Haloarchaea: Life at the Brink

Ben Farmer, University of Kentucky

IMG_20180705_150556What comes to mind when you think of extreme environments? The freezing tundra of Antarctica, or maybe the fiery lava flows of a Hawaiian volcanic zone? Those particularly interested in marine science may think of the deep ocean, perhaps the Marianas Trench. Whichever drastic environment you think of, one fascinating thing ties all of these extremes together: life finds a way to thrive in each of them.

Earth is home to as many as 1 trillion species, and the bulk of them are microbes (Locey and Lennon 2016). Microbes that are adapted to live in conditions that are inhospitable to most life on Earth are called extremophiles. Archaea and bacteria, the two domains of life aside from eukaryotes, represent the majority of extremophiles. While archaea were long thought to be a type of bacteria since the two appear very similar, archaea are more closely related to humans. Archaea are an important model organism because they have forged a niche in just about every habitat imaginable. Hot springs in Yellowstone National Park were among the first locations where archaea were discovered and owe their vibrant colors to these microbes (Oren and Rodriguez-Valera 2001).


Man-made salt pans of Bonaire, Dutch Caribbean, tinged pink by archaea. Halophiles dominate these artificial habitats. Credit: Benjamin van de Water, Flickr, 2009.

Haloarchaea are what I am studying this summer at the College of Charleston. Halo– is a prefix meaning “salt,” and haloarchaea are halophilic, or salt-loving. Perhaps the most famous location that haloarchaea have been found is in the Dead Sea – evidently not so dead after all. Haloarchaea are commonly found in water 10 times as salty as the ocean, in conditions known as hypersaline. Our goal is to investigate what adaptations have made that possible.

We know that the amino acid composition of halophiles is unusually acidic (Martin et al. 1999). Proteins of halophiles are therefore also unusually acidic, which allows their proteins to properly fold in hypersaline conditions. What we do not know is whether the expression of proteins can change at different salinities. Better understanding how proteins are adapted in haloarchaea lends itself to understanding extremophiles on a broader scale.

Mechanisms that allowed microbes to function in seemingly inhospitable environments were likely responsible for evolution of life on Earth (Rampelotto 2010). There are many habitats today that mimic extreme environments from both ancient history and current conditions on other planets, such as Mars. Martian soil is incredibly salty, a result of surface water that evaporated long ago (https://dornsife.usc.edu/labs/laketyrrell/life-in-hypersaline-environments/). Halophiles may have once lived in those hypersaline Martian waters. Therefore, knowledge that we gain about haloarchaea adaptations is valuable to our understanding of life both on Earth and elsewhere.


Many thanks to my mentor, Dr. Matthew Rhodes, who has introduced me to everything from cell culturing to python. This project is funded through the National Science Foundation and supported by the Fort Johnson REU Program, NSF DBI- 1757899.


Locey KJ, Lennon JT (2016) Scaling laws predict global microbial diversity. Proc Natl Acad Sci 113:5970–5975

Martin DD, Ciulla R a, Roberts MF (1999) Osmoadaptation in Archaea. Appied Enviromental Microbiol 65:1815–1825

Oren A, Rodriguez-Valera F (2001) The contribution of halophilic Bacteria to the red coloration of saltern crystallizer ponds. FEMS Microbiol Ecol 36:123–130

Rampelotto PH (2010) Resistance of microorganisms to extreme environmental conditions and its contribution to astrobiology. Sustainability 2:1602–1623



Playing with Plutei

Hailey Conrad, Rutgers University


Me! Photo Credit: Kady Palmer

Ocean acidification is known as climate change’s evil twin. When the pH of ocean water drops, carbonate ions in the water form carbonic acid instead of calcium carbonate. Calcium carbonate is the form of calcium that marine animals that have calcium-based skeletons (like us!) and shells use to build their bones and shells. Having smaller and weaker skeletons or shells impacts their ability to survive. However, some individuals within certain species or populations of species have genes that make them more resistant to ocean acidification. If these individuals are able to pass on these genes to their offspring, then the species has the ability to evolve in response to ocean acidification instead of going extinct. This summer I’m working with Dr. Bob Podolsky in College of Charleston’s Grice Marine Field Station to study the extent to which ocean acidification affects Atlantic purple sea urchins, Arbacia punctulata. We are specifically trying to see if any individuals within a population from Woods Hole, Massachusetts, have any heritable genetic resistance to the negative impacts of ocean acidification. We hypothesize that there will be genetic resistance given that the northern Atlantic coast naturally has lower levels of saturated calcium carbonate, so a population that has evolved to live in that type of environment should have some resistance to lower calcium carbonate levels already (Wang et al 2013). We’re using a basic cross breeding technique to rear Arbacia punctulata larvae to their plutei stage, when they have four main body rods. At this stage they look less like sea urchins than they do like Sputnik!


A sea urchin pluteus larvae with four body rods

Then, we will look to see if any of the male parents consistently produce male offspring that are more resistant to ocean acidification.  If males like these exist within this population, then the species has the capacity to evolve in response to ocean acidification, instead of going extinct! This is a very big deal, and could potentially be very hopeful. Even if we don’t get the results that we are hoping for, the results of this research could inform policy and management decisions.

Literature Cited:

Wang, Z. A., Wanninkhof, R., Cai, W., Byrne, R. H., Hu, X., Peng, T., & Huang, W. (2013). The marine inorganic carbon system along the Gulf of Mexico and Atlantic coasts of the United States: Insights from a transregional coastal carbon study. Limnology and Oceanography, 58(1), 325-342. doi:10.4319/lo.2013.58.1.0325

Thank you to the National Science Foundation and College of Charleston’s Grice Marine Laboratory for funding my project. And, special thanks to Dr. Bob Podolsky for being a wonderful and supportive mentor!