Olive-mill wastewater bacterial communities display a cultivar specific profile.

Culture-dependent and -independent approaches were employed to identify the bacterial community structure from olive-mill wastewater produced from three olive-fruit varieties. The 233 bacterial isolates recovered were phylogenetically related to 38 members of Firmicutes, Actinobacteria, α-Proteobacteria, β-Proteobacteria, γ-Proteobacteria, and Bacteroidetes. Employing a novel microarray-based approach (PhyloChip) a high bacterial diversity was revealed consisting of 18 different phyla with representatives from 99 different families. The bacterial diversity in olive-mill wastewater from the three olive tree varieties was dominated by α-, β-, γ-, δ-, ε-Proteobacteria, Firmicutes, Bacteroidetes, Chloroflexi, Cyanobacteria, and Actinobacteria. This in-depth analysis of the indigenous microbiota indicated a cultivar-specific bacterial profile. Interestingly, the common bacterial taxa present in all three varieties examined were restricted indicating that the bacterial communities present in the olive-mill wastewater are greatly influenced by the olive-fruit variety.