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Conventional design procedure for biological reactors assumes that the degradation of pollutant is either by suspended or attached biomass. Attached biomass includes biomass that collects and forms a thin layer of biofilm on the walls of a biological reactor, while suspended biomass is simply suspended within the liquid medium of the reactor. The degradation rate equation for the suspended biomass or the biofilm is then used to calculate the reactor size required to achieve a prescribed treatment efficiency. However, all real world-reactors (biological) contain both suspended and attached biomasses that degrade simultaneously the pollutant. Yet, which form of biomass is responsible for the degradation of pollutant at a faster rate? The objective of this project is to find out the form of biomass that is most dominant in degrading pollutant at a higher rate. Mathematical models for both suspended and attached biomass was used to perform a sensitivity analysis to evaluate the dominant form of biomass.
A strain caTC2R of Lactobacillus planatarum was originally isolated from a meat source which showed resistance to chloramphenicol and tetracycline. Plasmid and genetic analysis showed the presence of three plasmids of 10.6, 8.5 and 6.5kb sizes of which the 8.5kb plasmid encodes the gene for chloramphenicol resistance. The stability of this plasmid (8.5kb) was investigated by three different methods. The first method involved the use of acriflavine (50 and 100 microgram per mI.) and the second method involved subculturing at a restrictive temperature (40_C), while the third method was by extended incubation of bacterial cells in the presence of different carbohydrates. All three methods showed loss of the 8.5kb plasmid at high frequency (>= 25%). The other two plasmids were quite stable. The frequency of the loss of two or three characterization of this plasmid are underway to show the effect of the loss of this plasmid on other genes.
A number of strains of Leuconostoc species from our culture collection were tested for the antagonistic effect against lactic acid bacteria. One strain showed high activity against a strain of Lactobacillus. The
Leuconostoc strain was then grown overnight (16-18h) in MRS broth at 30 C. Cells were harvested by centrifugation. The pH of the Supernatant (4.1) was adjusted to 2.0, 7.O, and 11.0 with HCI or NaOH.
All four samples were filter sterilized and kept at 4_C. They were then tested on the tester strain. All except the sample at pH 11.0 showed zones of inhibition indicating that inhibition of the tester strain is independent of pH and the activity is destroyed by highly alkaline pH. The loss of activity was irreversible since the readjustment of the pH to 7.0 did not restore the activity. Heat treatment (autoclave for 15 min.) did not affect the activity ofthe filtrate. The activity was also completely destroyed by incubation of the filtrate with pronase, trypsin, alpha-chemotrypsin and papain suggesting that filtrate contains some protein or complex and is a bacteriocin. Plasmid and genetic characterization showed that a plasmid encodes the bacteriocin production gene. Experiments are underway to characterize this protein and the genes involved in the production of bacteriocin.
The t-complex is a complex genetic region which is found in 25% of wild Mus Domesticus (the house mouse). Dobrovolskia-Zavadskia in 1924 first discovered t-complex characteristics while studying the effects of mutations causing carcinogenesis. The t-complex was first identified as a recessive mutation on Chromosome17 that modified tail length. It affects embryonic viability, male sterility and meiotic transmission. In this project, an interspecific cross between M. domesticus strain C57BL1OJ and Mus spretus is used to determine the genetic recombination distance between two simple sequence repeat loci (SSR markers), D17NDS2 andD17NDS3, located on the proximal region of mouse Chromosome 17 (Chr 17). By typing 46 backcross offspring, we have measured the recombination distance between D17NDS2 and D17NDS3 to be 14.3 cM. Also by typing 21 backcrossed offspring, a recombination distance of 28.6 cM was measured between SSRmarkers D17MITl9 and D17Mll9. This cross is being used to generate offspring at the tenth backcross (N=10) generation with less than 1% of the Mus spretus genome. The selection for retention of the proximal region of Chr 17 from the M. spretus genome is done by typing of M. domesticus and M. spretus backcross offspring using SSR markers. Out of 206 backcrossed offspring typed, 81 were found to have retained some part of the proximal
region of the M. spretus genome. At this point we have obtained offspring at N=6 generation. The ultimate goal of this project is to create individual strains of mice which are congenic for small portions of Chr 17 from M. spretus on a M. domesticus genetic background. These congenic mice will be used to construct genomic DNA libraries from which the M. spretus chromosome segments will be cloned by differential Hybridization.
