GEOMICROBIOLOGY AND SYMBIOSES GROUP
Group leader: Junior Prof. Sharmishtha Dattagupta

Our research group uses an inter-disciplinary approach to study interactions between environmental geochemistry, microbes and macrofauna in ecosystems sustained by chemoautotrophy. Specifically we are interested in the initiation and evolution of symbioses between animals and chemoautotrophic bacteria.
These symbioses have been discovered worldwide at deep-sea vents, marine cold seeps and organic rich coastal sediments, and have evolved independently in seven different Eukaryotic phyla. They also involve phylogenetically diverse bacterial partners.

Ecosystems sustained entirely by chemoautotrophic microbes are found mostly at deep-sea vents and hydrocarbon seeps, but also in some terrestrial sulfidic caves, such as Movile cave (Romania) and Frasassi caves (Italy). Currently, our primary field site is the Frasassi cave system, where we have recently discovered the first example of an animal- chemoautotrophic bacteria symbiosis from a terrestrial ecosystem. The symbiosis involves an aquatic amphipod (genus Niphargus) and filamentous sulfur-oxidizing bacteria (genus Thiothrix). The symbiotic bacteria are attached to the Niphargus exoskeleton, and are distinct from Thiothrix phylotypes that form biofilms in the Frasassi cave waters.

The Frasassi cave system is at most one million years old and the Niphargus – Thiothrix symbiosis has likely evolved very recently in comparison with marine chemoautotrophic symbioses, many of which are tens to hundreds of million years old. Thus this symbiosis provides us an ideal opportunity to study the initiation and early evolution of this widespread phenomenon. We are currently using nuclear and mitochondrial markers to investigate the phylogenetics and population genetics of the Niphargus host. We are also analyzing symbiont abundance, diversity and function.

RELEVANT PUBLICATIONS

Dattagupta, S., Schaperdoth, I. , Montanari, A., Mariani, S., Kita, N., Valley, J. W. and Macalady, J. L. (2009) A recently evolved symbiosis between chemoautotrophic bacteria and a cave-dwelling amphipod. The ISME Journal. Published online. doi: 10.1038/ismej.2009.34

Macalady, J.L., Dattagupta, S., Schaperdoth, I., Jones D. S., Druschel, G. and Eastman, D. (2008). Niche differentiation among sulfur-oxidizing bacterial populations in cave waters. The ISME Journal, 1-2.