Dr. Mitchell Sogin,
Senior Scientist and
Director of the Josephine Bay Paul Center for
Comparative Molecular Biology and Evolution

Mitchell Sogin's CV >>

The Sogin laboratory employs comparative phylogenetic studies of genes and genomes to define patterns of evolution that gave rise to contemporary biodiversity. We are especially interested in discerning how the eukaryotic cell was invented as well as the identity of microbial groups that were ancestral to animals, plants, and fungi. Phylogenetic inferences based upon comparisons of ribosomal RNAs have discovered new evolutionary assemblages that are as genetically diverse and complex as plants, fungi, and animals. The nearly simultaneous separation of these eukaryotic groups (described as the eukaryotic "Crown") occurred approximately one billion years ago and was preceded by a succession of earlier diverging protist lineages. The basal eukaryotic lineages may be older than once thought possible; given the amitochondriate phenotype of early-diverging lineages, the presence of oxygen is not prerequisite to forming a nucleus. We are now using a combination of whole genome sequence analyses (Giardia lamblia and Nosema locustae) and large scale cDNA sequencing projects for as many as thirty different protists to explore genome diversity in ancestral eukaryotes. These data will provide a description of what came early in the evolution of nuclear genomes and will identify alternative genes for inferring phylogenetic relationships.

The ribosomal RNA databases also provide powerful tools for the emerging discipline of molecular ecology. Using the ribosomal RNA gene sequence and nucleic acid-based probe technology, it is possible to detect and monitor microorganisms including those that cannot be cultivated in the laboratory. This strategy has uncovered new habitats and major revelations about geographical distribution of microorganisms. We are currently exploring eukaryotic diversity in anoxic hydrothermal marine sediments and in the heavy-metal rich (20 mg/ml of iron), acidic (pH 2) rio Tinto of South Western Spain. Our objective is to understand the molecular basis for surviving these harsh environmental conditions.

More recently we have initiated a new project that will organize an International Census of Marine Microbes (ICoMM). Most of the genetic and metabolic diversity of Life is microbial. In the world’s oceans, microorganisms account for more than 90% of the biomass. The carbon content of these creatures equals 50-100 percent of the total estimated for all terrestrial plants. The number of microbes in oceans exceeds 36,000,000,000,000,000,000,000,000,000,000 cells. The abundances of viruses and phages are ten-fold higher. With such enormous populations, there is considerable potential for the accumulation of mutations leading to very high levels of genetic diversity and phenotypic variation. ICoMM’s goal is to develop a large-scale strategic plan that will describe the biodiversity of marine microorganisms.