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Chapter 12 : Isolation, Cultivation, and Diversity of Deep-Sea Piezophiles
Category: Applied and Industrial Microbiology
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This chapter focuses on the isolation, taxonomy, and diversity of piezophilic microorganisms and their habitats. Based upon several studies the authors have indicated that cultivated psychrophilic and piezophilic deep-sea bacteria could be affiliated with one of five genera within the Gammaproteobacteria subgroup: Shewanella, Photobacterium, Colwellia, Moritella, and Psychromonas, which was formally classified as ‘’an unidentified genus’’. The chapter describes taxonomic features of the piezophilic genera. For handling piezophiles for further study, JAMSTEC developed a deep-sea baropiezophile and thermophile isolation and cultivation system, referred to as the DEEPBATH system. The DEEPBATH system consists of four separate devices: (1) a pressure-retaining sampling device, (2) a dilution device under pressure conditions, (3) an isolation device, and (4) a cultivation device. From the analyses of 16S rRNA gene sequences after cultivation at 65 MPa, two groups of the bacterial genera Shewanella and Moritella were identified. The authors have analyzed the microbial community structures by the terminal restriction fragment length polymorphism for the bacterial 16S rRNA gene and determined that the community is drastically changed at different pressure conditions of cultivation using the DEEPBATH system. Piezophiles are characterized by high levels of unsaturated fatty acids in their cell membrane layers, but long-chain polyunsaturated fatty acid (PUFA) like EPA and DHA are not necessarily required for high-pressure growth. The diversity of piezophilic bacteria is closely linked with the global deep-sea ocean circulation, but some of the closed oceans, like the Japan Sea, also contain piezophilic bacteria taxonomically similar to deep-sea microbes in the open oceans.
Key Concept Ranking
- Restriction Fragment Length Polymorphism
Characterization of piezophilic growth properties.
Phylogenetic tree showing the relationships between isolated deep-sea piezophilic bacteria (in bold) within the Gammaproteobacteria subgroup determined by comparing 16S rRNA gene sequences using the neighbor-joining method (references for species description are indicated in the text). The scale represents the average number of nucleotide substitutions per site. Bootstrap values (percent) are shown for frequencies above the threshold of 50%.
The DEEPBATH system. The system is composed of four devices: (1) a pressure-retaining sampling device, (2) a dilution device under pressure conditions, (3) an isolation device, and (4) a cultivation device. The system is controlled by the monitoring and control console.
Changes in major fatty acid profiles during five consecutive high-pressure cultivations (65 MPa) of deep-sea sediment samples using the DEEPBATH system.
Phylogenetic tree showing the relationships of the Shewanella species within the Gammaproteobacteria subgroup constructed based on 16S rRNA gene sequences with the neighbor-joining method. The scale represents the average number of nucleotide substitutions per site. Bootstrap values (percent) were calculated from 1,000 trees. Psychrophilic and/or piezophilic bacteria are shown in bold.
The deep ocean circulation (data from reference 44 ). The Japan Sea, a closed ocean, is indicated by the star.
Growth profiles of the isolated bacteria from the Japan Sea sediment under different pressure conditions.
Whole-cell fatty acid composition of piezophilic isolates (type strains) a