J. Munoz

Production of acid and alkaline phosphatases by Myxococcus coralloides.

Acid and alkaline phosphatase ofMyxococcus coralloides were examined during vegetative growth in a liquid medium. Two extracellular phosphatases and two cell-bound phosphatases, acid and alkaline in both cases, were produced. The phosphatase production was unaltered by the presence of high concentrations of inorganic phosphate. Both enzymes were produced constitutively. These two hydrolases were released into the growth medium during the exponential growth phase (approximately 10% of total activity). The production of these enzymes was modified by the presence of organic acids and metal ions in the medium.

Emotion, Perception, and Natural Kinds

The question addressed in this paper is whether particular emotional experiences or episodes of an emotion (such as two experiences of happiness) belong to a natural kind. The final answer to this question is that although some, even many, single episodes of an emotion may group into a natural kind, belonging to a natural kind is a highly contextual matter. The proposal relies on two premises. First, a conception of natural kind-hood that follows Boyd’s Homeostatic Property Cluster Theory. Second, a view of emotional episodes that fits with the External Theory of Perception: typical emotional episodes are perceptual experiences of emotional affordances. After pointing out what candidates for emotional homeostatic properties could be like and suggesting some examples of emotional homeostatic mechanisms, the authors conclude that there are property clusters of emotional perceptions stabilized by homeostatic mechanisms. In spite of this, what counts as an emotional natural kind depends on many factors, not all of them natural: world properties, bodily and mental states of the agent, learning mechanisms that help us to satisfactorily navigate in the world, cultural differences that determine our perceptual style, as well as different interests which guide the explanation and prediction of emotional episodes.

DNase activity during the life cycle of Myxococcus coralloides and M. xanthus

Abstract DNase activity was measured during various stages of the life cycle of Myxococcus coralloides D. A high level of activity was maintained in vegetative cells, fruiting bodies and after myxospore induction by glycerol. In this microorganism, DNase specific activity increased during both the vegetative and developmental cycles. In contrast, Myxococcus xanthus DK101 exhibited a different DNase activity.