermentation, significant advantages may be gained by immobilization of microbial cells. Immobilization allows cells to be retained in the fermenter or to be readily recovered and recycled. Therefore, the hydraulic retention time and the biomass retention time are decoupled.

Oxidation of hydrogen sulfide by Thiobacilli.

It has been previously demonstrated that the chemoautotroph and facultative anaerobe, Thiobacillus denitrificans, may be cultured aerobically or anaerobically in batch and continuous reactors on H(2)S(g) under sulfide-limiting conditions. A process has been proposed for the removal of H(2)S from gases based on oxidation of H(2)S by T. denitrificans.