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The inactivation performances of different nonthermal plasmas are often compared with each other in terms of their decimal reduction values, typically obtained by linearizing selected segments of their inactivation curves. However, this approach is subjective and can result in uncertainties in the prediction of this parameter. To overcome this, in this paper, the application of models capable of describing inactivation curves in their entirety is considered. The authors employ the Baranyi and Weibull models, both commonly used for microbial inactivation by heat. An empirical model based on a third-order polynomial to seek greater accuracy is further proposed. Using these three inactivation models, predictions of decimal reduction values for 11 plasma inactivation studies of Bacillus subtilis spores are obtained and compared with their reported values. Although the agreement obtained between these different approaches is generally fair, the current practice of segmented linearization is shown to be overly simplistic. A rigorous model is therefore critical to capture the essentially nonlinear character of plasma inactivation kinetics and hence allow for an objective comparison of the performances of similar biocidal nonthermal plasmas. Index Terms--Bacillus subtilis spores, decimal reduction times, inactivation models, nonthermal plasmas.

The ability of atmospheric pressure glow discharges (APGD) to inactivate microorganisms has been demonstrated in a number of previous studies. However, most of this work has been performed using microorganisms that do not form biofilms and with the microorganisms supported on abiotic surfaces that discourage cell growth. When microorganisms attach to the surface of a food, they can extract nutrients from the food and proliferate at the surface. Often this growth takes the form of biofilms which comprise three-dimensional (3-D) networks of polysaccharides that attach microorganisms to surfaces and serve to protect them from external stresses; fresh foods, such as salad crops, frequently harbor biofilms. We believe that the use of APGD offers a potential for inactivating microorganisms on the surface of fresh foods that cannot be readily treated by other methods without inducing unacceptable changes to these foods. As a first step toward a full evaluation of the viability of the APGD technology for food safety control, we consider in this paper two key issues, namely: 1) whether atmospheric glow discharges can inactivate biofilm-forming microorganisms and 2) whether plasma treatment causes significant discoloration to food surfaces. Using the biofilm-forming bacterium Pantoea agglomerans and bell peppers (Capsicum annuum) as a typical example of plant tissue, we show that atmospheric He-[O.sub.2] plasmas can be effective inactivation agents without causing unacceptable levels of discoloration to the peppers, and that furthermore they are superior to the use of low-pressure ultraviolet sources. Index Terms--Atmospheric glow discharges, biofilm, decontamination, food-borne microorganisms, food surfaces, inactivation, sterilization.

Results show that both relA and hpt transposon insertion mutants of Listeria monocytogenes can not synthesize (p)ppGpp upon nutritional starvation. Data suggest that the ability to produce (p)ppGpp and mount a stringent response to adhesion are essential for biofilm growth and pathogenesis.

In silico analysis of the Listeria monocytogenes EGD genome has identified a putative cell wall-anchored protein (Lmo0435 [BapL]), which is similar to proteins involved in biofilm formation by staphylococci, and an insertion mutation is construction in Listeria monocytogenes to determine the affect of this protein on attachment to abiotic surfaces. The results have shown that the protein has contributed to the surface adherence of strains that possess BapL, but it is a requirement for all Listeria monocytogenes strains.

Sir,--Rachel Laudan ends her review of books on the alcoholic beverages of Mexico by wondering what future archaeologists might make of pulque's renaissance (October 2). Pulque is unique in that [...]

Sir,--Peter Thonemann's absorbing review ('Steak and beans', December 20 & 27,2013) mentions American soldiers destroying dairies in Normandy in 1944 because they associated their odours with rotting human flesh. In [...]

Sir,--In his review of Laurent Binet's novel HHhH, Adrian Tahourdin recycles the throwaway comment made by both Robert Gerwarth (in his biography of Reinhard Heydrich) and Binet that if penicillin [...]