Molecular analysis of hot spring microbial mats to study bacterial diversity and physiology
Year: 1996
Type: dissertation
Abstract: Molecular studies investigating 16S rRNA sequence diversity in cyanobacterial mat communities inhabiting hot springs in Yellowstone National Park have revealed that these communities contain numerous uncultivated microbial species.Here, attempts were made to cultivate from one of these mat communities the aerobic chemoorganotrophic bacteria whose 16S rRNA nucleotide sequences were previously observed using molecular retrieval techniques.By utilizing serial dilution enrichment culture and a variety of enrichment conditions, a diversity of bacterial isolates was obtained.16S rRNA sequence analysis revealed seven genotypically distinct isolates, including Thermus, proteobacterial, and Gram positive representatives.However, only one of these isolates, a β-proteobacterium, contained a 16S rRNA sequence previously observed in Octopus Spring mat.These results illustrate the differing views of microbial community composition which cultivation and molecular techniques provide, and demonstrate the problems encountered when using cultivation approaches to associate microbial activity with bacterial populations whose 16S rRNA sequences were detected in natural samples.One cultivation-independent approach to associate bacterial activity with retrieved 16S rRNA sequence types would be to selectively capture rRNA molecules synthesized by actively growing microorganisms incubated in the presence of a radiolabeled substrate, then quantify the relative extent of radiolabel incorporation into specific 16S rRNA molecules.Initial studies investigating the feasibility of this approach revealed that although logarithmically growing cyanobacterial cells incorporated photosynthetically fixed 14CO2 into rRNA, cyanobacteria inhabiting hot spring mats predominately incorporated 14CO2 into polyglucose during periods of illumination (between 77% and 85% of total incorporated carbon).Although photosynthetically active, the cyanobacteria of these mat communities do not appear to be rapidly growing, since only limited synthesis of growth-related macromolecules was detected.The fate of polyglucose reserves was investigated by allowing mat cyanobacteria to photoassimilate 14CO2 into polyglucose, then transferring samples to the dark, anaerobic conditions which mat communities experience at night.Radiolabel in the polysaccharide fraction decreased 74.7% after 12 hours dark incubation, of which 58.5% was recovered in radiolabeled fermentation products (i.e.[14C]acetate, 14CO2, and [14C]propionate).These results indicate tightly Ramsing, Michael Friederich, Mary Bateson, Sjila Santegoeds,.and Niels-Peter Revsbech.. Daily contact with these scientists improved both the quality of my life and the quality of my science.Garth James, Joe Sears,
Author: Stephen C. Nold
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W255507950