Preface

Gut microbes play a vital role in regulating human health and conduct a multitude of phys‐ iological and biochemical reactions with metabolic entities that play a key role in nutrition exchange between mammalian hosts and their intestinal microorganisms. The intestinal eco‐ system is shaped by interactions between intra- and interspecies communications, which elucidate its roles in human health. The use of culture-independent methods for studying host-associated microbial communities could prove invaluable in the expansion of our cur‐ rent knowledge. Next-generation sequence (NGS) targeting of the 16S rRNA gene allows comprehensive clarification of the sampled bacterial community and their associated move‐ ment with migratory humans and animals. The application of NGS will lead to a better un‐ derstanding of the whole picture of bacterial communities in migratory birds. Narrowing down the target bacteria using NGS will enable us to identify unknown pathogens or reveal the potential migration status of known pathogens that have not been noticed so far due to methodological constraints.

This renaissance in host-associated microbial ecology is spurred by advances in metagenom‐ ics tools. As never before, these tools collect massive amounts of information through func‐ tional and phylogenetic profiling of microbial isolates and complete microbial communities. Metagenomics tools have a huge potential to describe the diversity of microbiomes in gut microflora and most importantly directly in infectious samples. With rapid improvement in genomic sequencing techniques, the overall metagenomics approach is valuable for the dis‐ covery of new viruses, novel genes, and new pathways, and the surveillance of pathogens, host–virus interaction, and functional studies. The leads obtained through this exercise may have great impact on early diagnosis and treatment.

A healthy human body functions in sync with a wide array of gut microbes collectively known as the human gut microbiome. By conducting community composition investiga‐ tions in parallel with functional investigations (e.g., drug resistance), these methods will lead to an understanding of the mechanisms by which multidrug-resistant bacteria spread around the world, which are essential in our daily life such as in food metabolism. Various illnesses, including colon cancer, autism, obesity, and autoimmune diseases, have been linked to imbalanced gut microbiota. However, antibiotics are indispensable drugs, al‐ though administration of antibiotics in humans as well as in animals has shown to increase antibiotic resistance genes (ARGs) in the gut microbiome.

In addition, numerous studies have consistently shown that the gut microbiome is unique to each individual. Hence, depth of knowledge on the gut microbiota community and the fac‐ tors responsible for the shaping and spreading of ARGs are essential. This would in turn enable the development of custom-tailored food and drugs in the future. Hence, the book will give more precise information on gut microbes, which are associated in host organisms.

> **Ranjith N. Kumavath** Department of Genomic Science Central University of Kerala, India

**Section 1**

**Antimicrobial Resistance**
