Is yersinia pestis aerobic or anerobic?

It is a facultative anaerobe. In the presence of oxygen, it uses that, but it can function without it. These types of bacteria tend to grow faster in oxygen.

Edit- to answer Bacteria boy- here are two websites. The first, under #15 , lists Yersinia pestis as a facultative anaerobe. The second explains the differences between the different oxygen tolerances of bacteria. To quote: "tubes containing facultative anaerobes contain growth throughout when the bacteria are evenly distributed, but there is usually a heavier growth on the surface of the agar because they grow best in air"

When growing yersinia in a clinical setting, it is often better to grow in an anerobic environment. This is not because it grows better there. Whatever patient specimen you may have is contaminated with all kinds of other bacteria, and growing it anaerobically allows for the yersinia a great advantage over all of them. In other words, it would lose resources to contaminates if it was grown aerobically.

I'm a microbiologist too.

It is aerobic. See the first sentence of the link below.

Yersinia pestis is a facultative anaerobe, as the first answer said, but it infacts prefers to grow without oxygen. By trade as it were, its a fermenting bacteria (carries out fermentation reactions), but if oxygen is around, it doesn't adveresly affect it.

I can't give you any specific sources, as its just something i've learnt, but there are some indicators - for example the article the second person cited says that is an Enterobacteria - which means it likes to live in conditions similar to your gut, ie anaerobic.