Heavy metals are ubiquitous and persistent environmental pollutants that are introduced into the environment through anthropogenic activities, such as mining and smelting, as well as through other sources of industrial waste. Pseudomonas aeruginosa is a ubiquitous, environmentally important microbe that may employ many resistance mechanisms, such as the mer operon that reduces toxic Hg2+ to volatile Hg0, which then diffuses out of the cell. However, in bacteria, efflux systems are a more common resistance mechanism for dealing with heavy metals. The aim of this work was to study the prevalence of heavy metals resistance (HMR) in Ps. aeruginosa recovered from clinical and environmental samples, as well as studying production of biofilm and its correlation with heavy metals resistance. This book is suited for all kinds of students (Undergraduate and postgraduate) and doesn’t require any prerequisite knowledge of biology or chemistry. If any student is interested in entering the health care profession in some way, this book will give him a strong background in the biology of HMR bacteria, without overwhelming unnecessary details.