The effects of spores and toxin on mortality in <i>Bacillus thuringiensis</i>.

<p>A) The mortality rates for varying quantities of spores of <i>Bacillus thuringiensis</i> a Cry null strain supplemented with 60 pg of toxin (open circles, dashed line) or 180 pg of toxin (solid circles, solid line). A glm of the form y ~ Toxins + log(Spores+1) + Toxins* log(Spores+1) is fit and shown for both toxin doses (see S2 Table in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004775#ppat.1004775.s001" target="_blank">S1 Text</a> for parameter details) with S.E. shown. In both cases spore dose has a positive impact on mortality, and in the 60 pg case, there is a gap between zero spores and the next lowest dose. B) The mortality rates for 900 <i>Bacillus thuringiensis</i> spores supplemented with varying quantities of toxins (+/- S.E.) in two experiments. The fit curves are from a nonlinear regression with an exponential model (<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004775#ppat.1004775.e001" target="_blank">Eq 1</a>). This IAH model is not sufficiently threshold-like to describe the data; it overestimates low dose mortality.