Alright, as a quick recap, leptospira is a genus of tiny spiral gram-negative bacteria that can be seen under a darkfield microscope.

得！快速回顾一下：钩端螺旋体是一种细小的革兰氏阴性菌，它可以在暗视野显微镜中被观察到。

It's also too tiny to be seen with a light microscope, so to visualize it, you need a darkfield microscope with use of immunofluorescence is required.

这种细菌也因为体型太细而难以在光学显微镜下显像，所以为了能够看见钩端螺旋体，人们需要使用暗视野显微镜以及荧光染色剂。