Paths and patterns: the biology and physics of swimming bacterial populations.

The velocity distribution of swimming micro-organisms depends on directional cues supplied by the environment. Directional swimming within a bounded space results in the accumulation of organisms near one or more surfaces. Gravity, gradients of chemical concentration and illumination affect the motile behaviour of individual swimmers. Concentrated populations of organisms scatter and absorb light or consume molecules, such as oxygen. When supply is one-sided, consumption creates gradients; the presence of the population alters the intensity and the symmetry of the environmental cues. Patterns of cues interact dynamically with patterns of the consumer population. In suspensions, spatial variations in the concentration of organisms are equivalent to variations of mean mass density of the fluid. When organisms accumulate in one region whilst moving away from another region, the force of gravity causes convection that translocates both organisms and dissolved substances. The geometry of the resulting concentration-convection patterns has features that are remarkably reproducible. Of interest for biology are (1) the long-range organisation achieved by organisms that do not communicate, and (2) that the entire system, consisting of fluid, cells, directional supply of consumables, boundaries and gravity, generates a dynamic that improves the organisms' habitat by enhancing transport and mixing. Velocity distributions of the bacterium Bacillus subtilis have been measured within the milieu of the spatially and temporally varying oxygen concentration which they themselves create. These distributions of swimming speed and direction are the fundamental ingredients required for a quantitative mathematical treatment of the patterns. The quantitative measurement of swimming behaviour also contributes to our understanding of aerotaxis of individual cells.

Effect of yeast cultures on performance of lactating dairy cows: a field study.

Three hundred six lactating Holstein cows in the first 120 d of lactation from seven farms in Pennsylvania were used to evaluate supplementation of two Saccharomyces cerevisiae yeast cultures containing about 10(8) cfu/g viable yeast cells on milk production and composition. Cows were fed individually and grouped into three blocks based on lactation numbers 1, 2, and 3 or greater, and, within block, randomly assigned to one of three treatments for a 14-wk study. The three treatments were 1) control, 2) yeast culture fermented on ground cornmeal and corn gluten meal (5.3 x 10(10) cfu/d per cow), and 3) yeast culture fermented on cornmeal and soybean meal (5.1 x 10(10) cfu/d per cow). The three treatments were mixed with cornmeal and 114 g per cow was fed daily as a top-dressing. Milk production, milk fat and protein percentage, milk fat and protein production, and 3.5% FCM were not affected by either yeast treatment. There were no significant interactions of farm by treatment, lactation number by treatment, or week by treatment. No differences in performance were significant for early lactation cows that calved during the trial, but FCM tended to be higher for treatment than for the control cows. Daily DMI measured on 39 cows at one location did not differ among treatments. Yeast supplementation was not beneficial for any production parameters under the nutritional management programs of these seven dairy farms.

Synthesis of 2'-deoxy-L-fucopyranosylcarminomycinone and -epsilon-pyrromycinone as well as 2'-deoxy-D-erythro-pentopyranosyldaunomycinone, -carminomycinone, and -epsilon-pyrromycinone.

Treatment of di-O-acetyl-2-deoxy-L-fucopyranosyl bromide with carminomycinone and epsilon-pyrromycinone in the presence of mercuric bromide and mercuric cyanide afforded 3',4'-diO-acetyl-2'-deoxy-L-fucopyranosylcarminomycinone and -epsilon-pyrromycinone. Similarly, when di-O-acetyl-2-deoxy-D-erythrho-pentopyranosyl chloride was treated with daunomycinone, carminomycinone and epsilon-pyrromycinone, the di-O-acetyl derivatives of the anthracyclinone glycosides were obtained. Deacetylation of the previous acetates with sodium methoxide afforded 2'-deoxy-L-fucopyranosylcarminomycinone and -epsilon-pyrromycinone, as well as 2'-deoxy-D-erythro-pentopyranosyldaunomycinone, -carminomycinone, and -epsilon-pyrromycinone. 2'-Deoxy-L-fucopyranosylcarminomycinone was found to be more active than carminomycin at higher dosages on L1210.

Synthesis of episilon-rhodomycinone glycosides.

Twenty-six episilon-rhodomycinone glycosides have been synthesized. These include the episilon-rhodomycinone glycosides of 2-deoxy-L-fucose, 2-deoxy-L-rhamnose, and 2-deoxy-D-ribose as well as their 2-hydroxyl derivatives. NMR spectroscopy showed that all the glycosides prepared had the saccharide residues linked to position 10 of episilon-rhodomycinone and helped establish the anomeric purity and configuration of several glycosides. Preliminary screening results show that 2-deoxy-di-O-acetyl-D-ribopyranosyl-episilon-rhodomycinone has an activity T/C of 125 on P388 tumors.