To begin our discussion, we would like those interested in this subject
propose hypotheses about the role that biofilm formation plays in
1) bacterial survival and growth on plant surfaces and in the
2) the diversity of the microbial communities in these
3) the bacteria-plant interaction
As a reference, the excerpt above is included from the recent
message sent by Cindy Morris to the "biofilms at net.bio.net" address.
First of all, my personal plaudits to you and your colleagues for your
bold step into "The Unsaturated"........BRAVO!......HURRAY!........and
to suggest that there may be enough of us out there to have something
upon which to initiate discussions, debate, and collaboration. Count me
in! Although R.J. Palmer has already responded to item (3) above with
his comment on root exudates, let me take the liberty to state it in
terms of a hypothesis:
Hypothesis 1: Plants respond to their environment chemically in the
form of root exudates. Root exudates can act allelopathically to limit
the growth of some organisms (e.g. those that compete in some way or are
pathogenic). Conversely, root exudates may stimulate microbial
populations that provide something beneficial to the plant (e.g.
defense, nutrients, etc.).
Hypothesis 2: Plant species and microbial species have evolved
together. Therefore, specific plant/microbe (i.e. root/biofilm)
interactions (i.e. symbioses) are probably widespread and remain
Regarding item (2) in the excerpt from Cindy's message:
Hypothesis 3: Agricultural practices usually involve the establishment
of monocultures. Therefore, bacterial diversity (specifically,
activity) in cultivated soils should decrease compared to adjacent
native "control" soils.
Hypothesis 4: Many soil environments are subjected to a wide range of
seasonal fluctuations in soil moisture and temperature. Therefore,
there is probably an immense adaptive seasonal fluctuation in microbial
activity....which may or may not be correlated to changes in plant
Regarding item (1) in the excerpt from Cindy's message:
Hypothesis 5: Biofilms prevent dessication of individual cells and may
in fact be considered hygroscopic. Biofilms become increasingly
important in unsaturated environments as moisture becomes limiting and
confer a selective advantage to those species that are adapted to "a
life in film".
Looking forward to hearing from more of you "dry" types!
Center for Biofilm Engineering
Montana State University
Bozeman, MT 59717-3980
rick_v at erc.montana.edu