The main theme of this book is dealing with the evaluation whether arsenate is more toxic or arsenite and how much amount of arsenic will be accumulated by bacteria. This project also made me to learn and in searching of so many peculiar things that i have never studied before. The whole span for accomplishing this project will always indelible for me that how I face the problem and then troubleshoot them. All above I thanks to Almighty ALLAH who given me the opportunity a great strength to complete this project. And I am also thankful to my co-author Shadma Wahab for her valuable suggestions.