| Ocean is a complex but important ecosystem, and its vast sea area breed a large number of marine organisms. With this ecosystem, marine microorganism which play the multiple roles as producer, consumer and decomposer is the most significant part. Meanwhile, the special and changeable marine environment also creates the colourful marine microorganism and their varied functions. In which, brown seaweed degrading bacteria, because of the good application potential of brown seaweed, become more important than other marine microorganism. The aim of this work is to isolate and characterize the brown seaweed degrading bacteria, optimize its fermentation conditions and analyse its degradation mechanism with genome sequence. With this work, the in-depth study of brown seaweed and brown seaweed degrading bacteria will be easier to proceed.Firstly, we have collected six samples with different types and sources, and isolated brown seaweed degrading bacteria from them. As a result,39 bacterial strains within 29 different genus (with 4 suspected novel species) was isolated. Then, we have detected the degrading ability of these strains, and found that 16 strains have the ability to degrade brown seaweed. With these results, we have come to the conclusion that samples from sea area with high ratio of brown seaweed and targeted isolation method will be conducive to the isolation of brown seaweed degrading bacteria.Secondly, with the method of polyphasic taxonomy method, one novel genus (Pseudoroseovarius gen. nov.) and two novel species (Thalassomonas eurytherma sp. nov. and Algibacter alginolytica sp. nov.) was proposed. In which, Algibacter alginolytica sp. nov. HZ22T is the brown seaweed degrading bacterium. Meanwhile, three species in genus Roseovarius (Roseovarius crassostreae, Roseovarius sediminilitoris and Roseovarius halocynthiae) was reclassified to novel genus Pseudoroseovarius.Thirdly, Microbulbifer elongates strain HZ11, a brown seaweed degrading bacterium with preferable degrading ability, was used as the type strain to study the industrial fermentation condition for large scale production of oligo-alginate. We have compared different methods for its fermentation, optimized its fermentation conditions and characterized its crude enzymes. As a result, the industrial fermentation condition for large scale production of oligo-alginate using strain HZ 11 was proposed and testified with 5 L small scale fermentation cylinder.Fourthly, Microbulbifer elongates strain HZ 11 was subjected to genome sequencing and analysis. The high quality draft genome of strain HZ 11 consisted with 9 contig. The COG and KEGG analysis was processed and the result shows that strain HZ 11 have a preferance of polysaccharides as a result of large ratio of carbohydrate specific enzyme. The analysis of carbohydrate-active enzymes (CAZyme) obtains the classification of CAZyme family and the related predicted substrates. The metabolism pathway from major fermentable substrates (alginate, laminarin and mannitol) in brown seaweed to ethanol in strain HZ 11 was predicted, and the results reveals that strain HZ11 has the potential ability to produce ethanol from alginate.Finally, we have sequenced the genome of Algibacter alginolytica HZ22T and analysed its degradation mechanism of brown seaweed. The genome of strain HZ22T harbors 3,371 CDSs and 255 CAZymes, which appears the highest level (-7.5%) in the ratio of CAZymes among the reported strains in Flavobacteria. The location in genome, family classification and related substrates of all CAZymes was predicted.17 polysaccharide utilization loci (PUL) was predicted to be specific for marine polysaccharides especially algal polysaccharides from red, green and brown seaweeds. The transfer and regulate systems in PUL were predicted and analysed. Particularly, PUL N and PUL Q were predicted to be specific for alginate and the structure and connection of these two PUL was analysed. |
PDF Full Text Request