Metagenomic approaches have been so popular that not only biome in human guts but also microbes in soil, seawater, and air samples have become signiﬁcant targets of the studies of microbial heterogeneity in understanding ecological background, evolutionary adaptation, and environmental monitoring of microbial communities.
In particular, marine metagenomics, the metagenomic studies of seawaters, have been actively developed with an acutely increasing speed, mostly because of a wide spectrum of signiﬁcant applications. For example, a pioneering study of Sargasso Sea by Dr. Craig Venter disclosed a vast amount of novel species and genes of marine microorganisms that have been not identiﬁed in any means before. Recent studies of exploratory examination of microbes over a number of different locations in the globe, such as Tara Ocean and Malaspina Ocean Exploration Projects, have shown various new discoveries.
Moreover, changes in the marine environment due to the global warming effect and the pollution have become a major global problem. To maintain the healthy marine ecosystem, the advanced environmental monitoring and assessing systems are required. As a new monitoring technology, this metagenomic method has been expected for comprehensive analyses of the DNA of microorganisms living in seawater. This method drew attention as a means of understanding the dynamics of the marine environment.
As for the technical advancements, the amplicon-oriented methodologies of using 16S and 18S rRNAs as probes have been well established. Because of tremendous advancements of next-generation sequencer, more ampliﬁed coverage of sequencing genomic fragments has been possible in a very cost-efﬁcientway. For this reason, the randoms hot gun methods of marine metagenomics have been getting more popularity, particularly because functional examination of obtained sequences of genomic fragments is possible when they are discussed as novel genes.
According to the Authors knowledge, on the contrary, there are no textbooks or reference books on advanced methodologies of marine metagenomics so far, and it was an obstacle for new researchers to step into this research area. Here we publish textbook on marine metagenomics, whose readers will be a wide range from undergraduate students to advanced researchers. But, the main targets will be from the graduate students to marine scientists including environmental scientists. The purposes of this book are to introduce and to illustrate the state-of-the-art marine metagenome researches. We explain the methods of marine metagenomic analyses in an easyto-understand manner and introduce the latest knowledge of marine metagenomics based on the studies of the authors’ projects. We hope that this book can be used as a primer for new researchers and as a hands-on manual for experimental methods. Hope that this textbook should become a seminal milestone in this research ﬁelds and its relevant research domains.