The biodiscovery potential of marine bacteria: an investigation of phylogeny and function

A collection of marine bacteria isolated from a temperate coastal zone has been screened in a programme of biodiscovery. A total of 34 enzymes with biotechnological potential were screened in 374 isolates of marine bacteria. Only two enzymes were found in all isolates while the majority of enzyme activities were present in a smaller proportion of the isolates. A cluster analysis demonstrated no significant correlation between taxonomy and enzyme function. However, there was evidence of co-occurrence of some enzyme activity in the same isolate. In this study marine Proteobacteria had a higher complement of enzymes with biodiscovery potential than Actinobacteria; this contrasts with the terrestrial environment where the Actinobacteria phylum is a proven source of enzymes with important industrial applications. In addition, a number of novel enzyme functions were more abundant in this marine culture collection than would be expected on the basis of knowledge from terrestrial bacteria. There is a strong case for future investigation of marine bacteria as a source for biodiscovery.

Effect of elevated CO2 on the dynamics of particle-attached and free-living bacterioplankton communities in an Arctic fjord

In the frame of the European Project on Ocean Acidification (EPOCA), the response of an Arctic pelagic community (<3 mm) to a gradient of seawater pCO(2) was investigated. For this purpose 9 large-scale in situ mesocosms were deployed in Kongsfjorden, Svalbard (78 degrees 56.2' N, 11 degrees 53.6' E), in 2010. The present study investigates effects on the communities of particle-attached (PA; >3 mu m) and free-living (FL; <3 mu m > 0.2 mu m) bacteria by Automated Ribosomal Intergenic Spacer Analysis (ARISA) in 6 of the mesocosms, ranging from 185 to 1050 mu atm initial pCO(2), and the surrounding fjord. ARISA was able to resolve, on average, 27 bacterial band classes per sample and allowed for a detailed investigation of the explicit richness and diversity. Both, the PA and the FL bacterioplankton community exhibited a strong temporal development, which was driven mainly by temperature and phytoplankton development. In response to the breakdown of a picophytoplankton bloom, numbers of ARISA band classes in the PA community were reduced at low and medium CO2 (similar to 185-685 mu atm) by about 25 %, while they were more or less stable at high CO2 (similar to 820-1050 mu atm). We hypothesise that enhanced viral lysis and enhanced availability of organic substrates at high CO2 resulted in a more diverse PA bacterial community in the post-bloom phase. Despite lower cell numbers and extracellular enzyme activities in the post-bloom phase, bacterial protein production was enhanced in high CO2 mesocosms, suggesting a positive effect of community richness on this function and on carbon cycling by bacteria.

Consistent increase in dimethyl sulphide (DMS) in response to high CO2 in five shipboard bioassays from contrasting NW European waters

The ubiquitous marine trace gas dimethyl sulphide (DMS) comprises the greatest natural source of sulphur to the atmosphere and is a key player in atmospheric chemistry and climate. We explore the short term response of DMS and its algal precursor dimethyl sulphoniopropionate (DMSP) production and cycling to elevated carbon dioxide (CO2) and ocean acidification (OA) in five highly replicated 96 h shipboard bioassay experiments from contrasting sites in NW European shelf waters. In general, the response to OA throughout this region showed little variation, despite encompassing a range of biological and biogeochemical conditions. We observed consistent and marked increases in DMS concentrations relative to ambient controls, and decreases in DMSP concentrations. Quantification of rates of specific DMSP synthesis by phytoplankton and bacterial DMS gross production/consumption suggest algal processes dominated the CO2 response, likely due to a physiological response manifested as increases in direct cellular exudation of DMS and/or DMSP lyase enzyme activities. The variables and rates we report increase our understanding of the processes behind the response to OA. This could provide the opportunity to improve upon mesocosm-derived empirical modelling relationships, and move towards a mechanistic approach for predicting future DMS concentrations.

Towards the Industrial Production of Omega-3 Long Chain Polyunsaturated Fatty Acids from a Genetically Modified Diatom Phaeodactylum tricornutum.

The marine diatom Phaeodactylum tricornutum can accumulate up to 30% of the omega-3 long chain polyunsaturated fatty acid (LC-PUFA) eicosapentaenoic acid (EPA) and, as such, is considered a good source for the industrial production of EPA. However, P. tricornutum does not naturally accumulate significant levels of the more valuable omega-3 LC-PUFA docosahexaenoic acid (DHA). Previously, we have engineered P. tricornutum to accumulate elevated levels of DHA and docosapentaenoic acid (DPA) by overexpressing heterologous genes encoding enzyme activities of the LC-PUFA biosynthetic pathway. Here, the transgenic strain Pt_Elo5 has been investigated for the scalable production of EPA and DHA. Studies have been performed at the laboratory scale on the cultures growing in up to 1 L flasks a 3.5 L bubble column, a 550 L closed photobioreactor and a 1250 L raceway pond with artificial illumination. Detailed studies were carried out on the effect of different media, carbon sources and illumination on omega-3 LC-PUFAs production by transgenic strain Pt_Elo5 and wild type P. tricornutum grown in 3.5 L bubble columns. The highest content of DHA (7.5% of total fatty acids, TFA) in transgenic strain was achieved in cultures grown in seawater salts, Instant Ocean (IO), supplemented with F/2 nutrients (F2N) under continuous light. After identifying the optimal conditions for omega-3 LC-PUFA accumulation in the small-scale experiments we compared EPA and DHA levels of the transgenic strain grown in a larger fence-style tubular photobioreactor and a raceway pond. We observed a significant production of DHA over EPA, generating an EPA/DPA/DHA profile of 8.7%/4.5%/12.3% of TFA in cells grown in a photobioreactor, equivalent to 6.4 μg/mg dry weight DHA in a mid-exponentially growing algal culture. Omega-3 LC-PUFAs production in a raceway pond at ambient temperature but supplemented with artificial illumination (110 μmol photons m-2s-1) on a 16:8h light:dark cycle, in natural seawater and F/2 nutrients was 24.8% EPA and 10.3% DHA. Transgenic strain grown in RP produced the highest levels of EPA (12.8%) incorporated in neutral lipids. However, the highest partitioning of DHA in neutral lipids was observed in cultures grown in PBR (7.1%). Our results clearly demonstrate the potential for the development of the transgenic Pt_Elo5 as a platform for the commercial production of EPA and DHA.