Algal ice-binding proteins change the structure of sea ice.

نویسنده

  • James A Raymond
چکیده

Krembs et al. (1) reported that extracellular polymeric substances (EPS) produced by a sea ice diatom, Melosira, created convoluted ice-pore morphologies in sea ice, potentially increasing its habitability and primary productivity. The activity was reduced by heat treatment and glycosidase treatments, suggesting that a glycoprotein was involved. Based on our previous work (2), it is very likely that the active substance is an ice-binding protein (IBP). All sea ice diatoms examined so far secrete similar ∼25 kDa IBPs that bind to ice, distorting its shape as it grows (2). Similar proteins are found in ice-adapted bacteria and fungi (3) and even a sea ice amphipod that presumably acquired the gene from a diatom by horizontal transfer (4). Such proteins also have the ability to change the structure of sea ice. We recently identified another IBP secreted by an Antarctic euryhaline chlorophyte, Chlamydomonas sp. Its sequence bears no resemblance to the diatom IBPs, but it has similar effects on ice, resulting in the formation of highly irregular shapes (5). At natural concentrations, the Chlamydomonas IBP causes sea ice to freeze with a very fine structure composed of small brine pockets (Fig. 1) that trap brine and slow its drainage (Fig. 2) (5). Krembs et al. (1) attributed the reduced porosity of EPS sea ice to pore clogging by the EPS. Our results (5) suggest that the main factor in the case of Chlamydomonas is the highly irregular shape imposed on ice by the IBPs (Fig. 2 Inset). Various functions have been proposed for ice algal IBPs, including antifreeze activity, inhibition of the recrystallization of ice (which can damage cell membranes), and attachment to ice. Together, these studies (1, 5) point out a possible function of algal IBPs, retention of a liquid environment, without which survival is difficult.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Possible Role of Horizontal Gene Transfer in the Colonization of Sea Ice by Algae

Diatoms and other algae not only survive, but thrive in sea ice. Among sea ice diatoms, all species examined so far produce ice-binding proteins (IBPs), whereas no such proteins are found in non-ice-associated diatoms, which strongly suggests that IBPs are essential for survival in ice. The restricted occurrence also raises the question of how the IBP genes were acquired. Proteins with similar ...

متن کامل

Algal Clues to Antarctic Ice Shelf Ages

1111 Algal Clues to Antarctic Ice Shelf Ages The naturally high variability of sea ice extent in Antarctica and the short duration of instrumental records have combined to obscure any clear record of sea ice coverage change. Curran et al. (p. 1203; see the Perspective by Wolff) present an ice core record of methanesulfonic acid, a species produced by algae living at the edges of ice shelves, wh...

متن کامل

Regulation of Algal Blooms in Antarctic Shelf Waters by the Release of Iron From Melting Sea Ice

During summer 1995-96, we measured iron in the water column and conducted iron-enrichment bottle-incubation experiments at a station in the central Ross Sea (76ø30'S, 170ø40'W), first, in the presence of melting sea ice, and 17 days later, in ice-free conditions. We observed a striking temporal change in mixed-layer dissolved iron concentrations at this station, from 0.72-2.3 nM with sea ice pr...

متن کامل

Bacteria-algae relationships in Antarctic sea ice

Energy transfer in microbial food webs is partly quantified by the relationship between bacterial and algal biomass. Tight spatial relationships suggest active bacterial assimilation of dissolved photosynthate in temperate marine and fresh waters. However, studies in the Antarctic suggest that bacterial biomass generation from algal-derived dissolved organic matter is highly variable across sea...

متن کامل

Refined solution structure of type III antifreeze protein: hydrophobic groups may be involved in the energetics of the protein-ice interaction.

BACKGROUND Antifreeze proteins are found in certain fish inhabiting polar sea water. These proteins depress the freezing points of blood and body fluids below that of the surrounding sea water by binding to and inhibiting the growth of seed ice crystals. The proteins are believed to bind irreversibly to growing ice crystals in such a way as to change the curvature of the ice-water interface, le...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Proceedings of the National Academy of Sciences of the United States of America

دوره 108 24  شماره 

صفحات  -

تاریخ انتشار 2011