Marcella Pasqualetti

Planktothrix species are among the most widespread bloom-forming cyanobacteria in freshwater ecosystems and are of particular concern because of their ability to produce cyanotoxins and form persistent harmful algal blooms (HABs). Among them, Planktothrix agardhii and Planktothrix rubescens are the most extensively studied species and are responsible for a large proportion of bloom events reported in European lakes. This review synthesizes current knowledge on the taxonomy, ecophysiology, toxin production, environmental drivers, species interactions, and management of Planktothrix blooms, with a particular focus on European freshwater ecosystems. The available evidence highlights marked ecological differences between the two dominant species. P. agardhii is primarily associated with shallow, eutrophic, and well-mixed lakes, whereas P. rubescens is typically found in deep, stratified, and relatively transparent water bodies, where it forms persistent metalimnetic populations. These contrasting ecological strategies influence bloom development, toxin dynamics, detection, and management. Nutrient availability, light climate, temperature, water column stability, and biological interactions all contribute to bloom establishment and persistence, while climate change is expected to further modify bloom frequency, duration, and geographic distribution. The review also examines current monitoring and mitigation approaches, highlighting the limitations of conventional surface-based surveys for detecting deep P. rubescens populations and emphasizing the need for integrated monitoring strategies combining depth-resolved sampling, molecular tools, and toxin analyses. Overall, understanding the ecological and physiological diversity of Planktothrix species is essential for improving risk assessment, developing effective management measures, and mitigating the impacts of cyanobacterial blooms in European freshwaters.

In this study, seven Pleosporaceae strains isolated from the seagrass Posidonia oceanica and the jellyfish Pelagia noctiluca in the central Tyrrhenian Sea were characterized using a polyphasic approach (morpho-physiological, molecular, and phylogenetic analyses). Based on multi-locus phylogenetic inference and morphological characters, a new species, Tamaricicola fenicei sp. nov. was proposed. Multi-locus phylogenetic analyses, using the nuclear ribosomal regions of DNA (nrITS1-nr5.8S-nrITS2, nrLSU, and nrSSU) as well as the rpb2 and tef-1α gene sequences, strongly supported the new taxon. The phylogenetic inference, estimated using Maximum Likelihood and Bayesian Inference, clearly indicates that Tamaricicola fenicei sp. nov. forms a distinct clade within the monospecific genus Tamaricicola. The antimicrobial activity of the chloroformic and butanolic extracts from malt agar cultures of the new species exhibited interesting antiviral and antibiofilm properties. In particular, a MIC of 3.0 µg/mL was observed against the Echovirus E11 in Vero-76 cells; moreover, a biofilm BIC₅₀ reduction at 53 µg/mL was observed against Staphylococcus aureus ATCC 25923.

In this study, seven Pleosporaceae strains isolated from the seagrass Posidonia oceanica and the jellyfish Pelagia noctiluca in the central Tyrrhenian Sea were characterized using a polyphasic approach (morpho-physiological, molecular, and phylogenetic analyses). Based on multi-locus phylogenetic inference and morphological characters, a new species, Tamaricicola fenicis was proposed. Multi-locus phylogenetic analyses, using the nuclear ribosomal regions of DNA (nrITS1-nr5.8S-nrITS2, nrLSU, and nrSSU) as well as the rpb-2 and tef-1α gene sequences, strongly supported the new taxon. The phylogenetic inference, estimated using Maximum Likelihood and Bayesian Inference, clearly indicates that Tamaricicola fenicis sp. nov. forms a distinct clade within the monospecific genus Tamaricicola. The antimicrobial activity of the chloroformic and butanolic extracts from malt agar cultures of the new species exhibited interesting antiviral and antibiofilm properties. In particular, a MIC of 3.0 µg/mL was observed against the Echovirus E11 in Vero-76 cells; moreover, a biofilm BIC₅₀ reduction at 53 µg/mL was observed against Staphylococcus aureus ATCC25923.

Introduction: The marine environment is extremely complex and exerts strong evolutionary pressure often leading to the appearance of microbial strains with new metabolic competencies. Microorganisms in marine ecosystems are still largely unknown and should be explored and conserved for biodiversity preservation, possible ecosystem restoring, and other applications. Biodiversity conservation should become a basic ecological strategy of particular significance in relation to global change. In this context, the present research aimed at exploring the culturable mycobiota associated with the jellyfish Pelagia noctiluca, never studied before. In addition, the isolated strains were tested for potential application (antimicrobial activity and presence of genes related to the production of secondary metabolites).Methods: Five jellyfishes were collected in the coastal area of Giglio Island and processed to isolate epizoic fungi. The strains were identified using a polyphasic approach (morphological, physiological, and molecular) and their salt preference was also investigated. The antifungal and antibacterial activity were tested for each strain with agar plug diffusion test. The presence of some key genes related to the main pathways for the production of secondary metabolites in fungi, polyketide synthases (PKSs), and non-ribosomal peptide synthase (NRPSs), was also assessed.Results: A total of 164 isolates were obtained; after the dereplication, 40 morphotypes, and 23 species were identified. The phylogenetic analyses suggested the presence of new taxa belonging to Pleosporales: two new genera and species, and a new species of Tamaricicola. The detected mycobiota showed a relatively high diversity, if compared to other epizoic fungal communities. All isolated strains were marine fungi as confirmed by their salt preference and marked euryhalinism. The genes related to the two main pathways for the production of secondary metabolites in fungi, PKSs and NRPSs, were identified in four and nine strains, respectively. The antimicrobial activity was revealed in 70% of the strains, including the new taxa. The abundance of bioactive strains may be related to the potential involvement of epizoic fungi in host defense strategies. Moreover, these strains could show a high potential for further biotechnological applications particularly in the case of new taxa. All strains are maintained in culture collections.

In this study, 15 Lulworthiales strains isolated from the marine tunicate Halocynthia papillosa collected in the central Tyrrhenian Sea were characterized using a polyphasic approach (morpho-physiological, molecular, and phylogenetic analyses). Based on multi-locus phylogenetic inference and morphological characters, a new genus, Rambellisea, and two new species, R. halocynthiae and R. gigliensis (Lulworthiales), were proposed. Multi-locus phylogenetic analyses using the nuclear ribosomal regions of DNA (nrITS1-nr5.8S-nrITS2, nrLSU, and nrSSU) sequence data strongly supported the new taxa. Phylogenetic inference, estimated using Maximum Likelihood and Bayesian Inference, clearly indicates that Rambellisea gen. nov. forms a distinct clade within the order Lulworthiales. Moreover, the two new species were separated into distinct subclades, solidly supported by the analyses. This is the first report of Lulworthiales species isolated from animals.

The Kuril–Kamchatka Trench (North-West Pacific Ocean) is included in the deepest trenches (>9000 m). This study is the first that aims at uncovering the bathyal prokaryotic diversity (1000–2000 m) of this fascinating extreme environment. The analysis of α-diversity revealed that bacterial communities showed greater diversity than archaeal communities and that both communities were characterized by poor evenness (indicative of the presence of few dominant OTUs). The metabarcoding analysis showed that Proteobacteria (65.5–90.7%), Bacteroidetes (2.4–10.7%), and Actinobacteria (2.5–9.6%) were the highly represented phyla of bacteria, with Acinetobacter (21.5–62.5%) as the most abundant genus. Moreover, the recently described Pseudofrancisella genus, which has been isolated from estuarine environments, has been found among the major bacterial taxa. This work represents the first report stating the presence of this genus in bathyal waters. The archaeal communities were dominated by the phylum Thaumarchaeota (53.6–94.0%), with Nitrosopumilus (53.6–94%) as its representative genus. The functional diversity analysis revealed that overall, the bacterial communities had a higher involvement in the carbon and nitrogen biogeochemical cycles, with chemoheterotrophy (mostly aerobic), aromatic compound degradation, and nitrate reduction as the most represented functions. In the archaeal communities, the most represented ecological function was the aerobic oxidation of ammonia (first stage of nitrification), a functional feature characteristic of Nitrosopumilus.

In a previous work, some bacterial strains isolated from the Saline di Tarquinia marine salterns (Viterbo, Italy) showed very unusual growth profiles in relation to temperature and salinity variations when grown in solid media. In particular, Salinicola halophilus S28 showed optimal or suboptimal growth in a very wide range of NaCl concentrations, suggesting a great coping ability with salinity variations. These intriguing outcomes did not fit with the general Salinicola halophilus description as a moderately halophilic species. Therefore, this study profiles the actual physiological status of S28 cells subjected to different NaCl concentrations to provide evidence for the actual coping ability of strain S28 with broad salinity variations. Flow cytometry was selected as the evaluation method to study the physiological status of bacterial cells subjected to different salinity levels, monitoring the strain response at different growth phases over 72 h. Strain S28 showed maximal growth at 8% NaCl; however, it grew very well with no statistically significant differences at all salinity conditions (4–24% NaCl). Flow cytometric results provided clear evidence of its actual and strong ability to face increasing salinity, revealing a good physiological response up to 24% of NaCl. In addition, strain S28 showed very similar cell physiological status at all salinity levels, as also indicated by the flat growth profile revealed in the range of 4–24% NaCl. This is the first study regarding the physiological response during the growth of halophilic bacteria under different conditions of salinity via flow cytometry. This technique represents an effective tool for the investigation of the physiological status of each cell, even if it is somehow underrated and underused by microbiologists for this purpose.

Polyphenols and their intermediate metabolites are natural compounds that are spread worldwide. Polyphenols are antioxidant agents beneficial for human health, but exposure to some of these compounds can be harmful to humans and the environment. A number of industries produce and discharge polyphenols in water effluents. These emissions pose serious environmental issues, causing the pollution of surface or groundwater (which are used to provide drinking water) or harming wildlife in the receiving ecosystems. The treatment of high-polyphenol-content waters is mandatory for many industries. Nowadays, biotechnological approaches are gaining relevance for their low footprint, high efficiency, low cost, and versatility in pollutant removal. Biotreatments exploit the diversity of microbial metabolisms in relation to the different characteristics of the polluted water, modifying the design and the operational conditions of the technologies. Microbial metabolic features have been used for full or partial polyphenol degradation since several decades ago. Nowadays, the comprehensive use of biotreatments combined with physical-chemical treatments has enhanced the removal rates to provide safe and high-quality effluents. In this review, the evolution of the biotechnological processes for treating high-polyphenol-content water is described. A particular emphasis is given to providing a general concept, indicating which bioprocess might be adopted considering the water composition and the economic/environmental requirements. The use of effective technologies for environmental phenol removal could help in reducing/avoiding the detrimental effects of these chemicals. In addition, some of them could be employed for the recovery of beneficial ones.

Tomatoes are among the most consumed vegetables worldwide and represent a source of health-beneficial substances. Our study represents the first investigating the peel-associated epiphytic bacteria of red and purple (anthocyanin-rich) tomatoes subjected to organic and conventional farming systems. Proteobacteria was the dominant phylum (relative abundances 79–91%) in all experimental conditions. Enterobacteriaceae represented a large fraction (39.3–47.5%) of the communities, with Buttiauxella and Atlantibacter as the most represented genera. The core microbiota was composed of 59 operational taxonomic units (OTUs), including the majority of the most abundant ones. The occurrence of the most abundant OTUs differed among the experimental conditions. OTU 1 (Buttiauxella), OTU 2 (Enterobacteriales), and OTU 6 (Bacillales) were higher in red and purple tomatoes grown under organic farming. OTU 5 (Acinetobacter) had the highest abundance in red tomatoes subjected to organic farming. OTU 3 (Atlantibacter) was among the major OTUs in red tomatoes under both farming conditions. OTU 7 (Clavibacter) and OTU 8 (Enterobacteriaceae) had abundances ≥1% only in red tomatoes grown under conventional farming. PCA and clustering analysis highlighted a high similarity between the bacterial communities of red and purple tomatoes grown under organic farming. Furthermore, the bacterial communities of purple tomatoes grown under organic farming showed the lowest diversity and evenness. This work paves the way to understand the role of nutritional superior tomato genotypes, combined with organic farming, to modulate the presence of beneficial/harmful bacteria and supply healthier foods within a sustainable agriculture.

Pontimonas is currently described as a genus including only one species of slightly halophilic marine bacteria. Although some works revealed its presence in some hypersaline environments, the information on its habitat preference is still scant. This work investigated Pontimonas presence in selected ponds of the Saline di Tarquinia marine saltern and in the seawater intake area. The two-year metabarcoding survey documented its constant presence along the ponds establishing the salinity gradient and in a distinct basin with permanent hypersaline conditions (BSB). Pontimonas was higher in the ponds than in the sea, whereas it had similar abundances in the sea and in the BSB. Its representative OTUs showed significant trends according to different parameters. Along the salinity gradient, OTU1 abundance increased with decreasing water temperatures and increasing rainfalls, and it showed a maximum in January; OTU2 increased with increasing BOD₅ and it showed the highest abundances in the period August–October, and OTU 3194 increased at decreasing salinities. In BSB, a significant seasonal variation was shown by OTU 3194, which started increasing in spring to reach a maximum in summer. The results suggest that Pontimonas could easily settle in hypersaline habitats, having also broad euryhaline members and some possible extreme halophilic representatives.