Microbial Co-Cultures (IMAGE) Indiana University Caption In a search for the economical production of hydrogen gas biofuel, McKinlay is looking to create a metabolic relationship between two microbial species where each supplies the other with a nutrient required for survival. Credit James Usage Restrictions None 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.