AHL accumulation profiles of R. rubrum cultivated under different growth conditions. AHL levels obtained from HPLC analysis are given in mAUsOD-1 ml-1 and are therefore qualitative estimates. AHLs were extracted from supernatants of cultures grown under phototrophic (PHO), aerobic (AE) and microaerobic (MAER) conditions. For microaerobic cultures, the supernatant was harvested at two time points. MAER* refers to a later harvesting point at which PM production has stagnated. Cultivations under aerobic and microaerobic conditions were performed in bioreactors, whereas phototrophic cultures were grown in pyrex bottles. At top of graph, values indicate PM levels at harvest. PM value of 1.2 represents maximum PM levels and a value of 0.54 indicates a complete lack of PM formation.