S1 was the best, S2 was crap, but S3 was between. #4, who knows but I doubt it will be good or better than first season.

We missed s# and have started from scratch. Almost at the end of S1, S2 and S3 to go. S2 was not great, but is S3 really that bad? Really??? This trailer for S4 looked pretty good to me, but I've not heard anyone tell me S3 was good. Where did they go wrong?

It's a white blood cell (neutrophil) chasing a bacterium via chemotaxis.
Neutrophils are phagocytes, so one of the ways they neutralize foreign objects in the body is by engulfing them.

and here is a video of a neutrophil gobbling up fungal cell like they were power pellets:
here

ʍou ǝɹǝɥʍǝs1ǝ sıɥʇ buısn ʎ11ɐʇoʇ os ɯı ʞo