  We study the realization of supergroup gauge theories using negative branes
in string theory. We show that negative branes are intimately connected with
the possibility of timelike compactification and exotic spacetime signatures
previously studied by Hull. Isolated negative branes dynamically generate a
change in spacetime signature near their worldvolumes, and are related by
string dualities to a smooth M-theory geometry with closed timelike curves.
Using negative D3 branes, we show that $SU(0|N)$ supergroup theories are
holographically dual to an exotic variant of type IIB string theory on
$dS_{3,2} \times \bar S^5$, for which the emergent dimensions are timelike.
Using branes, mirror symmetry and Nekrasov's instanton calculus, all of which
agree, we derive the Seiberg-Witten curve for $\mathcal N=2 ~SU(N|M)$ gauge
theories. Together with our exploration of holography and string dualities for
negative branes, this suggests that supergroup gauge theories may be
non-perturbatively well-defined objects, though several puzzles remain.
