Heike Irmgard Baumann

Widespread Occurrence of Two Carbon Fixation Pathways in Tubeworm Endosymbionts: Lessons from Hydrothermal Vent Associated Tubeworms from the Mediterranean Sea

Vestimentiferan tubeworms (siboglinid polychetes) of the genus Lamellibrachia are common members of cold seep faunal communities and have also been found at sedimented hydrothermal vent sites in the Pacific. As they lack a digestive system, they are nourished by chemoautotrophic bacterial endosymbionts growing in a specialized tissue called the trophosome. Here we present the results of investigations of tubeworms and endosymbionts from a shallow hydrothermal vent field in the Western Mediterranean Sea. The tubeworms, which are the first reported vent-associated tubeworms outside the Pacific, are identified as Lamellibrachia anaximandri using mitochondrial ribosomal and cytochrome oxidase I (COI) gene sequences. They harbor a single gammaproteobacterial endosymbiont. Carbon isotopic data, as well as the analysis of genes involved in carbon and sulfur metabolism indicate a sulfide-oxidizing chemoautotrophic endosymbiont. The detection of a hydrogenase gene fragment suggests the potential for hydrogen oxidation as alternative energy source. Surprisingly, the endosymbiont harbors genes for two different carbon fixation pathways, the Calvin-Benson-Bassham (CBB) cycle as well as the reductive tricarboxylic acid (rTCA) cycle, as has been reported for the endosymbiont of the vent tubeworm Riftia pachyptila. In addition to RubisCO genes we detected ATP citrate lyase (ACL – the key enzyme of the rTCA cycle) type II gene sequences using newly designed primer sets. Comparative investigations with additional tubeworm species (Lamellibrachia luymesi, Lamellibrachia sp. 1, Lamellibrachia sp. 2, Escarpia laminata, Seepiophila jonesi) from multiple cold seep sites in the Gulf of Mexico revealed the presence of acl genes in these species as well. Thus, our study suggests that the presence of two different carbon fixation pathways, the CBB cycle and the rTCA cycle, is not restricted to the Riftia endosymbiont, but rather might be common in vestimentiferan tubeworm endosymbionts, regardless of the habitat.

Genome Sequence of Bacillus subtilis subsp. spizizenii gtP20b, Isolated from the Indian Ocean

Bacillus subtilis is an aerobic spore-forming Gram-positive bacterium that is a model organism and of great industrial significance as the source of diverse novel functional molecules. Here we present, to our knowledge, the first genome sequence of Bacillus subtilis strain gtP20b isolated from the marine environment. A subset of candidate genes and gene clusters were identified, which are potentially involved in production of diverse functional molecules, like novel ribosomal and nonribosomal antimicrobial peptides. The genome sequence described in this paper is due to its high strain specificity of great importance for basic as well as applied researches on marine organisms.

Draft Genome Sequence of the Marine Streptomyces sp. Strain PP-C42, Isolated from the Baltic Sea

Streptomyces, a branch of aerobic Gram-positive bacteria, represents the largest genus of actinobacteria. The streptomycetes are characterized by a complex secondary metabolism and produce over two-thirds of the clinically used natural antibiotics today. Here we report the draft genome sequence of a Streptomyces strain, PP-C42, isolated from the marine environment. A subset of unique genes and gene clusters for diverse secondary metabolites as well as antimicrobial peptides could be identified from the genome, showing great promise as a source for novel bioactive compounds.

Champacyclin, a New Cyclic Octapeptide from Streptomyces Strain C42 Isolated from the Baltic Sea

New isolates of Streptomyces champavatii were isolated from marine sediments of the Gotland Deep (Baltic Sea), from the Urania Basin (Eastern Mediterranean), and from the Kiel Bight (Baltic Sea). The isolates produced several oligopeptidic secondary metabolites, including the new octapeptide champacyclin (1a) present in all three strains. Herein, we report on the isolation, structure elucidation and determination of the absolute stereochemistry of this isoleucine/leucine (Ile/Leu = Xle) rich cyclic octapeptide champacyclin (1a). As 2D nuclear magnetic resonance (NMR) spectroscopy could not fully resolve the structure of (1a), additional information on sequence and configuration of stereocenters were obtained by a combination of multi stage mass spectrometry (MSn) studies, amino acid analysis, partial hydrolysis and subsequent enantiomer analytics with gas chromatography positive chmical ionization/electron impact mass spectrometry (GC-PCI/EI-MS) supported by comparison to reference dipeptides. Proof of the head-to-tail cyclization of (1a) was accomplished by solid phase peptide synthesis (SPPS) compared to an alternatively side chain cyclized derivative (2). Champacyclin (1a) is likely synthesized by a non-ribosomal peptide synthetase (NRPS), because of its high content of (d)-amino acids. The compound (1a) showed antimicrobial activity against the phytopathogen Erwinia amylovora causing the fire blight disease of certain plants.

Strong differences in the efficiency of digestive protease inhibitors of the cyanobacterium Planktothrix rubescens

The uptake of amino acids is essential for maintenance and growth of crustaceans and any other grazer. Amino acids serve as carbon (C) and nitrogen (N) sources, and some are essential because they cannot be synthesised by animals. The majority of arnino acids in food particles is bound in proteins that have to be cleaved by hydrolytic reactions to yield arnino acids or small peptides. Only these smaller units can be taken up easily by the epithelium o f the gut. Proteases liberated into the lumen o f the gut are responsible for the cleavage reactions. Trypsinand chymotrypsin-like serine proteases recently have been shown to be o f particular importance in the digestive processes of Daphnia (VoN ELERT et al. 2004). Cyanobacteria, in particular (PORTER 1973), are regarded as poor quality food due to their sizeand form-related constraints on ingestion as well as their potential toxicity (DEMOTT et al. 1991, BLOM et al. 2003) and nutritional inadequacy, as a result of the laek of polyunsaturated fatty acids (AHLGREN et al. 1990) and sterols (VoN ELERT et al. 2002). Diatoms and flagellates are generally considered as good quality food because o f their high eicosapentaenoic acid (EPA) and corresponding high phosphorus (P) content in contrast to the cyanobacteria, which are low quality food organisms, having both low EPA and P content (GULATI & DEMorr 1997). Another reason for the low food quality of cyanobacteria may be their production of serine protease inhibitors. Since their first description (OKINO et al. 1993), numerous other cyclic peptides and depsipeptides, which are efficient inhibitors of either trypsin or chymotrypsin, have been found in planktonic cyanobacteria. It can be hypothesised that ingested cyanobacterial filarnents are partially digested in the gut of the grazers, releasing the intracellular protease inhibitors that prevent the cleavage of proteins. As a result, the grazers become deficient in essential and nonessential arnino acids. In this study, protease inhibitors (PI) isolated from two strains of Planktothrix rubescens were tested against digestive trypsin-like proteases (TLP) isolated from crustaceans, collected from four Swiss lakes, that showed differences in the presence of Planktothrix rubescens. The goa! was to test whether the crustaceans of the different lakes would adapt their digestive proteases to the Planktothrix rubescens-derived inhibitors. Lakes Greifensee and Pfáffikersee are almost free of cyanobacterial populations while Lake Zürichsee exhibits a summer and auturnnal population of P. rubescens that can be stratified in the metalimnion for months. Lake Hallwilersee is a eutrophic, artificially oxygenated lake that develops extremely dense populations of P. rubescens throughout the year and exhibits extensive surface scums of this cyanobacterium in early surnmer.