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Microecology and evolution of two marine pathogens


Polz and Lerczak

Vibrio vulnificus and V. parahaemolyticus are among the most significant marine pathogens and dominate seafood-related illness in temperate regions. V. vulnificus is one of the most invasive bacterial pathogens and is held responsible for about 95% of seafood related deaths. Furthermore, it has been implicated in rising incidence of lethal wound infections acquired during recreational use of coastal waters. V. parahaemolyticus has been shown to be the causative agent of outbreaks of dysentery after consumption of contaminated shellfish harvested from temperate marine regions.

In this interdisciplinary study, we are exploring the genetic diversity of these co-existing pathogenic Vibrio populations and the conditions, which control their growth and relative abundances in a temperate estuarine environment. While total abundances of bacteria in the coastal ocean and in estuaries remain stable over time, the relative abundances of different species can vary dramatically with seasonal changes in environment conditions. Moreover, severely pathogenic and more harmless variants of the same bacterial species can co-exist in the environment and it remains unknown what triggers preferential growth in the environment of specific, dangerous variants. Specific goals are to:

  1. To characterize and model dynamics and reservoirs of V. vulnificus and V. parahaemolyticus populations over seasonal cycles of environmental change.
  2. To test the link between estuarine physics, nutrient and particle abundance and growth patterns of vibrio species over tidal cycles.
  3. To determine the ‘rules’ (extent and bounds) of recombination, gene transfer and clonality in co-occurring V. vulnificus, V. parahaemolyticus and related vibrios.
  4. To assess the diversity, mobility and evolutionary history of genes implicated in pathogenicity.

Our field investigations will take place in Plum Island Sound estuary in northeastern Massachusetts, a site where numerous ecological studies have been carried out in the past, including NSF sponsored Long-Term Ecological Reserve (LTER) investigations.


Martin Polz

Massachusetts Institute of Technology
Department of Civil & Environmental Engineering
48-421, Cambridge, MA 02139
Polz Lab Web site

Ph.D. 1997, Harvard University

Research Interests:
Identification of controlling factors of microbial community structure and population dynamics with special emphasis on bacteria influencing the speciation and transport of metals. Knowledge of diversity and dynamics of bacterial populations is crucial to the ultimate predictability of the fate of most environmental contaminants. This is especially true for bioremediation and natural attenuation applications where the success of in-situ degradation depends on population size and the continuous presence of bacterial strains with desirable metabolic capabilities. This necessitates the development of techniques that allow the assessment of microbial populations as they occur in the environment. Thus, the general approach used in my laboratory combines modern molecular biological methods with traditional pure-culture techniques as well as qualitative modeling to identify key factors guiding the activity of microorganisms in the environment. Ultimately, this research should lead to an ability to better predict and control processes involving microorganisms, ranging from successful bioremediation to avoidance of pathogen outbreaks in the environment.

Dr. Luisa Marcellino

Massachusetts Institute of Technology
Department of Civil & Environmental Engineering
48-421, Cambridge, MA 02139

Ph.D in Molecular Biology/Genetics, 1998, University of Lisbon, Portugal Thesis work done at the Center for Environmental Health Sciences, MIT

Current Project:
Assessing genomic diversity of bacteria of the genus Vibrio in some coastal environments in New England. One of the main goals of the project is to detect the presence of pathogenic Vibrios, such as V. vulnificus and V. parahaemolyticus which are responsible for a significant number of seafood-related ilnesses and deaths. DNA microarray technology is used in this project to set up a standardized platform of DNA probes that are specific for Vibrios and can be used in any marine environment.

Dr. Benjamin Kirkup

Jim Lerzcak