Lake Michigan surface waters impacted by fecal pollution were assessed to determine the occurrence of genetic markers for Bacteroides and Escherichia coli. Initial experiments with sewage treatment plant influent demonstrated that total Bacteroides spp. could be detected by PCR in a 25-to 125-fold-higher dilution series than E. coli and human-specific Bacteroides spp., which were both found in similar dilution ranges. The limit of detection for the human-specific genetic marker ranged from 0.2 CFU/100 ml to 82 CFU/100 ml culturable E. coli for four wastewater treatment plants in urban and rural areas. The spatial and temporal distributions of these markers were assessed following major rain events that introduced urban storm water, agricultural runoff, and sewage overflows into Lake Michigan. Bacteroides spp. were detected in all of these samples by PCR, including those with <1 CFU/100 ml E. coli. Human-specific Bacteroides spp. were detected as far as 2 km into Lake Michigan during sewage overflow events, with variable detection 1 to 9 days postoverflow, whereas the cow-specific Bacteroides spp. were detected in only highly contaminated samples near the river outflow. Lake Michigan beaches were also assessed throughout the summer season for the same markers. Bacteroides spp. were detected in all beach samples, including 28 of the 74 samples that did not exceed 235 CFU/100 ml of E. coli. Human-specific Bacteroides spp. were detected at three of the seven beaches; one of the sites demonstrating positive results was sampled during a reported sewage overflow, but E. coli levels were below 235 CFU/100 ml. This study demonstrates the usefulness of non-culture-based microbial-source tracking approaches and the prevalence of these genetic markers in the Great Lakes, including freshwater coastal beaches.

No abstract

Two different types of immobilized yeast bioreactors were examined for continuous fermentation of high-gravity worts. One of these is a fluidized bed reactor (FBR) that employs porous glass beads for yeast immobilization. The second system is a loop reactor containing a porous silicon carbide cartridge (SCCR) for immobilizing the yeast cells. Although there was some residual fermentable sugar in the SCCR system product, nearly complete attenuation of the wort sugars was achieved in either of the systems when operated as a two-stage process. Fermentation could be completed in these systems in only half the time required for a conventional batch process. Both the systems showed similar kinetics of extract consumption, and therefore similar volumetric productivity. As compared to the batch fermentation, total fusel alcohols were lower; total esters, while variable, were generally higher. The yeast biomass production was similar to that in a conventional fermentation process. As would be expected in an accelerated fermentation system, the levels of vicinal diketones (VDKs) were higher. To remove the VDKs, the young beer was heat-treated to convert the VDK precursors and processed through a packed bed immobilized yeast bioreactor for VDK assimilation. The finished product from the FBR system was found to be quite acceptable from a flavor perspective, albeit different from the product from a conventional batch process. Significantly shortened fermentation times demonstrate the feasibility of this technology for beer production.

No abstract

To date, in mammals except for the mouse and human, only one protamine variant has been isolated from sperm. These mammalian protamines share amino acid sequence homology with mouse protamine 1 (mP1), the tyrosine-containing variant. Southern blot analysis of restriction enzyme digests of hamster and rat liver DNA reveals the presence of sequences homologous to mP1, and also to mouse protamine 2 (mP2) cDNAs. Northern blots of hamster and rat total testis RNA probed with mP2 cDNA confirm that the protamine 2 gene in these species is transcribed into two size classes of mRNA of approximately 830 and 700 nucleotides. However, the relative abundance of the rat and hamster protamine 2 mRNAs (rP2 and hP2) in total testis is approximately 50-fold lower and 2- to 5-fold lower, respectively, than the mouse protamine 2 mRNA. Northern blot analysis of hamster and rat testis polysome gradients demonstrates that although the amount of rP2 mRNA and hP2 mRNA is reduced, both are present on polysomes. The decreased expression of rat and hamster protamine 2 mRNA relative to their protamine 1 counterparts contrasts protamine expression in the mouse testis, where approximately equal amounts of mP1 and mP2 protamine mRNAs are present. These results suggest differential expression of the P1 and P2 protamine genes in three closely related mammals.