Gonococcal polarization dynamics during adaptation to low oxygen levels

Abstract

Neisseria gonorrhoeae can switch between aerobic and microaerophilic lifestyles, but little is known about the dynamics of this transition. In particular, switching from respiration to partial denitrification is likely to affect the electrophysiology of these bacteria. Here, we use a Nernstian dye to measure the membrane potential of single planktonic cells while they continuously consume the oxygen in the growth medium. We show that cells undergo a characteristic pattern of transient depolarization followed by transient hyperpolarization at a critical oxygen concentration, reminiscent of the response to sudden changes in membrane voltage driven by gated ion-channels. Subsequently, the cells depolarize strongly to a near-constant membrane potential. In the presence of nitrite, the cells repolarize after a delay and the repolarization depends on the oxygen-dependent regulator fnr required for denitrification. The temporal behaviour of planktonic cells explains the complex spatio-temporal polarization pattern of the colonies formed by N. gonorrhoeae. This sexually transmitted human pathogen experiences different growth environments during transmission. Our results are an important step towards understanding how electrophysiology adapts to changing environments.