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Psychrophilic haloarchaea dominate life in Deep Lake, a monomictic hypersaline lake in the Vestfold Hills of Antarctica. Halorubrum lacusprofundi and Halohasta litchfieldiae represent ~ 10% and ~ 44% of the Deep Lake community, respectively. Their relative abundance has been linked to genomic distinctions including an ability to utilize specific nutrients. A gene transfer system was developed for Hrr. lacusprofundi, the first for any psychrophilic Archaea. A gene knockout was constructed for an acetamidase/formamidase gene, which represents a class of genes not previously experimentally studied in Archaea. Disruption of the gene resulted in the inability of cells to utilize acetamide for growth. By investigating the phylogeny of acetamidases/formamidases in Bacteria and Archaea and the environmental relevance of acetamide, it was concluded that accumulation of acetamide-related pollutants may promote the selection of species harboring acetamidase/formamidase genes. An integrative approach combining microscopy and quantitative proteomics enabled a comprehensive investigation of ecologically relevant mechanisms of growth, survival and speciation of the two species. Specific growth temperatures, substrates and growth phase led to biofilm formation in Hrr. lacusprofundi, with extracellular DNA and quorum sensing linked to biofilm formation. Sucrose metabolism in Hht. litchfieldiae was shown to increase carbohydrate uptake and glycolysis and decrease pyruvate uptake and metabolism, TCA cycle, glycerol metabolism and gluconeogenesis. Both species responded to low temperature by modifying their cell morphology and cell envelope, maintaining osmotic balance and translation initiation, and altering RNA turnover and tRNA modification. Distinctions between the two species included DNA protection and repair strategies and pathways for metabolism of glycerol and pyruvate. Low temperature enhanced the levels of CRISPR Cas proteins and the core gene expression machinery in Hht. litchfieldiae. A novel pathway for PHA granule synthesis was proposed in Hrr. lacusprofundi. Overall, the research identified specific characteristics that may enhance the competitiveness of each species, and therefore represents a strong advance for Antarctic microbial ecology, hypersaline systems, and biology of Archaea. The development of the gene knockout system combines well with the development of proteomic methods, providing a solid basis for future studies of these important lake species.

In an attempt to realize decentralized cooperation and coordination in a heterogeneousteam of autonomous mobile agents, we have proposed a platform to model many practicalissues encountered in the process. The system includes an unexplored environment and ateam of agents with different capabilities. The agents' movement follows trajectories limitedby speed and turning radius, and their actions may be affected by their orientation relativeto targets. The stochasticity introduced by task transition makes o-line task assignmentinapplicable.A basic distributed real-time assignment algorithm and an intelligent predictive decisionmaking strategy are proposed and compared. The results show that prediction can helpimprove the performance of cooperative agent teams engaged in search-and-engage missions.These algorithms are implemented with the assumption of perfect communication.The assumption of perfect communication is relaxed in the second part of the work reported,resulting in a truly decentralized system that is simulated in a somewhat simplermission scenario. Each agent in this decentralized model has its own subjective informationbase (SIB) based on limited observations and information sharing, and uses a set of informationfusion heuristics to maintain this SIB. The performance of the system is evaluatedrelative to the degree of information sharing. The results indicate that cooperation basedon information exchange { even if it is imperfect { can produce excellent performance.A hybrid communication strategy combining occasional limited-range communicationand opportunistic peer-to-peer synchronization is then proposed. Using Monte Carlo simulations,it is shown that this strategy can significantly supplement the efficacy of a diffusiveinformation sharing strategy.