  Bacteria are perhaps the simplest living systems capable of complex behaviour
involving sensing and coherent, collective behaviour an example of which is the
phenomena of swarming on agar surfaces. Two fundamental questions in bacterial
swarming is how the information gathered by individual members of the swarm is
shared across the swarm leading to coordinated swarm behaviour and what
specific advantages does membership of the swarm provide its members in
learning about their environment. In this article, we show a remarkable example
of the collective advantage of a bacterial swarm which enables it to sense
inert obstacles along its path. Agent based computational model of swarming
revealed that independent individual behaviour in response to a two-component
signalling mechanism could produce such behaviour. This is striking because
independent individual behaviour without any explicit communication between
agents was found to be sufficient for the swarm to effectively compute the
gradient of signalling molecule concentration across the swarm and respond to
it.
