Pressure is a physical parameter which influences the evolution and distribution of microbial life. Far from Earth?s surface, deep ocean trenches represent the upper boundaries of pressure in the biosphere. This is where scientists can study high pressure adaptations in their most extreme forms. No studies have yet characterized the diversity of microbial life in trenches. In order to do this, Doug Bartlett from UC San Diego and Wilford Schmidt from Univ. Puerto Rico-Mayaguez, will be using an untethered, free-falling, pressured-hardened device to sample bacterial and archaeal life in the deepest trench in the Atlantic Ocean, the Puerto Rico Trench (PRT), at a depth of 8.4 km (5.2 mi). They will profile the ambient environment in which these prokaryotes live (pressure, temperature, salinity, and current velocity). They will also chemically analyze the trench seawater and carry out total microbial cell counts and probe-based counts of particular microbial groups, perform DNA extractions and isolate and culture deep-dwelling microorganisms. It is these last two goals that are at the heart of the project. They will use the DNA to characterize the trench microbial community via indicator genes and community fingerprint techniques. Cultivation of these high pressuring loving microbes (called ?piezophiles?) is difficult since the culture vessels are under very high pressure and the samples are difficult to manipulate. The Bartlett laboratory has the expertise to culture piezophiles and so a major effort will be made to isolate pure cultures of some of the major microbial groups observed in the PRT, including members of the class ?Alphaproteobacteria?, order Flavobacteriales, order Planctomycetales, and subclass marine group I Crenarchaeota. They will also characterize the physiology and taxonomy of particular isolates. In the long term, these investigators are interested in studying the effect of decompression or pressurization on deep-trench or surface-water microbial assemblages because they are interested in understanding the unique abilities of piezophiles to survive and grow under very high pressures. Bartlett and Schmidt will develop outreach programs for pre-college and university students, in Puerto Rico and in southern California, to teach them about this research. Their efforts will include the development of a marine microbiology laboratory class. They will also create highlights from their research for the Birch Aquarium's Deep Ocean Exhibit.
This project involved the collection of samples from deep-sea trenches, including some of the deepest locations on Earth. The samples collected were used to assess the identity, diversity and adaptations of microorganisms that inhabit these remote alien-like environments. Samples were recovered over the course of seven cruises to the Puerto Rico Trench (four cruises), the Peru-Chile Trench, the New Britain Trench, and the Mariana Trench. The last cruise to benefit this grant was the highly publicized James Cameron Deepsea Challenge Expedition. In most cases there was no charge to the grant for ship time. In most cases autonomous untethered instruments were used to collect samples. They were used to collect trench seawater, sediment and animals in baited traps. Many of these instruments also filmed the deep-sea environment. Extensive information was obtained on the diversity of microbial life present in the Puerto Rico Trench. This included all three of the major branches of life and microbes associated with particles as well as those existing as free-living individual cells in the water column. Despite the fact that surface-water derived microorganisms regularly "rain" down from above, the communities of microorganisms present in the Puerto Rico Trench have more in common with microbes present in other deep-sea places than with the populations of microorganisms in the shallower environments above them. A major analysis of the genome properties (so called metagenome and single-cell genomes) of the microbes present in the Puerto Rico Trench was also performed. This indicated that the microbes present have larger genomes sizes than surface-water microbes, extensively sense their environment and regulate their gene expression, are well adapted for utilizing diverse nutrients, and surprisingly, are highly resistant to heavy metals. The DNA obtained from microbes and animals collected in trenches as a part of this grant will be a useful resource for future studies of the diversity and genomic properties of life at great oceanic depths. Many "extremophilic" microbes from the Puerto Rico Trench and from other trenches were cultivated under the conditions present in environment; including pressures as high as 15,000 pounds per square inch, near freezing temperatures and darkness. These cultures are a useful resource for future studies, including research on the biotechnological applications of deep-sea microbes.
