Nunzio Penna

Effect of heat stress on polyamine content and protein pattern in Skeletonema costatum

In the present paper we investigated the polyamine content and protein expression pattern in laboratory-reared Skeletonema costatum (Grev.) Cleve under temperature stress conditions. Putrescine, spermidine and to a lesser extent spermine were present in this alga. Free putrescine and spermidine increased after heat shock while a concomitant decrease in trichloroacetic acid (TCA)-soluble bound putrescine and spermidine occurred. After 40 min of 30 °C stress both were no longer detectable, whereas TCA-soluble bound spermine was present. The appearance of 83, 42, 40.7 and 35 kDa polypeptides was observed when S. costatum cells were subjected to heat treatment. Western blotting experiments revealed the presence in this diatom of ubiquitin and ubiquitin conjugates. Heat stress strongly increased the number of ubiquitin conjugate polypeptides of high molecular weight. No variation in the carbohydrate content was observed in response to stress. A possible role for these different metabolic events in the adaptive response of S. costatum to rapid temperature shifts has been hypothesized.

Mucilaginous masses in the Adriatic sea in the summer of 1989

Abstract This paper reports on one of the most recent episodes of mucilage formation in the central–northern part of the Adriatic coast in July–August 1989. The stretch of coast examined goes from the estuary of the River Po to the border of the Marche–Abruzzo coast (Italy). The possible events (nutrients, N/P ratio, particular climatic conditions) that cause the formation of the mucilage masses were examined and are discussed here. Furthermore, the oxygenation state of the water on the surface and on the bottom as well as the possible effects on molluscs were also examined. The field results indicated that no anoxia phenomena were found in bottom waters caused by mucilages, and that mollusc death was probably due to mechanical reasons. Finally the places where the mucillages formed and their subsequent movements are described.

Study on the maltooligosaccharide composition of mucilage samples collected along the northern Adriatic coast

The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause serious damage to the tourism and fishing industries along the Adriatic coast. Mucilage is presently thought to be the result of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). Three principal classes of compounds have been identified in organic matter by spectrometric determination: carbohydrates, proteins and lipids. Carbohydrates are suspected to play a role in the first steps of DOM aggregation. Despite its importance in understanding the processes leading to mucilage formation, our present knowledge of the composition of the mucilage carbohydrate fraction is incomplete. Due to its high sensitivity and specificity, liquid chromatography coupled with electrospray-ionization tandem mass spectrometry (LC-ESIMS/MS) is gaining an increasing importance as a powerful technique for carbohydrate purification and characterization in complex samples. In this work, LC-ESIMS/MS is proposed as a useful method for the investigation of the oligosaccharide content in mucilage samples. The approach was applied using 3-7 unit maltooligosaccharides as reference compounds. The composition of the investigated mucilage sample was further investigated combining LC-ESIMS/MS with classic approaches, such as spectroscopic techniques and liquid chromatography coupled with the refractory index LC-RI.

Potential environmental factors influencing mucilage formation in the northern Adriatic Sea

In the northern Adriatic Sea, Mediterranean Sea, the mucilage phenomenon is usually related to the aggregation of extracellular organic matter of phytoplanktonic origin under special seasonal and trophic conditions. Environmental factors, such as temperature, salinity, nitrogen, phosphorus and N/P ratio as well as polysaccharide and monosaccharide levels in the presence and absence of mucilage were investigated in the northern Adriatic Sea. Variations in temperature and salinity during spring in years characterised by mucilage events have been recognised having an important role in preparing a favourable physical environment where mucilage formation could take place. Since the DIN/TP ratio increased markedly during the spring months (March–April) in 2002, 2003 and 2004, preceding the early summer mucilage outbreaks, it appeared that the DIN/TP ratio may be a more robust predictor than the DIN/DIP ratio, which, although more commonly used, exhibited a discontinuous trend. The contents of total carbohydrates, including monosaccharides and polysaccharides, in seawater also varied according to the presence or absence of mucilage, with an increase of polysaccharide levels during the late spring or early summer in the period of the mucilage appearance. The role of carbohydrates in the macro-aggregate formation was also investigated.