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Appl. Environ. Microbiol., May 1997, 1762-1770, Vol 63, No. 5
PA Noble, KD Bidle and M Fletcher
The community compositions of free-living and particle-associated bacteria
in the Chesapeake Bay estuary were analyzed by comparing banding patterns
of stable low-molecular-weight RNA (SLMW RNA) which include 5S rRNA and
tRNA molecules. By analyzing images of autoradiographs of SLMW RNAs on
polyacrylamide gels, band intensities of 5S rRNA were converted to binary
format for transmission to a back-propagating neural network (NN). The NN
was trained to relate binary input to sample stations, collection times,
positions in the water column, and sample types (e.g., particle-associated
versus free-living communities). Dendrograms produced by using Euclidean
distance and average and Ward's linkage methods on data of three
independently trained NNs yielded the following results. (i) Community
compositions of Chesapeake Bay water samples varied both seasonally and
spatially. (ii) Although there was no difference in the compositions of
free-living and particle-associated bacteria in the summer, these community
types differed significantly in the winter. (iii) In the summer, most bay
samples had a common 121-nucleotide 5S rRNA molecule. Although this band
occurred in the top water of midbay samples, it did not occur in
particle-associated communities of bottom-water samples. (iv) Regardless of
the season, midbay samples had the greatest variety of 5S rRNA sizes. The
utility of NNs for interpreting complex banding patterns in electrophoresis
gels was demonstrated.
Copyright © 1997, American Society for Microbiology
Natural Microbial Community Compositions Compared by a Back-Propagating Neural Network and Cluster Analysis of 5S rRNA
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21202
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