Publikationen

It is assumed that the biological characteristics of the bacterial strains used in bioactivity tests have strong influences on their susceptibility against antibacterial compounds. Therefore, the selection of bacterial test strains may rush conclusions on the effect of macroalgal extracts and metabolites on bacteria. To proof this assumption, we have analysed the biological activities of crude extracts of 16 macroalgae from the coastal waters of Kiel Fjord (Germany), and tested their effect against a panel of 10 microorganisms comprising 5 standard test strains of bacteria and 5 macroalga-associated bacteria. Fourteen macroalgae (88\%) displayed antibacterial activity against at least one of the test strains. Despite the high proportion of extracts exhibiting antimicrobial activity, only 3 strains of the standard set were susceptible to macroalgal extracts and the overall activities were low (less than 80\% of inhibition). Most of active extracts inhibited Bacillus subtilis, while no inhibition effects were found against Erwinia amylovora, Escherichia coli, and the macroalga-associated bacteria. In contrast, all extracts produced stimulatory growth effects of at least two of the tested bacteria. While growth stimulation of standard set of bacteria was rare (22.5\% of total tests) with exception of plant pathogen Erwinia amylovora and two cases of Staphylococcus lentus, it was common among bacteria associated with macroalgae (77.5\%), especially Bacillus algicola, Pseudomonas marincola and both algal-pathogenic bacteria. This study demonstrates that macroalgal extracts can display different effects, i.e., inhibition or stimulation of bacterial growth depending on the origin of the test strains, which are derived from a standard panel or from the marine environment, respectively.

This is the first description of a functional chitinase gene within the crenarchaeotes. Here we report of the heterologues expression of the ORF BAB65950 from Sulfolobus tokodaii in E. coli. The resulting protein degraded chitin and was hence classified as chitinase (EC 3.2.4.14). The protein characterization revealed a specific activity of 75 mU/mg using colloidal chitin as substrate. The optimal activity of the enzyme was measured at pH 2.5 and 70 ?C, respectively. A dimeric enzyme configuration is proposed. According to amino acid sequence similarities chitinases are attributed to the two glycoside hydrolase families 18 and 19. The derived amino acid sequence of the S. tokodaii gene differed from sequences of these two glycoside hydrolase families. However, within a phylogenetic tree of protein sequences, the crenarchaeal sequence of S. tokodaii clustered in close proximity to members of the glycoside hydrolase family 18.

The biological resources of the oceans have been exploited since ancient human history, mainly by catching fish and harvesting algae. Research on natural products with special emphasis on marine animals and also algae during the last decades of the 20th century has revealed the importance of marine organisms as producers of substances useful for the treatment of human diseases. Though a large number of bioactive substances have been identified, some many years ago, only recently the first drugs from the oceans were approved. Quite astonishingly, the immense diversity of microbes in the marine environments and their almost untouched capacity to produce natural products and therefore the importance of microbes for marine biotechnology was realized on a broad basis by the scientific communities only recently. This has strengthened worldwide research activities dealing with the exploration of marine microorganisms for biotechnological applications, which comprise the production of bioactive compounds for pharmaceutical use, as well as the development of other valuable products, such as enzymes, nutraceuticals and cosmetics. While the focus in these fields was mainly on marine bacteria, also marine fungi now receive growing attention. Although culture-dependent studies continue to provide interesting new chemical structures with biological activities at a high rate and represent highly promising approaches for the search of new drugs, exploration and use of genomic and metagenomic resources are considered to further increase this potential. Many efforts are made for the sustainable exploration of marine microbial resources. Large culture collections specifically of marine bacteria and marine fungi are available. Compound libraries of marine natural products, even of highly purified substances, were established. The expectations into the commercial exploitation of marine microbial resources has given rise to numerous institutions worldwide, basic research facilities as well as companies. In Europe, recent activities have initiated a dynamic development in marine biotechnology, though concentrated efforts on marine natural product research are rare. One of these activities is represented by the Kieler Wirkstoff-Zentrum KiWiZ, which was founded in 2005 in Kiel (Germany).