An alkaliphile is an organism that lives and grows well in extremely alkaline conditions that are harmful to most life on Earth. To be considered an alkaliphile, the organism must have optimal growth in environments with a pH level of 9.0 or above.
Surviving and growing in an environment that has a high pH level is very difficult. Many processes in the cell are blocked by high pH levels. Alkaline conditions change DNA, and make the plasma membrane of the cell unstable. Alkaliphiles have two basic methods of dealing with these problems: Either they have a way of making the environment more acidic, or they have adapted the cellular processes, so that they work best in highly alkaline conditions. To find out which of the two mechanisms a specific organism uses, experiments are needed.