Second, b cells in adult mice have been shown to arise from pre-existing b cells, not from stem cells. To summarise, our results suggest that P. putida can sense competition by contact-dependent processes involving unknown ligand-receptor type of interaction. The response is elicited only when live or cell wall-intact cells are used and inert particles do not elicit any competitive response. Based on the results of the experiments involving different strains of bacteria, we infer that the observed phenomenon of physical contact-dependent induction of plasmid expression is generalized and is non-specific in nature. Such a strategy provides a definitive competitive edge to the organism displaying it. We further hypothesise that the above strategy may be more efficient than the one based on detection of possible diffusible molecules secreted by the competitor, since the lead time advantage would be considerable. We need to carry out similar studies using other plasmid-bearing species in order to conclude whether the phenomenon is widely prevalent among bacteria. It is likely that PyMT induces hyperplastic islets through a mechanism similar to b cell duplication and that these duplicated, differentiated cells do not depend on the continued expression of PyMT for their viability. Ants live in societies of hundreds of individuals sharing valuable resources essential for colony reproduction. These must be defended by efficiently distinguishing strangers from colony members. Ants do so using colonyspecific multi-component chemical cues, the cuticular hydrocarbon profiles, ICG-001 detected by their antennae. Ant bodies are indeed covered with a layer of chemicals including varied longchain hydrocarbons, many of which were shown to play a major role in nestmate recognition. CHC profiles are complex and dynamic, and vary qualitatively among species and quantitatively within species: colonies of the same species share the same CHCs but differ in their relative proportions. Nestmate recognition therefore requires fine discrimination of complex CHC mixtures differing in the relative amounts of many compounds. Comparison of multi-component mixtures and identification of individual components from such mixtures have been reported to be complex olfactory tasks requiring longer response times than simpler binary discrimination. However, upon intrusion by competitors or parasites, fast reactions are essential to defend and protect the colony because once an intruder has succeeded to enter the nest it is unlikely to be detected at all. We evaluated the speed of aggressive responses upon presentation of non-nestmate odors in the ant Camponotus aethiops, and explored whether essential cue integration steps take place at an early stage in the olfactory system by investigating the sidespecificity of responses to non-nestmate odors.