Methane oxidation in the deep ocean.
Bacterial methanotrophs provide at least three crucial services in the deep ocean: Oxidizing methane to biomass, thus preventing its emission to the atmosphere; supplying organic carbon to the trophic base of beautiful deep sea faunal communities; and in some cases, forming endosymbiotic partnerships with a variety of deep sea animals.
Cosmopolitan marine methanotrophs.
Dr. Tavormina's molecular work on marine methanotrophs has firmly established that two clades within Gammaproteobacteria form an extended planktonic 'methane biofilter' in many coastal ocean waters. This biofilter occurs at depths from 200 meters to the seafloor. A separate contingent of methanotrophs resides in oxic marine sediments (see representative phylogeny, below left). The two planktonic clades, referred to as OPU1 and OPU3, respond to specific geochemical drivers, and are described in greater detail under 'oxygen minimum zones.' Deep sea samples are collected in various ways, including by CTD rosette (right).
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The deep environmental sample processor (MBARI).
Dr. Tavormina worked in collaboration with the Monterey Bay Aquarium Research Institute on a NASA-funded project, to develop remote assays to monitor deep sea methanotrophs. Do methane fluxes trigger real-time changes in methanotroph populations? How dynamically do deep-sea methanotrophs respond to methane? Can this new technology be used in other remote searches for life?
The environmental sample processor is remotely operated instrumentation, deployed into the deep ocean and operated from shipboard or land. The d-ESP is outfitted with multiple analytics, and is sometimes called a 'lab in a can.' Telemetry from the d-ESP is analyzed in real time, so that scientists at ground level can instantly monitor the effects of geochemical shifts on microbial populations.
The environmental sample processor is remotely operated instrumentation, deployed into the deep ocean and operated from shipboard or land. The d-ESP is outfitted with multiple analytics, and is sometimes called a 'lab in a can.' Telemetry from the d-ESP is analyzed in real time, so that scientists at ground level can instantly monitor the effects of geochemical shifts on microbial populations.
Molecular profiling of environmental methanotrophs.
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Drawing on ARISA (automated ribosomal intergenic spacer analysis) as a template, Patricia developed MISA (monooxygenase intergenic spacer analysis). This technique generates an electropherogram 'fingerprint,' which describes the population of proteobacteria encoding pMMO-related proteins. The technique also allows hundreds of environmental samples to be processed and profiled in less than 48 hours, providing a highly efficient and cost-saving alternative to clone libraries. |
Faunal communities.
Few people outside of science realize that methane contributes a portion of the carbon needed to sustain deep sea communities, similar to how carbon dioxide feeds plants to form the basis of our land-based food chain. The faunal communities that rely on methane are extensive and beautiful. Patricia works to describe the players, and mechanisms of interaction, between specific methane oxidizing lineages and deep sea fauna. Additional details of this work are provided under 'model systems.' Shown below are Bathymodiolus mussels (left) and folliculinid ciliates (right). These organisms live intimately with methane oxidizing bacteria, and derive significant carbon from the association. (Photo credits: Geomar and G. Rouse.) Genus Methyloprofundus includes methanotrophic species that live within gill bacteriocytes. More information about genus Methyloprofundus is available under Model Systems.
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Current and future directions.
* The genome of the planktonic methanotroph 'OPU3' has recently been determined through work from Li et al, and Padilla et al. This information makes the cultivation of this lineage more tractable, to allow analysis of its role in marine methanotrophy.
* Folliculinid ciliates associate with a specific lineage of methanotroph that occurs in highly localized spots near the seafloor. Whether this association is a true symbiosis or not is an area of active investigation.
* Folliculinid ciliates associate with a specific lineage of methanotroph that occurs in highly localized spots near the seafloor. Whether this association is a true symbiosis or not is an area of active investigation.