Ecological and Biotechnological Relevance of Mediterranean Hydrothermal Vent Systems

Using a food web model to predict the effects of Hazardous and Noxious Substances (HNS) accidental spills on deep-sea hydrothermal vents from the Mid-Atlantic Ridge (MAR) region

Deep-sea hydrothermal vents host unique ecosystems but face risks of incidents with Hazardous and Noxious Substances (HNS) along busy shipping lanes such as the transatlantic route. We developed an Ecopath with Ecosim (EwE) model of the Menez Gwen (MG) vent field (MG-EwE) (Mid-Atlantic Ridge) to simulate ecosystem effects of potential accidental spills of four different HNS, using a semi-Lagrangian Dispersion Model (sLDM) coupled with the Regional Ocean Modelling System (ROMS) calibrated for the study area. Food web modelling revealed a simplified trophic structure with low energy efficiency. The MG ecosystem was vulnerable to disruptions caused by all tested HNS, yet it revealed some long-term resilience. Understanding these impacts is vital for enhancing Spill Prevention, Control, and Countermeasure plans (SPCC) in remote marine areas and developing tools to assess stressors effects on these invaluable habitats.

Effects of acidification on the biogeochemistry of unvegetated and seagrass marine sediments

Many studies addressed ocean acidification (OA) effects on marine life, whereas its effects on sedimentary organic matter (OM) have received less attention. We investigated differences in OM features in sediments from unvegetated and seagrass (Posidonia oceanica) beds in a shallow hydrothermal area (Aeolian Archipelago, Mediterranean Sea), under natural (8.1-8.0) and acidified (7.8-7.9) conditions. We show that a pH difference of -0.3 units have minor effects on OM features in unvegetated sediments, but relevant consequences within acidified seagrass meadows, where OM quantity and nutritional quality are lower than those under natural pH conditions. Effects of acidified conditions on OM biogeochemistry vary between unvegetated and seagrass sediments, with lower C degradation rates and longer C turnover time in the former than in the latter. We conclude that OA, although with effects not consistent between unvegetated and vegetated sediments, can affect OM quantity, composition, and degradation, thus having possible far-reaching consequences for benthic trophic webs.

Deciphering the evolvement of microbial communities from hydrothermal vent sediments in a global change perspective

Microbial communities first respond to changes of external environmental conditions. Observing the microbial responses to environmental changes in terms of taxonomic and functional biodiversity is therefore of great interest, particularly in extreme environments, where the already extreme conditions can become even harsher. In this study, sediment samples from three different shallow hydrothermal vents in Levante Bay (Vulcano Island, Aeolian Islands, Italy) were used to set up microcosm experiments with the aim to explore the microbial dynamics under changing conditions of pH and redox potential over a 90-days period. The leading hypothesis was to establish under microcosm conditions whether the starting microbial communities of the sediments evolved differently depending on their origin. To profile the dynamics of microbial populations over time, biodiversity, enzymatic profile, total cell abundance estimations, total/respiring cell ratio were estimated by using different approaches. An evident change in the microbial community structure was observed, mainly in the microcosm containing the sediment from the most acidified site, which was characterized by a highly diversified microbial community (in prevalence composed of Thermotoga, Desulfobacterota, Planctomycetota, Synergistota and Deferribacterota). An increase in microbial resistant forms (e.g., spore-forming species) with anaerobic metabolism was detected in all experimental conditions. Differential physiological responses characterized the sedimentary microbial communities. Proteolytic activity appeared to be stimulated under microcosm conditions, whereas the alkaline phosphatase activity was significantly depressed at low pH values, like those that were measured at the station showing intermediate pH-conditions. The results confirmed a differential response of microbial communities depending on the starting environmental conditions.

Probiotic Potential of Bacillus sp. 62A Isolated from a Marine Extreme Environment

Antimicrobial resistance is an important health concern globally, and probiotics are considered an alternative to minimize it. The present study examined the in vitro probiotic characteristics and in vivo immunomodulatory potential of Bacillus sp. 62A - an extremophile bacterium. Bacillus sp. 62A was evaluated in vitro for its cytotoxicity, hemolytic activity, antibiotic susceptibility, and resistance to gastrointestinal conditions (bile salts, low pH, and intestinal adherence). Additionally, the immunomodulatory effect of Bacillus sp. 62A was studied in mice. The animals were supplemented daily with phosphate-buffered saline (control) and Bacillus sp. 62A at 1 × 108 colony forming units (CFU). Samples were taken on days 5 and 10. Isolated splenocytes were challenged with Escherichia coli for immunological analyses and immune-related gene expression. Serum and feces were collected for IgA and IgG determination. Bacillus sp. 62A did not show cytotoxicity, hemolytic activity, or resistance to antibiotics. Furthermore, the bacterium has autoaggregation and intestinal adhesion capacities and grows in the presence of bile salts and low pH. Bacillus supplementation in mice improved respiratory burst activity, nitric oxide production, and IL-1β and IL-6 gene expressions, mainly at 10 days. After E. coli challenge, Bacillus supplementation in mice induced an anti-inflammatory response through a decrease in immunological parameters and an increase in IL-10 gene expression. Moreover, serum IgA and IgG and fecal IgG augmented in supplemented mice. In conclusion, Bacillus sp. 62A has biosafe and immunomodulatory probiotic potential.

Microbial communities inhabiting shallow hydrothermal vents as sentinels of acidification processes

Introduction

Shallow hydrothermal vents are considered natural laboratories to study the effects of acidification on biota, due to the consistent CO2 emissions with a consequent decrease in the local pH.

Methods

Here the microbial communities of water and sediment samples from Levante Bay (Vulcano Island) with different pH and redox conditions were explored by Next Generation Sequencing techniques. The taxonomic structure was elucidated and compared with previous studies from the same area in the last decades.

Results and discussion

The results revealed substantial shifts in the taxonomic structure of both bacterial and archaeal communities, with special relevance in the sediment samples, where the effects of external parameters probably act for a long time. The study demonstrates that microbial communities could be used as indicators of acidification processes, by shaping the entire biogeochemical balance of the ecosystem in response to stress factors. The study contributes to understanding how much these communities can tell us about future changes in marine ecosystems.

Volcanic-associated ecosystems of the Mediterranean Sea: a systematic map and an interactive tool to support their conservation

Background

Hydrothermal vents, cold seeps, pockmarks and seamounts are widely distributed on the ocean floor. Over the last fifty years, the knowledge about these volcanic-associated marine ecosystems has notably increased, yet available information is still limited, scattered, and unsuitable to support decision-making processes for the conservation and management of the marine environment.

Methods

Here we searched the Scopus database and the platform Web of Science to collect the scientific information available for these ecosystems in the Mediterranean Sea. The collected literature and the bio-geographic and population variables extracted are provided into a systematic map as an online tool that includes an updated database searchable through a user-friendly R-shiny app.

Results

The 433 literature items with almost one thousand observations provided evidence of more than 100 different volcanic-associated marine ecosystem sites, mostly distributed in the shallow waters of the Mediterranean Sea. Less than 30% of these sites are currently included in protected or regulated areas. The updated database available in the R-shiny app is a tool that could guide the implementation of more effective protection measures for volcanic-associated marine ecosystems in the Mediterranean Sea within existing management instruments under the EU Habitats Directive. Moreover, the information provided in this study could aid policymakers in defining the priorities for the future protection measures needed to achieve the targets of the UN Agenda 2030.

Thermophilic Carboxylesterases from Hydrothermal Vents of the Volcanic Island of Ischia Active on Synthetic and Biobased Polymers and Mycotoxins

Hydrothermal vents are geographically widespread and host microorganisms with robust enzymes useful in various industrial applications. We examined microbial communities and carboxylesterases of two terrestrial hydrothermal vents of the volcanic island of Ischia (Italy) predominantly composed of Firmicutes, Proteobacteria, and Bacteroidota. High-temperature enrichment cultures with the polyester plastics polyhydroxybutyrate and polylactic acid (PLA) resulted in an increase of Thermus and Geobacillus species and to some extent Fontimonas and Schleiferia species. The screening at 37 to 70°C of metagenomic fosmid libraries from above enrichment cultures identified three hydrolases (IS10, IS11, and IS12), all derived from yet-uncultured Chloroflexota and showing low sequence identity (33 to 56%) to characterized enzymes. Enzymes expressed in Escherichia coli exhibited maximal esterase activity at 70 to 90°C, with IS11 showing the highest thermostability (90% activity after 20-min incubation at 80°C). IS10 and IS12 were highly substrate promiscuous and hydrolyzed all 51 monoester substrates tested. Enzymes were active with PLA, polyethylene terephthalate model substrate, and mycotoxin T-2 (IS12). IS10 and IS12 had a classical α/β-hydrolase core domain with a serine hydrolase catalytic triad (Ser155, His280, and Asp250) in their hydrophobic active sites. The crystal structure of IS11 resolved at 2.92 Å revealed the presence of a N-terminal β-lactamase-like domain and C-terminal lipocalin domain. The catalytic cleft of IS11 included catalytic Ser68, Lys71, Tyr160, and Asn162, whereas the lipocalin domain enclosed the catalytic cleft like a lid and contributed to substrate binding. Our study identified novel thermotolerant carboxylesterases with a broad substrate range, including polyesters and mycotoxins, for potential applications in biotechnology. IMPORTANCE High-temperature-active microbial enzymes are important biocatalysts for many industrial applications, including recycling of synthetic and biobased polyesters increasingly used in textiles, fibers, coatings and adhesives. Here, we identified three novel thermotolerant carboxylesterases (IS10, IS11, and IS12) from high-temperature enrichment cultures from Ischia hydrothermal vents and incubated with biobased polymers. The identified metagenomic enzymes originated from uncultured Chloroflexota and showed low sequence similarity to known carboxylesterases. Active sites of IS10 and IS12 had the largest effective volumes among the characterized prokaryotic carboxylesterases and exhibited high substrate promiscuity, including hydrolysis of polyesters and mycotoxin T-2 (IS12). Though less promiscuous than IS10 and IS12, IS11 had a higher thermostability with a high temperature optimum (80 to 90°C) for activity and hydrolyzed polyesters, and its crystal structure revealed an unusual lipocalin domain likely involved in substrate binding. The polyesterase activity of these enzymes makes them attractive candidates for further optimization and potential application in plastics recycling.

Bacteria Associated with Benthic Invertebrates from Extreme Marine Environments: Promising but Underexplored Sources of Biotechnologically Relevant Molecules

Microbe–invertebrate associations, commonly occurring in nature, play a fundamental role in the life of symbionts, even in hostile habitats, assuming a key importance for both ecological and evolutionary studies and relevance in biotechnology. Extreme environments have emerged as a new frontier in natural product chemistry in the search for novel chemotypes of microbial origin with significant biological activities. However, to date, the main focus has been microbes from sediment and seawater, whereas those associated with biota have received significantly less attention. This review has been therefore conceived to summarize the main information on invertebrate–bacteria associations that are established in extreme marine environments. After a brief overview of currently known extreme marine environments and their main characteristics, a report on the associations between extremophilic microorganisms and macrobenthic organisms in such hostile habitats is provided. The second part of the review deals with biotechnologically relevant bioactive molecules involved in establishing and maintaining symbiotic associations.