Propionibacterium microaerophilum sp nov., a microaerophilic bacterium isolated from olive mill wastewater

A new Gram-positive, facultative anaerobic, microaerophilic bacterium, desi gnated strain M5(T), was isolated from a decantation reservoir of olive mil l wastewater. The cells were rod-shaped, non-motile, non-spore-forming and catalase-negative, Growth occurred at ph ranging from 4.5 to 9.5, with opti mum growth at 7.0. The optimum temperature for growth was around 30 degrees C. Although growth occurred under anaerobic and aerobic conditions, the opt imum O-2 concentration for growth was determined as 5% in the gas phase of the culture. During anaerobic growth, glucose or lactate were mainly fermen ted to propionate, acetate and CO2, In the presence of O-2 (more than 2%). glucose was oxidized completely to CO2, The G+C content of the DNA was 67.7 +/-0.6 mol% and 16S rRNA gene analysis revealed that the new isolate belon ged to the cluster of 'dairy' propionibacteria, Propionibacterium acidiprop ionici being its closest phylogenic relative (97.5% similarity), However, t he level of DNA relatedness between strain M5T and P. acidipropionici was 5 6.2%, Consequently, both the phenotypic (range of substrates used) and geno typic characteristics of strain M5(T) allow it to be assigned as a new spec ies of the genus Propionibacterium, Propionibacterium microaerophilum sp, n ov. The type strain is strain M5T(= CNCM 1-2360(T) = DSM 13435(T).