  Controlling the swimming behavior of bacteria is crucial, for example, to
prevent contamination of ducts and catheters. We show the bacteria modeled by
deformable microswimmers can accumulate in flows through straight microchannels
either in their center or on previously unknown attractors near the channel
walls. We predict a novel resonance effect for semiflexible microswimmers in
flows through wavy microchannels. As a result, microswimmers can be deflected
in a controlled manner so that they swim in modulated channels distributed over
the channel cross-section rather than localized near the wall or the channel
center.
  Thus, depending on the flow amplitude, both upstream orientation of swimmers
and their accumulation at the boundaries which can lead to surface rheotaxis
are suppressed. Our results suggest new strategies for controlling the behavior
of live and synthetic swimmers in microchannels.
