I am currently studying Prescott's Microbiology, 10th edition, by Willey, Sherwood, and Woolverton. Chapter 1.2 Microbes Have Evolved and Diversified for Billions of Years presents the following figure:
The authors then ask the question: Why are the probionts pictures above not considered cellular life?
I'm unsure of why the probionts are not considered to be cellular life. If I'm not mistaken, the probionts contained ribozymes, no? This means that they have the capacity to catalyse their own reproduction. And, according to the figure, later probionts also consisted of proteins, so I'm presuming that catalysis and reproduction were not issues here.
I would greatly appreciate it if people would please take the time to clarify this.