PubMed · 8000894
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J W Levchuk. Good validation practices: FDA issues.. https://pubmed.ncbi.nlm.nih.gov/8000894/
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Replication of Staphylococcus aureus is significantly enhanced in the presence of recombinant interleukin (IL)-1beta. In this study, specific binding of IL-1beta to the surface of S. aureus significantly increased growth of S. aureus in the presence of IL-1beta and IL-1ra in a concentration-dependent manner. Although IL-1ra enhanced the growth of S. aureus, there was a significant reduction in IL-1beta-mediated growth enhancement of S. aureus when 25-fold excess amounts of IL-1ra (in comparison with the IL-1beta concentration) were present in the culture medium. Thus, IL-1beta may influence the growth of S. aureus through a receptor-mediated event. By using 5 linear peptides spanning limited regions of IL-1beta, the growth-promoting regions were localized to amino acid residues 118-147 and 208-240. These results build on the newly evolved concept of direct interactions between the soluble mediators of inflammation and infectious agents.
A broth-based method is used to determine if exponential phase Escherichia coli R31, an STEC, is able to grow within 50 days under various combinations of sub-optimal temperatures and salt concentrations. From these data, the growth limits for combinations of temperature (7.7-37.0 degrees C) and water activity (0.943-0.987; NaCl as humectant) are defined and modelled using a nonlinear logistic regression model. That form of model is able to predict the combinations of salt concentration/water activity and temperature that will prevent the growth of E. coli R31 with selected levels of confidence. The model fitted the data with an approximate concordance rate of 97.3%. The minimum water activity that permitted growth occurred in the range 25-30 degrees C, the temperature range which optimises cell yield. At temperatures below this range the minimum water activity which allowed growth increased with decreasing temperature.
Transformants of bakers' yeast (Saccharomyces cerevisiae) can be generated when non-growing cells metabolize sugars (without additional nutrients) in the presence of plasmid DNA. These results suggest that there is a mechanism by which DNA can naturally be taken up by the yeast cell. Natural transformation does not take place in common complete or minimal yeast culture media such as YPD and YNB. The starvation conditions used in our experiments thus seem to be an important prerequisite for such transformation events.