Another explanation for the observed results could be that enzymes, loosed from the irradiated cells, might be hanging around in the soil and continuing their biochemical jobs. Even when degraded, enzymes have stable backbones that might be capable of catalyzing reactions, said Sudha Rajamani (opens a new tab), an astrobiologist at the Indian Institute of Science Education and Research, Pune who wasn’t involved in the study.

Sounds more plausible. Even without cells containing them to optimize the process, if enough of the biochemical components remained in the soil, even with broken up DNA and RNA strands, it seems plausible that the processes of life could continue for as long as there is an energy input, like keeping them in an incubator. Even to the point of going through most of the motions of life, including the assembly of enzymes.

They would need to either try with a mixture of minerals that never had any contact with any biological spillover (hard to do on Earth), or catalogue all the chemical compounds present in the breathing soil samples.