-An objective index, the Sludge Biotic Index (SBI), based on the microfauna associated with activated-sludge mixed liquor, has been devised to monitor activated-sludge plant performance. The proposed method makes it possible to define the biological quality of the sludge using numerical values (biotic index) of 0-10, and to group SBI values into four quality classes. The method is based on two ...

The rod-like, contractile stalk of the single-celled peritrich Vorticella Convalleria can collapse into a tightly coiled helix in less than 1/60 second, a rate ~1000 times its cell body size per second. The contractile stalk (25um-300um in length, ~ 4um diameter) consists of several membranes stiffened by extracellular fibers and helical assembly of larger protein bundles, known as batonets, su...

Contraction of Vorticella convallaria, a sessile ciliated protozoan, is completed within a few milliseconds and results in a retraction of its cell body toward the substratum by coiling its stalk. Previous studies have modeled the cell body as a sphere and assumed a drag force that satisfies Stokes' law. However, the contraction-induced flow of the medium is transient and bounded by the substra...

The stalk of Carcliesium and Vorticella coils by the action of a contractile organelle. The organelle lies within a thread of cytoplasm which is encased in a complex extracellular tube. Study with the light microscope and the electron microscope suggests that the structure of the tube and the course of the organelle determine the form of the coiling. The contractile organelle contains a system ...

Escherichia coli O157:H7 (EcO157), an agent of life threatening hemolytic-uremic syndrome, resides in ruminants and is released in feces at numbers as high as 10 million cells/gram. EcO157 could survive in manure for as long as 21 months, but we observed a 90% decrease in cells of an outbreak strain of EcO157 within half a day in wastewater from dairy lagoons. Although chemical, environmental a...