The real masters of life on Earth are not humans but nano-organisms and microbes. Microbiology represents the bedrock from which many newer developments in biotechnology have emanated. We humans have many microbial friends such as the bacteria that live within our body and protect us from disease, promote food digestion, produce vitamins and shape the immune system. On the other hand, some of the deadliest diseases are caused by certain viruses which are best considered as nano-organisms. The book aims to briefly describe some of the exciting new discoveries and researches in bacteria, viruses, microalgae, yeasts and other microbes. Some specific topics in the forefront and expanding frontiers of microbiology and nanobiology discussed in this monograph are the human microbiota, horizontal (lateral) gene transfers, infectious diseases, and the organisms concerned with the environmental, energy, pharmaceutical and healthcare dimensions. The monograph is intended to meet the needs of microbiology students, researchers and teachers in colleges, universities, agricultural and medical institutions. It would also be of use to those who already have some elementary knowledge of microbiology but wish to combine this knowledge in a purposeful analysis and appreciation of the newer microbial discoveries and processes in relation to biotechnology, plant molecular biology, and pharmacognosy.