Replication and active partition of integrative and conjugative elements (ICEs) of the SXT/R391 family : the line between ICEs and conjugative plasmids is getting thinner

Integrative and Conjugative Elements (ICEs) of the SXT/R391 family disseminate multidrug resistance among pathogenic Gammaproteobacteria such as Vibrio cholerae. SXT/R391 ICEs are mobile genetic elements that reside in the chromosome of their host and eventually self-transfer to other bacteria by conjugation. Conjugative transfer of SXT/R391 ICEs involves a transient extrachromosomal circular plasmid-like form that is thought to be the substrate for single-stranded DNA translocation to the recipient cell through the mating pore. This plasmid-like form is thought to be non-replicative and is consequently expected to be highly unstable. We report here that the ICE R391 of Providencia rettgeri is impervious to loss upon cell division. We have investigated the genetic determinants contributing to R391 stability. First, we found that a hipAB-like toxin/antitoxin system improves R391 stability as its deletion resulted in a tenfold increase of R391 loss. Because hipAB is not a conserved feature of SXT/R391 ICEs, we sought for alternative and conserved stabilization mechanisms. We found that conjugation itself does not stabilize R391 as deletion of traG, which abolishes conjugative transfer, did not influence the frequency of loss. However, deletion of either the relaxase-encoding gene traI or the origin of transfer (oriT) led to a dramatic increase of R391 loss correlated with a copy number decrease of its plasmid-like form. This observation suggests that replication initiated at oriT by TraI is essential not only for conjugative transfer but also for stabilization of SXT/R391 ICEs. Finally, we uncovered srpMRC, a conserved locus coding for two proteins distantly related to the type II (actin-type ATPase) parMRC partitioning system of plasmid R1. R391 and plasmid stabilization assays demonstrate that srpMRC is active and contributes to reducing R391 loss. While partitioning systems usually stabilizes low-copy plasmids, srpMRC is the first to be reported that stabilizes a family of ICEs

Counter Swarm Options | Capt Audette [video]

BIX Student Talk

Counter Swarm Options | Capt Audette [video]

BIX Student Talk

Autonomous Operations of Mobile Robots in a Full Range of Environments

CRUSER TechCon 2018 Research at NPS. Wednesday 1: SensingAutonomous Operations of Mobile Robots in a Full Range of Environments Xiaoping Yun, James Calusdian, and Matthew Audette Abstract: The objective of this project is to develop autonomous capabilities of mobile robots in a full range of real-world indoor and outdoor environments. The entire NPS campus including all the base ground and building structures are used as a testbed for testing and evaluation. The ultimate goal is to develop autonomous capabilities that allow mobile robots to travel from any one location on the campus to another location. Examples include going from Building 436 (Police Service) to the front entrance of Dudley Knox Library, or from Spanagel-429 to Hermann Hall Barbara McNitt Ballroom. To make this possible, the robots are required to navigate through a wide range of indoor and outdoor environments. A fleet of P3-AT wheeled mobile robots ruggedized for rough-terrain environments are utilized in the project. Through this large-scale experimentation, it is expected to learn lessons and discover challenges in deploying autonomous robots in complex, real-world situations. It is hoped that the knowledge gained on navigating the NPS campus is applicable to other installations and can be used to support battlefields in urban environments. This project is leveraged on the prior efforts in developing robot navigation and mapping algorithms for indoor and outdoor environments. The early efforts were limited to navigate in a laboratory space and a portion of the outdoor Academic Quad area between Root Hall and Bullard Hall. This project seeks to expand the study to cover the entire NPS campus. The robots are expected to navigate from one building to another, approach a building entrance using handicap wheelchair ramps if necessary, travel from one floor to another via elevators and from any room to another inside a building. The research is carried out by multiple thesis students in stages, and is focused on obstacle avoidance, localization, mapping, path planning, sensor integration, and data fusion. Navigation algorithms rely on real-time sensor measurements of the environment as well as the pre-existing map or building data. Google map, the campus map data, and the building floor layout data from the Public Works Office are used to build a pre-existing map to be used by the navigation algorithms. A combination of sensor suite including LiDAR, sonar, infrared, CCD camera, IMU sensor, Kinect sensor, and GPS receiver is integrated for sensing the environment in real time to identify objects that are not registered in the map data. The pre-existing map is updated whenever a new stationary object is detected by the onboard sensors

INTERACTIVE MAP MAKING FOR ROUTE PLANNING AND OBSTACLE AVOIDANCE IN AN UNSTRUCTURED OUTDOOR ENVIRONMENT

As autonomous ground robots fulfill greater roles within the military, there is a requirement for an operator to be able to quickly give minimal route-planning guidance in support of an autonomous mission. The objective of this thesis is to develop a route-planning algorithm that uses open-source satellite imagery to allow a user to plot a start point, a goal point, and identify large-scale obstacles within the robot’s operating area. In this thesis, we build on previous work that developed a potential field obstacle avoidance algorithm. We advance the development of the autonomous mission capability by creating a global path-planning algorithm. The algorithm uses the visibility graph and A* search method to produce the optimal path from the given start point to the goal. The navigation algorithm developed allows users to generate imagery-based obstacle maps in Google Earth Pro and successfully produces an optimal path in the form of global positioning satellite coordinates via extensive MATLAB code development. The method was evaluated on a ground robot navigating in an outdoor environment using the waypoints generated. The path-planning algorithm was successfully implemented, but due to difficulties encountered with the navigation node of the mobile robot, a complete verification was not possible. Improvements to the robot’s ability to traverse over rugged terrain will make this solution more viable for a wider range of outdoor environments.http://archive.org/details/interactivemapma1094560406Captain, United States Marine CorpsApproved for public release; distribution is unlimited

Autonomous Operations of Mobile Robots in a Full Range of Environments

CRUSER TechCon 2018 Research at NPS. Wednesday 1: SensingAutonomous Operations of Mobile Robots in a Full Range of Environments Xiaoping Yun, James Calusdian, and Matthew Audette Abstract: The objective of this project is to develop autonomous capabilities of mobile robots in a full range of real-world indoor and outdoor environments. The entire NPS campus including all the base ground and building structures are used as a testbed for testing and evaluation. The ultimate goal is to develop autonomous capabilities that allow mobile robots to travel from any one location on the campus to another location. Examples include going from Building 436 (Police Service) to the front entrance of Dudley Knox Library, or from Spanagel-429 to Hermann Hall Barbara McNitt Ballroom. To make this possible, the robots are required to navigate through a wide range of indoor and outdoor environments. A fleet of P3-AT wheeled mobile robots ruggedized for rough-terrain environments are utilized in the project. Through this large-scale experimentation, it is expected to learn lessons and discover challenges in deploying autonomous robots in complex, real-world situations. It is hoped that the knowledge gained on navigating the NPS campus is applicable to other installations and can be used to support battlefields in urban environments. This project is leveraged on the prior efforts in developing robot navigation and mapping algorithms for indoor and outdoor environments. The early efforts were limited to navigate in a laboratory space and a portion of the outdoor Academic Quad area between Root Hall and Bullard Hall. This project seeks to expand the study to cover the entire NPS campus. The robots are expected to navigate from one building to another, approach a building entrance using handicap wheelchair ramps if necessary, travel from one floor to another via elevators and from any room to another inside a building. The research is carried out by multiple thesis students in stages, and is focused on obstacle avoidance, localization, mapping, path planning, sensor integration, and data fusion. Navigation algorithms rely on real-time sensor measurements of the environment as well as the pre-existing map or building data. Google map, the campus map data, and the building floor layout data from the Public Works Office are used to build a pre-existing map to be used by the navigation algorithms. A combination of sensor suite including LiDAR, sonar, infrared, CCD camera, IMU sensor, Kinect sensor, and GPS receiver is integrated for sensing the environment in real time to identify objects that are not registered in the map data. The pre-existing map is updated whenever a new stationary object is detected by the onboard sensors

U.S. Marine Corps Big Ideas

Capt. Andrea Writt: High Altitude Bal/0011s and Smal/Sats for Space Resilience; Capt. Matthew Audette:Counter Swarm Options; Capt. Adrian Felder: Revolutionizing Tactical Networks with Free Space Optics; Capt. Anthony Vanderzee: Predicting the Spread of Terrorist Organizations; Capt. Caleb Wu: Wireless Sensor Networks for Tactical Ground Defense; Maj. Andrew Reaves: The New 29 Palms: Marine Corps Exercises in the BalticThe Big Ideas Exchange (BIX) is an NPS initiative that brings forward new and potentially game-changing thinking developed by NPS faculty and students to address grand challenges in American national securit