No abstract

We have isolated thirteen different bacterial strains as poly -caprolactone (PCL)-degrading bacteria from the Kurile and Japan Trenches at a depth of 5,000-7,000 m (deeper ocean bottoms). The isolates belong to the Shewanella, Moritella, Psychrobacter and Pseudomonas genera. This is the first record of PCL degrading bacteria isolated from deep-sea environments at depth of over 5,000 m. Six strains of the isolates, numbered CT01 in genus Shewanella, CT12, JT01 and JT04 in genus Moritella, JT05 in genus Psychrobacter, and JT08 in genus Pseudomonas were selected for investigation of their cell shapes, degrading abilities for several aliphatic polyesters, and growth profiles. The cell shapes of the strains, except JT05, were rod-shaped, non-spore-forming and motile by means of a single or multi polar flagella. The cell shapes of JT05 were coccal with no visible flagella. From the results of degradation tests on six different alihphatic polyesters, all strains could degrade only PCL. Strains CT01, CT12, JT01 and JT04 are psychrophilic and pressure tolerant bacteria and three strains except JT04 showed typical piezophilic growth profiles. Therefore, it is possible that these strains might play a role in degrading aliphatic polyesters under deep-sea conditions, ie., low-temperatures and high hydrostatic pressures.

The demand for n-3 long-chain polyunsaturated fatty acids (n-3LC-PUFAs), such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), will exceed their supply in the near future, and a sustainable source of n-3LC-PUFAs is needed. Thraustochytrids are marine protists characterized by anaerobic biosynthesis of DHA via polyunsaturated fatty acid synthase (PUFA-S). Analysis of a homemade draft genome database suggested that Parietichytrium sp. lacks PUFA-S but possesses all fatty acid elongase (ELO) and desaturase (DES) genes required for DHA synthesis. The reverse genetic approach and a tracing experiment using stable isotope-labeled fatty acids revealed that the ELO/DES pathway is the only DHA synthesis pathway in Parietichytrium sp. Disruption of the C20 fatty acid ELO (C20ELO) and ∆4 fatty acid DES (∆4DES) genes with expression of ω3 fatty acid DES in this thraustochytrid allowed the production of EPA and n-3docosapentaenoic acid (n-3DPA), respectively, at the highest level among known microbial sources using fed-batch culture.

Biodegradabilities of aliphatic polyesterˆbers and naturalˆbers were evaluated in deep sea water at the depth of about 2000 m oŠshore of Tottori Prefecture and deep sea water pumped up from the depth of 321 m at 2600 m oŠshore in Toyama bay. The breaking strengths of all soakedˆbers decreased considerably in one year.On the surfaces of the soakedˆbers, hollows engraved by biodegradation were observed. These results conˆrm that biodegradation takes place in the deep sea and in deep ocean water. Two kinds of PCL-degrading bacteria were isolated from the deep sea water. The phylogenetic analysis using the 16S rRNA gene sequence revealed that these strains belong to the Pseudomonas genus. The isolated bacteria showed growth and PCL degradation activity under low-temperature conditions.