The epothilone production levels in the mixed cultures (a) and statistical analysis of the relative increases in epothilone production (b). The relative increase (triangles connected by a solid line) was calculated as the ratio of the increased epothilone production in a mixed culture to epothilone production in the respective pure-culture control. The error bars represent the standard deviations. The productions of epothilones from the two individual cultures combined were taken as the pure-culture controls. The relative increases and the numbers of pairings in the corresponding range are displayed in (b). Std. Dev., standard deviation.