An Integrated View of Microbial Biofilms at Post Eruptive Vents on the EPR at 9°N

C. Vetriani*¹, T. Barkay¹, S. Borin², M. Crespo-Medina¹, R. Cruz¹, B. Govenar³, N. Le Bris⁴, G. Luther⁵, R. Lutz¹, D. Nuzzio⁶, I. Perez¹, T. Shank³, S. Sievert³, B. Wawrik⁷ & M. Yücel⁵

Corresponding author: vetriani@marine.rutgers.edu
¹Rutgers University, Department of Biochemistry and Microbiology and Institute of Marine and Coastal Sciences, New Brunswick, NJ 08901
²University of Milan, Department of Food Science and Microbiology, Milan, Italy 20133
³Woods Hole Oceanographic Institution, Department of Biology, Woods Hole, MA 02543
⁴IFREMER, Departement Environnement Profond, Plouzane, France, 29280
⁵University of Delaware, College of Marine and Earth Studies, Lewes, DE 19958
⁶Analytical Instrument Systems, Inc. Flemington, NJ 08822
⁷University of Oklahoma, Department of Botany and Microbiology, Norman, OK 73019

Abstract:
Early studies of deep-sea hydrothermal vents revealed the critical role of free-living and symbiotic microorganisms in sustaining the productivity of these ecosystems. In my laboratory, we are using an integrated approach to investigate the microbial colonization of newly formed vents on the East Pacific Rise (EPR) at 9°N, following the 2005-06 seafloor eruption. The goal of this project is to understand the role of microbial colonists at newly formed vents as “mediators” in the transfer of energy from the geothermal source to the higher trophic levels, and their role in altering fluid chemistry and in “conditioning” the vent environment for metazoans to settle. Following the 2005-06 volcanic eruption on the EPR, we designed and deployed several experimental microbial colonizers on active diffuse flow vents characterized by different temperatures (approximate range 20-60°C) chemical (different redox conditions), and biological (e.g., presence or absence of metazoan colonists) regimes. 16S rRNA and fuctional gene transcript surveys, along with metatranscriptomic analyses, indicated that Epsilonproteobacteria represented the dominant and active fraction of the chemosynthetic early microbial colonists, and that they expressed in-situ the genes involved in carbon dioxide fixation and nitrate respiration. Furthermore, our studies are revealing a possible role for heterotrophic bacteria that can use alternative carbon sources, such as n-alkanes, and could play a role in the detoxification of heavy metals.

Keywords:
Microbial biofilms, Epsilonproteobacteria, chemosynthesis, transcript analysis, heavy metal detoxification

Contributions to Integration and Synthesis:
We propose a model that links fluid chemistry, chemosynthetic and heterotrophic microbial processes (including the mobilization and detoxification of toxic heavy metals) and the colonization of newly formed vents. This model emphasizes the role of microbial biofilms in mediating the transfer of energy and carbon from the geothermal source to the higher trophic levels. Therefore, our study of microbial biofilms can be integrated with data on vent fluid chemistry (including measurements of the concentration of heavy metals, trace metals, organic carbon, reduction potential) and with data on larval settlement and patterns of animal colonization. Examples of open questions that we hope to address via an integrated collaborative approach include: What are the mechanisms of heavy metal detoxification at deep-sea vents? How does heavy metal detoxification affect vent colonization? How does the distribution and concentration of trace metals in vent fluids (e.g., molybdenum, tungsten) affect the distribution of microorganisms and microbial enzymatic functions at deep-sea vents?

Figures:
Figure 1. Microbial biofilm communities colonized newly formed deep-sea vents Vetriani_fig1.jpg