Black Smokers.....Isolation of two novel piezophiles.

A review of:
Ken Takai, Massayuki Miyazaki, Hisako Hirayama, Satoshi Nakagawa, Joel Querellou and Anne Godfroy. (2009). Isolation and physiological characterization of two novel, piezophilic, thermophilic chemolithoautotrophs from a deep-sea hydrothermal vent chimney.Environmental Microbiology. 11(8), 1983-1997.

In 1957 there was some pioneer research by Zobell and Morita on deep-sea piezophiles, since then there has been half a century of research yet still we are not fully aware of which microorganisms thrive in these deep sea vents. This is due to a number of reasons but typically when there have been samples collected at high expense these microorganisms cannot be cultured successfully. In this paper the authors have successfully cultivated and isolated two novel thermophilic piezophiles which are capable of chemolithoautotrophic growth from a black smoker chimney at the TAG field in the Mid-Atlantic Ridge.

The two strains (strains 106 and 108) were cultivated using a liquid serial dilution culture and a piezophilic cultivation technique. Liquid serial dilution cultures were made to estimate the abundance of culturable microorganisms (viable counts). Serial dilutions were carried out from the chimney sub samples under various cultivation conditions. The piezophilic cultivation techniques were where the enrichment and purification of the strains occurred after a 2 week incubation period. During the two week incubation period the strains were inoculated in test tubes containing MMJHS medium (1g of NaNO3, 1g of Na2S2O3 .5H2O, 1g of NaHCO3, 30g of elemental sulphur and 10ml of vitamin solution per litre of synthetic seawater. Takai et al. 2003) under a gas phase of 80% H2 + 20% CO2 (0.2 MPa) at 50°C. It must be noted that these were only two fragments from a very complex method where they also looked at the morphology, total direct cell counts, fluid chemistry, growth characteristics, energy and carbon sources, cellular fatty acid composition, nucleic acid analyses and whole-cell FISH analysis to help characterise each strain.

The results section describes the two strains morphological, physiological and metabolic properties. The authors found that strain 106 was a motile thin spiral that was 6-20µm long and 0.4-0.6µm wide with polar flagellum under piezophilic cultivation conditions but under conventional gas pressures were shorter, up to 4µm long. Strain 106 also uses reduced sulphur compounds as the electron donors, with nitrate and O2 as the electron acceptors. Cells of strain 108 were non-motile, short and oval, approximately 1-1.5µm long and 0.6-0.7µm wide with no flagellum observed. It is also a facultative chemoautotroph, capable of both chemolithoautotrophic growth with H2 and S oxidations and organotrophic growth with complex organics or organic acids using nitrate and O2 as the electron acceptors.

This paper was an interesting read with new methods in cultivation being utilised. The amount of methods used help to describe most of the characteristics of both strains and indeed required. The only criticism I would have is the order in which they displayed the paper with experimental methods being displayed after the results and discussion, I believe it would have made the results a little clearer when reading if you knew the exact methods they used before reading.

Additional reference: Takai et al., (2003) Isolation and phylogenetic diversity of members of previously uncultivated epsilon-Proteobacteria in deep-sea hydrothermal fields. FEMS Microbiol Lett. 218, 167-174