Physiological and Molecular Responses to Main Environmental Stressors of Microalgae and Bacteria in Polar Marine Environments

Abstract

The Arctic and Antarctic regions constitute 14% of the total biosphere. Although they differ in their physiographic characteristics, both are strongly affected by snow and ice cover changes, extreme photoperiods and low temperatures, and are still largely unexplored compared to more accessible sites. This review focuses on microalgae and bacteria from polar marine environments and, in particular, on their physiological and molecular responses to harsh environmental conditions. The data reported in this manuscript show that exposure to cold, increase in CO2 concentration and salinity, high/low light, and/or combination of stressors induce variations in species abundance and distribution for both polar bacteria and microalgae, as well as changes in growth rate and increase in cryoprotective compounds. The use of -omics techniques also allowed to identify specific gene losses and gains which could have contributed to polar environmental adaptation, and metabolic shifts, especially related to lipid metabolism and defence systems, such as the up-regulation of ice binding proteins, chaperones and antioxidant enzymes. However, this review also provides evidence that -omics resources for polar species are still few and several sequences still have unknown functions, highlighting the need to further explore polar environments, the biology and ecology of the inhabiting bacteria and microalgae, and their interactions.

Chlamydomonas Responses to Salinity Stress and Possible Biotechnological Exploitation

“…Omics studies also allowed to demonstrate that under salt stress, key enzymes such as those related to osmolytes metabolism are largely controlled by post-translational modifications and this may be true for other pathways as well and need further investigations [70]. Researches on salt stress are very important especially for less studied species, such as polar Chlamydomonas, which experience and will experience severe salinity variations due to seasonal freezing/melting cycles, as well as melting of sea ice due to climate changes, which may affect species biodiversity and distribution [4,144]. This review also points out that, besides proteomic and transcriptomic studies, very few data are available on osmosensors and on the signaling networks/upstream components mediating salt stress responses, although some more specific studies are emerging.…”

“…Marine organisms have evolved several mechanisms to inhabit extreme environments, in order to maintain cellular homeostasis and survive [3,4]. Unicellular green algae from the genus Chlamydomonas, due to their ability to withstand changing and extreme conditions, have been reported to live in a variety of environments, as wet soil, deserts, temporary pools, and even snow or sea ice, where they can face extreme salinity variations.…”

Life from a Snowflake: Diversity and Adaptation of Cold-Loving Bacteria among Ice Crystals

“…Indeed, microalgae are another important living component of ice communities, and very often their occurrence and distribution is related to those of bacteria. Bacterial populations have been proven to be strictly related to the algal blooms, with a role in their evolution but also in the consumption of algal exudates and therefore in the nutrient recycle processes [210,211]. Within these interactions, the production of extracellular polymers and cold enzymes can occur, by enhancing the coexistence of the microbial population [212,213].…”

Bioactivity Screening of Antarctic Sponges Reveals Anticancer Activity and Potential Cell Death via Ferroptosis by Mycalols

“…The Southern Ocean represents 9.6% of the world’s oceans and extends approximately 35 million km 2 . The Antarctic region is strongly affected by snow and ice-cover changes, extreme photoperiods, and low temperatures [ 8 ]. Due to these harsh characteristics, Antarctic organisms have evolved various physiological and behavioral adaptations [ 9 ].…”