Abstract:
Chemotaxis is a process in which bacteria sense
their chemical environment and move towards more
favorable conditions. Since plant colonization by bacteria
is a multifaceted process which requires a response to the
complex chemical environment, a finely tuned and sensitive
chemotaxis system is needed. Members of the Bacillus
subtilis group including Bacillus amyloliquefaciens are
industrially important, for example, as bio-pesticides. The
group exhibits plant growth-promoting characteristics, with
different specificity towards certain host plants. Therefore,
we hypothesize that while the principal molecular mechanisms
of bacterial chemotaxis may be conserved, the
bacterial chemotaxis system may need an evolutionary
tweaking to adapt it to specific requirements, particularly in
the process of evolution of free-living soil organisms,
towards plant colonization behaviour. To date, almost
nothing is known about what parts of the chemotaxis
proteins are subjected to positive amino acid substitutions,
involved in adjusting the chemotaxis system of bacteria
during speciation. In this novel study, positively selected
and purified sites of chemotaxis proteins were calculated,
and these residues were mapped onto homology models that were built for the chemotaxis proteins, in an attempt to
understand the spatial evolution of the chemotaxis proteins.
Various positively selected amino acids were identified in
semi-conserved regions of the proteins away from the
known active sites.
