Comparative Studies of the Growth of Pyrococcus furiosus and P. abyssi in Continuous Culture
Richard J. SHARPa, Neil RAVENa, and Anne GODFROYb
a Research Division, Centre for Applied Microbiology and Research, Porton Down Salisbury, SP4 OJG United Kingdom
b IFREMER, Centre de Brest, Plouzane, Brest, France
A gas lift bio-reactor (1) has been used to compare the growth characteristics of P furiosus (2) and P abyssi strain ST549 (3) in continuous culture. A range of organisms has been ascribed to the genus Pyrococcus based primarily on a limited range of physiological properties and the sequencing of their 16S rRNA. Amongst these, are organisms isolated from deep sea hydrothermal vents and assigned to the new species Pyrococcus abyssi (4). Their DNA differs significantly in %G+C and shows minimal hybridisation to the DNA of Pyrococcus furiosus. Despite clear differences at the nucleic acid level, the organisms appear morphologically similar with very similar growth profiles. Minor differences include temperature and pH optima, when cultured in closed bottles at atmospheric pressure in the presence of elemental sulfur. This study compares some of the physiological properties of a Pyrococcus abyssi strain, ST549 and P furiosus in continuous culture.
Pyrococcus abyssi ST549 grows at high cell densities under nitrogen sparging in a gaslift bioreactor. Cultures were found to develop foaming at nitrogen sparging rates above 0.2 vvm whereas P. furiosus cultures did produce extensive foaming until 0.5 vvm. Foaming resulted in lower cell densities and/or the inability to sustain a steady- state. At 0.2 vvm, however, equilibrium cell densities for P. abyssi of approximately 2 x 109 m1-1 were maintained. Unlike Pyrococcus furiosus VC-1, which grows well on maltose (5), Pyrococcus abyssi ST549 appears not to utilise maltose supporting initial studies which indicate that Pyrococcus abyssi ST549 grows preferentially on proteinaceous substrates.
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5. Raven, N. and Sharp, R (1997) FEMS Microbiol. Lett., 146, 135-141.
