Increasing the size of the clone libraries would help provide more conclusive data on the identity of the protist species involved. The clone library analysis showed that the

Day 0 cycloheximide-treated and -untreated libraries were statistically similar as expected, validating our approach. At other time points, the treatment and control libraries were statistically Anti-infection Compound Library mw different, indicating that cycloheximide did affect the protist ecology, which correlated with the improvement in the survival of E. coli O157:H7. In conclusion, our data point toward the role played by the protists in the reduction of E. coli O157:H7. We identified a number of protists that were present in our model compost, and it remains to be determined whether any of these species were responsible for the check details decline in observed E. coli O157:H7 counts. The isolation and identification of the protist(s) that mediate this effect was beyond the scope of this study; however, this is an active area of investigation in our laboratory. Whether similar protist species are present in other composts, such as cow, pig, and horse manure, or in raw manure, is poorly understood and will be investigated in the future as well. Further work is also needed to determine how different temperatures and moisture levels would affect protist-mediated killing of E. coli O157:H7.

Composting conditions designed to support the proliferation of protists, as well as bacteria and fungi, that are antagonistic to E. coli O157:H7 may provide improved methods for bioremediation. This work was supported by a United States Department of Agriculture Cooperative State Research, Education, and Extension Service (USDA-CSREES)

grant 2008-34163-19283 and by start-up Funds from the Department of Food Science and the College of Agricultural Sciences Lck at the Pennsylvania State University. We would like to thank Dr Stephen Knabel, Dr Mary Ann Bruns, Morgan Minyard and Dr Bindhu Verghese at the Pennsylvania State University for their valuable input and help with the clone library sequence data processing. We would also like to thank the Nucleic Acid Facility at the Pennsylvania State University for providing sequencing data. “
“Propionic acid bacteria (PAB) are important as starter cultures for the dairy industry in the manufacture of Swiss-type cheeses, in which they are involved in the formation of eyes and are responsible for the typical flavour and aroma. These characteristics are mainly due to the classical propionic acid fermentation, but also the conversion of aspartate to fumarate and ammonia by the enzyme aspartase and the subsequent reduction of fumarate to succinate, which occur in dairy Propionibacterium freudenreichii ssp. shermanii and ssp. freudenreichii starter strains. Additionally, the metabolism of free amino acids may be partly responsible for secondary fermentation and the subsequent split defects in cheese matrix.