Two mutants performed quite differently in term of survival on soybean seed. The survival of 532C d2 on seed was 54% higher than the parent strain after 20 days test. That result indicated that some changes did happened to Rhizobium in the process of growth and, perhaps on the dry seed. We successfully selected a more desiccation tolerant strain. Our experiment has proven that Darwin’s theory does apply to Rhizobium, just like numerous other situations.

However, 532C d1 was inferior to parent strain. This result is difficult to explain, since that mutant had successfully survived on dry seed for 2 months! The real world is extremely complex. What really happened behind this mutant is unknown. The most probable cause for the result is due to contamination. No matter how clean you keep the laboratory, it’s still very possible for foreign bacterium to enter the rhizobial culture and cause damage.

Although Darwin’s evolution theory is widely accepted and has been proved by numerous examples, there still something that are difficult to explain by this theory. Through this science project, we learned that we could change the microbes by proper ways to make the microbes do the job, as we want to. Meanwhile, we should also bear in mind that something beyond our control or our imagination still can happen. Such unexpected phenomenon is a challenge to the present knowledge system, which might lead to new discovery if we try to understand the reason behind it.