Robert M. Morris

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The most abundant class of bacterial ribosomal RNA genes detected in seawater DNA by gene cloning belongs to SAR11-an alpha-proteobacterial clade. Other than indications of their prevalence in seawater, little is known about these organisms. Here we report quantitative measurements of the cellular abundance of the SAR11 clade in northwestern Sargasso Sea(More)
Bacterioplankton belonging to the SAR11 clade of a-proteobacteria were counted by fluorescence in situ hybridization (FISH) over eight depths in the surface 300 m at the Bermuda Atlantic Time-series Study (BATS) site from 2003 to 2005. SAR11 are dominant heterotrophs in oligotrophic systems; thus, resolving their temporal dynamics can provide important(More)
We used terminal restriction fragment length polymorphism (T-RFLP), clone library, phylogenetic, and bulk nucleic acid hybridization analyses to identify and characterize spatial and temporal patterns in marine bacterioplankton communities at the Bermuda Atlantic Time-series Study (BATS) site. Nonmetric multidimensional scaling of monthly surface and 200-m(More)
Ecosystems are shaped by complex communities of mostly unculturable microbes. Metagenomes provide a fragmented view of such communities, but the ecosystem functions of major groups of organisms remain mysterious. To better characterize members of these communities, we developed methods to reconstruct genomes directly from mate-paired short-read metagenomes.(More)
Ecological studies indicate that aerobic anoxygenic phototrophic bacteria (AAP) that use bacteriochlorophyll to support phototrophic electron transport are widely distributed in the oceans. All cultivated marine AAP are alpha-3 and alpha-4 Proteobacteria, but metagenomic evidence indicates that uncultured AAP Gammaproteobacteria are important members of(More)
Bacteria and Archaea play critical roles in marine energy fluxes and nutrient cycles by incorporating and redistributing dissolved organic matter and inorganic nutrients in the oceans. How these microorganisms do this work at the level of the expressed protein is known only from a few studies of targeted lineages. We used comparative membrane metaproteomics(More)
Multiple reductive dehalogenase (RDase), hydrogenase (H2ase), and other respiration-associated (RA) oxidoreductase genes have been identified in cultured representatives of Dehalococcoides. Although their products are likely to play key roles in the environmentally important process of reductive dechlorination, very little information is available about(More)
Since their initial discovery in samples from the north Atlantic Ocean, 16S rRNA genes related to the environmental gene clone cluster known as SAR202 have been recovered from pelagic freshwater, marine sediment, soil, and deep subsurface terrestrial environments. Together, these clones form a major, monophyletic subgroup of the phylum Chloroflexi: While(More)
Although bacterioplankton and phytoplankton are generally perceived as closely linked in marine systems, specific interactions between discrete bacterioplankton and phytoplankton populations are largely unknown. However, measurements of bacterioplankton distributions during phytoplankton blooms may indicate specific microbial lineages that are responding to(More)
Anaerobic reductive dehalogenation by Dehalococcoides spp. is an ideal system for studying functional diversity of closely related strains of bacteria. In Dehalococcoides spp., reductive dehalogenases (RDases) are key respiratory enzymes involved in the anaerobic detoxification of halogenated compounds at contaminated sites globally. Although housekeeping(More)