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

M Koussemon, Y Combet-Blanc, BKC Patel, JL Cayol, P Thomas, JL Garcia and B Ollivier Laboratoire de microbiologie IRD,IFR-BAIM, Universites de Provence et de la Mediterranee, ESIL case 925, 13288 Marseille Cedex 9, France A new Gram-positive, facultative anaerobic, microaerophilic bacterium, designated strain M5(T), was isolated from a decantation reservoir of olive mill 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 optimum growth at 7.0. The optimum temperature for growth was around 30 degrees C. Although growth occurred under anaerobic and aerobic conditions, the optimum O(2) concentration for growth was determined as 5% in the gas phase of the culture. During anaerobic growth, glucose or lactate were mainly fermented to propionate, acetate and CO(2). In the presence of O(2) (more than 2%), glucose was oxidized completely to CO(2). The G+C content of the DNA was 67.7+/-0.6 mol% and 16S rRNA gene analysis revealed that the new isolate belonged to the cluster of 'dairy' propionibacteria, Propionibacterium acidipropionici being its closest phylogenic relative (97.5% similarity). However, the level of DNA relatedness between strain M5(T) and P. acidipropionici was 56.2%. Consequently, both the phenotypic (range of substrates used) and genotypic characteristics of strain M5(T) allow it to be assigned as a new species of the genus Propionibacterium, Propionibacterium microaerophilum sp. nov. The type strain is strain M5(T) (=CNCM I-2360(T)=DSM 13435(T)).