A novel promising laccase from the psychrotolerant and halotolerant Antarctic marine Halomonas sp. M68 strain

Microbial communities inhabiting the Antarctic Ocean show psychrophilic and halophilic adaptations conferring interesting properties to the enzymes they produce, which could be exploited in biotechnology and bioremediation processes. Use of cold- and salt-tolerant enzymes allows to limit costs, reduce contaminations, and minimize pretreatment steps. Here, we report on the screening of 186 morphologically diverse microorganisms isolated from marine biofilms and water samples collected in Terra Nova Bay (Ross Sea, Antarctica) for the identification of new laccase activities. After primary screening, 13.4 and 10.8% of the isolates were identified for the ability to oxidize 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and the dye azure B, respectively. Amongst them, the marine Halomonas sp. strain M68 showed the highest activity. Production of its laccase-like activity increased six-fold when copper was added to culture medium. Enzymatic activity-guided separation coupled with mass spectrometry identified this intracellular laccase-like protein (named Ant laccase) as belonging to the copper resistance system multicopper oxidase family. Ant laccase oxidized ABTS and 2,6-dimethoxy phenol, working better at acidic pHs The enzyme showed a good thermostability, with optimal temperature in the 40–50°C range and maintaining more than 40% of its maximal activity even at 10°C. Furthermore, Ant laccase was salt- and organic solvent-tolerant, paving the way for its use in harsh conditions. To our knowledge, this is the first report concerning the characterization of a thermo- and halo-tolerant laccase isolated from a marine Antarctic bacterium

Response to climate change in Antarctic benthos - Environmental change in Antarctic marine ecosystem: study of long term observations and ocean acidification experiments to better understand the destiny of three key benthic species in the Terra Nova Bay littoral (Ross Sea): Adamussium colbecki, Sterechinus neumayeri and Odontaster validus.

Climate changes effects include ocean acidification and, possibly, the alteration of frequency and magnitude of climate events, such as El Ni\uf1o. All environmental global changes are supposed to be a major threat to ecosystem, both terrestrial and marine. Despite the amazing bulk of literature on these last, few efforts have been devoted to polar regions, which are actually likely to be the most fragile environments on the Earth. In this work we want to elucidate the response, to environmental modifications, of three Antarctic benthic macroinvertebrates: the scallop Adamussium colbecki, the sea urchin Sterechinus neumayeri and the sea star Odontaster validus, inhabiting the littoral area of Terra Nova Bay (Ross Sea, Victoria Land). Using long term series, we investigated potential correlation between A. colbecki recruitment and environmental variables (sea ice cover duration and El Ni\uf1o events), reporting that A. colbecki recruitment is not affected by these variables. We also performed a manipulative experiment in the Mario Zucchelli Station to understand the effects of three pH levels (8.16, 7.8 and 7.6) on the three species, investigating the response of hard tissues and of the reproductive system. Results show that S. neumayeri spines are affected by low pH only at nanoscale and only in hardness property, while the shell of A. colbecki is not altered at all. As far as reproductive system, we found a significant effect in the gonado-somatic index and on stage development of A. colbecki, in addition to some damages in the gonad tissue, although not statistically significant. S. neumayeri shows the same disrupt tissue all over ovary and testes, although differences from the control are not statistically significant. Conversely, O. validus does not show any effect of low pH exposure at all. Further investigations are necessary to understand the energy costs of maintenance of the polar organisms and its potential consequence on individual life history and, thus, populations dynamic

Seawater carbonate chemistry and gonado-somatic index of three key Antarctic benthic macroinvertebrates

CO2 atmospheric pressure is increasing since industrial revolution, leading to a lowering of the ocean surface water pH, a phenomenon known as ocean acidification, with several reported effects on individual species and cascading effects on marine ecosystems. Despite the great amount of literature on ocean acidification effects on calcifying organisms, the response of their reproductive system still remains poorly known. In the present study, we investigated the histopathological effects of low pH on the gonads of three key macroinvertebrates of the Terra Nova Bay (Ross Sea) littoral area: the sea urchin Sterechinus neumayeri, the sea star Odontaster validus and the scallop Adamussium colbecki. After 1 month of exposure at control (8.12) and reduced (7.8 and 7.6) pH levels, we dissected the gonads and performed histological analyses to detect potential differences among treatments. Results showed significant effects on reproductive conditions of A. colbecki and S. neumayeri, while O. validus did not show any kind of alteration. Present results reinforce the need to focus on ocean acidification effects on soft tissues, particularly the gonads, whose damage may exert large effects on the individual fitness, with cascading effects on the population dynamic of the species

The impact of ocean acidification on the gonads of three key Antarctic benthic macroinvertebrates

CO2 atmospheric pressure is increasing since industrial revolution, leading to a lowering of the ocean surface water pH, a phenomenon known as ocean acidification, with several reported effects on individual species and cascading effects on marine ecosystems. Despite the great amount of literature on ocean acidification effects on calcifying organisms, the response of their reproductive system still remains poorly known. In the present study, we investigated the histopathological effects of low pH on the gonads of three key macroinvertebrates of the Terra Nova Bay (Ross Sea) littoral area: the sea urchin Sterechinus neumayeri, the sea star Odontaster validus and the scallop Adamussium colbecki. After 1 month of exposure at control (8.12) and reduced (7.8 and 7.6) pH levels, we dissected the gonads and performed histological analyses to detect potential differences among treatments. Results showed significant effects on reproductive conditions of A. colbecki and S. neumayeri, while O. validus did not show any kind of alteration. Present results reinforce the need to focus on ocean acidification effects on soft tissues, particularly the gonads, whose damage may exert large effects on the individual fitness, with cascading effects on the population dynamic of the species

Seawater carbonate chemistry and Robustness of Adamussium colbecki shell

Atmospheric pCO2 has increased since the industrial revolution leading to a lowering of the ocean surface water pH, a phenomenon called ocean acidification (OA). OA is claimed to be a major threat for marine organisms and ecosystems and, particularly, for Polar regions. We explored the impact of OA on the shell mechanical properties of the Antarctic scallop Adamussium colbecki exposed for one month to acidified (pH 7.6) and natural conditions (unmanipulated littoral water), by performing Scanning Electron Microscopy, nanoindentation and Vickers indentation on the scallop shell. No effect of pH could be detected either in crystal deposition or in the mechanical properties. A. colbecki shell was found to be resistant to OA, which suggests this species to be able to face a climate change scenario that may threat the persistence of the endemic Antarctic species. Further investigation should be carried out in order to elucidate the destiny of this key species in light of global change

Robustness of Adamussium colbecki shell to ocean acidification in a short-term exposure

Atmospheric pCO2 has increased since the industrial revolution leading to a lowering of the ocean surface water pH, a phenomenon called ocean acidification (OA). OA is claimed to be a major threat for marine organisms and ecosystems and, particularly, for Polar regions. We explored the impact of OA on the shell mechanical properties of the Antarctic scallop Adamussium colbecki exposed for one month to acidified (pH 7.6) and natural conditions (unmanipulated littoral water), by performing Scanning Electron Microscopy, nanoindentation and Vickers indentation on the scallop shell. No effect of pH could be detected either in crystal deposition or in the mechanical properties. A. colbecki shell was found to be resistant to OA, which suggests this species to be able to face a climate change scenario that may threat the persistence of the endemic Antarctic species. Further investigation should be carried out in order to elucidate the destiny of this key species in light of global change.Peer reviewe