@article{GhylinGarciaMoyaetal.2014, author = {Ghylin, Trevor W. and Garcia, Sarahi L. and Moya, Francisco and Oyserman, Ben O. and Schwientek, Patrick and Forest, Katrina T. and Mutschler, James and Dwulit-Smith, Jeffrey and Chan, Leong-Keat and Martinez-Garcia, Manuel and Sczyrba, Alexander and Stepanauskas, Ramunas and Grossart, Hans-Peter and Woyke, Tanja and Warnecke, Falk and Malmstrom, Rex and Bertilsson, Stefan and McMahon, Katherine D.}, title = {Comparative single-cell genomics reveals potential ecological niches for the freshwater acl Actinobacteria lineage}, series = {The ISME journal : multidisciplinary journal of microbial ecology}, volume = {8}, journal = {The ISME journal : multidisciplinary journal of microbial ecology}, number = {12}, publisher = {Nature Publ. Group}, address = {London}, issn = {1751-7362}, doi = {10.1038/ismej.2014.135}, pages = {2503 -- 2516}, year = {2014}, abstract = {Members of the acI lineage of Actinobacteria are the most abundant microorganisms in most freshwater lakes; however, our understanding of the keys to their success and their role in carbon and nutrient cycling in freshwater systems has been hampered by the lack of pure cultures and genomes. We obtained draft genome assemblies from 11 single cells representing three acI tribes (acI-A1, acI-A7, acI-B1) from four temperate lakes in the United States and Europe. Comparative analysis of acI SAGs and other available freshwater bacterial genomes showed that acI has more gene content directed toward carbohydrate acquisition as compared to Polynucleobacter and LD12 Alphaproteobacteria, which seem to specialize more on carboxylic acids. The acI genomes contain actinorhodopsin as well as some genes involved in anaplerotic carbon fixation indicating the capacity to supplement their known heterotrophic lifestyle. Genome-level differences between the acI-A and acI-B clades suggest specialization at the clade level for carbon substrate acquisition. Overall, the acI genomes appear to be highly streamlined versions of Actinobacteria that include some genes allowing it to take advantage of sunlight and N-rich organic compounds such as polyamines, di-and oligopeptides, branched-chain amino acids and cyanophycin. This work significantly expands the known metabolic potential of the cosmopolitan freshwater acI lineage and its ecological and genetic traits.}, language = {en} } @article{SrivastavaMcMahonStepanauskasetal.2016, author = {Srivastava, Abhishek and McMahon, Katherine D. and Stepanauskas, Ramunas and Großart, Hans-Peter}, title = {De novo synthesis and functional analysis of the phosphatase-encoding gene acI-B of uncultured Actinobacteria from Lake Stechlin (NE Germany)}, series = {International microbiology : official journal of the Spanish Society for Microbiology}, volume = {19}, journal = {International microbiology : official journal of the Spanish Society for Microbiology}, publisher = {Institut d'Estudis Catalans}, address = {Barcelona}, issn = {1139-6709}, doi = {10.2436/20.1501.01.262}, pages = {39 -- 47}, year = {2016}, abstract = {The National Center for Biotechnology Information [http://www.ncbi.nlm.nih. gov/guide/taxonomy/] database enlists more than 15,500 bacterial species. But this also includes a plethora of uncultured bacterial representations. Owing to their metabolism, they directly influence biogeochemical cycles, which underscores the the important status of bacteria on our planet. To study the function of a gene from an uncultured bacterium, we have undertaken a de novo gene synthesis approach. Actinobacteria of the acI-B subcluster are important but yet uncultured members of the bacterioplankton in temperate lakes of the northern hemisphere such as oligotrophic Lake Stechlin (NE Germany). This lake is relatively poor in phosphate (P) and harbors on average similar to 1.3 x 10(6) bacterial cells/ml, whereby Actinobacteria of the ac-I lineage can contribute to almost half of the entire bacterial community depending on seasonal variability. Single cell genome analysis of Actinobacterium SCGC AB141-P03, a member of the acI-B tribe in Lake Stechlin has revealed several phosphate-metabolizing genes. The genome of acI-B Actinobacteria indicates potential to degrade polyphosphate compound. To test for this genetic potential, we targeted the exoP-annotated gene potentially encoding polyphosphatase and synthesized it artificially to examine its biochemical role. Heterologous overexpression of the gene in Escherichia coli and protein purification revealed phosphatase activity. Comparative genome analysis suggested that homologs of this gene should be also present in other Actinobacteria of the acI lineages. This strategic retention of specialized genes in their genome provides a metabolic advantage over other members of the aquatic food web in a P-limited ecosystem.}, language = {en} }