Eneous distributions can arise from a homogenous cell population. PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/20135195 Still, cells could respond differently to infection, either on account of intrinsic or stochastic variations amongst cells. The authors modeled the effects of intrinsic variations in cellular response to infection, resulting either from various replication rates or from various burst thresholds. Variable bacterial division didn’t increase the model’s match for the phagocyte data, but variable burst threshold did, predicting that cells with virulent strains would burst at much higher bacterial densities than these with attenuated strains. The authors then considered stochastic variations among intrinsically identical cells. Assuming that bursts happen randomly as opposed to at a fixed threshold, they found that decreasing the price of bacterial division lowered the rate of population development and skewed the distribution in order that hostPLoS Biology | www.plosbiology.org| ecells had fewer bacteria, like phagocytes with attenuated strains. When the authors allowed the prices of both burst and bacterial division to rely on bacterial density, the model that described their data greater than all the other people combined density-independent lysis with density-dependent bacterial division. This model predicts that the intracellular replication rate of S. enterica will reduce as the quantity of intracellular bacteria increases and that the bursting rate will proceed at a continuous price, with random variations, no matter intracellular bacterial density. As ahead of, virulent and attenuated strains behaved differently–bacterial density had a greater effect around the intracellular division prices of virulent strains.With these insights into intra- and intercellular dynamics, the authors explored the effects of health-related intervention. Because some antibiotics kill bacteria living outside cells, they refined the model to account for extracellular survival. The model showed that lowering the price of intracellular bacterial replication leads to a decreased burst size–suggesting that the effectiveness of extracellular antibiotics will be increased if combined with antibiotics aimed at minimizing intracellular replication. These insights into the dynamic relationship in between bacterial division rate, host cell lysis, and extracellular survival–and therefore the probability of infecting new cells–offers a novel way of evaluating the efficacyof multi-drug therapies and the evolution of drug resistance. For instance, researchers can test regardless of whether administering intracellular and extracellular antibiotics simultaneously produces synergistic effects that clear an infection. The authors hope that other researchers will incorporate new experimental final results into a similar dynamical modeling approach– linking within- and among-cell microbe behavior to host response–to shed light on a wide range of host-pathogen interactions.Brown SP, Cornell SJ, Sheppard M, Grant AJ, Maskell DJ, et al. (2006) Intracellular demography as well as the dynamics of Salmonella enterica infections. DOI: 10.1371/Anemoside B4 chemical information journal. pbio.Sexual Selection Comes at a CostLiza Gross | DOI: 10.1371/journal.pbio.0040394 Males evolved extravagant plumage, towering antlers, and frenetic mating displays, Darwin proposed, mainly because that’s what females like. Why such preferences evolved continues to be controversial–one view holds that flashy males beget attractive sons with a lot more chance of attracting mates–but it is typically thought that sexual choice supplies some sort of indirect genetic benefit.