Afef Najjari

University of Tunis El Manar

Afef Najjari is an assistant professor of bioinformatics at the Faculty of Sciences, University of Tunis El Manar in Tunisia. Dr. Najjari has worked on a variety of national and international projects related to genomic and enzymatic diversity in lactic acid bacteria, as well as the diversity and adaptation of extremophilic microbes. Her current research interests include metagenomic data analysis, genome assemblies and annotations, and the development of biological databases. Dr. Najjari has published several articles in highly-ranked journals and has co-edited several books. She has also contributed to building capacity in bioinformatics at national and international levels.

2books edited

3chapters authored

Latest work with IntechOpen by Afef Najjari

This book focuses on how organisms survive in extreme conditions and the role of bioactive molecules in their adaptation to these environments. With their wide and versatile metabolic and enzymatic diversity, coupled with extraordinary physiological capacities, these enzymes and metabolites have been exploited to develop clean and sustainable industrial processes. Additionally, antibiotics, compatible solutes, and other compounds obtainable from these microbes are finding a variety of uses. We undertook this editorial project to make valuable contributions available to the research and academic community interested in extremophile adaptations and interactions under extreme environments. The editor is confident that the chapters in this book will be of interest to the research community.

Go to the book

Life in Extreme Environments

Edited by Afef Najjari

Books edited

Extremophilic Microbes and Metabolites

Edited by Afef Najjari

Chapters authored

Halocins, Bacteriocin-Like Antimicrobials Produced by the Archaeal Domain: Occurrence and Phylogenetic Diversity in Halobacteriales

By Afef Najjari, Hiba Mejri, Marwa Jabbari, Haitham Sghaier, Ameur Cherif and Hadda-Imene Ouzari

Members of extremely halophilic archaea, currently consisting of more than 56 genera and 216 species, are known to produce their specific bacteriocin-like peptides and proteins called halocins, synthesized by the ribosomal pathway. Halocins are diverse in size, consisting of proteins as large as 35 kDa and peptide “microhalocins” as small as 3.6 kDa. Today, about fifteen halocins have been described and only three genes, halC8, halS8 and halH4, coding C8, S8 and H4 halocins respectively have been identified. In this study, a total of 1858 of complete and nearly complete genome sequences of Halobacteria class members were retrieved from the IMG and Genbank databases and then screened for halocin encoding gene content, based on the BLASTP algorithm. A total of 61 amino acid sequences belonging to three halocins classes (C8, HalH4 and S8) were identified within 15 genera with the abundance of C8 class. Phylogenetic analysis based on amino acids sequences showed a clear segregation of the three halocins classes. Halocin S8 was phylogenetically more close to HalH4. No clear segregation on species and genera levels was observed based on halocin C8 analysiscontrary to HalH4 based analysis. Collectively, these results give an overview on halocins diversity within halophilic archaea which can open new research topics that will shed light on halocins as marker for haloarchaeal phylogentic delineation.

Part of the book: Extremophilic Microbes and Metabolites

Genome Analysis Provides Insights into the Osmoadaptation Mechanisms of Halomonas titanicae

By Afef Najjari

Here, we report the osmoadaptation strategies adopted by the halotolerant species Halomonas titanicae BH1(T) inferred from genome sequence analysis. BH strain was isolated in 2010 from a rusticated sample collected in 1991 from the wreck of the Titanic, genome deposited in the database under the accession number (CP059082.1). It showed a high salt tolerance ranging from 0.5 to 25% NaCl (w/v) (optimal growth at 10% NaCl) with no growth in the absence of NaCl. The phylogenomic analysis showed that the BH1 strain is more closely related to the Halomonas sedementi QX-2, a strain isolated from deep-sea sediments. The RAST (Rapid Annotation using Subsystem Technology) annotation revealed divergent mechanisms involved in the primary and secondary response to osmotic stress citing protein implicated in potassium transport, periplasmic glucan synthesis, choline and betaine upake system, biosynthesis of glycine-betaine, ectoine, and proline. These findings provide an overview of the osmoadaptive mechanisms of H. titanicae BH1, and could offer helpful information to future biotechnological applications like osmolyte synthesis and related applications.

Part of the book: Life in Extreme Environments

Introductory Chapter: Brief Overview of the Diversity of Secondary Metabolite in Extreme Environment – The Case of Halobacteria Based on Genome Sequence Mining

By Afef Najjari

Part of the book: Life in Extreme Environments

Afef Najjari

Latest work with IntechOpen by Afef Najjari

Life in Extreme Environments

Books edited

Extremophilic Microbes and Metabolites

Chapters authored

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