Soil Bacteria (IMAGE) Indiana University Caption Soils are one of the largest reservoirs of microbial diversity on Earth. It is not uncommon for a gram of soil to contain one trillion cells and ten thousand species of bacteria, including Actinomyces israelii (pictured). Credit <a target="_blank"href="https://commons.wikimedia.org/wiki/File:Actinomyces_israelii.jpg">GrahamColm at English Wikipedia</a> Usage Restrictions <a target="_blank" href="https://creativecommons.org/licenses/by/3.0/deed.en">Creative Commons Attribution 3.0 Unported</a> License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.