The contents of the book have been divided into 24 chapters. Each chapter opens with a brief introduction. Diversity of non-flowering plants and their use as bioresources, biotechnological potential, biomolecules from these plants and natural products from endophytes used in medicine have been dealt in separate chapters. The microbes which include viruses, mycoplasmas, bacteria, yeasts and fungi and non-flowering groups such as algae, lichens, bryophytes, pteridophytes and gymnosperms have been dealt separately, giving a concise account of their use as food supplements, medicine and industries. The microbial products such as antibiotic, vaccines, toxins are added to give an insight into the application of microbial metabolites. Impact of viruses, mycoplasmas, bacteria, yeasts and fungi causing various diseases in plants, insects, birds, animals and human have been discussed in detail. A short account of role of microbes in biogeochemical cycles and biodegradation has been added to emphasize the role of microbes in environmental pollution.