Shallow Hydrothermal Vent Bacteria and Their Secondary Metabolites with a Particular Focus on Bacillus

Heavy metal tolerance, and metal biosorption by exopolysaccharides produced by bacterial strains isolated from marine hydrothermal vents

The present study highlights heavy metal tolerance, EPS production, and biosorption capacity of four hydrothermal vent bacterial strains, namely Exiguobacterium aquaticum, Mammaliicoccus sciuri, Micrococcus luteus, and Jeotgalicoccus huakuii against As, Cd, Cr, Cu, Co, Pb and Ni. The biosorption assay showed high removal efficiency of As (83%) by E. aquaticum, Cd (95%) by M. sciuri, Cu (94%) by M. luteus, and Ni (89%) by J. huakuii and their produced EPS with these metals in aqueous solution were 84%, 85%, 98%, and 91%, respectively. The maximum EPS yield was attained by optimized medium composition consisting of 1% Xylose, and 1% NaCl at pH 7. In metal-amended conditions, the four bacterial strains showed induced EPS production in the initial concentrations. SEM with EDX and CLSM images showed that the growth and EPS production of bacterial strains were affected by metal ion concentrations. A phenol sulphuric acid method and BCA assay were used to identify both the carbohydrate and total protein content of four extracted EPS. A DPPH assay revealed that EPS influences free radical scavenging and has a highly enhanced synergistic effect with its antioxidant activity. FT-IR analysis of four extracted EPS showed the shifting of peaks in the functional groups of EPS before and after adsorption of metal ions. At pH 5 and after 60 min contact time metal removal efficiency and adsorption capacity increased as calculated for As, Cd, Cu, and Ni by four extracted EPS: (86%, 20 mg/g), (74%, 19 mg/g), (94%, 60 mg/g) and (89%, 32 mg/g) and (89%, 16 mg/g), (85%, 16 mg/g), (96%, 22 mg/g) and (91%, 16 mg/g), respectively. The Langmuir compared to the Freundlich model was found to better represent the adsorption by EPS providing maximum adsorption capacities for As (34.65 mg/g), Cd (52.88 mg/g), Cu (24.91 mg/g), and Ni (58.38 mg/g).

Characterization of an undocumented CO2 hydrothermal vent system in the Mediterranean Sea: Implications for ocean acidification forecasting

A previously undocumented shallow water hydrothermal field from Sicily (Southern Tyrrhenian Sea, Italy) is here described, based on a multidisciplinary investigation. The field, covering an area of nearly 8000 m2 and a depth from the surface to -5 m, was explored in June 2021 to characterise the main physico-chemical features of the water column, describe the bottom topography and features, and identify the main megabenthic and nektonic species. Twenty sites were investigated to characterise the carbonate system. Values of pH ranged between 7.84 and 8.04, ΩCa between 3.68 and 5.24 and ΩAr from 2.41 to 3.44. Geochemical analyses of hydrothermal gases revealed a dominance of CO2 (98.1%) together with small amounts of oxygen and reactive gases. Helium isotope ratios (R/Ra = 2.51) and δ13CCO2 suggest an inorganic origin of hydrothermal degassing of CO2 and the ascent of heat and deep-seated magmatic fluids to the surface. Visual census of fishes and megabenthos (mainly sessile organisms) allowed the identification of 64 species, four of which are protected by the SPA/BIO Protocol and two by the International Union for Conservation of Nature. The macroalgae Halopteris scoparia and Jania rubens and the sponge Sarcotragus sp. were the dominant taxa in the area, while among fishes Coris julis and Chromis chromis were the most abundant species. This preliminary investigation of San Giorgio vent field suggests that the site could be of interest and suitable for future experimental studies of ocean acidification.

Combined effects of copper oxide and nickel oxide coated chitosan nanoparticles adsorbed to styrofoam resin beads on hydrothermal vent bacteria

Microplastics are potential carriers of harmful contaminants but their combined effects are largely unknown. It needs intensive monitoring in order to achieve a better understanding of metal-oxide nanoparticles and their dispersion via microplastics such as styrofoam in the aquatic environment. In the present study, an effort was made to provide a preferable perception about the toxic effects of engineered nanoparticles (NPs), namely, copper oxide (CuO NPs), nickel oxide (NiO NPs), copper oxide/chitosan (CuO/CS NPs) and nickel oxide/chitosan (NiO/CS NPs). Characterizations of synthesized NPs included their morphology (SEM and EDX), functional groups (FT-IR) and crystallinity (XRD). Their combined toxic effect after adsorption to styrofoam (SF) was monitored using the hydrothermal vent bacterium Jeotgalicoccus huakuii as a model. This was done by determining MIC (minimum inhibitory concentration) through a resazurin assay measuring ELISA, growth, biofilm inhibition and making a live and dead assay. Results revealed that at high concentrations (60 mg/10 mL) of CuO, CuO/CS NPs and 60 mg of SF adsorbed CuO and CuO/CS NPs inhibited the growth of J. huakuii. However, NPs rather than SF inhibited the growth of bacteria. The toxicity of NPs adsorbed on plain SF was found to be less compared to NPs alone. This study revealed new dimensions regarding the positive impacts of SF at low concentrations. Synthesized NPs applied separately were found to affect the growth of bacteria substantially more than if coated to SF resin beads.