Preface

Extremophilic microbes are microorganisms that can grow under a remarkable range of extreme environments such as glacial deserts, hot springs, ocean floors, hypersalted environments, and rocks of the Earth's mantle. These microbes include acidophiles, alkalophiles, halophiles, barophiles, (hyper), thermophiles, and psychrophiles. These hostile environments shelter the rich biodiversity of extremophiles that could belong to one of three domains of life (bacteria, archaea and eukaryote). These microbes have evolved several mechanisms to ensure genomic integrity, cell division, and energy conservation in extreme conditions. They present a wide and versatile metabolic and enzymatic diversity coupled with extraordinary physiological adaptabilities to extreme environments. These enzymes and metabolites have been exploited to develop clean and sustainable industrial processes. Antibiotics, compatible solutes, and other compounds obtainable from these microbes are also finding a variety of uses. Recently, several investigations have been started to study the phylogenetic relationship between extremophilic microbes through the analysis of their genome sequences. Hence, comparative genomic analyses of genomes allowed for the identification of distinctive genes and metabolic pathways involved in the extremophilic way of life. This book presents a detailed portrait of the diversity and metabolic potential and applications of extremophilic microbes through several approaches and helps the reader to understand the role of metabolites in environmental adaptations.

## **Afef Najjari and Hadda-Imene Ouzari**

Department of Biology, Faculty of Sciences of Tunis - University of Tunis El Manar, Campus Universities, Tunis, Tunisia

#### **Haïtham Sghaier**

National Center for Nuclear Sciences and Technology, Sidi Thabet Higher Institute for Biotechnology, Ariana, Tunisia

**Ameur Cherif** Higher Institute for Biotechnology - University of Manouba, Ariana, Tunisia

**II**

**Chapter 8 129**

A Review on Electro-Rheological Fluid (ER) and Its Various Technological

*by Sudipto Datta, Ranjit Barua and Jonali Das*

Applications

**1**

**Chapter 1**

Metabolites

*and Eman Damra*

**Abstract**

gene editing

**1. Introduction**

Enhancement and Identification

Screening for microbial secondary metabolites (SMs) has attracted the attention of the scientific community since 1940s. In fact, since the discovery of penicillin, intensive researches have been conducted worldwide in order to detect and identify novel microbial secondary metabolites. As a result, the discovery of novel SMs has been decreased significantly by using traditional experiments. Therefore, searching for new techniques to discover novel SMs was one of the most priority objectives. However, the development and advances of omics-based techniques such as metabolomics and genomics have revealed the potential of discovering novel SMs which were coded in the microorganisms' DNA but not expressed in the lab media or might be produced in undetectable amount by detecting the biosynthesis gene clusters (BGCs) that are associated with the biosynthesis of secondary metabolites. Nowadays, the development and integration of gene editing tools such as CRISPR-Cas9 in metabolomics provide a successful platform for the identification and detection of known and

**Keywords:** secondary metabolites, metabolomics, genomic, CRISPR-Cas9, secondary metabolites identification, production of secondary metabolites, microorganisms,

The term secondary metabolites (SMs) was first mentioned in 1891 by A. Kossel.

Microbial secondary metabolites have attracted the scientific world's attention, since the discovery of penicillin in 1940s. After that, the identification and characterization of SMs have reached the highest level between 1940s and 1960s, and this period is called as "the golden era of SMs discovery" [1, 2]. A lot of compounds have been characterized and reported during the golden era and are still utilized till now. Unfortunately, the discovery of approved novel chemical scaffolds of secondary metabolites has significantly decreased after the golden era [1]. The possible explanation of the decreasing in the SMs' identification might be due to the following: (1) using the biosynthetic modules that are used for SMs' production

of Microbial Secondary

*Ahmed M. Shuikan, Wael N. Hozzein,* 

novel SMs and also to increase the production of SMs.

*Mohammed M. Alzharani, Maram N. Sandouka,* 

*Sulaiman A. Al Yousef, Sulaiman A. Alharbi* 
