Fig. 2.

Experimental design. (1) Selection of strains based on their transcript profiles. All the genes tested showed a consistently higher expression in the absence of oxygen than in its presence, with four different nutrient limitations. (2) Knockout mutants of anaerobiosis-induced genes were constructed. Each mutant carried two specific tags. (3) Competitive fermentation: the knockout mutants were grown and pooled in equal proportion prior to injection into a steady-state chemostat culture of the reference strain ygr059wΔ : : uptag. The culture was sampled every 24 h for a period of 9 days. (4) qrtPCR was performed on daily samples, using a tag-corresponding specific primer and a common primer for all strains. (5) Determination of fitness compared to the pooled reference strain ygr059wΔ : : downtag.