Effects of territorial intrusions on eavesdropping neighbors: communication networks in nightingales

Animal communication often occurs in communication networks in which multiple signalers and receivers are within signaling range of each other. In such networks, individuals can obtain information on the quality and motivation of territorial neighbors by eavesdropping on their signaling interactions. In songbirds, extracting information from interactions involving neighbors is thought to be an important factor in the evolution of strategies of territory defense. In a playback experiment with radio-tagged nightingales Luscinia megarhynchos we here demonstrate that territorial males use their familiar neighbors' performance in a vocal interaction with an unfamiliar intruder as a standard for their own response. Males were attracted by a vocal interaction between their neighbor and a simulated stranger and intruded into the neighbor's territory. The more intensely the neighbor had interacted with playback, the earlier the intrusions were made, indicating that males eavesdropped on the vocal contest involving a neighbor. However, males never intruded when we had simulated by a second playback that the intruder had retreated and sang outside the neighbor's territory. These results suggest that territorial males use their neighbors' singing behavior as an early warning system when territorial integrity is threatened. Simultaneous responses by neighboring males towards unfamiliar rivals are likely to be beneficial to the individuals in maintaining territorial integrity.

Analysis of the networks controlling the antimicrobial-peptide-dependent induction of Klebsiella pneumoniae virulence factors

Antimicrobial peptides (APs) impose a threat to the survival of pathogens, and it is reasonable to postulate that bacteria have developed strategies to counteract them. Polymyxins are becoming the last resort to treat infections caused by multidrug-resistant Gram-negative bacteria and, similar to APs, they interact with the anionic lipopolysaccharide. Given that polymyxins and APs share the initial target, it is possible that bacterial defense mechanisms against polymyxins will be also effective against host APs. We sought to determine whether exposure to polymyxin will increase Klebsiella pneumoniae resistance to host APs. Indeed, exposure of K. pneumoniae to polymyxin induces cross-resistance not only to polymyxin itself but also to APs present in the airways. Polymyxin treatment upregulates the expression of the capsule polysaccharide operon and the loci required to modify the lipid A with aminoarabinose and palmitate with a concomitant increase in capsule and lipid A species containing such modifications. Moreover, these surface changes contribute to APs resistance and also to polymyxin-induced cross-resistance to APs. Bacterial loads of lipid A mutants in trachea and lungs of intranasally infected mice were lower than those of wild-type strain. PhoPQ, PmrAB, and the Rcs system govern polymyxin-induced transcriptional changes, and there is a cross talk between PhoPQ and the Rcs system. Our findings support the notion that Klebsiella activates a defense program against APs that is controlled by three signaling systems. Therapeutic strategies directed to prevent the activation of this program could be a new approach worth exploring to facilitate the clearance of the pathogen from the airways.

Location-Awareness for Radios and Networks: Part I

The papers in this special issue focus on the topic of location awareness for radio and networks. Localization-awareness using radio signals stands to revolutionize the fields of navigation and communication engineering. It can be utilized to great effect in the next generation of cellular networks, mining applications, health-care monitoring, transportation and intelligent highways, multi-robot applications, first responders operations, military applications, factory automation, building and environmental controls, cognitive wireless networks, commercial and social network applications, and smart spaces. A multitude of technologies can be used in location-aware radios and networks, including GNSS, RFID, cellular, UWB, WLAN, Bluetooth, cooperative localization, indoor GPS, device-free localization, IR, Radar, and UHF. The performances of these technologies are measured by their accuracy, precision, complexity, robustness, scalability, and cost. Given the many application scenarios across different disciplines, there is a clear need for a broad, up-to-date and cogent treatment of radio-based location awareness. This special issue aims to provide a comprehensive overview of the state-of-the-art in technology, regulation, and theory. It also presents a holistic view of research challenges and opportunities in the emerging areas of localization.