Filamentous Bacteriophages and the Competitive Interaction between Pseudomonas aeruginosa Strains under Antibiotic Treatment: a Modeling Study

Filamentous phages are a frontier in bacterial pathogenesis, but the impact of these phages on bacterial fitness is unclear. In particular, Pf phages produced by Pa promote antibiotic tolerance but are metabolically expensive to produce, suggesting that competing pressures may influence the prevalence of Pf+ versus Pf− strains of Pa in different settings.

Invasion of coral reefs of Lakshadweep atolls by a central Indo-Pacific corallimorph

Worldwide, coral reefs are in decline due to mass bleaching, natural calamities, diseases, and anthropogenic stressors that expose large swathe of unutilized substratum which is later occupied by other benthic organisms like corallimorpharians, anemones, macroalgae etc. In the current work, we describe for the first time, the competitive interaction between a corallimorph and hard corals, observed in Kavaratti and Chetlat atolls in the tropical Indian Ocean, which is the first reported instance of an invasion of corallimorpharian in the entire Lakshadweep islands. The corallimorph, Rhodactis bryoides Haddon & Shackleton, 1893, is identified by morphological and molecular analysis. It is found that the species has no previous records from the western Indian Ocean region. Since the competitive interaction among reef organisms for space will have significant repercussions on the entire reef ecosystem in the future, we observed the pace of invasion for six months and calculated the relative abundance of the corallimorph using transects. None of the previous factors causing a corallimorpharia outbreak viz., external disturbances and nutrient enrichment were observed in this region. However, these tropical atolls are prone to occasional bleaching during the summer seasons. Further investigation needs to be conducted on the biology of this species, the interaction with other benthic groups and the environmental descriptors promoting the invasion.

Following the Customers: Dynamic Competitive Repositioning

We consider dynamic repositioning when competing firms try to follow the evolution of consumer preferences while taking into account the competitive interaction, both in terms of static market competition and the dynamic effects of different firm positionings. We fully characterize the dynamic market equilibrium, which includes the timing of the firms’ repositionings depending on consumer preferences. As consumer preferences evolve away from where both firms are located, one firm first moves to follow consumer preferences, with the second firm only moving if the consumer preferences continue evolving away from that firm. The model predicts rich market dynamics, where firms stay for some period in different positionings if consumer preferences are in a relatively middle ground or where a firm repositions to follow consumer preferences but then repositions back to the original position if consumer preferences return. We find that, when the variability of the consumer preferences or the discount rate is greater or when the importance of the repositioning attribute is smaller, firms are less likely to follow consumer preferences. Firms are more heterogeneous in their responses, which leads to longer periods of differentiation when the variability of the consumer preferences, the discount rate, or the importance of the repositioning attribute increases. We also find that competing firms reposition less frequently than what is socially optimal and what collusion would imply, and we find more differentiation under collusion than under competition. This paper was accepted by Matthew Shum, marketing.

Leadership Games: Multiple Followers, Multiple Leaders, and Perfection

Over the last years, algorithmic game theory has received growing interest in AI, as it allows to tackle complex real-world scenarios involving multiple artificial agents engaged in a competitive interaction. These settings call for rational agents endowed with the capability of reasoning strategically, which is achieved by exploiting equilibrium concepts from game theory.