Bacteroides Species (IMAGE) Howard Hughes Medical Institute Caption Many Bacteroides species (a mixture of five shown in this color-enhanced micrograph) reside in the human gut and secrete toxins that bacteria must neutralize to survive. Credit Kevin Cutler/Mougous Lab/UW/HHMI Usage Restrictions Must use credit. 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.