cultivating the organisms. 



Three microbial assemblages have been characterized using 5S 

 rRNA sequences: the bacterial symbionts of invertebrates that 

 surround deep-sea hydrothermal vents (Stahl et al., 1984), the 

 bacteria inhabiting the 91°C source pool of Octopus Springs in 

 Yellowstone National Park, Wyoming (Stahl et al., 1985), and the 

 microorganisms inhabiting a copper leaching pond 



Strategies for Obtaining rRNA Sequences 

 from Natural Populations 



Usng UuM-Kngown Prete 



MMwram.nl et Rauthra Abindanc. 



ot Unlqu. rDMA. .nd rRNA. In 



Vlen>bl«l PopuMkjn 



Figure 1. 



at the Chino Mine in New Mexico (Lane et al., 1985). The 

 resolution of a phylogenetic analysis using the relatively small 5S 

 rRNA is considerably less than that possible with the greater 

 number of sequence position available in the 16S or 23S rRNAs (Pace 

 et al. , 1986) . 



The cDNA approach was used to examine a microbial mat in 

 Yellowstone Park (Weller and Ward, 1989; Ward et al., 1990) that 

 was previously studied by isolating organisms from the mat (see 

 Brock, 1978) . The molecular approach confirmed earlier suspicions 

 that many members of the mat community had not been cultured in the 

 laboratory. 



Efforts are under way to identify the composition of marine 

 picoplankton collected from oligotrophic oceanic waters using 



III-3 



