Spontaneous mutations and mutational responses to penicillin treatment in the bacterial pathogen Streptococcus pneumoniae D39

Bacteria with functional DNA repair systems are expected to have low mutation rates due to strong natural selection for genomic stability.However,our study of the wild-type Streptococcus pneumoniae D39,a pathogen responsible for many common diseases,revealed a high spontaneous mutation rate of 0.02 per genome per cell division in mutation-accumulation(MA)lines.This rate is orders of magnitude higher than that of other non-mutator bacteria and is characterized by a high mutation bias in the A/T direction.The high mutation rate may have resulted from a reduction in the overall efficiency of selection,conferred by the tiny effective population size in nature.In line with this,S.pneumoniae D39 also exhibited the lowest DNA mismatch-repair(MMR)efficiency among bacteria.Treatment with the antibiotic penicillin did not elevate the mutation rate,as penicillin did not induce DNA damage and S.pneumoniae lacks a stress response pathway.Our findings suggested that the MA results are applicable to within-host scenarios and provide insights into pathogen evolution.

Correction:Spontaneous mutations and mutational responses to penicillin treatment in the bacterial pathogen Streptococcus pneumoniae D39

Due to technical errors,Ho-Ching T.Tsui and Malcolm E.Winkler,both collaborators who made substantial contributions to this work and were previously acknowledged,did not receive emails regarding authorship consent and were inadvertently omitted from the author list.We have now rectified this oversight and added them to the author list.

Functional characterization of an orexin neuropeptide in amphioxus reveals an ancient origin of orexin/orexin receptor system in chordate

Amphioxus belongs to the subphylum cephalochordata, an extant representative of the most basal chordates, whose regulation of endocrine system remains ambiguous. Here we clearly demonstrated the existence of a functional orexin neuropeptide in amphioxus, which is able to interact with orexin receptor, activate both PKC and PKA pathways, decrease leptin expression, and stimulate lipogenesis. We also showed the transcription level of amphioxus orexin was affected by fasting or temperature,indicating a role of this gene in the regulation of energy balance. In addition, the expression of the amphioxus orexin was detected at cerebral vesicle, which has been proposed to be a homolog of the vertebrate brain. These data collectively suggest that a functional orexin neuropeptide has already emerged in amphioxus, which provide insights into the evolutionary origin of orexin in chordate and the functional homology between the cerebral vesicle and vertebrate brain.

UAV rendezvous based on Nash bargain

Purpose–The purpose of this paper is to find a solution for the unmanned aerial vehicle(UAV)rendezvous problem,which should be feasible,optimal and not time consuming.In the existing literatures,the UAV rendezvous problem is always presented as a matter of simultaneous arrival.They focus only on the time consistency.However,the arrival time of UAVs can vary according to the rendezvous position.The authors should determine the best rendezvous position with considering UAVs’maneuver constraint,so that UAVs can construct a formation in a short time.Design/methodology/approach–The authors present a decentralized method in which UAVs negotiate with each other for the best rendezvous positions by using Nash bargain.The authors analyzed the constraints of the rendezvous time and the UAV maneuver,and proposed an objective function that allows UAVs to get to their rendezvous positions as fast as possible.Bezier curve is adopted to generate smooth and feasible flight trajectories.During the rendezvous process,UAVs adjust their speed so that they can arrive at the rendezvous positions simultaneously.Findings–The effectiveness of the proposed method is verified by simulation experiments.The proposed method can successfully and efficiently solve the UAV rendezvous problem.Originality/value–As far as the authors know,it is the first time Nash bargain is used in the UAV rendezvous problem.The authors modified the Nash bargain method and make it distributed,so that it can be computed easily.The proposed method is much less consuming than ordinary Nash bargain method and ordinary swarm intelligence based methods.It also considers the UAV maneuver constraint,and can be applied online for its fast calculation speed.Simulations demonstrate the effectiveness of the proposed method.