Rocap, G. MIT, gabrielle@alum.mit.edu
Chisholm, S. MIT, chisholm@mit.edu

 
COEXISTENCE OF ECOTYPES WITH DISPARATE PHOTOPHYSIOLOGIES INFERRED FROM GENETIC DIVERSITY IN NATURAL POPULATIONS OF PROCHLOROCOCCUS
 
Prochlorococcus is the dominant phototroph in the temperate oceans. Physiological studies of cultured isolates have demonstrated that there are at least two distinct ecotypes of Prochlorococcus, adapted for growth at high and low light intensities. Phylogenetic relationships among these isolates based on sequences at the ribosomal RNA locus (16S, 23S and ITS) also support this distinction. High-light adapted isolates are closely related to each other and cluster together in a shallow clade, while the low light adapted isolates are more divergent. To determine if Prochlorococcus isolates are representative of those in natural populations in the Sargasso Sea we constructed environmental libraries by PCR amplifying cyanobacterial rRNAs from DNA isolated from whole water filters. Clones representative of both high and low-light adapted isolates were present in a single sample from a well mixed water column in February 1997. Comparisons to libraries constructed from surface and deep waters of a stratified water column in June of 1996 will also be presented and abiotic factors (light, nutrients, metals) which likely play roles in structuring distributions of the ecotypes will be discussed.
 
Day: Tuesday, Feb. 2
Time: 09:45 - 10:00am
Location: Hilton of Santa Fe
 
Code: SS40TU0945H