Microbial diversity in four Mediterranean irciniid sponges.

This paper describes a dataset of microbial communities from four different sponge species: Irciniaoros (Schmidt, 1864), Irciniavariabilis (Schmidt, 1862), Sarcotragusspinosulus Schmidt, 1862 and Sarcotragusfasciculatus (Pallas, 1766). The examined sponges all belong to Demospongiae (Class); Keratosa (Subclass); Dictyoceratida (Order); Irciniidae (Family). Samples were collected by scuba diving at depths between 6-14 m from two sampling sites of rocky formations at the northern coast of Crete (Cretan Sea, eastern Mediterranean) and were subjected to metabarcoding for the V5-V6 region of the 16S rRNA gene.

A polyphasic taxonomic approach in isolated strains of Cyanobacteria from thermal springs of Greece.

Strains of Cyanobacteria isolated from mats of 9 thermal springs of Greece have been studied for their taxonomic evaluation. A polyphasic taxonomic approach was employed which included: morphological observations by light microscopy and scanning electron microscopy, maximum parsimony, maximum likelihood and Bayesian analysis of 16S rDNA sequences, secondary structural comparisons of 16S-23S rRNA Internal Transcribed Spacer sequences, and finally environmental data. The 17 cyanobacterial isolates formed a diverse group that contained filamentous, coccoid and heterocytous strains. These included representatives of the polyphyletic genera of Synechococcus and Phormidium, and the orders Oscillatoriales, Spirulinales, Chroococcales and Nostocales. After analysis, at least 6 new taxa at the genus level provide new evidence in the taxonomy of Cyanobacteria and highlight the abundant diversity of thermal spring environments with many potential endemic species or ecotypes.

Bioactive polar lipids from Chroococcidiopsis sp. (Cyanobacteria).

Many studies indicate that various bioactive metabolites subsist in cyanobacteria. Glycolipids of cyanobacteria are reported as molecules that exert specific bioactivities. In this study, total lipids of Chroococcidiopsissp., a coccoid cyanobacterium isolated from a Greek cave, were separated into neutral and polar-lipids and the latter were further fractionated by high-performance liquid chromatography (HPLC). Each polar lipid fraction was tested in vitro for its ability to inhibit platelet-activating factor (PAF)- and thrombin-induced washed rabbit platelet aggregation and/or to cause platelet aggregation. The structures of the most active fractions were elucidated by biological assays and identified by electrospray mass spectrometry. One fraction was a potent inhibitor of PAF-induced platelet aggregation. Structural studies of this fraction indicated the existence of phospho-glyco analog of ceramide. Another fraction that was a potent inhibitor of PAF- as well as of thrombin-induced platelet aggregation was structurally elucidated as a phospho-acetylated glyco-analog of diglyceride. The fraction that induced platelet aggregation was identified as a phospho-acetylated-glyco analog of ceramide. These novel bioactive polar lipids in cyanobacteria in regard to the structure and biological activity may contribute to the allergic character of cyanobacteria.

Characterization of bioactive glycolipids from Scytonema julianum (cyanobacteria).

Cyanobacteria serve as a rich source of novel bioactive metabolites. Few studies on glycolipids reported them as having specific biological activities. In this study, total lipids of Scytonema julianum, a filamentous cyanobacterium isolated from a Greek cave, were separated into neutral and phospho- and glycolipids, and the latter were further fractionated by high-performance liquid chromatography (HPLC). Each glycolipid fraction was tested in vitro for its ability to inhibit platelet-activating factor (PAF)- and thrombin-induced washed rabbit platelet aggregation and/or to cause platelet aggregation. The structures of the most active fractions were elucidated by biological assays, by chemical determinations and identified by electrospray mass spectrometry. One fraction was a potent inhibitor of PAF-induced platelet aggregation. Structural studies of this fraction indicated the existence of a phosphoglyco-analog of acyl-sphingosine. Two fractions causing platelet aggregation were detected and identified as phosphoglycolipids. The first one was identified as a phosphoglyco-analog of acyl-acetylated sphingosine and the second one as a glyco-analog of phosphatidylglycerol. The presence of the above bioactive compounds demonstrates new types of lipids in cyanobacteria in regard to the structure and biological activity. In addition, the identified bioactive lipids may contribute to the allergic character of cyanobacteria.

Isolation and structural elucidation of biologically active phospholipids from Scytonema julianum (cyanobacteria).

The role of platelet-activating factor (PAF) as a mediator appeared in rather primitive organisms like protozoans and was maintained in more evolved organisms. No reports exist for the presence of PAF or PAF analogues - or even compounds that exhibit PAF-like activity - in cyanobacteria, even though they belong to a a group of organisms at a low evolutionary level where the content of alkylacyl forms of ether lipids is expected to be high. In addition, cyanobacteria serve as a rich source of novel bioactive metabolites. In the present study the total lipids of a strain of Scytonema julianum, a filamentous cyanobacterium isolated from a Greek cave, were separated into neutral lipids and phospholipids, the latter being further fractionated by HPLC. Each phospholipid fraction was tested in vitro for its ability to inhibit PAF-, arachidonic acid- and ADP-induced washed-rabbit-platelet aggregation and/or to cause platelet aggregation. Two types of phospholipids causing platelet aggregation were detected and shown to be an acetylsphingomyelin and an acylacetylglycerol phosphoacetylated glycolipid. The existence of the sphingomyelin analogues is very important, since ceramides, cerebrosides and related lipids are intracellular second messengers. The identification of the phosphoglycoglycerolipid demonstrates a new type of lipid in cyanobacteria, namely one that exhibits a biological activity very similar to that of PAF. Its presence reinforces the concept that PAF is a member of a large family of lipid mediators, apparently having different physiological roles in prokaryotic and eukaryotic organisms. In addition, Scytonema julianum contains a phosphatidylcholine (C(16:0)/(18:2)), even though bacteria in general seldom contain choline-containing phosphoacylglycerols.