While microbial mats at methane seeps, like this one, are home to many microbes, deep-sea sediment has a billion bacteria in every milliliter of mud, whether at a seep or in the middle of the ocean.
Microbial Mat
Image courtesy of A. Thurber, Oregon State University, OCNMS, NOAA OER, and Ocean Exploration Trust: NA-121. Download larger version (jpg, 2.8 MB).

While microbial mats at methane seeps, like this one, are home to many microbes, deep-sea sediment has a billion bacteria in every milliliter of mud, whether at a seep or in the middle of the ocean.

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