Estimating Morphological Diversity *
In
an computer assisted image analysis of microbial community
diversity, the operator typically acquires 36 exposures
through a photo microscope of different random fields
from one prepared slide of the uniformly dispersed,
microbial community sample. Each photograph is scanned
and digitally segmented to yield an improved image
that has been reduced to only the objects of interest
(the microbes themselves). A pattern recognition routine
then classifies the richness of microbial morphotypes
on each image and reports the cumulative frequency
of each morphotype found.
The index of morphological diversity d of the organisms
found in a community sample is defined by one of several
formulas, all suggested by Boltzmann's work in
thermodynamics, for example
d = - p1 log p1 - p2
log p2 - p3 log p3
- . . . ,
where pj is the frequency of organism type
j in the sample.
How quickly does this index of diversity converge
to its maximum observed value? How many microbes (hence
images) must be examined before one can with confidence
know the value of the diversity index that is truly
reflective of the diversity that exists within the
community sample?
The deliverable from this project will be an interactive
Excel macro prepared in Visual Basic that provides
a sequential decision algorithm for how many photos
must be processed and analyzed. The first photo is
scanned, image processed, and diversity computed.
The second photo is processed similarly and its data
are joined with the first to compute a more accurate
estimate of diversity. The third photo is processed
and its data are aggregated with the data from the
first two photos to estimate the diversity. And so
forth.
When can we break off the process? When is it no longer
worthwhile to continue? With what confidence can we
state the diversity of this population at the n-th
step? Since the answers depend on the intrinsic diversity
present in the community being examined, communities
spanning a range of diversity will be provided for
evaluation.
*This summary prepared by C. R. MacCluer and R. E.
Svetic with the assistance of F. B. Dazzo, Professor
of Microbiology at Michigan State University.
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