Difference between revisions of "Team:BIT-China/Description"

For plasmid-based expression system, the plasmid segregational instability has been the limit step in both scientific research and large-scale industry production. Generation of plasmid-free cells will sharply decrease the efficiency and profit due to the slacker’s increasing proliferation ability while producing no target substances.

Enhancing the plasmid stability is our main goal. To control the intracellular plasmid numbers, the first step is to sense the plasmid numbers.

Equip the bacteria with a plasmid-sensing logically adjustable cell killer (P-SLACKiller), we select the inhibitor protein as a signal which can indicate the intracellular plasmid numbers.

There is a basic rule: when the plasmid numbers are above the threshold, we regard it as a normally-working bacterium and the P-SLACKiller won’t start; however, when the plasmid numbers are below the threshold, we judge it as a slacker and the P-SLACKiller will kill these slackers.

Previous work realize the plasmid maintenance through making the plasmid encode essential factors for the host.

Resistance screening and auxotrophic bacteria are dependent on the selecting process [1]. The plasmid-free bacteria cannot survive under specific selections, such as antibiotics.

According to the natural mechanisms for plasmid maintenance, many new strategies are developed, so called plasmid addiction system (PAS) or post-segregational killing system (PSK) [2]. However, these mechanism are still under exploration.

As we know, the employed antibiotics must be removed in pharmaceutical or GMP-based fermentation processes and it’s not an applicable option in industrial fermentation.

In our project, we aim to use an intracellular signal correlated with the plasmid numbers and realize the selection process without any human interference. This design will greatly simplify the spawn rejuvenation.

With no antibiotics added, we also want to improve the previous approaches by realizing the quantification of plasmid copy numbers. See our design.