Bacillus nematocida B16 has been shown to use “Trojan horse” mechanism in pathogenesis that has characteristics of “social” behavior. The ComP-ComA system, a conserved quorum sensing system in the genus Bacillus, functions in many physiological processes including competence development, lipopeptide antibiotic surfactin production, degradative enzyme production and even some unknown functions. Here we investigated the requirement of ComP-ComA system in B. nematocida B16 for its pathogenicity against nematodes. The ΔcomP mutant displayed deficiencies in attracting and killing nematodes, due to the absence of attractive signal molecules and the decreased expressions of virulence factors, respectively. Contrarily, a complemented comP mutant at least partially resumed its pathogenicity. Our data from transcriptional analysis further confirmed that this signaling system directly or indirectly regulated the expressions of two major virulence proteases in the infection of B. nematocida B16. Bioinformatics analyses from comparative genomics also suggested that the potential target genes of transcription factor ComA were involved in the processes such as the synthesis of attractants, production of extracellular degradative enzymes and sortase, secondary metabolites biosynthesis, regulation of transcription factors, mobility, as well as transporters, most of which were different from a saprophytic relative B. subtilis 168. Therefore, our investigation firstly revealed that the participation and necessity of ComP-ComA signaling system in bacterial pathogenesis.
With the introduction of global navigation satellite systems (GNSSs) in aviation, there has been increased dependency on GNSS position. Multi-constellation GNSS services and equipment will remain a solution for many aircraft positions in safety. Multi-constellation GNSS can improve robustness and navigation performance. Therefore, advanced receiver autonomous integrity monitoring (advanced RAIM or ARAIM) technology is being developed as an augmentation method for GNSS users under multi-constellation. ARAIM can allow increased service level globally and provide vertical guidance during the approach phase for aircrafts. Since the traditional ARAIM algorithm uses the average allocation strategy to allocate integrity and continuity risk, an allocation approach based on the particle swarm optimization (PSO) algorithm is presented in this article. Different allocation strategies for integrity and continuity risk are chosen as different particles, and the weighted sum of vertical protection level corresponding to different fault subsets is selected as the fitness function to optimize the allocation strategy and the corresponding VPL. Based on real GNSS data, the ARAIM algorithm under multi-constellation is analyzed. The experimental results demonstrate that the integrity and continuity risk allocation method based on the proposed algorithm optimizes the VPL and improves the global availability of ARAIM under multi-constellation.
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